Methods for alkali metal recovery and / or aluminum recovery

Abstract

Methods of performing alkali metal recovery, and associated systems, are generally described. Some methods comprise performing one or more steps that allow for the recovery of alkali metal from a material. Some methods described herein may advantageously allow for the recovery of multiple desirable products from a material (e.g., both an alkali metal and iron) and / or may allow for the recovery of a desirable product from a material while also allowing for the recovery of one or more reagents employed during the recovery process.

Description

[0001] METHODS FOR ALKALI METAL RECOVERY AND / OR ALUMINUM RECOVERY

[0002] RELATED APPLICATIONS

[0003] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 689,592, filed August 30, 2024, and entitled “Methods for Alkali Metal Recovery and / or Aluminum Recovery,” which is hereby incorporated by reference in its entirety for all purposes.

[0004] TECHNICAL FIELD

[0005] Methods of performing alkali metal recovery, and associated systems, are generally described.

[0006] SUMMARY

[0007] Methods of performing alkali metal recovery, and associated systems, are generally described. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and / or a plurality of different uses of one or more systems and / or articles.

[0008] Certain embodiments relate to methods.

[0009] In some embodiments, a method comprises exposing a slurry comprising a solid and a liquid to CaO, wherein the solid comprises a complex oxide of an alkali metal and / or hydroxide of an alkali metal, wherein exposing the slurry to the CaO causes alkali metal ions to be leached from the complex oxide of the alkali metal and / or the hydroxide of the alkali metal, and wherein exposing the slurry to the CaO causes Al3+ions to be leached from the complex oxide of the alkali metal and / or the hydroxide of the alkali metal to generate A1(OH)4‘ ions dissolved in the liquid; and exposing the liquid to a precipitating agent to precipitate alumina.

[0010] In some embodiments, a method comprises exposing a slurry comprising a solid to a ferrous reducing agent and a catalyst for the ferrous reducing agent, wherein the solid comprises a compound comprising Fe3+, and wherein the solid comprises a complex oxide of an alkali metal and / or hydroxide of an alkali metal; and exposing the slurry to CaO to leach ions of the alkali metal from the complex oxide of the alkali metal and / or the hydroxide of the alkali metal.

[0011] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present

[0012] - 1 -

[0013] #14343296vl specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures:

[0016] FIGs. 1A and IB together show an exemplary method 100.

[0017] DETAILED DESCRIPTION

[0018] Methods of performing alkali metal recovery, and associated systems, are generally described. Some methods comprise performing one or more steps that allow for the recovery of alkali metal from a material. Some methods described herein may advantageously allow for the recovery of multiple desirable products from a material (e.g., both an alkali metal and iron) and / or may allow for the recovery of a desirable product from a material while also allowing for the recovery of one or more reagents employed during the recovery process.

[0019] FIGs. 1A and IB show one non-limiting example of a method described herein. The method 100 shown in FIGs. 1A and IB comprises the eleven steps 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, and 122. Some methods comprise performing all of the steps of the method 100. Some methods comprise performing some, but not all, of the steps of the method 100. Some methods comprise performing none of the steps of the method 100. Additionally, methods may comprise performing some or all of the steps shown in the order of the method 100 and / or may comprise performing some of the steps of the method 100 in a different order than the order of the method 100.

[0020] Steps of the method 100 as different steps may be performed for periods of time that overlap or for periods of time that do not overlap. Steps that are performed over periods of time that overlap may be performed on the same portion of a slurry for periods of time that overlap (e.g., with reference to FIGs. 1A and IB, as two examples, the steps 104 and 106 may be performed on the same slurry together and / or the steps 120 and 122 may be performed on the - 2 -

[0021] #14343296vl same liquid together). It is also possible for a method described herein to be performed in a manner such that a slurry is being continuously formed and processed where one part of the slurry (e.g., a downstream part) is subjected to a later step in the method while another part of the slurry (e.g., an upstream part) is subjected to an earlier step in the method.

[0022] Further details regarding the method steps of the method 100, and associated materials, are provided in further detail below.

[0023] The first step of the method 100 is the step 102, which comprises exposing a slurry comprising a solid to a ferrous reducing agent and a catalyst for the ferrous reducing agent. Exposure of a slurry to a ferrous reducing agent and a catalyst may be performed in a variety of suitable manners. In some embodiments, such exposure comprises introducing the slurry, the ferrous reducing agent, and the catalyst into a reaction vessel (e.g., a sealed reaction vessel). The slurry may be formed prior to its introduction into a reaction vessel (e.g., a slurry may be introduced in slurry form into a reaction vessel) or the slurry may be formed in the reaction vessel (e.g., a solid and a liquid may be introduced separately into a reaction vessel and then agitated to form a slurry).

[0024] In some embodiments, the exposure may occur in a reaction vessel. The exposure may be considered to begin upon the placement of the last such component into the reaction vessel and / or the exposure may be considered to end upon the removal of one or more such components from the reaction vessel.

[0025] Some suitable solids present during the first step of the method 100 (e.g., that are exposed to a ferrous reducing agent and a catalyst for the ferrous reducing agent) comprise a complex oxide of an alkali metal and / or a complex hydroxide of an alkali metal (e.g., in addition to a compound comprising Fe3+). Complex oxides of alkali metals may comprise cations of the alkali metal, oxygen anions, and one or more further components. Similarly, complex hydroxides of alkali metals may comprise cations of the alkali metal, hydroxide anions, and one or more further components. In some embodiments, a complex oxide of an alkali metal comprises Al3+and / or a complex hydroxide of an alkali metal comprises Al3+.

[0026] The “alkali metals,” as used herein, are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). In some embodiments, a solid described herein comprises Na (e.g., in the form of Na+ions).

[0027] In some embodiments, a slurry present during the first step of the method 100 comprises a solid that is present in red mud and / or bauxite residue. In some such embodiments, such a slurry may comprise red mud and / or bauxite residue. Non-limiting examples of the solids - 3 -

[0028] #14343296vl present in red mud include bauxite, compounds comprising hydrated iron (e.g., goethite and / or ferrihydrite), hematite, sodalite, and titania. The iron-containing compounds in the foregoing list may further include Al3+. For instance, an iron-containing compound in the foregoing list (e.g., an iron-containing mineral in bauxite, goethite, ferrihydrite, hematite) may comprise iron and may further comprise Al3+that is substituted for some of the iron that would otherwise be present therein. In some embodiments, an iron-containing compound on which one or more steps described herein are performed comprises Fe3+and that is partially substituted by Al3+.

