Abstract: The invention provides a method of controlling silica in the liquor circuit of the Bayer process. The method involves addition of a promoter material to enhance the precipitation of DSP and includes adding one or more silica dispersion materials or dry silica forms to those parts of the circuit where precipitation of DSP and removal of silica from solution is desirable; for example the desilication stage of a Bayer process plant. The removal of DSP from solution reduces silica concentration in the liquor and thereby enables better control of process issues such as silica contamination in alumina product and DSP formation in later stages of the process where precipitation as scale onto vessel walls and equipment is problematical. As a result, the invention provides a significant reduction in the total cost of operating a Bayer process.

Abstract: A process for the production of alumina trihydrate by alkaline digestion of bauxite using the Bayer process in which aluminate liquor and insoluble residues are separated using a solid/liquid separation device (E; W2; DC) characterised in that the said slurry (21a; 41; 230?) is at least partially passed through a hydrocyclone (H1; H21; H22; H3) to improve and accelerate the separation of the sodium aluminate liquor from the insoluble residues in the slurry (21a; 41; 230?) containing the said liquor and the said residues and that supplies or is derived from the said liquid-solid separation device. In a first embodiment, at least one hydrocyclone is used at the upstream side of the settler-thickener, as clarifier of the pregnant liquor. In a second embodiment, at least one hydrocyclone is used as a thickener of insoluble residue mud. In a third embodiment, a hydrocyclone is used in combination with the causticisation settler.

Abstract: The present invention relates ways to increase the output of a high quality product from the aluminum hydroxide recovery processes such as the Bayer process. The invention is a method of increasing the size of precipitated aluminum hydroxide while not reducing the total production amounts. The invention relates to the use of a crystal growth modifier compositions added to the precipitation liquor to increase the particle size distribution of the precipitated alumina trihydrate.

Abstract: The present invention relates to the use of lithium salts and/or magnesium salts for the precipitation of aluminum oxides present in aqueous media.

Abstract: A process for obtaining one or more metal fluoride or metal oxide compounds from treatment of a feed material containing aluminium ore, includes the steps of contacting the feed material with a fluorine acid solution to form gaseous silicon fluoride and aqueous soluble metal fluorides and/or metal fluosilicates, processing the aqueous reaction products to form a solid reaction product containing metal fluorides, processing to remove low boiling point compounds and heating said solid reaction product to a temperature to drive off metal fluoride in gaseous form. The feed material may include aluminium ores and/or titanium ores, coal or other carbonaceous materials containing mineral impurities, or other minerals such as mica. Processes for the production of aluminium and titanium compounds are also described.

Abstract: The present invention discloses method of recovering valuable metals, such as vanadium, molybdenum, nickel from the catalysts spent in the VRDS process for desulfurization of pertroleum. The method comprises leaching water-insoluble reactants after reacting the pre-treated waste crystals in solution of sodium hydroxide, maintaining the filtrate at pH 9.5 by adding sulfhuric acid or hydrochloric acid and then heating the filtrate, removing aluminium oxide from the soltuion, aerating the filtrate continously or priodically and agitating the filtrate below pH 1 at 80-100° C., thereby precipitating molybdenum oxide and vanadium oxide, and leaching and washing the precipitated molybdenum oxide and vanadium oxide.

Abstract: The suspended solids content of a process stream in a process for digesting bauxite ore to produce alumina is reduced by contacting the stream with silicon-containing polymers.

Abstract: A process for removing anionic impurities from a caustic aluminate solution having aqueous tetrahydroxy aluminate ions is described. A caustic aluminate solution is obtained such that anionic impurities are partially or substantially substituted into tetrahydroxy aluminate ions to form substituted aluminate ions. A suitable calcium compound, such as quicklime, is reacted in a conventional slaker (10) with a slaking solution, for example water, and stored in an agitated storage tank (12). The resulting slurry is pumped to a reaction vessel (14) where it is reacted with a caustic aluminate solution under appropriate conditions such that the calcium compound is converted into tricalcium aluminate (TCA) precipitate. Upon reaction substituted aluminate ions are substantially incorporated within the TCA precipitate to form a substituted TCA precipitate enabling the anionic impurities to be removed from the solution via the substituted TCA precipitate for disposal or recovery.

