Processes for preparing alumina and various other products

Abstract

There is provided a process for preparing alumina. The process comprise leaching an aluminum-containing material (for example an industrial waste product chosen from red mud, fly ashes and a mixture thereof), with HCl so as to obtain a leachate comprising aluminum ions and a solid, and separating the solid from the leachate. Then, the process comprises reacting the leachate with HCl so as to obtain a liquid and a precipitate comprising the aluminum ions in the form of AlCl 3 , and separating the precipitate from the liquid. Then, the precipitate is reacted with a base. Finally, the process comprises heating the precipitate under conditions effective for converting the precipitate into Al 2 O 3 .

What is claimed is: 
     
         1 . A process for preparing alumina, said process comprising:
 leaching an aluminum-containing material, that is an industrial waste product chosen from red mud, fly ashes and a mixture thereof, with HCl so as to obtain a leachate comprising aluminum ions and a solid, and separating said solid from said leachate;   reacting said leachate with HCl so as to obtain a liquid and a precipitate comprising said aluminum ions in the form of AlCl 3 , and separating said precipitate from said liquid;   reacting the precipitate with a base; and   heating said precipitate under conditions effective for converting the precipitate into Al 2 O 3 .   
     
     
         2 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 25 to about 45 weight %. 
     
     
         3 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 25 to about 45 weight % at a temperature of about 125 to about 225° C. 
     
     
         4 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 25 to about 45 weight % at a temperature of about 160 to about 190° C. 
     
     
         5 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 25 to about 45 weight % at a temperature of about 160 to about 175° C. 
     
     
         6 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 25 to about 45 weight % at a temperature of about 185 to about 190° C. 
     
     
         7 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 18 to about 45 weight %. 
     
     
         8 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 18 to about 45 weight % at a temperature of about 125 to about 225° C. 
     
     
         9 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 18 to about 45 weight % at a temperature of about 160 to about 190° C. 
     
     
         10 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 18 to about 45 weight % at a temperature of about 160 to about 175° C. 
     
     
         11 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 18 to about 45 weight % at a temperature of about 185 to about 190° C. 
     
     
         12 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 18 to about 32 weight % at a temperature of about 125 to about 225° C. 
     
     
         13 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 18 to about 32 weight % at a temperature of about 160 to about 190° C. 
     
     
         14 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 18 to about 32 weight % at a temperature of about 160 to about 175° C. 
     
     
         15 . The process of  claim 1 , wherein said aluminum-containing material is leached with HCl having a concentration of about 18 to about 32 weight % at a temperature of about 185 to about 190° C. 
     
     
         16 . The process of any one of  claims 1  to  15 , wherein said liquid comprises at least one iron chloride. 
     
     
         17 . The process of  claim 16 , wherein said at least one iron chloride is FeCl 2 , FeCl 3  or a mixture thereof. 
     
     
         18 . The process of  claim 16  or  17 , wherein said liquid is concentrated to a concentrated liquid having a concentration of said at least one iron chloride of at least 30% by weight; and then hydrolyzed at a temperature of about 155 to about 350° C. 
     
     
         19 . The process of  claim 16  or  17 , wherein said liquid is concentrated to a concentrated liquid having a concentration of said at least one iron iron chloride of at least 30% by weight; and then said at least one iron chloride is hydrolyzed at a temperature of about 155 to about 350° C. while maintaining a ferric chloride concentration at a level of at least 65% by weight, to generate a composition comprising a liquid and precipitated hematite, and recovering said hematite. 
     
     
         20 . The process of  claim 16  or  17 , wherein said at least one iron chloride is hydrolyzed at a temperature of about 165 to about 170° C. 
     
     
         21 . The process of  claim 16  or  17 , wherein said liquid is concentrated to a concentrated liquid having a concentration of said at least one iron chloride of at least 30% by weight; and then said at least one iron chloride is hydrolyzed at a temperature of about 155 to about 350° C. while maintaining a ferric chloride concentration at a level of at least 65% by weight, to generate a composition comprising a liquid and precipitated hematite; recovering said hematite; and recovering rare earth elements and/or rare metals from said liquid. 
     
     
         22 . The process of  claim 21 , wherein said at least one iron chloride is hydrolyzed at a temperature of about 155 to about 170° C. 
     