[0029] In some embodiments, exposing a slurry to a ferrous reducing agent and a catalyst for the ferrous reducing agent comprises converting a compound comprising hydrated iron (e.g., hydrated Fe3+) into a compound comprising non-hydrated iron (e.g., non-hydrated Fe3+and / or non-hydrated Fe2+). For instance, such exposure may comprise the conversion of a compound comprising hydrated iron into hematite and / or magnetite. It is also possible for such exposure to further comprise generating magnetite from hematite (e.g., from hematite generated from a compound comprising non-hydrated iron).

[0030] In some embodiments, exposing a slurry to a ferrous reducing agent and a catalyst for the ferrous reducing agent causes Fe3+present in the solid to be reduced to Fe2+. This may cause the generation of magnetite (e.g., magnetite comprising the Fe2+generated by this process).

[0031] In some embodiments, exposing a slurry to a ferrous reducing agent and a catalyst for the ferrous reducing agent comprises expelling Al3+from a compound present in the slurry. The Al3+may be present in a compound in a material that further comprises a compound comprising Fe3+, such as a compound in which the Fe3+is partially substituted by Al3+. In such instances, reduction of the Fe3+to Fe2+may also cause Al3+to be expelled from the compound. In some embodiments, the Al3+is present in a compound that further comprises a complex oxide of an alkali metal and / or a complex hydroxide of an alkali metal. The expelled Al3+may be remain in ion form (e.g., as an ion dissolved in a liquid present in the slurry, as an ion present in a solid suspended in the slurry). In some embodiments, the Al3+is expelled as Al3+present in Al(0H)4‘ ions.

[0032] Ferrous reducing agents described herein may comprise iron cations (e.g., Fe2+). The ferrous reducing agents may be capable of reducing and / or configured to reduce a species present in the solid. As one example, a ferrous reducing agent may be capable of reducing and / or configured to reduce Fe3+present therein to Fe2+. As another example, a ferrous reducing agent may be capable of reacting with Fe3+to yield a solid comprising both the Fe3+and Fe2+from the ferrous reducing agent. Some methods comprise reducing a species present in a solid - 4 -

[0033] #14343296vl (e.g., Fe3+) by a ferrous reducing agent and / or forming a solid comprising both Fe3+and Fe2+arising from the ferrous reducing agent. Non-limiting examples of ferrous reducing agents include species comprising Fe2+(e.g., FeSC ) and organic molecules that can perform the reductions described herein (e.g., complex carbohydrates, such as starch).

[0034] Catalysts for ferrous reducing agents described herein may be capable of catalyzing and / or configured to catalyze the reduction of a species present in a solid (e.g., Fe3+) by a ferrous reducing agent. Some catalysts for ferrous reducing agents are capable of catalyzing and / or configured to catalyze the reduction of Fe3+in a compound comprising Fe3+(e.g., goethite, ferrihydrite, hematite) to Fe2+to form a compound comprising a species comprising both Fe3+and Fe2+(e.g., magnetite). Some methods comprise reducing a species present in a solid (e.g., Fe3+) by a ferrous reducing agent whose action is catalyzed by a catalyst for a ferrous reducing agent described herein.

[0035] In some embodiments, a catalyst for a ferrous reducing agent catalyzes the reduction of a species present in a solid by solubilizing the solid in a liquid present in a slurry suspending the solid. Solubilizing the solid may allow it to interact with the ferrous reducing agent. The solubilization may be to a relatively low degree (e.g., the Fe3+may be rendered sparingly soluble in the liquid). As one example, in some embodiments, a catalyst for a ferrous reducing agent solubilizes Fe3+(e.g., in a liquid present in a slurry in which a solid comprising the Fe3+is suspended) so that it can be reduced to Fe2+by the ferrous reducing agent in solution. In some embodiments, a catalyst for a ferrous reducing agent is a strong base, such as an alkali metal hydroxide. For instance, a catalyst for a ferrous reducing agent may comprises a type of alkali metal also present in the solid (e.g., an alkali metal that is present in a complex oxide of an alkali metal and / or a complex hydroxide of an alkali metal present in the solid). Non-limiting examples of suitable catalysts for ferrous reducing agents include hydroxides (e.g., NaOH) and species including organic ions (e.g., species including CN’ ions).

[0036] Slurries described herein may comprise a liquid, such as water.

[0037] In one non-limiting example, a slurry that initially comprises, consists essentially of, and / or consists of sodalite, titania, hematite, goethite, and water is exposed to NaOH and FeSO4 to yield a slurry comprising, consisting essentially of, and / or consisting of sodalite, magnetite, hematite, NaAl(0H)4, and water.

[0038] The species present in the slurries present during the first step of the method 100 may be present in various suitable relative amounts.

[0039] - 5 -

[0040] #14343296vl In some embodiments, an initial weight ratio of a ferrous reducing agent to a solid in a slurry is greater than or equal to 50 kg / ton, greater than or equal to 75 kg / ton, greater than or equal to 100 kg / ton, greater than or equal to 125 kg / ton, greater than or equal to 150 kg / ton, greater than or equal to 175 kg / ton, greater than or equal to 200 kg / ton, greater than or equal to 225 kg / ton, greater than or equal to 250 kg / ton, greater than or equal to 275 kg / ton, greater than or equal to 300 kg / ton, greater than or equal to 325 kg / ton, greater than or equal to 350 kg / ton, or greater than or equal to 375 kg / ton. In some embodiments, an initial weight ratio of a ferrous reducing agent to a solid in a slurry is less than or equal to 400 kg / ton, less than or equal to 375 kg / ton, less than or equal to 350 kg / ton, less than or equal to 325 kg / ton, less than or equal to 300 kg / ton, less than or equal to 275 kg / ton, less than or equal to 250 kg / ton, less than or equal to 225 kg / ton, less than or equal to 200 kg / ton, less than or equal to 175 kg / ton, less than or equal to 150 kg / ton, less than or equal to 125 kg / ton, less than or equal to 100 kg / ton, or less than or equal to 75 kg / ton. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 50 kg / ton and less than or equal to 400 kg / ton, or greater than or equal to 250 kg / ton and less than or equal to 400 kg / ton). Other ranges are also possible.