Abstract: There is provided a process for preparing aluminium chloride comprising: leaching aluminium dross residues with HCl so as to obtain a mixture comprising a solid and a liquid; and hydrochlorinating the liquid obtained from the mixture, so as to form a precipitate comprising aluminium chloride. Such a sequence can also be used for preparing alumina. In such a case, the process can further comprise the step of converting the so-obtained aluminium chloride into alumina. In the processes previously defined, the solid so-obtained can also be leached with H2SO4, thereby generating a leachate. The leachate can also eventually be hydrochlorinated so as to increase the yield of the desired product obtained i.e. alumina or aluminium chloride.

Abstract: The invention provides methods for purifying caustic feed streams using membranes that comprise polysulfonamide matrices.

Abstract: A method for treating a polymetallic sulfide ore containing gold and/or silver, and further containing base metals selected from the group consisting of iron, aluminum, chromium, titanium, copper, zinc, lead, nickel, cobalt, mercury, tin, and mixtures thereof, is disclosed. The method comprises the steps of grinding the polymetallic sulfide ore to produce granules, oxidizing the granules to produce oxidized granules, and chloride leaching the granules using a brine solution including dissolved halogens, as well as chloride and bromide salts.

Abstract: To provide a process for producing inorganic spheres having a substantially uniform particle size with high productivity. In a process for producing inorganic spheres, which comprises a step of injecting an alkaline aqueous liquid containing an inorganic compound into a laminar flow of an organic liquid containing a surfactant through micropores to form a W/O type emulsion, and a step of solidifying droplets of the aqueous liquid containing an inorganic compound in the W/O type emulsion by an acid to form inorganic spheres, as the organic liquid, one which is brought into contact with an acid in a state of the W/O type emulsion or after separated from the W/O type emulsion, or one which is brought into contact with the aqueous liquid and then separated and recovered, is used.

Abstract: The present invention relates ways to increase the output of a high quality product from the aluminum hydroxide recovery processes such as the Bayer process. The invention is a method of increasing the size of precipitated aluminum hydroxide while not reducing the total production amounts. The invention relates to the use of a crystal growth modifier compositions added to the precipitation liquor to increase the particle size distribution of the precipitated alumina trihydrate.

Abstract: A method for increasing the floccule size and volume of alumina trihydrate during the Bayer processing of bauxite ore using a flocculant in conjunction with a water continuous polymer. The addition of the flocculant and the water continuous polymer to the alumina trihydrate slurry following the security filtration and settling producing trihydrate that is put through the calcination process to produce purified alumina or used as seed for the precipitation process.

Abstract: A black composite oxide particle includes a composite oxide having Fe, Mg and Al as metal components. The particle contains Fe, Mg and Al in amounts of 30 to 55 mass %, 1 to 10 mass %, and 1 to 10 mass %, respectively, and has an atomic ratio of Fe3+/Fe2+ of 0.8 to 10. Also described is a method for producing the black composite oxide particle. In an embodiment, the particle includes a hydrated composite oxide represented by an empirical formula: Fe2+aFe3+bMgcAldOe·nH2O. The black composite oxide particle is suitable as a black pigment for a coating material, an ink, toner particles, a rubber and a plastic, and is reduced with respect to the load on the environment and excellent in blackness.

Abstract: This invention relates to a process for reducing the contaminants in condensate resulting from the conversion of bauxite to alumina.

Abstract: A process for the removal and causticisation of sodium oxalate and/or sodium sulphate from a Bayer process liquor containing sodium carbonate and one or both of sodium oxalate and sodium sulphate in an alumina refinery is described. The process is based on the observation that to efficiently causticise sodium oxalate solutions, it is first necessary to remove the aluminate ion from solution, optionally with recovery of the aluminate ion in some later step. This is effected by removing aluminate ions from the Bayer liquor through the formation of a carbonate bearing hydrocalumite and/or sulpha-bearing hydrocalumite. The liquor may then be treated with sufficient lime to remove and causticise any residual carbonate ions and some or all of the oxalate ions present so that any reacted lime solids thus formed can be separated and safely disposed of.

Abstract: A method for the production of aluminum from bauxites containing aluminum monohydate of the diaspore or boehmite type which may contain more than 1.5% by weight of calcium carbonates. The ore is digested by producing feeding a suspension produced from milled bauxite ore and concentrated aluminate liquor to a plant with a series of autoclaves and a series of regulators supplying tubular reheaters across the autoclaves with steam. The suspension first travels across the series of autoclaves, and on exiting, the digestion of the ore is practically complete, and the suspension then travels across the series of regulators. The condensation water from the steam coming from the regulator and feeding the reheater is collected in a purge pot. Within the series of regulators, the suspension is diluted on entering a regulator with the water coming from the condensation of the steam from one or several upstream regulators.