     
         23 . The process of  claim 21  or  22 , further comprising, after recovery of said rare earth elements and/or said rare metals, reacting said liquid with HCl so as to cause precipitation of MgCl 2 , and recovering same. 
     
     
         24 . The process of  claim 22  or  23 , further comprising calcining MgCl 2  into MgO. 
     
     
         25 . The process of  claim 22  or  23 , further comprising calcining MgCl 2  into MgO and recycling the gaseous HCl so-produced by contacting it with water so as to obtain a composition having a concentration of about 25 to about 45 weight % and using said composition for leaching said aluminum-containing material. 
     
     
         26 . The process of  claim 22  or  23 , further comprising calcining MgCl 2  into MgO and recycling the gaseous HCl so-produced by contacting it with water so as to obtain a composition having a concentration of about 18 to about 45 weight % and using said composition for leaching said aluminum-containing material. 
     
     
         27 . The process of any one of  claims 22  to  26 , further comprising, downstream of recovery of said rare earth elements and/or rare metals, recovering NaCl from said liquid, reacting said NaCl with H 2 SO 4 , and substantially selectively precipitating Na 2 SO 4 . 
     
     
         28 . The process of any one of  claims 22  to  27 , further comprising, downstream of recovery of said rare earth elements and/or rare metals, recovering KCl from said liquid, reacting said KCl with H 2 SO 4 , and substantially selectively precipitating K 2 SO 4 . 
     
     
         29 . The process of any one of  claims 22  to  26 , further comprising, downstream of recovery of said rare earth elements and/or rare metals, recovering NaCl from said liquid, carrying out an electrolysis to generate NaOH and NaOCl. 
     
     
         30 . The process of any one of  claims 22  to  26  and  29 , further comprising, downstream of recovery of said rare earth elements and/or rare metals, recovering KCl from said liquid, reacting said KCl, carrying out an electrolysis to generate KOH and KOCl. 
     
     
         31 . The process of  claim 16  or  17 , wherein said liquid is concentrated to a concentrated liquid having a concentration of said at least one iron chloride of at least 30% by weight; and then said at least one iron chloride is hydrolyzed at a temperature of about 155 to about 350° C. while maintaining a ferric chloride concentration at a level of at least 65% by weight, to generate a composition comprising a liquid and precipitated hematite; recovering said hematite; and extracting NaCl and/or KCl from said liquid. 
     
     
         32 . The process of  claim 31 , further comprising reacting said NaCl with H 2 SO 4  so as to substantially selectively precipitate Na 2 SO 4 . 
     
     
         33 . The process of  claim 31 , further comprising reacting said KCl with H 2 SO 4  so as to substantially selectively precipitate K 2 SO 4 . 
     
     
         34 . The process of  claim 31 , further comprising carrying out an electrolysis of said NaCl to generate NaOH and NaOCl. 
     
     
         35 . The process of  claim 31 , further comprising carrying out an electrolysis of aid KCl to generate KOH and KOCl. 
     
     
         36 . The process of any one of  claims 1  to  15 , wherein said liquid comprises magnesium ions and said liquid is reacted with HCl in order to precipitate MgCl 2 . 
     
     
         37 . The process of any one of  claims 1  to  15 , wherein said liquid comprises magnesium ions and said liquid is reacted with HCl by sparging said liquid with HCl in order to precipitate MgCl 2 . 
     
     
         38 . The process of any one of  claims 1  to  37 , wherein said process comprises separating said solid from said leachate and washing said solid so as to obtain silica having a purity of at least 95%. 
     
     
         39 . The process of any one of  claims 1  to  37 , wherein said process comprises separating said solid from said leachate and washing said solid so as to obtain silica having a purity of at least 98%. 
     
     
         40 . The process of any one of  claims 1  to  37 , wherein said process comprises separating said solid from said leachate and washing said solid so as to obtain silica having a purity of at least 99%. 
     
     
         41 . The process of any one of  claims 1  to  40 , wherein said process comprises reacting said leachate with gaseous HCl so as to obtain said liquid and said precipitate comprising said aluminum ions, said precipitate being formed by crystallization of AlCl 3 .6H 2 O. 
     