[0041] When a slurry comprises two or more types of ferrous reducing agents and / or two or more types of solids, the initial weight ratio of any individual type of ferrous reducing agent to any individual type of solid may be in one or more of the above-referenced ranges, the initial weight ratio of any individual type of ferrous reducing agent to any individual or combination of types of solids may be in one or more of the above-referenced ranges, the initial weight ratio of any combination of types of ferrous reducing agents to any individual or combination of types of solids may be in one or more of the above-referenced ranges, and / or the initial weight ratio of all types of ferrous reducing agents to all types of solids may be in one or more of the abovereferenced ranges.

[0042] In some embodiments, an initial weight ratio of a catalyst for a ferrous reducing agent to a solid in a slurry is greater than or equal to 50 kg / ton, greater than or equal to 100 kg / ton, greater than or equal to 150 kg / ton, greater than or equal to 200 kg / ton, greater than or equal to 250 kg / ton, greater than or equal to 300 kg / ton, greater than or equal to 350 kg / ton, greater than or equal to 400 kg / ton, greater than or equal to 450 kg / ton, greater than or equal to 500 kg / ton, greater than or equal to 550 kg / ton, greater than or equal to 600 kg / ton, or greater than or equal to 650 kg / ton. In some embodiments, an initial weight ratio of a catalyst for a ferrous reducing agent to a solid in a slurry is less than or equal to 700 kg / ton, less than or equal to 650 kg / ton, less than or equal to 600 kg / ton, less than or equal to 550 kg / ton, less than or equal to 500

[0043] - 6 -

[0044] #14343296vl kg / ton, less than or equal to 450 kg / ton, less than or equal to 400 kg / ton, less than or equal to 350 kg / ton, less than or equal to 300 kg / ton, less than or equal to 250 kg / ton, less than or equal to 200 kg / ton, less than or equal to 150 kg / ton, or less than or equal to 100 kg / ton.

[0045] Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 50 kg / ton and less than or equal to 700 kg / ton, or greater than or equal to 250 kg / ton and less than or equal to 700 kg / ton). Other ranges are also possible.

[0046] When a slurry comprises two or more types of catalysts for ferrous reducing agents and / or two or more types of ferrous reducing agents, the initial weight ratio of any individual type of catalyst for a ferrous reducing agent to any individual type of ferrous reducing agent may be in one or more of the above-referenced ranges, the initial weight ratio of any individual type of catalyst for a ferrous reducing agent to any individual or combination of types of ferrous reducing agents may be in one or more of the above-referenced ranges, the initial weight ratio of any combination of types of catalysts for ferrous reducing agents to any individual or combination of types of ferrous reducing agents may be in one or more of the above-referenced ranges, and / or the initial weight ratio of all types of catalysts for ferrous reducing agents to all types of ferrous reducing agents may be in one or more of the above-referenced ranges.

[0047] In some embodiments, one or more solids initially make up greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 45 wt%, greater than or equal to 50 wt%, greater than or equal to 55 wt%, greater than or equal to 60 wt%, or greater than or equal to 65 wt% of a slurry. In some embodiments, one or more solids initially make up less than or equal to 70 wt%, less than or equal to 65 wt%, less than or equal to 60 wt%, less than or equal to 55 wt%, less than or equal to 50 wt%, less than or equal to 45 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, or less than or equal to 15 wt% of a slurry. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 10 wt% and less than or equal to 70 wt% of a slurry). Other ranges are also possible.

[0048] When a slurry comprises two or more types of solids, each type of solid may individually make up a wt% of a slurry in one or more of the above-referenced ranges, any combination of types of solids may together make up a wt% of a slurry in one or more of the above-referenced ranges, and / or all of the types of solids may together make up a wt% of the slurry in one or more of the above-referenced ranges.

[0049] - 7 -

[0050] #14343296vl Exposing a slurry to a ferrous reducing agent and a catalyst may be performed at a variety of suitable temperatures. In some embodiments, the exposure of a slurry to a ferrous reducing agent and a catalyst is performed at a temperature of greater than or equal to 40 °C, greater than or equal to 50 °C, greater than or equal to 60 °C, greater than or equal to 70 °C, greater than or equal to 80 °C, greater than or equal to 90 °C, greater than or equal to 100 °C, greater than or equal to 110 °C, greater than or equal to 120 °C, greater than or equal to 130 °C, greater than or equal to 140 °C, greater than or equal to 150 °C, greater than or equal to 160 °C, greater than or equal to 170 °C, greater than or equal to 180 °C, greater than or equal to 190 °C, greater than or equal to 200 °C, greater than or equal to 210 °C, greater than or equal to 220 °C, greater than or equal to 230 °C, or greater than or equal to 240 °C. In some embodiments, the exposure of a slurry to a ferrous reducing agent and a catalyst is performed at temperature of less than or equal to 250 °C, less than or equal to 240 °C, less than or equal to 230 °C, less than or equal to 220 °C, less than or equal to 210 °C, less than or equal to 200 °C, less than or equal to 190 °C, less than or equal to 180 °C, less than or equal to 170 °C, less than or equal to 150 °C, less than or equal to 140 °C, less than or equal to 130 °C, less than or equal to 120 °C, less than or equal to 110 °C, less than or equal to 100 °C, less than or equal to 90 °C, less than or equal to 80 °C, less than or equal to 70 °C, less than or equal to 60 °C, or less than or equal to 50 °C. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 40 °C and less than or equal to 250 °C, or greater than or equal to 80 °C and less than or equal to 150 °C). Other ranges are also possible.

[0051] When a slurry is exposed to a ferrous reducing agent and a catalyst, the temperature of a solid present in the slurry, the temperature of the ferrous reducing agent, the temperature of the catalyst, and / or the temperature of a liquid present in the slurry may be in one or more of the above-described ranges. The above-referenced ranges may characterize the spatial and / or time averaged temperature and / or the mode temperature over space and / or time of such exposure.

[0052] Exposing a slurry to a ferrous reducing agent and a catalyst may be performed for a variety of suitable times. In some embodiments, the exposure occurs for greater than or equal to 20 minutes, greater than or equal to 40 minutes, greater than or equal to 60 minutes, greater than or equal to 80 minutes, greater than or equal to 100 minutes, greater than or equal to 120 minutes, greater than or equal to 140 minutes, greater than or equal to 160 minutes, greater than or equal to 180 minutes, greater than or equal to 200 minutes, or greater than or equal to 220 minutes. In some embodiments, the exposure occurs for less than or equal to 240 minutes, less than or equal to 220 minutes, less than or equal to 200 minutes, less than or equal to 180

[0053] - 8 -

[0054] #14343296vl minutes, less than or equal to 160 minutes, less than or equal to 140 minutes, less than or equal to 120 minutes, less than or equal to 100 minutes, less than or equal to 80 minutes, less than or equal to 60 minutes, or less than or equal to 40 minutes. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 20 minutes and less than or equal to 240 minutes). Other ranges are also possible.

