Abstract: A process for the production of alumina from siliceous minerals containing substantial quantities of combined aluminium and calcium comprises the steps of treating the finely divided mineral with a hot acid liquor containing chloride, fluoride and calcium ions to extract alumina values from the mineral; recovering aluminium chloride from the liquid extract; recycling one fraction of the spent extract to the mineral extraction stage; and treating another fraction of the spent extract to regenerate hydrogen chloride gas for re-use in the process.

Abstract: Metal ion impurities are removed from phosphoric acid by adding to the acid a precipitant comprising ions of calcium and fluorine to cause precipitation of a fluoride solid which contains ions of magnesium, and other metals (e.g., Al, N.sub.a) which were in the impure acid. A preferred precipitant comprises calcium fluoride, such as the sludge obtained by treating pond water from a phosphoric acid plant with calcium ions (e.g. lime and/or limestone).

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: 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: Alumina is recovered from aluminum sulfate leach liquors by treatment of the liquor with HCl gas to the point of incipient crystallization of AlCl.sub.3.6H.sub.2 O, extraction of the resulting solution with a tertiary amine to remove iron, further treatment with HHl gas to precipitate AlCl.sub.3.6H.sub.2 O and roasting of the AlCl.sub.3.6H.sub.2 O to Al.sub.2 O.sub.3.

Abstract: Aluminum chlorohydroxide represented by the formula Al.sub.2 (OH).sub.x Cl.sub.y in which x and y range from 1 to 4 and 5 to 2, respectively, is produced by reacting hydrochloric acid with an amount of aluminum oxide or hydroxide which is equal to or slightly greater than the stoichiometric amount for obtaining aluminum trichloride, in the temperature range of from 160.degree. to 270.degree. C, and in the pressure range of from 0.1 to 50 kg/cm.sup.2.

Abstract: An apparatus for the production of pure alumina from alumina and silicate containing raw materials comprising means to feed said raw material into the top of an acid resistant leaching tower; means to continuously feed a leaching liquor containing hydrochloric acid into the bottom of said leaching tower, means to continuously flow said leaching liquor upward through said raw material to leach out the alumina as a solution of aluminum chloride, means to withdraw said solution enriched in aluminum chloride toward the top of said tower zone; means to withdraw said raw material solid residue from the bottom of said tower zone to convey said solid residue from said leaching tower into a separation zone at a level higher than the level of said leaching tower; and means to separate said solid residue from said carrier liquid in said separation zone.

Abstract: Aqueous AlF.sub.3 enriched crystallization mother liquors contaminated with P.sub.2 O.sub.5 values and having less than 5% free acidity are treated with a material which provides bismuth ions in the mother liquor in amounts small enough to insure that the Bi/PO.sub.4 mole ratio remains below about 1.05. Under these conditions, the bismuth and P.sub.2 O.sub.5 react essentially quantitatively to form a BiPO.sub.4 precipitate by which the P.sub.2 O.sub.5 can be separated from the mother liquor. Bismuth can be regenerated from the BiPO.sub.4 and recycled for further use in the process.The invention finds utility in the preparation of AlF.sub.3 by the reaction of an aluminum ore and P.sub.2 O.sub.5 contaminated HF or H.sub.2 SiF.sub.6 such as that available as a by-product of wet process phosphoric acid manufacture. The AlF.sub.3 reaction product is recovered by a crystallization step which, because it is normally only about 70 to 90% efficient, produces a mother liquor containing substantial amounts of AlF.sub.3.

Abstract: An aluminum-containing ore such as a kaolin or montmorillonite clay is treated with a fluorine acid such as HF or H.sub.2 SiF.sub.6 to produce aluminum fluoride (AlF.sub.3) which is recovered from the liquid phase of the reaction mixture by crystallization as AlF.sub.3 . 3H.sub.2 O crystals which are then dried and dehydrated to yield AlF.sub.3. The crystallization mother liquor is recycled to the process to recover its AlF.sub.3 values. The AlF.sub.3 . 3H.sub.2 O crystals and separated solid phase of the reaction mixture are washed to recover AlF.sub.3 values and the wash streams are recycled to the process. To produce alumina, the AlF.sub.3 is pyrohydrolyzed to Al.sub.2 O.sub.3 and HF. The HF is absorbed in the crystallization mother liquor and recycled with the mother liquor to the ore treatment step. All or a part of fluorine acid requirements can also be supplied from any suitable source such as, for example, a wet process phosphoric acid facility which is a plentiful source of inexpensive fluorine.

Abstract: A process for the production of pure alumina from alumina and silicate containing raw materials comprising feeding said raw material into the top of an acid resistant leaching tower; continuously feeding a leaching liquor containing hydrochloric acid into the bottom of said leaching tower, continuously flowing said leaching liquor upward through said raw material to leach out the alumina as a solution of aluminum chloride, withdrawing said solution enriched in aluminum chloride toward the top of said tower zone; withdrawing said raw material solid residue from the bottom of said tower zone to convey said solid residue from said leaching tower into a separation zone at a level higher than the level of said leaching tower; and separating said solid residue from said carrier liquid in said separation zone.Apparatus for producing alumina according to this method includes the corresponding means.