     
         42 . The process of any one of  claims 1  to  40 , wherein said process comprises reacting said leachate with dry gaseous HCl so as to obtain said liquid and said precipitate comprising said aluminum ions, said precipitate being formed by crystallization of AlCl 3 .6H 2 O. 
     
     
         43 . The process of  claim 41  or  42 , wherein said gaseous HCl has a HCl concentration of at least 85% by weight. 
     
     
         44 . The process of  claim 41  or  42 , wherein said gaseous HCl has a HCl concentration of at least 90% by weight. 
     
     
         45 . The process of  claim 41  or  42 , wherein said gaseous HCl has a HCl concentration of about 90% by weight. 
     
     
         46 . The process of  claim 41  or  42 , wherein said gaseous HCl has a concentration of about 90% to about 95% by weight. 
     
     
         47 . The process of any one of  claims 41  to  46 , wherein during said crystallization of AlCl 3 .6H 2 O, said liquid is maintained at a concentration of HCl of about 25 to about 35% by weight. 
     
     
         48 . The process of any one of  claims 41  to  46 , wherein during said crystallization of AlCl 3 .6H 2 O, said liquid is maintained at a concentration of HCl of about 30 to about 32% by weight. 
     
     
         49 . The process of any one of  claims 41  to  48 , wherein said crystallization is carried out at a temperature of about 45 to about 65° C. 
     
     
         50 . The process of any one of  claims 41  to  48 , wherein said crystallization is carried out at a temperature of about 50 to about 60° C. 
     
     
         51 . The process of any one of  claims 1  to  50 , wherein said process comprises converting AlCl 3 .6H 2 O into Al 2 O 3  by carrying out a calcination of AlCl 3 .6H 2 O. 
     
     
         52 . The process of any one of  claims 1  to  51 , wherein said process comprises heating said precipitate at a temperature of at least 1200° C. for converting AlCl 3 .6H 2 O into Al 2 O 3 . 
     
     
         53 . The process of any one of  claims 1  to  51 , wherein said process comprises heating said precipitate at a temperature of at least 1250° C. for converting AlCl 3 .6H 2 O into Al 2 O 3 . 
     
     
         54 . The process of any one of  claims 1  to  51 , wherein said process comprises heating said precipitate at a temperature of at least 900° C. for converting AlCl 3 .6H 2 O into Al 2 O 3 . 
     
     
         55 . The process of any one of  claims 1  to  54 , wherein said process comprises converting AlCl 3 .6H 2 O into alpha-Al 2 O 3 . 
     
     
         56 . The process of any one of  claims 1  to  51 , wherein said process comprises heating said precipitate at a temperature of at least 350° C. for converting AlCl 3 .6H 2 O into Al 2 O 3 . 
     
     
         57 . The process of any one of  claims 1  to  51 , wherein said process comprises heating said precipitate at a temperature of about 350° C. to about 500° C. for converting AlCl 3 .6H 2 O into Al 2 O 3 . 
     
     
         58 . The process of any one of  claims 1  to  51 , wherein said process comprises heating said precipitate at a temperature of about 375° C. to about 450° C. for converting AlCl 3 .6H 2 O into Al 2 O 3 . 
     
     
         59 . The process of any one of  claims 1  to  51 , wherein said process comprises heating said precipitate at a temperature of about 375° C. to about 425° C. for converting AlCl 3 .6H 2 O into Al 2 O 3 . 
     
     
         60 . The process of any one of  claims 1  to  51 , wherein said process comprises heating said precipitate at a temperature of about 385° C. to about 400° C. for converting AlCl 3 .6H 2 O into Al 2 O 3 . 
     
     
         61 . The process of any one of  claims 56  to  60 , wherein said process comprises converting AlCl 3 .6H 2 O into beta-Al 2 O 3 . 
     
     
         62 . The process of any one of  claims 1  to  61 , wherein converting AlCl 3 .6H 2 O into Al 2 O 3  is carried out in the presence of steam. 
     
     
         63 . The process of any one of  claims 1  to  62 , wherein converting AlCl 3 .6H 2 O into Al 2 O 3  comprises carrying out a calcination via a two-stage circulating fluid bed reactor. 
     
     
         64 . The process of any one of  claims 1  to  62 , wherein converting AlCl 3 .6H 2 O into Al 2 O 3  comprises carrying out a calcination via a two-stage circulating fluid bed reactor that comprises a preheating system. 
     