[0055] In some embodiments, a slurry is exposed to a ferrous reducing agent and a catalyst for a period of time in one or more of the ranges described above. It is also possible for a slurry to be exposed to a ferrous reducing agent and a catalyst and then for a period of time in one or more of the above-referenced ranges to be allowed to elapse before any subsequent processing steps are performed. Additionally, the temperature may have a value as described above over such periods of time.

[0056] Exposing a slurry to a ferrous reducing agent and a catalyst may comprise mixing. For instance, the ferrous reducing agent and / or the catalyst may be contacted with and / or suspended in the slurry, and this slurry may be mixed. Such mixing may be performed at a variety of suitable speeds. In some embodiments, this mixing is performed at greater than or equal to 200 rpm, greater than or equal to 300 rpm, greater than or equal to 400 rpm, greater than or equal to 500 rpm, greater than or equal to 600 rpm, greater than or equal to 700 rpm, greater than or equal to 800 rpm, greater than or equal to 900 rpm, greater than or equal to 1000 rpm, greater than or equal to 1100 rpm, greater than or equal to 1200 rpm, greater than or equal to 1300 rpm, greater than or equal to 1400 rpm, greater than or equal to 1500 rpm, greater than or equal to 1600 rpm, greater than or equal to 1700 rpm, greater than or equal to 1800 rpm, or greater than or equal to 1900 rpm. In some embodiments, this mixing is performed at less than or equal to 2000 rpm, less than or equal to 1900 rpm, less than or equal to 1800 rpm, less than or equal to 1700 rpm, less than or equal to 1600 rpm, less than or equal to 1500 rpm, less than or equal to 1400 rpm, less than or equal to 1300 rpm, less than or equal to 1200 rpm, less than or equal to 1100 rpm, less than or equal to 1000 rpm, less than or equal to 900 rpm, less than or equal to 800 rpm, less than or equal to 700 rpm, less than or equal to 600 rpm, less than or equal to 500 rpm, less than or equal to 400 rpm, or less than or equal to 300 rpm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 200 rpm and less than or equal to 2000 rpm, or greater than or equal to 600 rpm and less than or equal to 1200 rpm). Other ranges are also possible.

[0057] The above-referenced ranges may characterize the average and / or the mode mixing rate.

[0058] Such mixing may be performed for periods of time and / or at temperatures as described above.

[0059] - 9 -

[0060] #14343296vl In some embodiments, subsequent to exposing a slurry to a ferrous reducing agent and a catalyst, and / or during one or more of the steps that follow step 102 in FIGs. 1A and / or IB, the slurry may be cooled (e.g., to room temperature, to a temperature below the temperature at which the exposure was performed). In such embodiments, the cooling may cause one or more species dissolved in the liquid (e.g., any iron ions dissolved therein) to precipitate therefrom.

[0061] The second step of the method 100 is the step 104, which comprises removing the ferrous reducing agent from a slurry. When the ferrous reducing agent is a solid, this may be accomplished by physical separation methods, such as filtering (e.g., vacuum filtering). It is also possible for one or more chemical separation methods to be employed for this purpose. This may allow for recovery of the ferrous reducing agent for further use subsequent to its use for reducing iron present in the solid. Removal of a ferrous reducing agent from a slurry may comprise complete removal of the ferrous reducing agent or may comprise removal such that residual and / or trace amounts thereof remain.

[0062] The third step of the method 100 is the step 106, which comprises removing the catalyst for the ferrous reducing agent from the slurry. When the catalyst for the ferrous reducing agent is a solid, this may be accomplished by physical separation methods, such as filtering (e.g., vacuum filtering). It is also possible for one or more chemical separation methods to be employed for this purpose. This may allow for recovery of the catalyst for the ferrous reducing agent for further use subsequent to its use for reducing iron present in the solid. Removal of a catalyst for a ferrous reducing agent from a slurry may comprise complete removal of the catalyst for the ferrous reducing agent or may comprise removal such that residual and / or trace amounts thereof remain.

[0063] The fourth step of the method 100 is the step 108, which comprises transferring the slurry to a reaction vessel. When one or more prior steps are performed in a reaction vessel (e.g., when the slurry has previously been exposed to a ferrous reducing agent and a catalyst for a ferrous reducing agent in a vessel), the vessel to which the slurry is transferred may be a second, different reaction vessel. This may advantageously allow for the first reaction vessel to be cleaned and / or employed to perform prior steps with a different slurry. In some embodiments, different reaction vessels employed during a method described herein may have differences that render them particularly suitable for the portion(s) of the method that they are employed to perform. As one example, in some embodiments, a reaction vessel employed during the fifth step of the method 100 is able to withstand the oxidizing conditions present

[0064] - 10 -

[0065] #14343296vl during the performance of this step. It is also possible for a method to comprise performing all steps in a single reaction vessel.

[0066] The fifth step of the method 100 is the step 110, which comprises exposing the slurry to CaO. This may desirably result in the leaching of ions of an alkali metal from a material present in the slurry (e.g., from sodalite present therein). In other words, the CaO may act as a leaching agent and / or facilitate the leaching of such alkali metal ions from such a material. Such alkali metal ions may comprise alkali metal ions initially present in a material present in the slurry (e.g., prior to the exposure of the slurry to a ferrous reducing agent and / or a catalyst for the ferrous reducing agent). In some embodiments, such alkali metal ions comprise Na+ions, which may result in the generation of NaOH. In methods comprising both the steps 102 and 110 and for which the catalyst for the ferrous reducing agent is NaOH, the amount of NaOH generated during the step 110 may be in excess of the amount of NaOH added to the slurry in the step 102.

[0067] In some embodiments, exposing a slurry to CaO may cause the leaching of Al3+ions from a solid from which alkali metal ions are leached. This may result in the generation of further A1(OH)4 ions in a liquid present in the slurry.

