CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority on US 61/726,079 filed on November 14, 2012, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to improvements in the field of chemistry applied to the purification of aluminum ions and/or manufacture of aluminum-based products.

BACKGROUND OF THE DISCLOSURE

[0003] It can be the that most of the commercial alumina is produced by the Bayer Process. It is also possible to produce hydrated alumina by other methods. Several other methods result in the inclusion of high levels of one or more impurities.

[0004] Low purity specialty alumina can be used as a refractory material (resistant to very high temperatures), as a ceramic and in the electrolytic production of aluminum metal.

[0005] However, for certain applications, high purity alumina (HPA) is required. Many synthetic precious stones have a high purity alumina base, including ruby, topaz and sapphire. These crystals are used mostly in jewelry, infrared, UV and laser optics, and as a high-end electronic substrate.

[0006] Half of the world's annual production of ultra-pure alumina goes into making synthetic sapphire for use in fiber optics and, more recently, in LED lighting for home and automotive markets. It is also used in the production of high-pressure sodium vapor lamp tubes and the manufacturing of video and computer equipment, as well as in metallographic polishing and the polishing of optic and electronic materials. [0007] There is a growth in HPA annual worldwide demand, which according to certain market experts should rise from 9,000 tons in 2012 to over 15,000 tons in 2015. This should lead to a substantial supply deficit of about 6,000 tons per year caused notably by the global increase of light emitting diodes (LED) demand.

[0008] A number of methods for preparing high purity alumina have been proposed that start with pure aluminum metal, organoaluminum compounds or alums. These in general start with a high cost material or generate products not recyclable to the process when calcined and are therefore not applicable to commercial production.

[0009] There is thus a need for providing an alternative to the existing solutions for purifying aluminum ions and/or for preparing alumina that has a high purity.

SUMMARY OF THE DISCLOSURE

[0010] According to one aspect, there is provided a process for purifying aluminum ions comprising : precipitating the aluminum ions under the form of AI(OH) ₃ at a given pH value; and converting the AI(OH) ₃ into AICI ₃ by reacting AI(OH) ₃ with HCI and precipitating the AICI ₃ ; and heating the AICI ₃ under conditions effective for converting AICI ₃ into

Al ₂ 0 ₃ .

[0011] According to another aspect, there is provided a process for purifying aluminum ions comprising : precipitating the aluminum ions under the form of AI(OH) ₃ at a pH of about 7 to about 10; and converting the AI(OH) ₃ into AICI ₃ by reacting AI(OH) ₃ with HCI and precipitating the AICI ₃ ; and heating the AICI ₃ under conditions effective for converting AICI ₃ into

Al ₂ 0 ₃ .

[0012] According to another aspect, there is provided a process for purifying aluminum ions comprising : precipitating the aluminum ions under the form of AI(OH) ₃ at a pH of about 7 to about 10; and converting the AI(OH) ₃ into AICI ₃ by reacting AI(OH) ₃ with HCI and precipitating the AICI ₃ ; and heating the AICI ₃ under conditions effective for converting AICI ₃ into Al ₂ 0 ₃ and optionally recovering gaseous HCI so-produced.

[0013] According to another aspect, there is provided a process for preparing aluminum comprising : precipitating the aluminum ions under the form of AI(OH) ₃ at a pH of about 7 to about 10; converting the AI(OH) ₃ into AICI ₃ by reacting AI(OH) ₃ with HCI and precipitating the AICI ₃ ; heating the AICI ₃ under conditions effective for converting AICI ₃ into Al ₂ 0 ₃ ; and converting the Al ₂ 0 ₃ into aluminum. [0014] According to another aspect, there is provided a process for preparing aluminum comprising : precipitating the aluminum ions under the form of AI(OH)3 at a pH of about 7 to about 10; converting the AI(OH) ₃ into AICI ₃ by reacting AI(OH) ₃ with HCI and precipitating the AICI ₃ ; heating the AICI ₃ under conditions effective for converting AICI ₃ into Al ₂ 0 ₃ and optionally recovering gaseous HCI so-produced; and converting the Al ₂ 0 ₃ into aluminum.

[0015] According to another aspect, there is provided a process for purifying aluminum ions comprising : precipitating the aluminum ions under the form of AI(OH) ₃ at a given pH value; and converting the AI(OH) ₃ into AICI3 by reacting AI(OH) ₃ with HCI and precipitating the AICI ₃ ; and heating the AICI ₃ under conditions effective for converting AICI3 into AI2O3 and optionally recovering gaseous HCI so-produced.

[0016] According to another aspect, there is provided a process for preparing aluminum comprising : precipitating the aluminum ions under the form of AI(OH) ₃ at a given pH value; converting the AI(OH) ₃ into AICI ₃ by reacting AI(OH) ₃ with HCI and precipitating the AICI ₃ ; heating the AICI ₃ under conditions effective for converting AICI ₃ into Al ₂ 0 ₃ ; and converting the Α) ₂ 0 ₃ into aluminum.

[0017] According to another aspect, there is provided a process for preparing aluminum comprising : precipitating the aluminum ions under the form of AI(OH) ₃ at a given pH value; converting the AI(OH) ₃ into AICI ₃ by reacting AI(OH) ₃ with HCI and precipitating the AICI ₃ ; heating the AICI ₃ under conditions effective for converting AICI ₃ into Al ₂ 0 ₃ and optionally recovering gaseous HCI so-produced; and converting the Al ₂ 0 ₃ into aluminum.

[0018] According to another aspect, there is provided a process for preparing aluminum comprising converting AI2O3 obtained by a process as defined in in the present disclosure into aluminum.

BRIEF DESCRIPTION OF DRAWINGS

[0019] In the following drawings, which represent by way of example only, various embodiments of the disclosure :

[0020] Figs. 1A, 1 B and 1 C show a bloc diagram of an example of process according to the present disclosure;

[0021] Fig. 2 is a schematic representation of an example of a process for purifying/concentrating HCI according to the present disclosure; and [0022] Fig. 3 is a schematic representation of an example of a process for purifying/concentrating HCI according to the present disclosure.

DETAILLED DESCRIPTION OF VARIOUS EMBODIMENTS

[0023] Further features and advantages will become more readily apparent from the following description of various embodiments as illustrated by way of examples only and in a non-limitative manner.

[0024] The expression "red mud" as used herein refers to an industrial waste product generated during the production of alumina. For example, such a waste product can contain silica, aluminum, iron, calcium, titanium. It can also contains an array of minor constituents such as Na, K, Cr, V, Ni, Ba, Cu, n, Pb, Zn etc. For example, red mud can comprises about 15 to about 80 % by weight of Fe ₂ 0 ₃ , about 1 to about 35 % by weight AI2O3, about 1 to about 65 % by weight of Si0 ₂ , about 1 to about 20 % by weight of Na ₂ 0, about 1 to about 20 % by weight of CaO, and up to about 35 % by weight of Ti0 ₂ . According to another example, red mud can comprise about 30 to about 65 % by weight of Fe ₂ 0 ₃ , about 10 to about 20 % by weight Al ₂ 0 ₃ , about 3 to about 50 % by weight of Si0 ₂ , about 2 to about 10 % by weight of Na ₂ 0, about 2 to about 8 % by weight of CaO, and from 0 to about 25 % by weight of Ti0 ₂ .