     
         65 . The process of  claim 64 , wherein said preheating system comprises a plasma torch. 
     
     
         66 . The process of  claim 65 , wherein said plasma torch is effective for preheating air entering into a calcination reactor. 
     
     
         67 . The process of  claim 65 , wherein said plasma torch is effective for generating steam that is injected into a calcination reactor. 
     
     
         68 . The process of  claim 65 , wherein said plasma torch is effective for generating steam that is as fluidization medium in a fluid bed reactor. 
     
     
         69 . The process of process of any one of  claims 1  to  68 , wherein converting AlCl 3 .6H 2 O into Al 2 O 3  comprises carrying out a one-step calcination. 
     
     
         70 . The process of process of any one of  claims 1  to  69 , wherein said process comprises converting AlCl 3 .6H 2 O into Al 2 O 3  by carrying out a calcination of AlCl 3 .6H 2 O, said calcination comprising steam injection. 
     
     
         71 . The process of  claim 70 , wherein steam is injected at a pressure of about 200 to about 700 psig. 
     
     
         72 . The process of  claim 70 , wherein steam is injected at a pressure of about 300 to about 700 psig. 
     
     
         73 . The process of  claim 70 , wherein steam is injected at a pressure of about 400 to about 700 psig. 
     
     
         74 . The process of  claim 70 , wherein steam is injected at a pressure of about 550 to about 650 psig. 
     
     
         75 . The process of  claim 70 , wherein steam is injected at a pressure of about 575 to about 625 psig. 
     
     
         76 . The process of  claim 70 , wherein steam is injected at a pressure of about 590 to about 610 psig. 
     
     
         77 . The process of any one of  claims 70  to  76 , wherein steam is injected and a plasma torch is used for carrying fluidization. 
     
     
         78 . The process of any one of  claims 70  to  76 , wherein steam is injected and a plasma torch is used for carrying fluidization. 
     
     
         79 . The process of any one of  claims 62  and  70  to  78 , wherein said steam is overheated. 
     
     
         80 . The process of any one of  claims 1  to  79 , wherein said process comprises converting AlCl 3 .6H 2 O into Al 2 O 3  by carrying out a calcination of AlCl 3 .6H 2 O in which is provided by the combustion of a fossil fuel, carbon monoxide, propane, natural gas, a Refinery Fuel Gas, coal, or chlorinated gases and/or solvants. 
     
     
         81 . The process of any one of  claims 1  to  79 , wherein said process comprises converting AlCl 3 .6H 2 O into Al 2 O 3  by carrying out a calcination of AlCl 3 .6H 2 O that is provided by the combustion of gas mixture that is a an incoming smelter gas or a reducer offgas. 
     
     
         82 . The process of any one of  claims 1  to  79 , wherein said process comprises converting AlCl 3 .6H 2 O into Al 2 O 3  by carrying out a calcination of AlCl 3 .6H 2 O that is provided by the combustion of gas mixture that comprises:
 CH 4 : 0 to about 1% vol; 
 C 2 H 6 : 0 to about 2% vol; 
 C 3 H 8 : 0 to about 2% vol; 
 C 4 H 10 : 0 to about 1% vol; 
 N 2 : 0 to about 0.5% vol; 
 H 2 : about 0.25 to about 15.1% vol; 
 CO: about 70 to about 82.5% vol; and 
 CO 2 : about 1.0 to about 3.5% vol. 
 
     
     
         83 . The process of  claim 82 , wherein O 2  is substantially absent from said mixture. 
     
     
         84 . The process of any one of  claims 1  to  79 , wherein said process comprises converting AlCl 3 .6H 2 O into Al 2 O 3  by carrying out a calcination of AlCl 3 .6H 2 O in which is provided by electric heating, gas heating or microwave heating. 
     
     
         85 . The process of any one of  claims 1  to  79 , wherein converting AlCl 3 .6H 2 O into Al 2 O 3  comprises carrying out a calcination by means of fluid bed reactor. 
     
     
         86 . The process of  claim 85 , wherein the fluid bed reactor comprises a metal catalyst chosen from metal chlorides. 
     
     
         87 . The process of  claim 86 , wherein the fluid bed reactor comprises FeCl 3 , FeCl 2  or a mixture thereof. 
     
