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: 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.

Abstract: Process for recovering aluminum in the form of a specific acid sulfate from an initial solution containing aluminum in the form of dissolved aluminum sulfate hydrate in which the specific acid sulfate is of the formula Al.sub.2 (SO.sub.4).sub.3.0.5H.sub.2 SO.sub.4.11 to 12 H.sub.2 O and in which the initial solution is sequentially treated in a series of crystallizers, wherein successive crystallizers are maintained at a predetermined decreased generally fixed temperature such that in each crystallizer a state of supersaturation of aluminum acid sulfate exists and the parameters attendant operation of each crystallizer insure that a state of static equilibrium of precipitation of product is generally reached before the process solution/slurry is passed to a successive crystallizer, or filtered for recovery of product.

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: There is disclosed a continuous process for the manufacture of aluminum sulfate by the reaction of sulfuric acid with an alumina-containing solid in an aqueous suspension. The reaction stream is passed into a continuous flow reaction zone that is maintained at a temperature controlled from 225.degree. to 260.degree. F. and under superatmospheric pressure, preferably, autogenic pressure. The reactants are passed through the reaction zone with a residence time of from 5 to about 45 minutes, sufficient to achieve from 78% to 100% completion of the reaction. An intimate admixture of the reactants is achieved by blending the reactants in a mixing zone wherein the combined streams are diverted into helical flow with repeated reversal in the direction of rotation of the helical flow during passage through the mixing zone.

Abstract: A method of obtaining alumina of high purity from aluminous mineral containing impurities in which the mineral is attacked with a sulphuric acid liquor followed by separation of a liquid phase from the resulting solid residue comprising(1) mixing the liquid phase with a liquor containing HCl and H.sub.2 SO.sub.4 at elevated temperature,(2) cooling the mixture with the precipitation of hydrated aluminum chlorosulphate having the formula AlSO.sub.4 Cl.6- 7H.sub. 2 O,(3) separating the precipitate from the remaining liquor which contains the major part of the impurities in solution,(4) suspending the separated precipitate in a hydrochloric acid liquor,(5) chlorinating the suspension by introduction of gaseous HCl with precipitation of AlCl.sub.3.6H.sub. 2 O,(6) separating the precipitated AlCl.sub.3.6H.sub. 2 O, and(7) pyrolizing the separated precipitate to produce alumina of high purity and gaseous HCl.

Abstract: The invention is a method for working-up shale while recovering metals therefrom and the sulphur content thereof. The method comprises crushing the shale and leaching and roasting the shale. The sulphur content is oxidized and converted into sulphuric acid, concentrated sulphur dioxide or sulphur. The leaching operation is effected with sulphuric acid. The leached metals are recovered in a manner known per se and the residual solution is passed to the roasting stage.

Abstract: The red mud by-product of the Bayer process by which aluminum oxide is reed from bauxite as an aluminate, is digested with concentrated sulfuric acid or with sulfur trioxide gas to produce sulfates that can be leached out to the resulting mass with water. The solution is then heated at a pH of 1 to precipitate titanium oxide hydrate by hydrolysis. The remaining sulfates of the solution are then obtained in solid form by evaporation, or by precipitation with acetone, and the solid is then roasted to convert the aluminum and iron to the oxide. After leaching out the sodium sulfate with water, the aluminum and iron oxide are separated by the Bayer process, which works in this case even though x-ray diffusion patterns show that the aluminum oxide is mainly .alpha.Al.sub.2 O.sub.3.

Abstract: A process for the extraction of alumina from aluminum-containing silicates is disclosed. The process comprises acid leaching of the raw material, iron extraction, precipitation of the aluminum fraction as the aluminum chloride hexahydrate, removal of sodium chloride and calcination to alumina. The process can be made continuous with substantial regeneration and recycling of process components.

Abstract: An improvement in the process for recovering aluminum from alunite ore disclosed in U.S. Pat. Nos. 3,890,425 and 3,890,426, the improvement being in the recovery of potassium sulfate by crystallization from the leaching solution resulting from potassium hydroxide leaching of the roasted ore, the improvement consisting of adding potassium hydroxide to the concentrated leach liquor prior to crystallization to increase the concentration of the potassium ion so that increased recoveries of potassium sulfate are obtained at a given temperature over those obtained when this procedure is not used. By this procedure a yield is obtained at a temperature below that which is required to obtain the same yield when potassium hydroxide is not used so that the high temperatures formerly necessary to hold enough potassium sulfate in solution for an economic crystallization are avoided.

Abstract: Hexagonal plate crystals of aluminum sulfate are produced in chemically pure form by a process which comprises cooling a heated saturated solution of chemically impure aluminum sulfate acidified with sulfuric acid to precipitate crystals of aluminum sulfate, heating the slurry of the cooled solution containing the precipitated aluminum sulfate crystals to a predetermined temperature wherein the temperature is maintained for a time sufficient to dissolve a portion of the crystals in the solution, cooling the heated slurry to precipitate aluminum sulfate crystals, and separating the precipitated crystals from the slurry.

Abstract: A process for recovering aluminum from alunite ore directed to providing a residue for the Bayer leach step substantially free of impurities so that a high A/C ratio Bayer leach liquor is produced, which comprises roasting the ore in particulate form to drive off water and sulfur as SO.sub.2 and to convert aluminum sulfate to alumina, leaching the residue containing aluminum values with water and filtering to remove potassium sulfate and other soluble sulfates, hot leaching the residue with sulfuric acid to convert the alumina therein to soluble aluminum sulfate followed by filtering to remove silicon dioxide and other solid impurities, crystallizing the aluminum sulfate to further remove impurities, heating the residue to convert the aluminum sulfate to alumina and drive off any remaining sulfur as SO.sub.2, and digesting the alumina calcine with sodium hydroxide under standard Bayer conditions at a high A/C ratio to provide a high A/C ratio solution from which a "sandy" aluminum hydroxide is precipitated.

Abstract: A method of producing an alumina bearing product in which the alumina is substantially soluble in cold alkali including the steps of contacting an aluminium bearing material with concentrated sulphuric acid containing 30 to 100 weight percent sulphuric acid, heat treating the acid and material to cause the acid to react with the material to form a substantially anhydrous hard product and decomposing the product by heat treatment to produce the alumina bearing product. The alumina values may be recovered from the resulting alumina bearing product using the known Bayer process. The process has particular application to non-bauxitic ores.

Abstract: The specific feature of the present method is that in the process solution resulting in the processing of alunite with the object of producing alumina and potassium sulphate therefrom, an excess amount of sodium ions is maintained with respect to the potassium ions.The method is advantageous in that it ensures a higher yield of potassium sulphate and a lower contamination of the final products with respect to sodium and potassium ions.

Abstract: A method for processing bauxites according to the Bayer technology, with an increased yield in Al.sub.2 O.sub.3 and with decreased caustic soda losses, starting particularly from goethite bauxites of boehmite and/or diaspore type and carrying out the digestion at 180.degree.C to 300.degree.C using an aluminate liquor containing Na.sub.2 O.sub.caustic in a concentration of 80 to 300 g./l. The digestion is carried out in the presence of a calcium compound in an amount corresponding to 2 to 6 % of CaO calculated for the dry weight of bauxite and of a sulfate salt in an amount corresponding to 1.0 to 7.0 g./l. of sulfate ion concentration, whereby the goethite content of the bauxite is converted into hematite. The process provides advantageous conditions for the complete dissolution of the boehmite and diaspore content of bauxite in the vicinity of the equilibrium molar ratio, and enables to recover efficiently the caustic soda losses in the Bayer process itself, requiring no supplementary operation.