Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
  • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
  • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
  • C01F7/0646—Separation of the insoluble residue, e.g. of red mud
  • C01F7/0653—Separation of the insoluble residue, e.g. of red mud characterised by the flocculant added to the slurry
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
  • C01F7/46—Purification of aluminium oxide, aluminium hydroxide or aluminates
  • C01F7/47—Purification of aluminium oxide, aluminium hydroxide or aluminates of aluminates, e.g. removal of compounds of Si, Fe, Ga or of organic compounds from Bayer process liquors
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
  • C01F7/46—Purification of aluminium oxide, aluminium hydroxide or aluminates
  • C01F7/47—Purification of aluminium oxide, aluminium hydroxide or aluminates of aluminates, e.g. removal of compounds of Si, Fe, Ga or of organic compounds from Bayer process liquors
  • C01F7/473—Removal of organic compounds, e.g. sodium oxalate
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
  • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
  • C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
  • C22B3/41—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds using a solution of normally solid organic compounds, e.g. dissolved polymers, sugars, or the like
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S210/00—Liquid purification or separation
  • Y10S210/902—Materials removed
  • Y10S210/908—Organic

Definitions

• the present invention relates to a process and an apparatus for removing water-insoluble substances from solutions of aqueous metal extracts by addition of water-soluble cationic polyelectrolytes which comprise dimethylaminopropylacrylamides which have been neutralized or quaternized by mineral acids and subsequently polymerized.
• aluminum is obtained from aluminum oxide which is prepared worldwide from bauxite by the process of Karl Joseph Bayer.
• milled bauxite is digested with a hot aqueous sodium hydroxide solution and the aluminum is converted into sodium aluminate which is soluble in the digestion solution at high temperatures and precipitates when the temperature is lowered.
• U.S. Pat. No. 4,578,255 describes a process for reducing the concentration of water-insoluble humic acid-like impurities from digestion solutions of the Bayer process by partial precipitation of these impurities by means of water-soluble. polymeric quaternary ammonium salts, in particular by means of homopolymers of diallyldimethylammonium chloride monomers.
• This object is achieved by a process for removing water-insoluble substances from solutions of aqueous metal extracts by addition of at least one water-soluble cationic polyelectrolyte which comprises at least 50 mol % of diallylaminoalkyl(meth)acrylamide, preferably dimethylaminopropylacrylamide, which has been neutralized or quaternized by at least one mineral acid and subsequently polymerized, based on the total amount of the polyelectrolyte.
• the cationic polyelectrolyte preferably comprises at least 70 mol %, particularly preferably at least 90 mol %, of diallylaminoalkyl(meth)acrylamide, preferably dimethylaminopropylacrylamide, which has been neutralized or quaternized by means of mineral acid and subsequently polymerized, based on the total amount of the polyelectrolyte.
• the cationic polyelectrolyte is very particularly preferably a homopolymer of diallylaminoalkyl(meth)-acrylamide, preferably dimethylaminopropylacrylamide, which has been neutralized or quaternized by means of mineral acid and subsequently polymerized.
• the homopolymers and the copolymers can be prepared by known polymerization methods.
• the purity of the DMAPAA is important for achieving a quotient of limiting viscosity and molar ratio of ACA and DMAPAA of at least 200 ml/g.
• DMAPAA should be essentially free of bifunctional compounds, i.e. they may be present in only a very small proportion in the DMAPAA.
• Bifunctional compounds cause crosslinking in the polymer and thus lead to the formation of water-insoluble constituents which impair the product effectiveness in use. The degree of crosslinking therefore has to be kept sufficiently low for the water solubility of the polymerization products not to be significantly impaired.
• N-allylacrylamide can be formed from DMAPAA by elimination of dimethylamine.
• t he amount of N-allylacrylamide should not exceed 30 ppm.
• the salt of the basic monomers with acids or the reaction product with quaternizing agents such as methyl chloride or dimethyl sulfate is formed first.
• An aqueous solution of the monomer which has been converted in this way into a cation together with a proportion of acrylamide is subsequently prepared and polymerized by free-radical polymerization.
• the polymerization can be initiated by redox systems, for example the system sodium bisulfite/potassium peroxodisulfate, by initiators which decompose thermally, for example, azobisisobutyronitrile, or by photochemically generated radicals, for example from the isopropyl ether of benzoin.
• redox systems for example the system sodium bisulfite/potassium peroxodisulfate
• initiators which decompose thermally for example, azobisisobutyronitrile
• photochemically generated radicals for example from the isopropyl ether of benzoin.
• the polymerization gives a highly viscous solution, a rubber-like gel or a brittle solid.