     
         88 . The process of  claim 86 , wherein the fluid bed reactor comprises FeCl 3 . 
     
     
         89 . The process of any one of  claims 1  to  88 , wherein said process is a semi-continuous process. 
     
     
         90 . The process of any one of  claims 1  to  88 , wherein said process is a continuous process. 
     
     
         91 . The process of any one of  claims 1  to  90 , wherein said process is effective for providing an Al 2 O 3  recovery yield of at least 93%. 
     
     
         92 . The process of any one of  claims 1  to  90 , wherein said process is effective for providing an Al 2 O 3  recovery yield of about 90% to about 95%. 
     
     
         93 . The process of any one of  claims 1  to  92 , wherein said process is effective for providing a Fe 2 O 3  recovery yield of at least 98%. 
     
     
         94 . The process of any one of  claims 1  to  92 , wherein said process is effective for providing a Fe 2 O 3  recovery yield of about 98% to about 99.5%. 
     
     
         95 . The process of any one of  claims 1  to  94 , wherein said process is effective for providing a MgO recovery yield of at least 96%. 
     
     
         96 . The process of any one of  claims 1  to  94 , wherein said process is effective for providing a MgO recovery yield of about 96 to about 98%. 
     
     
         97 . The process of any one of  claims 1  to  96 , wherein said aluminum-containing material is leached at a pressure of about 4 to about 10 barg. 
     
     
         98 . The process of any one of  claims 1  to  96 , wherein said aluminum-containing material is leached at a pressure of about 4 to about 8 barg. 
     
     
         99 . The process of any one of  claims 1  to  96 , wherein said aluminum-containing material is leached at a pressure of about 5 to about 6 barg. 
     
     
         100 . The process of any one of  claims 1  to  99 , further comprising, before leaching said aluminum-containing material, a pre-leaching removal of fluorine optionally contained in said aluminum-containing material. 
     
     
         101 . The process of any one of  claims 1  to  100 , comprising leaching said aluminum-containing material with HCl so as to obtain said leachate comprising aluminum ions and said solid, separating said solid from said leachate; and further treating said solid so as to separate SiO 2  from TiO 2  that are contained therein. 
     
     
         102 . The process of any one of  claims 1  to  100 , comprising leaching said aluminum-containing material with HCl so as to obtain said leachate comprising aluminum ions and said solid, separating said solid from said leachate; and further treating said solid with HCl so as to separate SiO 2  from TiO 2  that are contained therein. 
     
     
         103 . The process of any one of  claims 1  to  100 , comprising leaching said aluminum-containing material with HCl so as to obtain said leachate comprising aluminum ions and said solid, separating said solid from said leachate; and further treating said solid with HCl at a concentration of less than 20% by weight, at a temperature of less than 85° C., in the presence of MgCl, so as to separate SiO 2  from TiO 2  that are contained therein. 
     
     
         104 . The process of any one of  claims 1  to  103 , wherein said precipitate is reacted with said base so as to convert AlCl 3  into Al(OH) 3 . 
     
     
         105 . The process of any one of  claims 1  to  103 , wherein said precipitate is reacted with said base so as to convert AlCl 3  into Al(OH) 3  and then said precipitate is heated under conditions effective for converting Al(OH) 3  into Al 2 O 3 . 
     
     
         106 . The process of any one of  claims 1  to  103 , wherein said precipitate is reacted with said base so as to convert AlCl 3  into Al(OH) 3  and then said Al(OH) 3  is heated in the presence of steam and under conditions effective for converting said Al(OH) 3  into Al 2 O 3 . 
     
     
         107 . The process of any one of  claims 1  to  103 , wherein said precipitate, before being reacted with said base, is recrystallized. 
     
     
         108 . The process of any one of  claims 1  to  103 , wherein said precipitate, before being reacted with said base, is purified by means of a crystallization thereby obtaining AlCl 3 .6H 2 O and a liquor. 
     
     
         109 . The process of any one of  claims 1  to  103 , wherein said precipitate, before being reacted with said base, is recrystallized, thereby obtaining AlCl 3 .6H 2 O and a liquor, and separating said crystallized precipitate from said liquor, and wherein said crystallized precipitate is treated with said base in order to convert AlCl 3 .6H 2 O into Al(OH) 3 . 
     