Abstract: Mesoporous aluminum oxides with high surface areas have been synthesized using inexpensive, small organic templating agents instead of surfactants. Optionally, some of the aluminum can be framework-substituted by one or more other elements. The material has high thermal stability and possesses a three-dimensionally randomly connected mesopore network with continuously tunable pore sizes. This material can be used as catalysts for dehydration, hydrotreating, hydrogenation, catalytic reforming, steam reforming, amination, Fischer-Tropsch synthesis and Diels-Alder synthesis, etc.

Abstract: In a metal oxide nanoparticle and a synthetic method thereof, and in particular to maghemite (?-Fe2O3) nanoparticles usable as a superhigh density magnetic recording substance by having good shape anisotropy and magnetic characteristics, hematite (?-Fe2O3) nanoparticles usable as a precursor to the maghemite or a catalyst, maghemite and hematite-mixed nanoparticles and a synthetic method thereof, the method for synthesizing metal oxide nanoparticles includes forming a reverse micelle solution by adding distilled water, a surfactant and a solvent to metallic salt not less than trivalent, precipitating and separating gel type amorphous metal oxide particles by adding proton scavenger to the reverse micelle solution; adjusting a molar ratio of metal oxide to the surfactant by washing the gel type amorphous metal oxide particles with a polar solvent; and crystallizing metal oxide nanoparticles through heating or reflux after dispersing the gel type amorphous metal oxide particles in a non-polar solvent having a h

Abstract: A method of producing an Indium Tin Oxide powder is described. A method of producing an Indium Tin Oxide powder comprising the steps of: (1) mixing a raw aqueous solution containing indium ions and tin ions and having a proportion of divalent tin ions in the tin ions of 50 wt % or more with an alkali aqueous solution, (2) separating the product into solid and liquid, and (3) calcinating the resulted solid.

Abstract: Disclosed is a method for making amorphous spherical particles of zirconium titanate and crystalline spherical particles of zirconium titanate comprising the steps of mixing an aqueous solution of zirconium salt and an aqueous solution of titanium salt into a mixed solution having equal moles of zirconium and titanium and having a total salt concentration in the range from 0.01 M to about 0.5 M. A stearic dispersant and an organic solvent is added to the mixed salt solution, subjecting the zirconium salt and the titanium salt in the mixed solution to a coprecipitation reaction forming a solution containing amorphous spherical particles of zirconium titanate wherein the volume ratio of the organic solvent to aqueous part is in the range from 1 to 5. The solution of amorphous spherical particles is incubated in an oven at a temperature ?100° C. for a period of time ?24 hours converting the amorphous particles to fine or ultrafine crystalline spherical particles of zirconium titanate.

Abstract: Nanoscale corundum powders are obtained by first producing an Al2O3 precursor by adding seed crystals to an aqueous solution of an aluminium compound and adding a base and then converting the Al2O3 precursor into corundum by calcination at a high temperature. Before the calcination, the salts that are present in addition to the Al2O3 precursor are separated off. The resulting product is calcined at temperatures of 700 to 975° C. and any fines that may be present are removed. The resulting corundum powders can be sintered at temperatures of ?1200° C. to produce compacts or components of multiple layer systems.

Abstract: An improved process is described for the preparation of surface modified hydrotalcite. The process comprises reacting a precursor of magnesium and aluminium in the presence of suitable alkali carbonate at high temperature. The product has a BET surface area of ?20 m2/gm and average particle size of ?0.5 ?m and is useful as halogen scavenger and fire retardant.

Abstract: A method of dewatering an aqueous mineral suspension comprising introducing into the suspension a flocculating system comprising, a) a substantially non-ionic polymeric flocculant and b) an anionic polymeric flocculant, characterised in that, the substantially non-ionic polymeric flocculant is added to the suspension before the addition of the anionic polymeric flocculant. The method is useful for flocculating China clay suspensions, suspensions of s welling clays, calcium carbonate suspensions, titanium dioxide suspensions, suspensions of coal tailings, red mud and phosphate slimes etc.