[0068] The leaching of alkali metal ions and / or Al3+ions may cause a change in the crystal structure of the solid.

[0069] In one non-limiting example, a slurry that comprises, consists essentially of, and / or magnetite, a garnet comprising calcium, hematite consists of sodalite, magnetite, hematite, NaAl(OH)4, and water (e.g., a slurry present subsequent to the performance of the step 102 in FIG. 1A) is exposed to CaO to form a slurry comprising, consisting essentially of, and / or consisting of, NaAl(OH)4, NaOH, and water. The amount of NaAl(OH)4 present may be higher after the CaO exposure than before the CaO exposure.

[0070] Exposure of a slurry to CaO may be performed in a variety of suitable manners. In some embodiments, such exposure comprises introducing the slurry and the CaO into a reaction vessel (e.g., a sealed reaction vessel). The slurry may be formed prior to its introduction into a reaction vessel (e.g., a slurry may be introduced in slurry form into a reaction vessel) or the slurry may be formed in the reaction vessel (e.g., a solid and a liquid may be introduced separately into a reaction vessel and then agitated to form a slurry). As noted above, the slurry may be a slurry that is present at the end of one or more of the above-described method steps.

[0071] In such embodiments, the exposure may occur in a reaction vessel. In some embodiments, the exposure may be considered to begin upon the placement of the last such

[0072] - 11 -

[0073] #14343296vl component into the reaction vessel and / or the exposure may be considered to end upon the removal of one or more such components from the reaction vessel.

[0074] The species present in the slurries present during the fifth step of the method 100 may be present in various suitable relative amounts.

[0075] In some embodiments, an initial weight ratio of CaO to a solid in a slurry is greater than or equal to 50 kg / ton, greater than or equal to 75 kg / ton, greater than or equal to 100 kg / ton, greater than or equal to 125 kg / ton, greater than or equal to 150 kg / ton, greater than or equal to 175 kg / ton, greater than or equal to 200 kg / ton, greater than or equal to 225 kg / ton, greater than or equal to 250 kg / ton, greater than or equal to 275 kg / ton, greater than or equal to 300 kg / ton, greater than or equal to 325 kg / ton, greater than or equal to 350 kg / ton, or greater than or equal to 375 kg / ton. In some embodiments, an initial weight ratio of CaO to a solid in a slurry is less than or equal to 400 kg / ton, less than or equal to 375 kg / ton, less than or equal to 350 kg / ton, less than or equal to 325 kg / ton, less than or equal to 300 kg / ton, less than or equal to 275 kg / ton, less than or equal to 250 kg / ton, less than or equal to 200 kg / ton, less than or equal to 150 kg / ton, or less than or equal to 100 kg / ton. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 50 kg / ton and less than or equal to 400 kg / ton, or greater than or equal to 250 kg / ton and less than or equal to 400 kg / ton). Other ranges are also possible.

[0076] When a slurry comprises two or more types of solids, the weight ratio of CaO to each type of solid may be in one or more of the above-referenced ranges and / or the weight ratio of CaO to all of the types of solids together may be in one or more of the above-referenced ranges.

[0077] In some embodiments, solids initially make up greater than or equal to 5 wt%, greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 45 wt%, greater than or equal to 50 wt%, or greater than or equal to 55 wt% of the slurry when the slurry is exposed to CaO. In some embodiments, solids initially make up less than or equal to 60 wt%, less than or equal to 55 wt%, less than or equal to 50 wt%, less than or equal to 45 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 15 wt%, or less than or equal to 10 wt% of the slurry when the slurry is exposed to CaO. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 5 wt% and less than or equal to 60 wt%, or greater than or equal to 20 wt% and less than or equal to 40 wt%). Other ranges are also possible.

[0078] - 12 -

[0079] #14343296vl When a slurry comprises two or more types of solids, each type of solid may individually make up a wt% of a slurry in one or more of the above-referenced ranges, any combination of types of solids may together make up a wt% of a slurry in one or more of the above-referenced ranges, and / or all of the types of solids may together make up a wt% of the slurry in one or more of the above-referenced ranges.

[0080] The exposure of a slurry to CaO may be performed at a variety of suitable temperatures. In some embodiments, the exposure of a slurry to CaO is performed at a temperature of greater than or equal to 40 °C, greater than or equal to 50 °C, greater than or equal to 60 °C, greater than or equal to 70 °C, greater than or equal to greater than or equal to 80 °C, greater than or equal to 90 °C, greater than or equal to 100 °C, greater than or equal to 110 °C, greater than or equal to 120 °C,, greater than or equal to 130 °C, greater than or equal to 140 °C, greater than or equal to 150 °C, greater than or equal to 160 °C, greater than or equal to 170 °C, greater than or equal to 180 °C, or greater than or equal to 190 °C. In some embodiments, the exposure of a slurry to a ferrous reducing agent and a catalyst is performed at temperature of less than or equal to 200 °C, less than or equal to 190 °C, less than or equal to 180 °C, less than or equal to 170 °C, less than or equal to 160 °C, less than or equal to 150 °C, less than or equal to 140 °C, less than or equal to 130 °C, less than or equal to 120 °C, less than or equal to 110 °C, less than or equal to 100 °C, less than or equal to 90 °C, less than or equal to 80 °C, less than or equal to 70 °C, less than or equal to 60 °C, or less than or equal to 50 °C. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 40 °C and less than or equal to 200 °C, or greater than or equal to 80 °C and less than or equal to 130 °C). Other ranges are also possible.

[0081] When a slurry is exposed to CaO, the temperature of a solid present in the slurry, the temperature of the CaO, and / or the temperature of a liquid present in the slurry may be in one or more of the above-described ranges. The above-referenced ranges may characterize the spatial and / or time averaged temperature and / or the mode temperature over space and / or time of such exposure.

[0082] Exposing a slurry to CaO may be performed for a variety of suitable times. In some embodiments, the exposure occurs for greater than or equal to 20 minutes, greater than or equal to 40 minutes, greater than or equal to 60 minutes, greater than or equal to 80 minutes, greater than or equal to 100 minutes, greater than or equal to 120 minutes, greater than or equal to 140 minutes, greater than or equal to 160 minutes, greater than or equal to 180 minutes, greater than or equal to 200 minutes, or greater than or equal to 220 minutes. In some embodiments, the exposure occurs for less than or equal to 240 minutes, less than or equal to 220 minutes, less

[0083] - 13 -

[0084] #14343296vl than or equal to 200 minutes, less than or equal to 180 minutes, less than or equal to 160 minutes, less than or equal to 140 minutes, less than or equal to 120 minutes, less than or equal to 100 minutes, less than or equal to 80 minutes, less than or equal to 60 minutes, or less than or equal to 40 minutes. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 20 minutes and less than or equal to 240 minutes). Other ranges are also possible.