     
         110 . The process of any one of  claims 1  to  103 , wherein said process comprises:
 leaching said aluminum-containing material, that is an industrial waste product chosen from red mud, fly ashes and a mixture thereof, with HCl so as to obtain said leachate comprising aluminum ions and said solid, and separating said solid from said leachate; 
 reacting said leachate with HCl so as to obtain said liquid and said precipitate comprising said aluminum ions in the form of AlCl 3 , and separating said precipitate from said liquid; 
 crystallizing or recrystallizing said precipitate so as to obtain a purified precipitate and a liquor; 
 reacting said purified precipitate with a base; and 
 heating said purified precipitate under conditions effective for converting the purified precipitate into Al 2 O 3 . 
 
     
     
         111 . The process of any one of  claims 1  to  103 , wherein said process comprises:
 leaching said aluminum-containing material, that is an industrial waste product chosen from red mud, fly ashes and a mixture thereof, with HCl so as to obtain said leachate comprising aluminum ions and said solid, and separating said solid from said leachate; 
 reacting said leachate with HCl so as to obtain said liquid and said precipitate comprising said aluminum ions in the form of AlCl 3 .6H 2 O, and separating said precipitate from said liquid; 
 purifying said AlCl 3 .6H 2 O by means of at least one crystallization and/or at least one ion exchange resin, thereby obtaining purified AlCl 3 .6H 2 O and a liquor; 
 reacting said purified AlCl 3 .6H 2 O with a base in order to convert said purified AlCl 3 .6H 2 O into Al(OH) 3 ; and 
 heating said Al(OH) 3  under conditions effective for converting Al(OH) 3  into Al 2 O 3 . 
 
     
     
         112 . The process of any one of  claims 1  to  103 , wherein said process comprises:
 leaching said aluminum-containing material, that is an industrial waste product chosen from red mud, fly ashes and a mixture thereof, with HCl so as to obtain said leachate comprising aluminum ions and said solid, and separating said solid from said leachate; 
 reacting said leachate with HCl so as to obtain said liquid and said precipitate comprising said aluminum ions in the form of AlCl 3 .6H 2 O, and separating said precipitate from said liquid; 
 purifying said AlCl 3 .6H 2 O by means of at least one crystallization and/or at least one ion exchange resin, thereby obtaining purified AlCl 3 .6H 2 O and a liquor; 
 reacting said purified AlCl 3 .6H 2 O with a base in order to convert said purified AlCl 3 .6H 2 O into Al(OH) 3 ; and 
 heating said Al(OH) 3  in the presence of steam and under conditions effective for converting Al(OH) 3  into Al 2 O 3 . 
 
     
     
         113 . The process of any one of  claims 1  to  103 , wherein said process comprises:
 leaching said aluminum-containing material, that is an industrial waste product chosen from red mud, fly ashes and a mixture thereof, with HCl so as to obtain said leachate comprising aluminum ions and said solid, and separating said solid from said leachate; 
 reacting said leachate with HCl so as to obtain said liquid and said precipitate comprising said aluminum ions in the form of AlCl 3 .6H 2 O, and separating said precipitate from said liquid; 
 purifying said AlCl 3 .6H 2 O by means of at least one crystallization and/or at least one ion exchange resin, thereby obtaining purified AlCl 3 .6H 2 O and a liquor; 
 reacting said purified AlCl 3 .6H 2 O with a base in order to convert said purified AlCl 3 .6H 2 O into Al(OH) 3 ; 
 purifying said Al(OH) 3  by means of at least one crystallization and/or at least one ion exchange resin; and 
 heating said purified Al(OH) 3  in the presence of steam and under conditions effective for converting Al(OH) 3  into Al 2 O 3 . 
 
     
     
         114 . The process of  claim 111  or  112 , wherein said purifying of said AlCl 3 .6H 2 O is carried out by means of at least one crystallization. 
     
     
         115 . The process of  claim 111  or  112 , wherein said purifying of said AlCl 3 .6H 2 O is carried out by means of at least two crystallizations. 
     
     
         116 . The process of  claim 113 , wherein said purifying of said AlCl 3 .6H 2 O is carried out by means of at least one crystallization. 
     
     
         117 . The process of  claim 113 , wherein said purifying of said AlCl 3 .6H 2 O is carried out by means of at least two crystallizations. 
     