Abstract: The present invention is directed to a system for recovering metal values from metal-bearing materials. During a reactive process, a seeding agent is introduced to provide a nucleation site for the crystallization and/or growth of solid species which otherwise tend to passivate the reactive process or otherwise encapsulate the metal value, thereby reducing the amount of desired metal values partially or completely encapsulated by such material. The seeding agent may be generated in a number of ways, including the recycling of residue or the introduction of foreign substances. Systems embodying aspects of the present invention may be beneficial for recovering a variety of metals such as copper, gold, silver, nickel, cobalt, molybdenum, zinc, rhenium, uranium, rare earth metals, and platinum group metals from any metal-bearing material, such as ores and concentrates.

Abstract: A process in which material comprising an aqueous liquid with dispersed particulate solids is pumped as a fluid then allowed to stand and rigidify and the rigidification is improved whilst retaining the pump ability of the material by combining polymeric particles with the material during or prior to pumping the material, wherein the polymeric particles comprise water soluble polymer which has an intrinsic viscosity of at least 3 dl/g. The process of the invention more effectively minimises the area taken up by a stack of the material of given volume whilst maintaining the pumpability of the material. This invention is particularly suited to material that comprises red mud from the Bayer alumina process.

Abstract: The present disclosure relates to a method for removing anions such as nitrate ion, sulfate ion, chloride ion, and phosphate ion existing in underground water, surface water or waste water. The method involves adding alumina cement and a calcium compound to the water containing the anion followed by applying an electric field thereto, thereby forming a chemical precipitate which is an insoluble complex salt. The disclosure also relates to a continuous process for removing the anion by continuously performing the above method for removing anions.

Abstract: Methods for sol-gel processing that generally involve mixing together an inorganic metal salt, water, and a water miscible alcohol or other organic solvent, at room temperature with a macromolecular dispersant material, such as hydroxypropyl cellulose (HPC) added. The resulting homogenous solution is incubated at a desired temperature and time to result in a desired product. The methods enable production of high quality sols and gels at lower temperatures than standard methods. The methods enable production of nanosize sols from inorganic metal salts. The methods offer sol-gel processing from inorganic metal salts.

Abstract: Processes for treating iron containing waste streams are provided. According to these processes, metal-containing compounds, particularly iron oxides are produced. These methods may, for example, be used in the processing of the waste streams from the chlorination of titanium-bearing raw materials and involve the use of certain combinations of neutralization and precipitation steps.

Abstract: A method is provided for efficient processing of spent potliner, separating and recycling/utilizing the liquid and solid products generated during processing. The method includes the steps of crushing and screening the potliner freed from metal debris, pulverizing the potliner suspended in a hot aqueous slurry by autogenous grinding in a tumbler in the presence of air, subjecting the potliner to a series of leaching, thickening and filtering steps followed by separation of the potliner into Bayer Liquor, solid sodium fluoride, quality carbon product and mineral matter characterized by low cyanide and fluoride leachability. About 85% of the water required for potliner processing is recovered and recycled into the process.

Abstract: The invention relates to methods and a device for the removal of non-water soluble substances from solutions of aqueous metal extracts, by addition of at least one water-soluble cationic polyelectrolyte, containing a diallylaminoalkyl(meth)acrylamide, neutralised or quaternised with mineral acid and subsequently polymerised, preferably dimethylaminopropylacrylamide.

Abstract: A process for the removal and causticisation of sodium oxalate and/or sodium sulphate from a Bayer process liquor containing sodium carbonate and one or both of sodium oxalate and sodium sulphate in an alumina refinery is described. The process is based on the observation that to efficiently causticise sodium oxalate solutions, it is first necessary to remove the aluminate ion from solution, optionally with recovery of the aluminate ion in some later step. This is effected by removing aluminate ions from the Bayer liquor through the formation of a carbonate-bearing hydrocalumite and/or sulphate-hearing hydrocalumite. The liquor may then be treated with sufficient lime to remove and causticise any residual carbonate ions and some or all of the oxalate ions present so that any reacted lime solids thus formed can be separated and safely disposed of.

Abstract: The claimed invention is a method for separating Bayer process red mud from a Bayer process liquor which comprises adding to a Bayer process liquor containing red mud an effective amount of a water soluble synthetic flocculant, dextran and starch combination. The flocculant is added anywhere in the slurry containing the red mud suspended in Bayer process liquor, or in a liquor slurry containing bauxite prior to or during digestion. Once the flocculant combination is added, it is mixed sequentially with the Bayer process liquor and the red mud contained in the Bayer process liquor is removed by sedimentation, centrifugation or filtration.