[0085] In some embodiments, a slurry is exposed to CaO for a period of time in one or more of the ranges described above. It is also possible for a slurry to be exposed to CaO and then for a period of time in one or more of the above-referenced ranges to be allowed to elapse before any subsequent processing steps are performed. Additionally, the temperature may have a value as described above over such periods of time.

[0086] Exposing a slurry to CaO may comprise mixing. For instance, the CaO may be contacted with and / or suspended in the slurry, and this slurry may be mixed. Such mixing may be performed at a variety of suitable speeds. In some embodiments, this mixing is performed at greater than or equal to 200 rpm, greater than or equal to 300 rpm, greater than or equal to 400 rpm, greater than or equal to 500 rpm, greater than or equal to 600 rpm, greater than or equal to 700 rpm, greater than or equal to 800 rpm, greater than or equal to 900 rpm, greater than or equal to 1000 rpm, greater than or equal to 1100 rpm, greater than or equal to 1200 rpm, greater than or equal to 1300 rpm, greater than or equal to 1400 rpm, greater than or equal to 1500 rpm, greater than or equal to 1600 rpm, greater than or equal to 1700 rpm, greater than or equal to 1800 rpm, or greater than or equal to 1900 rpm. In some embodiments, this mixing is performed at less than or equal to 2000 rpm, less than or equal to 1900 rpm, less than or equal to 1800 rpm, less than or equal to 1700 rpm, less than or equal to 1600 rpm, less than or equal to 1500 rpm, less than or equal to 1400 rpm, less than or equal to 1300 rpm, less than or equal to 1200 rpm, less than or equal to 1100 rpm, less than or equal to 1000 rpm, less than or equal to 900 rpm, less than or equal to 800 rpm, less than or equal to 700 rpm, less than or equal to 600 rpm, less than or equal to 500 rpm, less than or equal to 400 rpm, or less than or equal to 300 rpm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 200 rpm and less than or equal to 2000 rpm, or greater than or equal to 600 rpm and less than or equal to 1200 rpm). Other ranges are also possible.

[0087] The above-referenced ranges may characterize the average and / or the mode mixing rate. Such mixing may be performed for periods of time and / or at temperatures as described above.

[0088] - 14 -

[0089] #14343296vl The sixth step of the method 100 is the step 112, which comprises recovering magnetite. The magnetite may be magnetite that is created upon exposure to a ferrous reducing agent and a catalyst for a ferrous reducing agent and / or may comprise magnetite initially present in the solid. Recovery of the magnetite may comprise physical recovery methods (e.g., filtration, such as vacuum filtration, magnetic separation, and / or flocculation) and / or chemical separation.

[0090] The seventh step of the method 100 is the step 114, which comprises removing the remaining solids from the slurry to yield a liquid. Removal of the solids from the liquid may comprise physical separation methods (e.g., filtration, such as vacuum filtration). Solids removed from the slurry may include iron oxides (e.g., hematite) and / or calcium silicates (e.g., garnets comprising calcium). Removing the solids from the slurry may yield water comprising dissolved ions, such as water comprising dissolved alkali metal ions (e.g., Na+ions), hydroxide ions, and / or A1(OH)4‘ ions. The eighth step of the method 100 is the step 116, which comprises transferring a liquid from the slurry (e.g., a liquid remaining after the removal of magnetite, and / or other solids, therefrom) to a reaction vessel.

[0091] When one or more prior steps are performed in a reaction vessel (e.g., when the slurry comprising the liquid has previously been exposed to CaO in a vessel, and / or when the slurry comprising the liquid has previously been exposed to a ferrous reducing agent and a catalyst for the ferrous reducing agent in a vessel), the vessel to which the liquid from the liquid is transferred may be a second, different reaction vessel (or a third, different vessel if the slurry from which the liquid originated has already been in two different reaction vessels). This may advantageously allow for the first (and / or second) reaction vessel(s) to be cleaned and / or employed to perform prior steps with a different slurry. In some embodiments, a reaction vessel employed during the eighth step of the method 100 is able to withstand the oxidizing conditions present during the performance of this step. As noted above, it is also possible for a method to comprise performing all steps in a single reaction vessel and / or for a method to comprise performing two or more steps in the same reaction vessel.

[0092] The ninth step of the method 100 is the step 118, which comprises exposing the liquid to a precipitating agent. The precipitating agent may cause the precipitation of alumina (e.g., from A1(OH)4‘ ions present in the liquid). Other species dissolved in the liquid prior to the exposure of the liquid to the precipitating agent, such as ions of an alkali metal and / or hydroxide ions, may remain dissolved in the liquid during and / or after such precipitation. Without wishing to be bound by any particular theory, it is believed that precipitating alumina from the liquid may advantageously result in the generation of a relatively pure hydroxide of an alkali metal (e.g., an

[0093] - 15 -

[0094] #14343296vl alkali metal originating from sodalite originally present in a solid present in the slurry from which the liquid originated) dissolved in the liquid. In some such embodiments, the liquid remaining after alumina precipitation may consist of and / or consist essentially of water and a dissolved hydroxide of an alkali metal. In some embodiments, all or substantially all of any Al(0H)4‘ ions present in the liquid prior to exposure thereof to a precipitating agent may be precipitated upon such exposure.

[0095] Exposure of a liquid to a precipitating agent may be performed in a variety of suitable manners. In some embodiments, such exposure comprises introducing the liquid and the precipitating agent into a reaction vessel (e.g., a sealed reaction vessel). As noted above, the liquid may be liquid from a slurry that is present at the end of one or more of the abovedescribed method steps.

[0096] In such embodiments, the exposure may occur in a reaction vessel. In some embodiments, the exposure may be considered to begin upon the placement of the last such component into the reaction vessel and / or the exposure may be considered to end upon the removal of one or more such components from the reaction vessel.

[0097] In some embodiments, a precipitating agent generates an oxidation-reduction potential of greater than 200 mV in the liquid. One non-limiting example of a suitable precipitating agent is hydrogen peroxide (e.g., 20 wt% H2O2).