     
         118 . The process of  claim 116  or  117 , wherein said purifying of said Al(OH) 3  is carried out by means of at least one crystallization. 
     
     
         119 . The process of  claim 116  or  117 , wherein said purifying of said Al(OH) 3  is carried out by means of at least two crystallizations. 
     
     
         120 . The process of any one of  claims 108  to  119 , wherein said liquor is further treated with another base, thereby converting AlCl 3  contained therein into Al(OH) 3 . 
     
     
         121 . The process of any one of  claims 108  to  119 , wherein said liquor is further treated with another base, thereby converting AlCl 3  contained therein into Al(OH) 3  and reacting the so-obtained Al(OH) 3  with said AlCl 3 .6H 2 O before said purification thereof. 
     
     
         122 . The process of any one of  claims 1  to  121 , wherein said aluminum-containing material is red mud. 
     
     
         123 . The process of any one of  claims 1  to  121 , wherein said aluminum-containing material is fly ashes. 
     
     
         124 . The process of any one of  claims 1  to  121 , wherein said aluminum-containing material is a mixture of fly ashes and red mud. 
     
     
         125 . The process of any one of  claims 1  to  124 , wherein said base is KOH. 
     
     
         126 . The process of any one of  claims 1  to  124 , wherein said base is NaOH. 
     
     
         127 . The process of any one of  claims 1  to  124 , wherein said base is NH 4 OH. 
     
     
         128 . A process for preparing alumina, said process comprising:
 leaching an aluminum-containing material, that is an industrial waste product, with HCl so as to obtain a leachate comprising aluminum ions and a solid, and separating said solid from said leachate;   reacting said leachate with HCl so as to obtain a liquid and a precipitate comprising said aluminum ions in the form of AlCl 3 , and separating said precipitate from said liquid;   reacting the precipitate with a base; and   heating said precipitate under conditions effective for converting the precipitate into Al 2 O 3 .   
     
     
         129 . A process for preparing alumina, said process comprising:
 leaching an aluminum-containing material with HCl so as to obtain a leachate comprising aluminum ions and a solid, and separating said solid from said leachate;   reacting said leachate with HCl so as to obtain a liquid and a precipitate comprising said aluminum ions in the form of AlCl 3 , and separating said precipitate from said liquid;   reacting the precipitate with a base; and   heating said precipitate under conditions effective for converting the precipitate into Al 2 O 3 .   
     
     
         130 . A process for preparing alumina, said process comprising:
 leaching an aluminum-containing material, that is an industrial waste product, with an acid so as to obtain a leachate comprising aluminum ions and a solid, and separating said solid from said leachate;   reacting said leachate with HCl so as to obtain a liquid and a precipitate comprising said aluminum ions in the form of AlCl 3 , and separating said precipitate from said liquid;   reacting the precipitate with a base; and   heating said precipitate under conditions effective for converting the precipitate into Al 2 O 3 .   
     
     
         131 . A process for preparing alumina, said process comprising:
 leaching an aluminum-containing material with an acid so as to obtain a leachate comprising aluminum ions and a solid, and separating said solid from said leachate;   reacting said leachate with HCl so as to obtain a liquid and a precipitate comprising said aluminum ions in the form of AlCl 3 , and separating said precipitate from said liquid;   reacting the precipitate with a base; and   heating said precipitate under conditions effective for converting the precipitate into Al 2 O 3 .   
     
     
         132 . A process for preparing aluminum, said process comprising:
 obtaining alumina by means of a process as defined in any one of  claims 1  to  131 ; and   converting said Al 2 O 3  into aluminum.   
     
     
         133 . The process of  claim 132 , wherein said conversion of Al 2 O 3  into aluminum is carried out by means of the Hall-Héroult process. 
     
     
         134 . The process of  claim 132 , wherein said conversion of Al 2 O 3  into aluminum is carried out by using a reduction environment and carbon at temperature below 200° C. 
     
     
         135 . The process of  claim 132 , wherein said conversion of Al 2 O 3  into aluminum is carried out by means of the Wohler Process. 
     
     
         136 . The process of  claim 132 , wherein said conversion of Al 2 O 3  into aluminum is carried out by converting Al 2 O 3  into Al 2 S 3  and then converting Al 2 S 3  into aluminum.