[0025] The expression "fly ashes" as used herein refers to an industrial waste product generated in combustion. For example, such a waste product can contain various elements such as silica, oxygen, aluminum, iron, calcium. For example, fly ashes can comprise silicon dioxide (Si0 ₂ ) and aluminium oxide (Al ₂ 0 ₃ ). For example, fly ashes can further comprises calcium oxide (CaO) and/or iron oxide (Fe ₂ 0 ₃ ). For example fly ashes can comprise fine particles that rise with flue gases. For example, fly ashes can be produced during combustion of coal. For example, fly ashes can also comprise at least one element chosen from arsenic, beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead, manganese, mercury, molybdenum, selenium, strontium, thallium, and/or vanadium. For example, fly ashes can also comprise rare earth elements. For example, fly ashes can be considered as an aluminum-containing material.

[0026] The expression "slag" as used herein refers to an industrial waste product comprising aluminum oxide and optionally other oxides such as oxides of calcium, magnesium, iron, and/or silicon.

[0027] The term "hematite" as used herein refers, for example, to a compound comprising a-Fe ₂ 0 ₃ , y-Fe ₂ 0 ₃ , β-FeO.OH or mixtures thereof.

[0028] Terms of degree such as "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% or at least ±10% of the modified term if this deviation would not negate the meaning of the word it modifies.

[0029] For example, precipitating the aluminum ions under the form of AI(OH) ₃ can be carried out at a pH of about 9 to about 10, about 9.2 to about 9.8, about 9.3 to about 9.7 or about 9.5.

[0030] For example, precipitating the aluminum ions can be carried out by reacting the aluminum ions with an acid or with a base.

[0031] For example, the acid can be H ₂ S0 ₄ , HCI, HN0 ₃ etc.

[0032] For example, the base can be NaOH, KOH etc.

[0033] For example, precipitating the aluminum ions can be carried out by reacting the aluminum ions with AICI ₃ .

[0034] For example, precipitating the aluminum ions can be carried out by reacting a basic composition comprising the aluminum ions with an acid.

[0035] For example, precipitating the aluminum ions can be carried out by reacting a basic composition comprising the aluminum ions with HCI and/or AICI ₃ .

[0036] For example, precipitating the aluminum ions can be carried out by reacting an acidic composition comprising the aluminum ions with a base. [0037] For example, precipitating the aluminum ions can be carried out by reacting an acidic composition comprising the aluminum ions with a NaOH and/or KOH.

[0038] For example, precipitation of the aluminum ions can be carried out at a temperature of about 50 to about 75 °C, about 55 to about 70 °C, or about 60 to about 65 °C.

[0039] For example, a first precipitation of the aluminum ions can be carried out at the pH of about 7 to about 10 by reacting the aluminum ions with HCI and/or AICI3 and wherein a second precipitation is carried out by reacting the aluminum ions with HCI and/or AICI3 in a reaction media maintained at a value of about 7 to about 9, about 7.5 to about 8.5, about 7.8 to about 8.2 or about 8.

[0040] For example, a first precipitation of the aluminum ions can be carried out at the pH of about 7 to about 10 by reacting a basic composition comprising the aluminum ions with HCI and wherein a second precipitation is carried out by reacting the aluminum ions with AICI3 in a reaction media maintained at a value of about 7 to about 9, about 7.5 to about 8.5, about 7.8 to about 8.2 or about 8.

[0041] For example, a first precipitation of said aluminum ions under the form of AI(OH) ₃ can be carried out at said pH of about 7 to about 10 by reacting the aluminum ions with HCI and/or AICI ₃ and wherein a second precipitation of the aluminum ions under the form of AI(OH)3 is carried out by reacting said aluminum ions with HCI and/or AICI ₃ in a reaction media maintained at a value of about 7 to about 9.

[0042] For example, the aluminum ions can be precipitated under the form of AI(OH) ₃ at a given pH value that can be for example of about 7 to about 10.

[0043] For example, the second precipitation can be carried out at a temperature of about 50 to about 75 °C, about 55 to about 70 °C, or about 60 to about 65 °C.

[0044] For example, reacting with HCI can comprise digesting in HCI. [0045] For example, reacting with HCl can comprise sparging with HCl.

[0046] For example, converting the AI(OH)3 into the AICI3 can be carried out by reacting the AI(OH)3 with the HCl, the HCl having a concentration of 5 to about 14 moles per liter, 6 to about 13 moles per liter, about 7 to about 12 moles per liter, about 8 to about 1 1 moles per liter, about 9 to about 10 moles per liter, about 9.2 to about 9.8 moles per liter, about 9.3 to about 9.7 moles per liter, or about 9.5 moles per liter.

[0047] For example, converting the AI(OH) ₃ into the AICI ₃ can be carried out by reacting the AI(OH)3 with the HCl at a temperature of about 80 to about 120 °C, about 90 to about 1 10 °C, about 95 to about 105 °C, or about 97 to about 103 °C.

[0048] For example, the obtained AICI3 can be purified by means of an ion exchange resin. For example, ion exchange resins can be an anionic exchange resin.

[0049] For example, AICI3 can be precipitated under the form of AICI ₃ »6H ₂ 0 at a temperature of about 100 to about 120 °C, about 105 to about 1 15 °C, about 108 to about 1 12 °C, or about 109 to about 1 1 °C.

[0050] For example, AICI ₃ can be precipitated under the form of AICl3«6H ₂ 0, under vacuum, at a temperature of about 70 to about 90 °C, about 75 to about 85 °C, or about 77 to about 83 °C.

[0051] For example, the precipitated AICI3 can then be solubilized in purified water and then recrystallized.

[0052] For example, AICI3 can be solubilized in purified water, the solubilization being carried out at a pH of about 3 to about 4, or about 3.2 to about 3.8.

[0053] For example, precipitating AICI ₃ is carried out by crystallizing the AICI3 under the form of AICI ₃ «6H ₂ 0.

[0054] For example, converting AICI ₃ into Al ₂ 0 ₃ can be carried out under an inert atmosphere. [0055] For example, converting AICI ₃ into Al ₂ 0 ₃ can be carried out under an atmosphere of nitrogen, argon or a mixture thereof.

[0056] For example, converting AICI3 into Al ₂ 0 ₃ can be carried out under an atmosphere of steam (water vapor).

[0057] For example, HCI can be recovered.

[0058] For example, the recovered HCI can be purified and/or concentrated.