• DMAPAA dimethylaminopropylacrylamide
• the polyelectrolytes which can be used in a process according to the invention preferably have a degree of polymerization of at least 90%, particularly preferably at least 95% and very particularly preferably at least 98%. A degree of polymerization of 100% is most preferred.
• the polyelectrolytes to be used according to the invention preferably have, at a proportion of 40% by weight of polyelectrolyte and 60% by weight of water, based on the total mass, a viscosity of from 1000 to 14 000 mPa*s, particularly preferably a viscosity of from 4000 to 8000 mPa*s, to be determined by the Brookfield method at 20° C. using a Spindle IV.
• the polyelectrolytes which can be used in the process of the invention can be prepared, transported and used in the process of the invention either as liquids or as water-in-water dispersions or as granulated materials.
• Water-in-water dispersions make it possible for the polyelectrolytes to be dissolved in aqueous solutions quickly without formation of lumps.
• Polyelectrolytes in granulated form are easy to handle and to transport.
• granulated materials are preferably prediluted or converted into dispersions.
• the polyelectrolyte is used in the process of the invention in a final concentration of the polyelectrolyte of from 1 to 500 ppm, particularly preferably from 2 to 250 ppm and very particularly preferably from 5 to 50 ppm, based on the digestion solution.
• the polyelectrolytes described are highly heat resistant even in caustic solutions and are preferably used in digestions solutions at elevated temperatures, particularly preferably at temperatures of from 80 to 110° C.
• the process of the invention is applied to aqueous solutions which are formed in metal extraction for preparing titanium dioxide, particularly preferably to aqueous solutions which are obtained in the “sulfate” process for producing titanium dioxide.
• a slag obtainable from ilmenite (FeTiO 3 ) by reduction with coke is treated with concentrated sulfuric acid at 100-180° C. and the digestion cake obtained in this way is dissolved in hot water or sodium hydroxide solution, with or without addition of iron for reducing trivalent iron, resulting in precipitation of hydrated titanium dioxide which is calcined in a rotary tube furnace at from 800 to 1000° C. to form finely particulate anatase or at >1000° C. to form coarsely particulate rutile or at from 800 to 1000° C. in the presence of rutile nuclei to form finely particulate rutile.
• the cationic polyelectrolyte used in the process of the invention forms both organic and inorganic colloidal and dispersed water-insoluble solids.
• the process of the invention is applied to aqueous solutions which are used in metal extraction for preparing aluminum oxide, preferably by the Bayer process.
• the hot digestion solution is then cooled somewhat and the larger insoluble particles are separated off in a coarse filter, usually a sand filter.
• the coarse filter is generally followed by a further fine filter which removes very fine insoluble particles from the solution.
• the coarse and fine filters are washed with water at regular intervals or continuously to free them of deposits.
• the aluminate solution is cooled to such an extent that aluminate hydroxide precipitates.
• the aluminum hydroxide which has been precipitated in this way is then classified, i.e. large solid particles are separated off and finer solids, usually those having a diameter of ⁇ 45 ⁇ m, are reused as seed crystals for further precipitation.
• the coarse fraction of the aluminum hydroxide precipitation is washed with water and converted into aluminum oxide by calcination.
• the remaining digestion solution is then heated again and, if appropriate, concentrated by evaporation and/or further sodium hydroxide is added and/or impurities are removed from the solution.
• the bauxite raw materials contain from 0.01 to 0.25% of carbon.
• these carbon compounds are converted into humins, oxalates and carbonates.
• Some of these substances, for example the humins and oxalates, are present in water-insoluble form as dispersed solid particles and/or colloids which cannot be separated off by conventional filtration methods.
• the Bayer process therefore preferably comprises at least the following steps:
• the cationic polyelectrolytes to be used according to the invention can be introduced into the digestion solution at a plurality of points between step a) and step d), but have to be added at least before the final filtration step prior to the aluminum hydroxide precipitation.
• the above-described cationic. polyelectrolyte is preferably added before and/or after the coarse separation of step b), with the cationic polyelectrolyte preferably being introduced into the washing water used in the coarse separation.
• the clear mother liquor from the separation of step d) is preferably at least partly worked up by purification and/or addition of sodium carbonate and/or concentration by evaporation and/or heating and at least partly reused for the digestion of step a).
• the cationic polyelectrolyte can also be solely or additionally introduced into the process during the work-up.
• At least one anionic electrolyte can advantageously also be added to the digestion solution.
• anionic electrolytes based on acrylamide and acrylic acid are described, for example, in EP 0 256 312 B1, which is hereby incorporated by reference into the present disclosure.
• the anionic electrolytes can be added to the digestion solution in the same process step as the cationic polyelectrolytes or in a subsequent process step. However, it should be ensured that the cationic polyelectrolyte is added first and has sufficient time to interact with the organic impurities before the anionic polyelectrolyte is added.