Abstract: The present invention relates to a process for the recovery of gallium from Bayer process liquors. Bayer process liquor is obtained from alumina industries and contains 450 g/L Na2O, 80 g/L Al2O3 and 190±20 ppm of gallium. The present invention utilizes an organic and inorganic phase for a two stage separation process to recover gallium with high purity.

Abstract: In order to provide a method for effectively separating red mud generated during alumina-extraction treatment of an alumina ore containing goethite as an iron component, the alumina ore containing goethite as an iron component is treated with an alkaline solution at 110-160° C., to thereby take up alumina components through extraction, and a settling aid formed of a water-soluble polymer including, as an effective component, a copolymer containing, as a monomer component, a vinylhydroxamic acid compound or a salt thereof (A) and having an average molecular weight of at least 2,000 is added to the resultant extract, to thereby settle the red mud for separation thereof.

Abstract: The present invention is directed to a process for recovering metal values from metal-bearing materials. During a reactive process, a seeding agent is introduced to provide a nucleation site for the crystallization and/or growth of solid species which otherwise tend to passivate the reactive process or otherwise encapsulate the metal value, thereby reducing the amount of desired metal values partially or completely encapsulated by such material. The seeding agent may be generated in a number of ways, including the recycling of residue or the introduction of foreign substances. Processes embodying aspects of the present invention may be beneficial for recovering a variety of metals such as copper, gold, silver, nickel, cobalt, molybdenum, zinc, rhenium, uranium, rare earth metals, and platinum group metals from any metal-bearing material, such as ores and concentrates.

Abstract: Aqueous suspensions of paints in waste waters can be treated to detackify the paint and facilitate its removal by contacting the paint suspension at a pH of from about 5 to about 14 with a polyarylamine that is produced by reacting an aldehyde with an arylamine in the presence of an acid in an aqueous suspension. The same polyarylamine can also be used for reducing the color content of highly colored liquids. Compositions containing the polyarylamine are also described.

Abstract: A process is disclosed for the treatment of an alumina process feedstock prior to transferring the treated feedstock to an alumina process for extracting refined alumina from the treated feedstock. The treatment process includes the following steps: (a) heating the alumina process feedstock to a temperature of 400C. to 650C. by direct contact with combustion gases, and (b) cooling the heated feedstock to a temperature at which it can be handled and fed to the alumina process. The treatment process is characterised by controlling the contact time of the solid alumina process feedstock at temperatures in the above range in step (a) to less than 5 minutes.

Abstract: The present invention provides an improved process for the production of alumina trihydrate crystals. Through the addition of a hydroxamated polymer at various stages of the process for production of these alumina trihydrate crystals, an upward shift in the particle size distribution of the alumina trihydrate crystals occurs. In one embodiment, the hydroxamated polymer is added to a filtered aqueous solution, which comprises no more than about 10 mg of insoluble solids per liter. In another embodiment, the hydroxamated polymer is added to an aqueous solution comprising insoluble solids after precipitation of alumina trihydrate crystals has commenced. Optionally, alumina trihydrate seed crystals may be added to the aqueous solution to initiate or encourage crystal formation.

Abstract: A process is described for the treatment of spent pot lining material from electrolyte reduction cells, this spent material having a substantial content of cryolite. The spent material is first leached with water at a dilution and a time sufficient to dissolve substantially all water soluble fluorides, after which the solid residue is separated from the liquid. The solid residue obtained is then subjected to a caustic leach with an aqueous sodium hydroxide solution containing about 20 to 50 g/L of NaOH and thereafter the solid residue is separated from the liquid.

Abstract: A process is provided for the treatment of an alumina process feedstock prior to transferring the treated feedstock to an alumina process for extracting refined alumina from the treated feedstock. The treatment process includes: (a) heating the alumina process feedstock to a temperature of 400° C. to 650° C. by direct contact with combustion gas, and (b) cooling the heated feedstock to a temperature at which it can be handled and fed to the alumina process. The treatment process also includes controlling the contact time of the alumina process feedstock at temperatures in step (a) to ensure decomposition of alumina trihydrate and alumina monohydrate. The process also includes: (i) limiting the maximum temperature of incoming gas to a stage of the process in which the alumina process feedstock reaches the above temperature range of 400° C. to 650° C.