[0059] For example, the recovered HCI can be gaseous HCI and can be treated with H ₂ S0 ₄ so as to reduce the amount of water present in the gaseous HCI.

[0060] For example, the recovered HCI can be gaseous HCI and can be passed through a packed column so as to be in contact with a H ₂ S0 ₄ countercurrent flow so as to reduce the amount of water present in the gaseous HCI.

[0061] For example, the column can be packed with polypropylene or polytrimethylene terephthalate.

[0062] For example, the concentration of gaseous HCI can be increased by at least 50, 60, or 70 %.

[0063] For example, the concentration of gaseous HCI can be increased up to at least 50, 60, or 70 %.

[0064] For example, the recovered HCI can be gaseous HCI and can be treated with CaC so as to reduce the amount of water present in the gaseous HCI.

[0065] For example, the recovered HCI can be gaseous HCI and can be passed through a column packed with CaCI ₂ so as to reduce the amount of water present in the gaseous HCI.

[0066] For example, the concentration of gaseous HCI can be increased from a value below the azeotropic point before treatment to a value above the azeotropic point after treatment. [0067] For example, gaseous HCI can be concentrated and/or purified by means of H ₂ S0 ₄ . For example, gaseous HCI can be passed through a packed column where it is contacted with a H ₂ S0 ₄ countercurrent flow. For example, by doing so, concentration of HCI can be increased by at least 50 wt %, at least 60 wt %, at least 70 wt %, at least 75 wt %, at least 80 wt %, about 50 wt % to about 80 wt %, about 55 wt % to about 75 wt %, or about 60 wt %. For example, the column can be packed with a polymer such as polypropylene or polytrimethylene terephthalate (PTT).

[0068] For example, gaseous HCI can be concentrated and/or purified by means of CaCI ₂ . For example, gaseous HCI can be passed through a column packed with CaCI ₂ .

[0069] For example, the processes can further comprise converting alumina (Al ₂ 0 ₃ ) into aluminum. Conversion of alumina into aluminum can be carried out, for example, by using the Hall-Heroult process. References is made to such a well known process in various patents and patent applications such as US 20100065435; US 20020056650; US 5,876,584; US 6,565,733. Conversion can also be carried out by means of other processes such as those described in US 7,867,373; US 4,265,716; US 6,565,733 (converting alumina into aluminum sulfide followed by the conversion of aluminum sulfide into aluminum.)

[0070] For example, gaseous HCI can be concentrated and/or purified by means of LiCI. For example, gaseous HCI can be passed through a column packed with LiCI.

[0071] For example, HCI can be distilled through a rectification column in which heat is provided from aluminium chloride decomposition. For example, HCI generated from conversion of AICI ₃ into ΑΙ ₂ 0 ₃ can then be optionally purified by means of a distillation (for example in a rectification column). Such HCI being already hot since being generated from conversion of AICI3 into Al ₂ 0 ₃ . The same can also be done when converting other metal chlorides, rare earth chlorides or rare metal chlorides into their corresponding oxides. Decomposition and/or calcination reactors, and from any spray roasting device (for example, magnesium chloride, mixed oxides chlorides) can be fed to reboiler of the column.

[0072] For example, converting Al ₂ 0 ₃ into aluminum can be carried out by means of the Hall-Heroult process.

[0073] For example, converting Al ₂ 0 ₃ into aluminum can be carried out by converting Al ₂ 0 ₃ into A S ₃ and then converting AI ₂ S ₃ into aluminum.

[0074] For example, the aluminum ions can be obtained from various manner. For example, the aluminum ions can be obtained by leaching an aluminum-containing material.

[0075] For example, the aluminum-containing material can be an aluminum-containing ore. The aluminum-containing ore can be chosen from aluminosillicate minerals, clays, argillite, nepheline, mudstone, beryl, cryolite, garnet, spinel, kaolin, bauxite and mixtures thereof. The aluminum-containing material can also be a recycled industrial aluminum-containing material such as slag. The aluminum-containing material can also be red mud or fly ashes.

[0076] For example, the aluminum ions can be obtained by leaching the aluminum-containing material.

[0077] For example, the aluminum-containing material can be alumina, aluminum hydroxide, aluminum chloride or aluminum metal (or aluminum in its metallic form).

[0078] For example, the aluminum ions can be obtained by: leaching the aluminum-containing material with an acid so as to obtain a leachate and a solid residue; and separating the leachate from the solid residue.

[0079] For example, the aluminum ions can be obtained by: leaching the aluminum-containing material with an acid so as to obtain a leachate and a solid residue; separating the leachate from the solid residue; and reacting the leachate with a base.

[0080] For example, the aluminum ions can be obtained by : leaching the aluminum-containing material comprising iron ions (for example Fe ²⁺ and/or Fe ³⁺ ) with an acid so as to obtain a leachate and a solid residue; optionally removing at least a portion of the iron ions from the leachate; and separating the leachate from the solid residue.

[0081] For example, the aluminum ions can be obtained by : leaching the aluminum-containing material comprising iron ions (for example Fe ²⁺ and/or Fe ³⁺ ) with an acid so as to obtain a leachate and a solid residue; optionally removing at least a portion of the iron ions from the leachate; separating the leachate from the solid residue; and reacting the leachate with a base. [0082] For example, precipitation of iron ions can be carried out at a pH comprised between 10.5 and 14.0; 10.5 and 13.0; 10.5 and 12.0; 10.5 and 11.5; or 10.5 and 11.

[0083] For example, precipitation of iron ions can be carried out at a pH of at least about 10.0, at least about 10.5, at least about 11.0, at least about 11.5, at least about 12.0, about 10.5 to about 14.5, about 10.5 to about 11.0, about 11.0 to about 14.0, about 11.0 to about 13.0, or about 11.0 to about 12.0.

[0084] For example, precipitation of iron ions be carried out at a pH of about 10.8 to about 11.8, about 11 to about 12, about 11.5 to about 12.5, about 11.0 to about 11.6, about 11.2 to about 11.5, about 10.5 to about 12, about 11.5 to about 12.5, or about 11.8 to about 12.2, about 1.0, about 11.1, about 11.2, about 11.3, about 11.4, about 11.5, about 11.6, about 11.7, about 11.8, about 11.9, or about 12.0.

[0085] For example, the aluminum ions can be obtained by:

leaching the aluminum-containing material with an acid so as to obtain a composition comprising the aluminum ions and other metal ions; and at least partially removing the other metal ions from the composition by substantially selectively precipitating at least a portion the other metal ions.

[0086] For example, the aluminum ions can be obtained by:

leaching the aluminum-containing material with an acid so as to obtain a composition comprising the aluminum ions and other metal ions; and at least substantially selectively removing the other metal ions or the aluminum ions from the composition.

[0087] For example, removal of the other metal ions or the aluminum ions can be carried out by, for example, by means of a precipitation, extraction and/or isolation by means of a liquid-liquid extraction optionally with the use of an extracting agent.