• R 1 is hydrogen or a methyl radical
• R 2 and R 3 may be identical or different and are each a methyl or ethyl radical and
• X is a branched or unbranched alkylene radical having from 1 to 5 carbon atoms
• Such compounds are described as dispersants in EP 0 256 312 B1.
• the anionic polyelectrolytes are obtained by polymerization methods known per se.
• the polymerization of the monomers is preferably carried out in aqueous solution or in mixtures of water and water-miscible solvents such as alcohols, for example isopropanol.
• the initiation of the polymerization can be effected in a manner analogous to the initiation described for the cationic polymers.
• the anionic polyelectrolytes which can be used in a process according to the invention preferably have a molecular weight of from 500 to 50 000, determined by gel permeation chromatography, and/or preferably have a degree: of polymerization of at least 90%, particularly preferably at least 95% and very particularly preferably at least 98%. A degree of polymerization of 100% is most preferred.
• the clear mother liquor from the filtration step into which the anionic polyelectrolyte has been introduced has further cationic polyelectrolyte introduced into it.
• the polyelectrolytes are preferably introduced as a function of the proportion of humic acid in the digestion solution as regulating parameters.
• Both the cationic polyelectrolyte, and/or the anionic polyelectrolyte can be added a number of times in various steps of the Bayer process.
• a further aspect of the present invention is an apparatus for carrying out the Bayer process for the preparation of aluminum oxide from bauxite, which comprises at least one digestion vessel, a solids separation and a precipitation vessel or a filtration apparatus and has an addition point for at least one cationic polyelectrolyte comprising at least a proportion of 50 mol % of diallylaminoalkyl(meth)-acrylamide, preferably dimethylaminopropylacrylamide, which has been neutralized or quaternized by means of mineral acid and subsequently polymerized, based on the total amount of the polyelectrolyte.
• This addition point is preferably configured as a filling port for aqueous solutions or dispersions or as a mixing chamber with access to the digestion solution.
• the addition point can be located on any apparatus for carrying out the Bayer process which is located before the final separation of solids prior to the precipitation step.
• a bauxite mixture of 60% by weight of Weipa A bauxite and 40% of Boke bauxite having a carbon content of about 2.0% was subjected to the Bayer digestion process on a pilot plant scale.
• a 1% strength by weight aqueous cationic homopolymer solution prepared from quaternized and subsequently polymerized dimethylaminopropylacrylamides was added to the alkaline digestion solution to bring it to a final concentration of 40 ppm of cationic polymer and the mixture was stirred for 3 minutes.
• Homopolyelectrolytes having viscosities of 1500, 3900 and 6450 mPas*s determined on a 40% strength by weight aqueous solution, based on the total amount, at 20° by the Brook method using a Spindel type IV at 10 rpm were used.
• the final volume of the digestion solution was 1000 ml in a measuring cylinder. After a further settling time of 5 minutes, the turbidity of a sample of the clear supernatant liquid was measured at a wavelength of 691 nm by means of a Philipps PU 8620 spectral photometer.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Inorganic Chemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Metallurgy (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Environmental & Geological Engineering (AREA)
• Separation Of Suspended Particles By Flocculating Agents (AREA)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
• Removal Of Specific Substances (AREA)
• Laminated Bodies (AREA)
• Detergent Compositions (AREA)

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• 2001
  • 2001-04-20 DE DE10119685A patent/DE10119685A1/de not_active Ceased
• 2002
  • 2002-04-06 AU AU2002302510A patent/AU2002302510B2/en not_active Ceased
  • 2002-04-06 CA CA002444080A patent/CA2444080A1/fr not_active Abandoned
  • 2002-04-06 DE DE50213798T patent/DE50213798D1/de not_active Expired - Fee Related
  • 2002-04-06 BR BR0209024-4A patent/BR0209024A/pt not_active Application Discontinuation
  • 2002-04-06 AT AT02730121T patent/ATE440972T1/de not_active IP Right Cessation
  • 2002-04-06 CN CNA028120760A patent/CN1516747A/zh active Pending
  • 2002-04-06 RU RU2003132542/02A patent/RU2294390C2/ru active
  • 2002-04-06 WO PCT/EP2002/003869 patent/WO2002086173A1/fr not_active Application Discontinuation
  • 2002-04-06 EP EP02730121A patent/EP1383934B1/fr not_active Expired - Lifetime
  • 2002-04-06 US US10/475,264 patent/US20040131521A1/en not_active Abandoned
  • 2002-06-04 UA UA20031110439A patent/UA77179C2/uk unknown
• 2006
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