# US 8,784,754 B2 · Method for preparing high-purity alumina > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,784,754 B2 - Document ID: US8784754B2 - Status: Granted - Kind: B2 - Application number: 13/641,203 - Filed: 2011-04-15 - Published: 2013-02-28 - Granted: 2014-07-22 - Earliest claimed: 2010-04-16 - Assignees: HMR GmbH - Applicants: Jae Hoon Hu - Inventors: Jae Hoon Hu - Web page: https://patentgrep.com/patent/US8784754B2 ## CPC - B01D 9/0036: {Crystallisation on to a bed of product crystals; Seeding} - C01F 7/06: by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process (obtaining aluminium oxide or hydroxide from the resulting aluminate solution C01F7/14) - C01F 7/46: Purification of aluminium oxide, aluminium hydroxide or aluminates (C01F7/028 takes precedence) - C01P 2006/80: Compositional purity - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - C01F: COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides or polysulfides of magnesium, calcium, strontium, or barium C01B17/42; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia or cyanogen containing nitrogen and non-metals and optionally metals C01B21/082; amides or imides of silicon C01B21/087}; metal {imides or} amides C01B21/092, {C01B21/0923}; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20; {double sulfates of magnesium with sodium or potassium C01D5/12; with other alkali metals C01D15/00, C01D17/00}) - C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS ## Abstract The present invention relates to a method for preparing high-purity aluminum, the method comprising: a mother liquor preparing step for preparing a mother liquor by dissolving and aging ordinary aluminum hydroxide; a refining step for adding pulp to absorb impurities from the prepared mother liquor after the mother liquor preparing step; and an obtaining step for obtaining high-purity alumina by adding a seed into the mother liquor and precipitating a precipitate, and filtering, washing, and recrystallizing the precipitate, and calcining the precipitate. Thus, the present invention enables an environmentally-friendly and low-cost preparation of high-purity alumina. ## Claims ### Claim 1 A method for high-purity alumina, the method comprising: a mother liquor preparing step of preparing a mother liquor by dissolving and aging aluminum hydroxide; a refining step of adding pulp to absorb impurities from the prepared mother liquor, after the mother liquor preparing step to form refined mother liquor; and an obtaining step of obtaining high-purity alumina, after the refining step, wherein the obtaining step is a step of obtaining the high-purity alumina by adding a seed to the refined mother liquor to form a precipitate, filtering, washing and dissolving the precipitate, recrystallizing the dissolved precipitate by neutralizing the dissolved precipitate, again filtering and washing the recrystallized precipitate, mixing a small amount of aluminum fluoride (AlF3) with the washed recrystallized precipitate, and then calcining the mixed precipitate. ### Claim 2 (depends on 1) The method of claim 1, wherein the mother liquor preparing step comprising: a dissolving step of preparing a mother liquor by adding a caustic soda (NaOH) solution and aluminum hydroxide into a dissolution bath and dissolving the aluminum hydroxide; and an aging step of aging impurities while slowly decreasing a temperature of the mother liquor dissolved through the dissolving step of preparing the mother liquor during a predetermined aging time. ### Claim 3 A method for high-purity alumina, the method comprising: a dissolving step of preparing a mother liquor by adding a caustic soda (NaOH) solution and aluminum hydroxide into a dissolution bath and dissolving the aluminum hydroxide; an aging step of aging impurities while slowly decreasing a temperature of the mother liquor dissolved through the dissolving step during a predetermined aging time; a refining step of adding and dispersing an absorbent made of pulp into the mother liquor aged through the aging step, thereby absorbing the impurities in the mother liquor into the absorbent; a first filtering step of separating the pulp having the impurities absorbed thereinto, filtering the mother liquor and then providing the filtered mother liquor to a precipitation bath, after the refining step; a precipitating step of precipitating aluminum hydroxide by adding an aluminum hydroxide seed into the mother liquor of the precipitation bath, after the first filtering step; a polarizing step of separating a precipitate having a small particle size and a precipitate having a large particle size, after the precipitating step; a second filtering step of filtering the mother liquor containing the precipitate having the large particle size in the polarizing step, thereby recycling the filtered mother liquor as the caustic soda solution; a recrystalizing step of washing the precipitate remaining in the second filtering step, dissolving aluminum hydroxide in an acid and then neutralizing the dissolved aluminum hydroxide using alkali, thereby recrystalizing the precipitate; a third filtering step of collecting the recrystalized precipitate in the recrystalizing step and filtering and washing the collected precipitate; and a calcining step of mixing aluminum fluoride (AlF3) with the collected precipitate washed in the third filtering step and then calcining the mixed precipitate at 1050° C. or more for 1 hour or more. ### Claim 4 (depends on 2) The method of claim 2, wherein, in the dissolving step, the weight ratio of aluminum oxide to sodium carbonate (Al2O3/Na2CO3) in the dissolved mother liquor is 0.68 or more. ### Claim 5 (depends on 2) The method of claim 2, wherein, in the dissolving step, the concentration of the caustic soda (NaOH) solution is 230 g/1 or more, based on the sodium carbonate (Na2CO3). ### Claim 6 (depends on 2) The method of claim 2 , wherein, in the aging step, the aging temperature of the mother liquor is maintained at 90° C. to 130° C. ### Claim 7 (depends on 6) The method of claim 6, wherein, in the aging step, the aging time for aging the impurities is 1 hour or more. ### Claim 8 (depends on 3) The method of claim 3, wherein the precipitating step is performed at an initial temperature of 70° C. or more. ### Claim 9 (depends on 3) The method of claim 3, wherein, in the precipitating step, the precipitation time taken to precipitate the aluminum hydroxide is 72 hours or more. ### Claim 10 (depends on 3) The method of claim 3, wherein, in the precipitating step, the weight ratio of aluminum oxide to sodium carbonate (Al2O3/Na2CO3) in the aluminum hydroxide finally obtained in the precipitating step is 0.40 or less. ### Claim 11 (depends on 3) The method of claim 3, wherein the recrystalizing step is a step of dissolving the precipitate precipitated in the precipitating step in an acid compound selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid and acetic acid, and then neutralizing the dissolved precipitate using an alkali compound selected from the group consisting of caustic soda, ammonia and sodium acetate, thereby recrystalizing the precipitate. ### Claim 12 (depends on 11) The method of claim 11, wherein aluminum fluoride (AlF3) of 0.3% based on the weight of a product is mixed with a cake prepared in the recrystalizing step, and the mixed cake is then calcined.