[0088] For example, the aluminum ions can be obtained by:

leaching the aluminum-containing material with an acid so as to obtain a composition comprising the aluminum ions and other metal ions; and at least substantially selectively removing the other metal ions or the aluminum ions from the composition by substantially selectively precipitating the other metal ions or the aluminum ions from the composition.

[0089] For example, the aluminum ions can be obtained by:

leaching the aluminum-containing material with an acid so as to obtain a composition comprising the aluminum ions and other metal ions; and at least substantially selectively removing the other metal ions or the aluminum ions from the composition by substantially selectively precipitating the other metal ions or the aluminum ions from the composition.

[0090] The other metal ions can be ions from at least one metal chosen from Ti, Zn, Cu, Cr, Mn, Fe, Ni, Pb, In, rare earth elements, and rare metals etc.

[0091] For example, the rare earth element can be chosen from scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. For example, the at least one rare metal can be chosen from indium, zirconium, lithium, and gallium. These rare earth elements and rare metals can be in various form such as the elemental form (or metallic form), or under the form of chlorides, oxides, hydroxides etc.

[0092] For example, the aluminum ions can be obtained by:

leaching the aluminum-containing material with an acid so as to obtain a leachate comprising aluminum ions and a solid, and separating the solid from the leachate; and reacting the leachate with HCI so as to obtain a liquid and a precipitate comprising the aluminum ions in the form of AICI3, and separating the precipitate from the liquid.

[0093] The acid used for leaching aluminum-containing material can be HCI, H ₂ S0 ₄ , HNO3 or mixtures thereof. More than one acid can be used as a mixture or separately. Solutions made with these acids can be used at various concentration. For example, concentrated solutions can be used. For example, 6 M or 12 M HCI can be used. For example, about 6 M to about 12 M HCI can be used. For example, up to 100 % wt H2SO4 can be used.

[0094] The leaching can be carried out under pressure. For example, the pressure can be about 10 to about 300 psig, about 25 to about 250 psig, about 50 to about 200 psig or about 50 to about 150 psig. The leaching can be carried out for about 30 minutes to about 5 hours. It can be carried out at a temperature of about 60 to about 300 °C, about 75 to about 275 °C or about 100 to about 250 °C.

[0095] For example, the leaching can be carried out at a pH of about 0.5 to about 2.5., about 0.5 to about 1 .5, or about 1 ; then, when iron is present, iron can be precipitated at a pH of at least about 9.5, 10, 10.5, 1 1 , 1 .5; then aluminum can be precipitated at a pH of about 7 to about 1 1 , about 7.5 to about 10.5, or about 8 to about 9.

[0096] The leaching can be carried out under pressure into an autoclave. For example, it can be carried out at a pressure of 5 KPa to about 850 KPa, 50 KPa to about 800 KPa, 100 KPa to about 750 KPa, 150 KPa to about 700 KPa, 200 KPa to about 600 KPa, or 250 KPa to about 500 KPa. The leaching can be carried out at a temperature of at least 80 °C, at least 90 °C, or about 100 °C to about 1 10 °C. In certain cases it can be done at higher temperatures so as to increase extraction yields in certain ores.

[0097] After the leaching, various bases can be used for raising up the pH such as KOH, NaOH, Ca(OH) ₂ , CaO, MgO, Mg(OH) ₂ , CaC0 ₃ , Na ₂ C0 ₃ , NaHC0 ₃ , , or mixtures thereof.

[0098] For example, iron ions, when present, can be precipitated. When precipitating iron ions, the iron ions can be precipitated by means of an ionic precipitation and they can precipitate in the form of various salts, hydroxides or hydrates thereof. For example, the iron ions can be precipitated as Fe(OH)3, Fe(OH) ₂ , hematite, geotite, jarosite or hydrates thereof.

[0099] For example, aluminum ions can be precipitated. When precipitating aluminum ions, the aluminum ions can be precipitated by means of an ionic precipitation and they can precipitate in the form of various salts, (such as chlorides, sulfates) or hydroxides or hydrates thereof. For example, the aluminum ions can be precipitated as AI(OH) ₃ , AICI ₃ , AI ₂ (S0 ₄ ) ₃ , or hydrates thereof.

[00100] For example, the processes can comprise precipitating the aluminum ions by adjusting the pH at a value of about 7 to about 10 or about 8 to about 10. The processes can further comprise adding a precipitating agent effective for facilitating precipitation of the aluminum ions. For example, the precipitating agent can be a polymer. For example, the precipitating agent can be an acrylamide polymer.

[00101] For example, iron ions can be precipitated under the form of Fe ³⁺ , Fe ²⁺ , and a mixture thereof.

[00102] For example, precipitated iron ions can be under the form of Fe(OH) ₂ , Fe(OH) ₃ ), or a mixture thereof.

[00103] For example, the processes can comprise reacting dry individual salts (for example Na or K salts) obtained during the processes with H ₂ S0 ₄ and recovering HCI while producing marketable K2SO4 and a ₂ S0 ₄ and recovering hydrochloric acid of about 15 to about 90 % wt.

[00104] For example, sodium chloride produced in the processes can undergo a chemical reaction with sulfuric acid so as to obtain sodium sulfate and regenerate hydrochloric acid. Potassium chloride can undergo a chemical reaction with sulfuric acid so as to obtain potassium sulfate and regenerate hydrochloric acid. Sodium and potassium chloride brine solution can alternatively be the feed material to adapted small chlor-alkali electrolysis cells. In this latter case, common bases (NaOH and KOH) and bleach (NaOCI and KOCI) are produced.

[00105] For example, the processes can further comprise, after recovery of the rare earth elements and/or rare metals, recovering NaCI from the liquid, reacting the NaCI with H ₂ S0 ₄ , and substantially selectively precipitating Na ₂ S0 ₄ .

[00106] For example, the processes can further comprise, downstream of recovery of the rare earth elements and/or rare metals, recovering KCI from the liquid, reacting the KCI with H2S0 ₄ , and substantially selectively precipitating K ₂ S0 ₄ .

[00107] For example, the processes can further comprise, downstream of recovery of the rare earth elements and/or rare metals, recovering NaCI from the liquid, carrying out an electrolysis to generate NaOH and NaOCI.

[00108] For example, the processes can further comprise, downstream of recovery of the rare earth elements and/or rare metals, recovering KCI from the liquid, reacting the KCI, carrying out an electrolysis to generate KOH and KOCI.

[00109] For example, the processes can further comprise reacting the NaCI with H ₂ SO ₄ so as to substantially selectively precipitate Na ₂ S0 ₄ .

[00110] For example, the processes can further comprise reacting the KCI with H ₂ SO4 so as to substantially selectively precipitate K2SO4. [00111] For example, the processes can further comprise carrying out an electrolysis of the NaCI to generate NaOH and NaOCI.

[00112] For example, the processes can further comprise carrying out an electrolysis of the KCI to generate KOH and KOCI.