[0098] The exposure of a liquid to a precipitating agent may be performed at a variety of suitable temperatures. In some embodiments, the exposure of a liquid to a precipitating agent is performed at a temperature of greater than or equal to 20 °C, greater than or equal to 25 °C, greater than or equal to 30 °C, greater than or equal to 35 °C, greater than or equal to 40 °C, greater than or equal to 45 °C, greater than or equal to 50 °C, or greater than or equal to 55 °C. In some embodiments, the exposure of a liquid to a precipitating agent is performed at temperature of less than or equal to 60 °C, less than or equal to 55 °C, less than or equal to 50 °C, less than or equal to 45 °C, less than or equal to 40 °C, less than or equal to 35 °C, less than or equal to 30 °C, or less than or equal to 25 °C. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 20 °C and less than or equal to 60 °C). Other ranges are also possible.

[0099] When a liquid is exposed to a precipitating agent, the temperature of the precipitating agent and / or the temperature of the liquid may be in one or more of the above-described ranges. The above-referenced ranges may characterize the spatial and / or time averaged temperature and / or the mode temperature over space and / or time of such exposure.

[0100] - 16 -

[0101] #14343296vl Exposing a liquid to a precipitating agent may be performed for a variety of suitable times. In some embodiments, the exposure occurs for greater than or equal to 60 minutes, greater than or equal to 80 minutes, greater than or equal to 100 minutes, greater than or equal to 120 minutes, greater than or equal to 140 minutes, or greater than or equal to 160 minutes. In some embodiments, the exposure occurs for less than or equal to 240 minutes, less than or equal to 180 minutes, less than or equal to 160 minutes, less than or equal to 140 minutes, less than or equal to 120 minutes, less than or equal to 100 minutes, or less than or equal to 80 minutes. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 60 minutes and less than or equal to 180 minutes). Other ranges are also possible.

[0102] In some embodiments, a liquid is exposed to a precipitating agent for a period of time in one or more of the ranges described above. It is also possible for a liquid to be exposed to a precipitating agent and then for a period of time in one or more of the above-referenced ranges to be allowed to elapse before any subsequent processing steps are performed. Additionally, the temperature may have a value as described above over such periods of time.

[0103] Exposing a liquid to a precipitating agent may comprise mixing. For instance, the precipitating agent may be contacted with and / or suspended in the liquid, and this liquid may be mixed. Such mixing may be performed at a variety of suitable speeds. In some embodiments, this mixing is performed at greater than or equal to 200 rpm, greater than or equal to 300 rpm, greater than or equal to 400 rpm, greater than or equal to 500 rpm, greater than or equal to 600 rpm, greater than or equal to 700 rpm, greater than or equal to 800 rpm, greater than or equal to 900 rpm, greater than or equal to 1000 rpm, greater than or equal to 1100 rpm, greater than or equal to 1200 rpm, greater than or equal to 1300 rpm, greater than or equal to 1400 rpm, greater than or equal to 1500 rpm, greater than or equal to 1600 rpm, greater than or equal to 1700 rpm, greater than or equal to 1800 rpm, or greater than or equal to 1900 rpm. In some embodiments, this mixing is performed at less than or equal to 2000 rpm, less than or equal to 1900 rpm, less than or equal to 1800 rpm, less than or equal to 1700 rpm, less than or equal to 1600 rpm, less than or equal to 1500 rpm, less than or equal to 1400 rpm, less than or equal to 1300 rpm, less than or equal to 1200 rpm, less than or equal to 1100 rpm, less than or equal to 1000 rpm, less than or equal to 900 rpm, less than or equal to 800 rpm, less than or equal to 700 rpm, less than or equal to 600 rpm, less than or equal to 500 rpm, less than or equal to 400 rpm, or less than or equal to 300 rpm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 200 rpm and less than or equal to 2000 rpm, or greater than or equal to 600 rpm and less than or equal to 1200 rpm). Other ranges are also possible.

[0104] - 17 -

[0105] #14343296vl The above-referenced ranges may characterize the average and / or the mode mixing rate. Such mixing may be performed for periods of time and / or at temperatures as described above.

[0106] The tenth step of the method 100 is the step 120, which comprises recovering a hydroxide of an alkali metal. The hydroxide of the alkali metal may comprise an alkali metal that was leached from sodalite as described elsewhere herein. The hydroxide may be recovered as a hydroxide or may be recovered as an oxide. For instance, the hydroxide may be recovered as an oxide that will undergo a reaction to form a hydroxide upon exposure to water. One nonlimiting example of a hydroxide of an alkali metal that may be recovered is NaOH (e.g., as NaOH and / or as Na2O). In some embodiments, recovery of a hydroxide of an alkali metal comprises recovering a liquid in which ions of the alkali metal are dissolved (e.g., recovery of aqueous NaOH). Recovery of the hydroxide of the alkali metal may comprise physical recovery methods (e.g., filtration, such as vacuum filtration, washing, such as washing with warm DI water) and / or chemical separation. In some embodiments, recovery comprises alternatively performing vacuum filtration and washing with warm DI water.

[0107] The eleventh step of the method 100 is the step 122, which comprises recovering alumina. Recovery of the alumina may comprise physical recovery methods (e.g., filtration, such as vacuum filtration) and / or chemical separation as described above with respect to the step 120. In some embodiments, a hydroxide of an alkali metal may be separated from alumina by such recovery methods, and one or both of the hydroxide of the alkali metal and the alumina may be recovered as a product (e.g., the alumina as a solid product, the hydroxide of the alkali metal as a liquid comprising the dissolved hydroxide of the alkali metal).

[0108] While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the

[0109] - 18 -

[0110] #14343296vl foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods, if such features, systems, articles, materials, and / or methods are not mutually inconsistent, is included within the scope of the present invention.

[0111] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0112] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0113] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0114] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily

[0115] - 19 -

[0116] #14343296vl including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0117] As used herein, “wt%” is an abbreviation of weight percentage. As used herein, “at%” is an abbreviation of atomic percentage. Unless context indicates to the contrary, the amounts described herein are based on mass and the percentage amounts described herein are based on mass percentages.