Abstract: The present invention provides an &agr;-alumina powder, which is suitable for use as a filler for silicon rubber or the like for manufacturing a heat-conductive sheet. The &agr;-alumina powder includes &agr;-alumina particles having an average particle diameter of not less than about 2 &mgr;m and not more than about 5 &mgr;m, a particle size distribution such that a ratio of 90 wt % diameter D90 to 10 wt % diameter D10 represented by D90/D10 is not more than about 2, and a crystalline form represented by an index A of more than about 0.40 and not more than about 0.50, wherein the index A is obtained by substituting X-ray intensities I(110), I(300) and I(116) at (110) plane, (300) plane and (116) plane, respectively, determined by X-ray diffraction, into the following formula (I): A={I(110)+I(300)}/{2×I(116)}  (I).

Abstract: The process according to the invention to raise simultaneously to an optimum level the temperature and concentration of an aqueous medium intended for use in bauxite ore digestion in an alumina production plant according to the Bayer process, which includes successive phases (a) to (f) in which: a) the aqueous medium coming from digestion containing pregnant liquor is cooled and evaporated in a multiple staged flash evaporation zone; b) the sterile residue is separated, the aluminium trihydroxide is precipitated and the aqueous medium, consisting of spent liquor, intended for use in digestion is recovered; c) if need be, the required quantity of water, additional to that already evaporated in phase (a) is eliminated by evaporation in a specific evaporation section; d) the aqueous medium intended for use in digestion is heated in several stages; e) the flash vapour generated in each of the stages of the evaporation phase (a) is used in each of the stages of the heating phase (d); f) the aqueous medium in

Abstract: A method of flocculating suspended solids in a Bayer process liquor comprising adding to the liquor an effective amount of a polymer comprising salicylic acid groups.

Abstract: A process in which material comprising an aqueous liquid with dispersed particulate solids is pumped as a fluid then allowed to stand and rigidify and the rigidification is improved whilst retaining the pumpability of the material by combining polymeric particles with the material during or prior to pumping the material, wherein the polymeric particles comprise water soluble polymer which has an intrinsic viscosity of at least 3 dl/g. The process of the invention more effectively minimises the area taken up by a stack of the material of given volume whilst maintaining the pumpability of the material. This invention is particularly suited to material that comprises red mud from the Bayer alumina process.

Abstract: The present invention is directed to a process for recovering metal values from metal-bearing materials. During a reactive process, a seeding agent is introduced to provide a nucleation site for the crystallization and/or growth of solid species which otherwise tend to passivate the reactive process or otherwise encapsulate the metal value, thereby reducing the amount of desired metal values partially or completely encapsulated by such material. The seeding agent may be generated in a number of ways, including the recycling of residue or the introduction of foreign substances. Processes embodying aspects of the present invention may be beneficial for recovering a variety of metals such as copper, gold, silver, nickel, cobalt, molybdenum, zinc, rhenium, uranium, rare earth metals, and platinum group metals from any metal-bearing material, such as ores and concentrates.

Abstract: A process for preparing a nanocrystalline material comprising at least a first ion and at least a second ion different from the first ion, and wherein at least the first ion is a metal ion, is described. The process comprises contacting a metal complex comprising the first ion and the second ion with a dispersing medium suitable to form the nanocrystalline material and wherein the dispersing medium is at a temperature to allow formation by pyrolysis of the nanocrystalline material when contacted with the metal complex.

Abstract: The present invention comprises a method for reducing the viscosity of the settled mud or underflow of a raked thickener thereby reducing the torque necessary to move the rake blade through the settled mud. The method includes the step of delivering a viscosity modifier to the settled mud and in front of the rake blade by pumping the viscosity modifier down the rake arm to an area in front of the rake blade. The method also includes an improved rake mechanism that includes a means for delivering viscosity modifier to the settled mud and in front of the rake blade. The present invention also includes a method for increasing the rate of consolidation of flocculated solids in a slurry.

Abstract: A method for processing alumina-bearing ores such as bauxite to recover iron, aluminum, silicon and titanium metal values therefrom the method comprising the steps of adding the alumina-bearing ores to a digester containing an acid to provide a mixture of acid and alumina-bearing ores and heating the mixture to dissolve soluble compounds of at least one of iron, aluminum, silicon and titanium to provide a digest containing dissolved salts of the soluble compounds and to provide a gas component. Thereafter, the digest is treated with water to dissolve water soluble salts therein to provide a slurry comprised of a liquid containing water and the dissolved soluble salts and a solid component comprised of silica. The solid component is separated from the liquid and the pH of the liquid is adjusted to form an aluminate and an iron-containing precipitate.