[00113] For example, produced NaCI can undergo chemical reaction with H2SO4 to produce Na ₂ S0 and HCI at a concentration at or above azeotropic concentration. Moreover, KCI can undergo chemical reaction with H2SO4 to produce K2SO4 and HCI having a concentration that is above the azeotropic concentration. Sodium and potassium chloride brine solution can be the feed material to adapted small chlor-alkali electrolysis cells. In this latter case, common bases (NaOH and KOH) and bleach (NaOCI and KOCI) are produced as well as HCI.

[00114] Various options are available to convert NaCI and KCI with intent of recovering HCI. One example can be to contact them with highly concentrated sulfuric acid (H ₂ S0 ₄ ), which generates sodium sulphate (Na ₂ S0 ₄ ) and potassium sulfate (K ₂ S0 ₄ ), respectively, and regenerates HCI at a concentration above 90% wt. Another example, is the use of a sodium and potassium chloride brine solution as the feed material to adapted small chlor- alkali electrolysis cells. In this latter case, common bases (NaOH and KOH) and bleach (NaOCI and KOCI) are produced. The electrolysis of both NaCI and KCI brine is done in different cells where the current is adjusted to meet the required chemical reaction. In both cases, it is a two-step process in which the brine is submitted to high current and base (NaOH or KOH) is produced with chlorine (Cl ₂ ) and hydrogen (H ₂ ). H ₂ and Cl ₂ are then submitted to a common flame where highly concentrated acid in gas (100% wt.) phase is produced and can be used directly, for example, in a stage requiring dry highly concentrated acid.

[00115] NaCI recovered from the processes of the present disclosure can, for example, be reacted with S0 ₂ , so as to produce HCI and Na ₂ S0 ₄ . Such a reaction that is an exothermic reaction can generate steam that can be used to activate a turbine and eventually produce electricity. [00116] For example, steam (or water vapor) can be injected and a plasma torch can be used for carrying fluidization.

[00117] For example, steam (or water vapor) can be injected and a plasma torch can be used for carrying fluidization.

[00118] For example, the steam (or water vapor) can be overheated.

[00119] For example, converting AICI ₃ into AI2O3 can comprise carrying out a calcination by means of carbon monoxide (CO).

[00120] For example, converting AICI ₃ into AI2O3 can comprise carrying out a calcination by means of a Refinery Fuel Gas (RFG).

[00121] For example, calcination can be carried out by injecting water vapor or steam and/or by using a combustion source chosen from fossil fuels, carbon monoxide, a Refinery Fuel Gas, coal, or chlorinated gases and/or solvants.

[00122] For example, calcination can be carried out by means of a rotary kiln.

[00123] For example, calcination can be carried out by injecting water vapor or steam and/or by using a combustion source chosen from natural gas or propane.

[00124] For example, calcination can be carried out by providing heat by means of electric heating, gas heating, microwave heating,

[00125] For example, calcination can be carried out by using an electrical road.

[00126] For example, the fluid bed reactor can comprise a metal catalyst chosen from metal chlorides.

[00127] For example, the fluid bed reactor can comprise a metal catalyst that is FeCI ₃ , FeCI ₂ or a mixture thereof.

[00128] For example, the fluid bed reactor can comprise a metal catalyst that is FeCI ₃ .

[00129] For example, the preheating system can comprise a plasma torch. [00130] For example, steam can be used as the fluidization medium heating. Heating can also be electrical.

[00131] For example, a plasma torch can be used for preheating the calcination reactor.

[00132] For example, a plasma torch can be used for preheating air entering in the calcination reactor.

[00133] For example, a plasma torch can be used for preheating a fluid bed.

[00134] For example, the calcination medium can be substantially neutral in terms of 0 ₂ (or oxidation). For example, the calcination medium can favorize reduction (for example a concentration of CO of about 100 ppm).

[00135] For example, the calcination medium is effective for preventing formation of Cl ₂ .

[00136] For example, the processes can comprise converting AIC »6H ₂ 0 into Al ₂ 0 ₃ by carrying out a calcination of AICI ₃ »6H ₂ 0 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 : O 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

C0 ₂ : about 1 .0 to about 3.5% vol.

[00137] Such a mixture can be efficient for reduction in off gas volume of 15.3 to 16.3%; therefore the capacity increases of 15.3 to 16.3 % proven on practical operation of the circulating fluid bed. Thus for a same flow it represents an Opex of 0.65*16.3% = 10.6%.

[00138] For example, the air to natural gas ratio of (Nm ³ /h over Nm ³ /h) in the fluid bed can be about 9.5 to about 10

[00139] For example, the air to CO gas ratio of (Nm ³ /h over Nm ³ /h) in the fluid bed can be about 2 to about 3.

[00140] For example, the processes can comprise, before leaching the aluminum-containing material, a pre-leaching removal of fluorine optionally contained in the aluminum-containing material.

[00141] For example, the processes can comprise leaching of the aluminum-containing material with HCI so as to obtain the leachate comprising aluminum ions and the solid, separating the solid from the leachate; and further treating the solid so as to separate S1O2 from ΤΊΟ2 that are contained therein.

[00142] For example, the processes can comprise leaching the aluminum- containing material with HCI so as to obtain the leachate comprising aluminum ions and the solid, separating the solid from the leachate; and further treating the solid with HCI so as to separate Si0 ₂ from T1O2 that are contained therein.

[00143] The following examples are non-limitative.

Example 1

Purification of aluminum ions extracted from an aluminum-containing material sample

Argillite

[00144] The argillite is ground up in the wet phase in a ball grinder (see (1) in Figs. 1A, B and 1 C). The mixture of water and roughly crushed argillite coming from the mine is fed into the grinder, where the mineral is reduced to less than 100 microns. The mud falls by gravity into a mixer outfitted with two impellers, which ensures a good homogeneity. When the mixture reaches the desired density, the contents of the mixer are pumped to an accumulation bunker, which will serve to feed the mud to the autoclave. When the bunker has reached the quantity of mud needed for the next batch, the grinding is put on hold.

Acid

[00145] The acid fed to the leaching (2) comes from two sources. The major portion is recycled spent acid coming from the high-purity alumina process. This acid contains around 20 to 22 wt. % of hydrochloric acid (HCI) and 10 to 1 1 % of AICI ₃ . If excess acid is required, a small quantity of fresh 36% acid is used.

Leaching

[00146] The mud of argillite and acid is fed to the autoclave of 32 m ³ in stoichiometric proportion. The autoclave is then hermetically sealed, mixed well and heated by indirect contact with the steam-fed jacket. As the temperature rises, the steam pressure increases such that the reaction reaches a temperature of 175° C and a pressure of around 7.5 barg. At the end of the leaching cycle, the metals contained in the argillite are converted into chloride. The mixture is then cooled by indirect contact with the cooling water in the reactor jacket. When the mixture reaches 70 to 80° C, the leached mud is transferred by air pressure to two buffer reservoirs maintained in communicating vessels. Then the reactor is empty, another leaching cycle can commence.