[0118] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0119] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

[0120] - 20 -

[0121] #14343296vl

Claims

1. CLAIMSWhat is claimed is:

1. A method, comprising: exposing a slurry comprising a solid and a liquid to CaO, wherein the solid comprises a complex oxide of an alkali metal and / or hydroxide of an alkali metal, wherein exposing the slurry to the CaO causes alkali metal ions to be leached from the complex oxide of the alkali metal and / or the hydroxide of the alkali metal, and wherein exposing the slurry to the CaO causes Al3+ions to be leached from the complex oxide of the alkali metal and / or the hydroxide of the alkali metal to generate Al(0H)4‘ ions dissolved in the liquid; and exposing the liquid to a precipitating agent to precipitate alumina.

2. A method, comprising: exposing a slurry comprising a solid to a ferrous reducing agent and a catalyst for the ferrous reducing agent, wherein the solid comprises a compound comprising Fe3+, and wherein the solid comprises a complex oxide of an alkali metal and / or hydroxide of an alkali metal; and exposing the slurry to CaO to leach ions of the alkali metal from the complex oxide of the alkali metal and / or the hydroxide of the alkali metal.

3. A method as in any preceding claim, further comprising, prior to exposing the slurry to CaO, exposing the slurry to a ferrous reducing agent and a catalyst for the ferrous reducing agent.

4. A method as in any preceding claim, wherein, prior to exposing the slurry to the ferrous reducing agent and the catalyst for the ferrous reducing agent, the slurry comprises a compound comprising Fe3+.

5. A method as in any preceding claim, wherein the slurry comprises bauxite residue.

6. A method as in any preceding claim, wherein the slurry comprises red mud.

7. A method as in any preceding claim, wherein the red mud comprises bauxite.- 21 -#14343296vl8. A method as in any preceding claim, wherein the Fe3+is hydrated.

9. A method as in any preceding claim, wherein exposing the slurry to the ferrous reducing agent and the catalyst for the ferrous reducing agent generates magnetite from the compound comprising Fe3+.

10. A method as in any preceding claim, wherein the alkali metal is Na.

11. A method as in any preceding claim, wherein the complex oxide of the alkali metal and / or the complex hydroxide of the alkali metal comprises Al3+.

12. A method as in any preceding claim, wherein the slurry comprises water.

13. A method as in any preceding claim, wherein the ferrous reducing reagent is FeSC .

14. A method as in any preceding claim, wherein the catalyst for the ferrous reducing agent is NaOH.

15. A method as in any preceding claim, wherein an initial weight ratio of the ferrous reducing agent to the solid is greater than or equal to 50 kg / ton and less than or equal to 400 kg / ton.

16. A method as in any preceding claim, wherein an initial weight ratio of the catalyst for the ferrous reducing agent to the solid is greater than or equal to 50 kg / ton and less than or equal to 700 kg / ton.

17. A method as in any preceding claim, wherein solids initially make up greater than or equal to 10 wt% and less than or equal to 70 wt% of the slurry.

18. A method as in any preceding claim, wherein the exposure of the slurry to the ferrous reducing agent and the catalyst for the ferrous reducing agent is performed at a temperature of greater than or equal to 40 °C and less than or equal to 250 °C.- 22 -#14343296vl19. A method as in any preceding claim, wherein the exposure of the slurry to the ferrous reducing agent and the catalyst for the ferrous reducing agent is performed for greater than or equal to 20 minutes and less than or equal to 240 minutes.

20. A method as in any preceding claim, wherein the exposure of the slurry to the ferrous reducing agent and the catalyst for the ferrous reducing agent comprises mixing.

21. A method as in any preceding claim, wherein the mixing is performed at greater than or equal to 200 rpm and less than or equal to 2000 rpm.

22. A method as in any preceding claim, wherein the exposure of the slurry to the ferrous reducing agent and the catalyst for the ferrous reducing agent is performed in a sealed reaction vessel.

23. A method as in any preceding claim, further comprising removing the ferrous reducing agent from the slurry prior to exposing the slurry to CaO.

24. A method as in any preceding claim, further comprising removing the catalyst for the ferrous reducing agent from the slurry prior to exposing the slurry to CaO.

25. A method as in any preceding claim, further comprising transferring the slurry to a second reaction vessel prior to exposing the slurry to the CaO.

26. A method as in any preceding claim, wherein the slurry is exposed to the CaO in the second reaction vessel.

27. A method as in any preceding claim, wherein the second reaction vessel is a sealed reaction vessel.

28. A method as in any preceding claim, wherein an initial weight ratio of the CaO to an initial amount of the solid is greater than or equal to 50 kg / ton and less than or equal to 400 kg / ton.- 23 -#14343296vl29. A method as in any preceding claim, wherein solids initially make up greater than or equal to 5 wt% and less than or equal to 60 wt% of the slurry when the slurry is exposed to the CaO.

30. A method as in any preceding claim, wherein the exposure of the slurry to CaO is performed at a temperature of greater than or equal to 40 °C and less than or equal to 200 °C.

31. A method as in any preceding claim, wherein the exposure of the slurry to the CaO is performed for greater than or equal to 20 minutes and less than or equal to 240 minutes.

32. A method as in any preceding claim, wherein the exposure of the slurry to the CaO comprises mixing.

33. A method as in any preceding claim, wherein the mixing is performed at greater than or equal to 200 rpm and less than or equal to 2000 rpm.

34. A method as in any preceding claim, further comprising transferring the liquid to a third reaction vessel prior to exposing the liquid to the precipitating agent.

35. A method as in any preceding claim, wherein the liquid is exposed to the precipitating agent in the third reaction vessel.

36. A method as in any preceding claim, wherein the third reaction vessel is a sealed reaction vessel.

37. A method as in any preceding claim, wherein the precipitating agent is H2O2.

38. A method as in any preceding claim, wherein the exposure of the liquid to the precipitating agent is performed at a temperature of greater than or equal to 20 °C and less than or equal to 60 °C.- 24 -#14343296vl39. A method as in any preceding claim, wherein the exposure of the liquid to the precipitating agent is performed for greater than or equal to 60 minutes and less than or equal to 180 minutes.

40. A method as in any preceding claim, wherein the exposure of the liquid to the precipitating agent comprises mixing.

41. A method as in any preceding claim, wherein the mixing is performed at greater than or equal to 200 rpm and less than or equal to 2000 rpm.

42. A method as in any preceding claim, further comprising recovering a hydroxide of the alkali metal.

43. A method as in any preceding claim, further comprising recovering the magnetite.

44. A method as in any preceding claim, further comprising recovering alumina.- 25 -#14343296vl

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