Silica mud

[00147] The leached mud contains a solid phase that is principally purified silica (Si0 ₂ ) (3a) in suspension in a solution of various metal chlorides. The mud is kept in suspension in the reservoirs by an impeller. The mud is fed continuously to two filter presses operating in duplex mode for separation purposes (3).

Silica filtration [00148] The two filter presses are identical and operate in fully automated manner. The functions of opening, closing, and emptying the cake are mechanized, and also a set of automatic cocks makes it possible to control the flow rate of the fluids. Each filter goes through the following stages, but staggered in time: preparation, filtration, compression, washing and drying, unloading of the cake to return to the preparation mode.

[00149] The preparation consists in feeding a preliminary layer of a filtering aid suspended in water. The mixture is prepared in the preliminary layer tank. With the help of a pump, the mixture is fed between the plates of the filter and returned to the tank. When the return water is clear and all the mixture has been circulated, the filter is ready for a filtration cycle.

[00150] In filtration mode, the suspension of leached mud is fed to the filter by a pump from the buffer reservoirs. The preliminary layer which is present makes it possible to hold back almost all the solid present in the mud and the resulting filtrate is free of particles in suspension. The mother liquor is sent to a buffer reservoir to be pumped to the iron precipitation stage (4). The mud accumulates between the plates until the filter pressure reaches a limit pressure.

[00151] The press then switches to compression mode. Still receiving the mud in filtration, hydraulic membranes between the filter plates are pressurized to extract more filtrate from the cake. This stage makes it possible to both maintain a more constant flow rate and to reduce the content of liquid of the cake. Finally, the press reaches its saturation. While the second press is placed in filtration mode, the first press goes into washing/drying mode.

[00152] For the washing, water is fed between the plates to displace the liquid contained in the cake. To prevent contamination of the mother liquor, the wash is returned to the buffer reservoirs and mixed in with the mud in filtration. After this, the cake is dried by passing compressed air between the plates. [00153] Once the cycle is completed, the press is opened by the hydraulic jack and the plates are separated one by one by an automated mechanical device. During the separation of the plates, the cake will drop by gravity into a chute beneath the filter.

Neutralization of the silica cake

[00154] The washed cake is sent to a blade mixer in which the pH of the solid is measured. A pH greater than 6.5 is maintained by the addition of caustic soda with a dispensing pump. The neutralized and homogenized mixture is then conveyed to an open semitrailer of 20 cubic yards and then transported for disposal.

Preparation of iron hydroxide (Fe(OH) ₃ ) and hematite (Fe ₂ 0 ₃ )

[00155] Figs. 1A, 1 B and 1 C are similar. The process of Figs. 1A and 1 C describes the production of hematite (see 4 and 4b) while the process of Fig. 1 B describes the production of iron hydroxide (see 4' and 4b'). In Fig. 1 C, some additional steps concerning recirculation or reusing HCI are provided. Moreover, Fig. 1 C comprises additional steps 18, 19 and 20. Step 18 relates to a further passage into an ion exchange resin so as to recover at least one rare earth element and/or at least one rare earth metal (for example under the form of a chloride). In step 19, the at least one rare earth element or at least one rare earth metal is going through calcination and then an oxide form of the at least one rare earth element and/or at least one rare earth metal is recovered in step 19a.

[00156] The mother liquor is pumped at constant rate across cartridge filters to the first iron precipitation reactor (4 and 4'). This reservoir is well mixed and the temperature is controlled to 65° C with the help of a heating coil. The pH is continuously metered and the solution is maintained at pH=12 by addition of 50% caustic soda with the help of a dispensing pump. The precipitation reaction converts the iron chloride and the other metal chlorides into hydroxides, which leads to a gradual precipitation and agglomeration of the solid crystals. Iron hydroxide can eventually be converted into hematite (see 4 and 4b). The liquor is then fed consecutively to two other precipitation reactors when the pH is also controlled by the addition of caustic soda and the temperature maintained by a coil. At the exit from the last reactor, the liquor is fed to a gravity decanter. Preparation of hematite can be carried out as described in PCT/CA2012/000541 filed on June 4, 2012.

[00157] The purpose of the gravity decanter is to produce a thickened mud of the largest crystals. These crystals will serve for the seeding in the first precipitation reactor. Seeding can be used in this type of reactor to promote the creation of precipitates ((hematite) (4b) or (iron hydroxide) (4b')) that are larger and more easy to filter.

[00158] The filtration of the hematite is carried out with the help of two automated filter presses similar to those used for the silica. Please refer to the section devoted to the filtration of the silica for a functional description. The mother liquor is sent to a buffer reservoir to be pumped to the aluminum precipitation reactor.

[00159] The washed cake is sent to a blade mixer where the pH of the solid is metered. A pH less than 8 is maintained by the addition of hydrochloric acid (HCI) with the help of a dispensing pump. The neutralized and homogenized mixture is then conveyed to an open semitrailer of 20 cubic yards and transported for disposal.

Precipitation of primary and secondary aluminum

[00160] The primary precipitation of the aluminum (5) can be similar to the precipitation of iron. However, the pH of the mother liquor is adjusted to 9.5 by adding HCI. Since the mother liquor has been purified of all other metals, the obtained precipitate is white and with purity of at least 98.5%.

[00161] The mother liquor is pumped at constant rate across guard filters to the first main reactor for precipitation of aluminum hydroxide (5). This reservoir is maintained in suspension by an impeller and the temperature is controlled at 65° C with the help of a heating coil. The pH is metered continuously and the solution maintained at pH=9.5 by addition of HCI using a dispensing pump. The precipitation reaction allows for obtaining aluminum hydroxide (5), which results in a gradual precipitation and agglomeration of solid crystals. The liquor is then sent consecutively to two other precipitation reactors where the pH is also controlled by the adding of acid and the temperature maintained by a coil. At the exit from the last reactor, the liquor is fed to a gravity decanter.

[00162] A secondary precipitation can optionally be done to produce aluminum hydroxide (AI(OH) ₃ ) from the flow of aluminum chloride (AICI ₃ ) coming from a further stage of the process described in the present disclosure. The secondary reactor is well mixed, maintained at a pH of 8.0 by addition of 50% caustic soda. The neutralization being greatly exothermal, the reactor is cooled by means of a coil. At the exit from the reactor, the secondary liquor is combined with the mother liquor to feed the main precipitation reactor.

[00163] The purpose of the gravity decanter is to produce a thickened mud of the largest crystals. These crystals are pumped from the bottom of the decanter to the first precipitation reactor to seed the crystallization.

[00164] The rest of the mud and the supernatant fluid of the decanter are sent to a repulping tank from which the mixture will be pumped to the centrifuge type separator/washer.

[00165] The mud is fed by batches to the separator. The centrifuge separator is made up of a drum turning at a speed of around 1500 revolutions per minute (rpm). This action allows the solid to be squeezed out and the liquor to be expelled at the start, followed by washing with atomization of water on the cake. The dissolved salts are than displaced into the liquid up to the acceptable purity. Once the batch is washed, the solid is fed by a conveyor, via a buffer hopper, to the plate dryer. [00166] A plate dryer is fed continuously with the wet aluminum hydroxide. The solid cascades from one plate to another thanks to a rotating rake. Steam heats the plates and allows a gradual evaporation of the moisture from the cake. At the bottom exit from the dryer, the aluminum hydroxide contains less than 2% moisture. The powder is sent to the hopper of a pneumatic conveyor system in dilute phase. The powder is then conveyed to the storage silos of the HPA process.

Dissolution of (AI(OH) ₃ ) / crystallization of AICI ₃

[00167] Aluminum hydroxide (ΑΙ(ΟΗ) ₃ ) (2 wt. % moisture, maximum 5 wt. %) was fed in a first reactor for example with the help of a dispensing system that combines a pneumatic system and a loading screw. The pneumatic part of the dispensing system enables a fluidization of the solid and facilitates its flow to the loading screw. The reaction of dissolving (or digesting) the aluminum hydroxide, activated by heat, occurs in the presence of concentrated hydrochloric acid (37 wt. % HCI), spent acid, and purified water (6).

[00168] A loading sequence is used during the filling of the first reactor. First of all, purified water coming from a nano water sector is fed to the reactor. After this, an acid is added : for example fresh acid (37% HCI). The acid can also comprise spent acid coming for example from washing residue of the strainer of a first crystallizer (dilute HCI) (8)and/or from on the other hand filtrate from the filtration at the exit from a second crystallizer (12) (rich in aluminum chloride). In (6), water and acid are added to the reactor in such proportions that the resulting solution attains a concentration of 9.5 M (29.3 wt. %). When the level of liquid in the reactor is sufficient to cover the first level of agitator blades, the feeding of solid (hydroxide) begins. The dissolution reactor is double-wall and the input of heat comes via saturated steam. The reactor is likewise outfitted with baffles as well as a two-level bladed agitator of turbine type to ensure the uniform dispersion of the solid in the acid solution and facilitate the dissolving of the AI(OH) ₃ . In this digesting reactor in (6), the aluminum hydroxide, under the action of the hydrochloric acid, is transformed into aluminum chloride (AICI ₃ ). The reaction is activated by heat and lasts about 3 hours (operating temperature of about 90 to about 1 10° C) transform the aluminum hydroxide into aluminum chloride. The event of the digester can also connected to the events collector and sent to the central purifier.

[00169] Once the hydroxide is dissolved, the solution of aluminum chloride is temporarily transferred to a tank where more than one batch can built up before moving on to the crystallization. At the exit from this tank, the solution of aluminum chloride can be filtered and/or purified (7) to remove the residual impurities coming from the hydroxide portion of the plant (silica, iron and sodium). For example, the solution can be purified by means of at least one exchange resin such as an anion exchange resin. The anion exchange resin can be, for example, chosen from Purolite™ resins such as A830, A500, S930 and mixtures thereof. Once filtered and/or purified, the solution is sent to a crystallization/evaporation reactor, where the first crystallization stage (8) begins. This reactor is also outfitted with a steam-heated external exchanger, a cold water condenser, and a recirculation pump allowing the contents of the reactor to be put through the exchanger. The condenser of the crystallizer is connected to a vacuum pump to ensure a vacuum during the reaction. Under the action of vacuum and heat, a major portion of the water is evaporated or incorporated into the structure of the crystals (50% or more). In the crystallizer, the aluminum chloride is bound to water molecules to form aluminum chloride hexahydrate (AICl ₃ »6H20), thus forming solid crystals. The crystallization makes it possible to separate the aluminum chloride from impurities which are always present in the solution. The speed of crystallization is controlled so as to minimize the impurities trapped inside the crystals. The evaporation stage lasts approximately about 0.5 to about 6 hours at 80° C. In this stage, the water fraction removed by evaporation is sent to an absorption column to treat the residual acid fumes before being vented into the atmosphere. [00170] After this, the solution containing 35 wt. % of solid can optionally be drained through the bottom of the reactor and pumped to the second stage of the first crystallization. Fresh acid (HCI 37 wt. %) can be added to reach a concentrated solution of 20 wt. % of acid. During this second stage, the adding of acid lowers the solubility of the aluminum chloride and causes it to crystallize. The crystallization yield may vary from 50 to 84 wt. %. The event of the crystallizer can also also connected to the events collector and sent to the central purifier.

[00171] Once the crystallization (8) is finished, the solution rich in crystals of aluminum chloride hexahydrate is transferred to an agitated reactor. From this tank, the solution is gradually fed to a band filter where it is filtered under vacuum (9). The first portion of the filtrate, containing residual impurities (NaCI, FeC ) as well as acid and aluminum chloride, is returned to the leaching of the hydroxide section of the plant. A washing with concentrated hydrochloric acid is done during the filtration, making it possible to separate and recover the uncrystallized aluminum chloride. The washing residue is sent to a tank before being reused in the previously mentioned digestion. Once the cake has been removed, the filter band is washed with nano water in order to keep the equipment free of contaminants. The box beneath the filter band is connected to a fan drawing the vapors (water and acid) released by the solution being filtered. The exit of this fan is connected to the events collector and sent to the main purifier.

[00172] Once the product of the first AICI3 crystallization is filtered (90 wt. % solid), it is fed to a second digestion reactor. The crystals of aluminum chloride hexahydrate are solubilized (10), in presence of purified water (nano water) to reform aluminum chloride. This solubilization makes it possible to release residual impurities which may have become trapped in the crystals during the first crystallization. The solubilization is promoted by an addition of heat and lasts about 3 hours to ensure a complete transformation. The reactor for the second dissolution is similar to the first. Once the crystals are solubilized, the solution is drained through the bottom of the reactor and filtered and/or purified to remove residual impurities. Purification (1 1) can be carried by means of an ion exchange resin such as an anion exchange resin. The anion exchange resin can be, for example, chosen from Purolite™ resins such as A830, A500, S930 and mixtures thereof.After this filtration, the solution of aluminum chloride is sent to two tanks, used alternately, for a first quality inspection. These tanks have an inclined bottom to facilitate complete emptying of the tank between batches. Moreover, the event of these tanks is connected to the events collector and sent to the central purifier. Once the quality of the batch is approved, it is transferred to a second crystallization/evaporation (12). Similar to the first (8), this stage makes it possible to evaporate, under the action of heat and vacuum, a major portion of the water to form crystals of AICI ₃ »6H ₂ 0 (around 50 wt. % or more of water is evaporated or included in the crystals). After the second crystallization, the solution of hexahydrate is transferred to an agitated tank before being gradually fed to the band filter (13). The crystals are filtered under vacuum and rinsed with concentrated hydrochloric acid (37 wt. %). The entire filtrate is recovered to be used in the first digestion. After the filtration, the crystals are dried and kept in two silos, used alternately, to ensure a control of the quality. All the stages of the second crystallization are done under an inert atmosphere (nitrogen atmosphere) to preserve the purity of the product.

[00173] After the second crystallization (12), the aluminum chloride hexahydrate is filtered, washed and dried sent by batch to a stage of thermal decomposition and calcination (14) where the acid and water are evaporated to be recovered at the acid regeneration section (15). The decomposition/calcination is done in a rotary furnace at variable speed where the temperature gradually rises from 300° C at the entry to reach around 1250° C at its maximum. Cooling of the alumina is done inside the furnace in order to reach an exit temperature less than 100° C. By heating the crystals of aluminum chloride hexahydrate, the residual water and HCI coming from the washing solution are evaporated. Once the temperature of decomposition is reached (about 170° C), the crystals are transformed into aluminum oxide, giving off water and HCI. When the temperature becomes greater than 300° C, calcination of the aluminum hydroxide makes it possible to generate alumina (AI2O3) giving off water vapor as the reaction product. The two reactions are done under nitrogen atmosphere to ensure there is no contamination by infiltrations of external air. The water and acid vapors generated by the decomposition/calcination are recovered to be sent to the acid regeneration stage (15). The furnace operates under constant vacuum to ensure a stable flow rate of vapors to the regeneration. A vacuum pump generates the vacuum. The feeding of the rotary furnace is done by a double rotary valve which is tight to prevent escape of acid fumes or entry of external air. The inside of the furnace is lined with alumina to prevent contamination of the product in event of wear or breakage. The heating of the furnace will be done indirectly by microwave or by radiant heating (gas/electricity).

[00174] The calcination stage (14) is followed by a grinding stage where the size of the alumina particles is mechanically homogenized (16). Water and hydrochloric acid are added to dilute all the impurities which might still be found in the process. Filtration/washing is also carried out in (16) to eliminate the impurities (very fine particles of alumina and residual acid) that will be sent on for treatment of wastes. The alumina undergoes a last thermal treatment to eliminate the residual water present after the grinding and the filtration. The temperature of the thermal treatment does not exceed 300° C. The "roasting" stage is followed by a cooling stage before the alumina is put in storage (17).

Recovery of acid

[00175] The vapors of water and acid (HCI) generated in the stage of decomposition/calcination (14) are cooled before being brought into contact with purified water (nano-filtration) in a ceramic packed column. The resulting acid is concentrated to about 33% by weight and without impurities.

Operating mode of the absorption columns

[00176] Each absorption system operates, for example, with at least three resin columns operating by three different modes, either purification, polishing or regeneration. The purification column performs the bulk of the work, consisting in eliminating the impurities, while the polishing column finishes the absorption of impurities. These first two columns operate in series. The last regeneration column is in a process of overlapping of its absorption properties. For the overlapping phase, one has at first a back-wash stage, making it possible to fluidize the resin particles in the column so as to eliminate the effects of channeling and particle segregations. After this, one moves on to the regeneration, which is done by circulating a washing solution (NaOH or HCI) through the resin. Once the regeneration is finished, one performs two rinsing stages (one slow, the other fast) with demineralized water in order to remove the washing solution, as well as the sodium ions if necessary.

[00177] Each absorption system can be outfitted with two tanks to contain the product in liquid form and the resin washing solution, respectively.

[00178] Each tank can have a pump to send the liquid to the columns at a precise flow rate and this should be done without passing a given feed pressure threshold.

[00179] For the design of the columns themselves, that is, their diameter, their height, and the quantity of resin that they contain, one can rely on the data assembled in the technical documents of Purolite™ such as those enclosed with the letter for the three different types of resin. The number of bed volumes of aluminum chloride solution can be estimated at about 300.

Example 2

HCI gas enrichment and purification: H ₂ S0 ₄ route

[00180] H ₂ S0 ₄ can be used for carrying out purification of HCI. It can be carried out by using a packing column with H ₂ S0 ₄ flowing counter currently (see Fig. 2). This allows for converting the recovered HCI into HCI having a concentration above the azeotropic point (20.1 % wt) and increase its concentration by about 60 to about 70% at minimum. [00181] Water is absorbed by H ₂ S0 ₄ and then H2SO4 regeneration is applied where H2SO4 is brought back to a concentration of about 95 to about 98% wt. Water release at this stage free of sulphur is recycled back and used for crystallization dissolution, etc. Packing of the column can comprise polypropylene or polytrimethylene terephthalate (PTT).

[00182] Combustion energy can be performed with off gas preheating air and oxygen enrichment. Oxygen enrichment: +20°C represents flame temperature by: 400°C maximum.

Example 3

HCI gas enrichment and purification: calcium chloride to calcium chloride hexahydrate (absorption / desorption process)

[00183] As shown in Fig. 3, CaCI ₂ can be used for drying HCI. In fact, CaCI ₂ can be used for absorbing water contained into HCI. In such a case, CaCI ₂ is converted into its hexachloride form (CaCI ₂ · 6H ₂ 0) and one saturated system is eventually switched into regeneration mode where hot air is introduced to regenerate the fixed bed. Such an ion / exchange type process can be seen in Fig. 3 and the cycle can be inversed to switch from one column to another one. According to another embodiment, another salt can be used instead of CaCI ₂ in order to remove water from HCI. For example, LiCI can be used.

[00184] The person skilled in the art would understand that the processes described in examples 2 and 3 can be used in various different manners. For example, these processes can be combined with the various processes presented in the present disclosure. For example, such purifications techniques can be integrated to the process shown in Fig. 1 , For example, it can be used downstream of at least one of step 5, 8, 12, 13, 14 and 15 (see Fig. 1 ).

[00185] The person skilled in the art would also understand that the processes exemplified in example 1 can be carried out by using different starting materials i.e. aluminum-containing materials other than argillite that was used in example 1. Such other aluminum-containing materials can be, for example, those previously mentioned in the present application. The person skilled in the art would thus understand how to adapt and modify the processes described in the examples when using such a different starting material.

[00186] It was found that the processes of the present disclosure are quite efficient for producing high purity alumina. For example, it was observed that high purity alumina at purity levels of 99.99% (4N) or 99.999% (5N) can be obtained. Therefore, the processes of the present disclosure propose an interesting alternative to the existing solutions for manufacturing high purity. It was found that such processes were quite efficient and economical since allowing for recycling HCI, thereby being environmental friendly and lowering costs.

[00187] While a description was made with particular reference to the specific embodiments, it will be understood that numerous modifications thereto will appear to those skilled in the art. The scope of the claims should not be limited by specific embodiments and examples provided in the present disclosure and accompanying drawings, but should be given the broadest interpretation consistent with the disclosure as a whole.