Method to extract high-grade magnetite from olivine

Abstract

A method for extracting an iron oxide composition from a mafic and / or ultramafic rock comprises introducing a mafic and / or ultramafic rock and CO2 to a first reactor, reacting the mafic and / or ultramafic rock and CO2 in the first reactor, thereby yielding a first reactor effluent comprising one or more iron silicate compounds and one or more products of the reaction in the first reactor; separating the first reactor effluent into a first stream comprising the one or more iron silicate compounds and a second stream comprising the one or more reaction products of the first reactor; introducing the first stream and water to a second reactor; and reacting the first stream and water in the second reactor, thereby yielding a second reactor effluent comprising one or more iron oxide compounds, water, and silica.

Description

Atty Docket No. 395 / 46 PCTMETHOD TO EXTRACT HIGH-GRADE MAGNETITE FROM OLIVINECROSS-REFERENCE TO RELATED APPLICATIONSThis application claims the benefit of U.S. Provisional Patent Application No. 63 / 730,641 , filed on December 11 , 2024, the entire contents of which are incorporated by reference herein.TECHNICAL FIELD

[0001] The disclosed technology relates to processing naturally occurring minerals containing iron compounds to synthesize iron compounds suitable for substantially carbon-free iron production.BACKGROUND

[0002] Global steel demand has surged in recent years, driven by population and economic growth, and is expected to continue rising. Steel production depends heavily on coal, which is used as a reducing agent to extract iron from ore and to provide carbon content in steel. Over the last decade, CO2 emissions from the iron and steel sector have increased, largely due to higher steel demand. While the direct CO2 intensity of crude steel production has decreased slightly in recent years, primarily from the use of scrap steel, efforts must be accelerated to align with the Net Zero Emissions by 2050 Scenario (“NZE”). Although steel’s CO2 emission intensity has remained relatively stable, it must significantly decrease to meet NZE targets. A fundamental shift in steel production methods is necessary to achieve this transformation.

[0003] The first step in steelmaking is the reduction of the Fe ore (which is an oxide) to elemental Fe. In a traditional process, the reduction step is carried out in a blast furnace (BF) where carbon monoxide (CO) derived from coal is the most commonly used reducing agent. The reduction of the Fe ore is accompanied by the production of CO2 with emissions of up to 2 tons C02 / ton steel. Alternative processes, such as direct reduced iron (DRI), use syngas, which is a mixture of CO and H2, as the reducingAtty Docket No. 395 / 46 PCT agent and thus can reduce the CO2 footprint by up to 50% or even 100% if zero-carbon H2 is used. However, high-grade ores that contain >67wt% Fe are required for a DRI process because operating temperatures (800-1 ,000°C) are much lower than the melting point of Fe (1 ,538°C) and impurities cannot be easily removed as slag as in a BF-based process.

[0004] Limited quantities of high-grade ores have restricted the use of DRI to only a small percentage of the world’s steel production. Technologies that increase the availability of high-grade ores for the DRI process can be a key strategy to decarbonize steel production.

[0005] U.S. Patent No. 12,006,212 describes a method for producing iron oxide as magnetite through processing olivine and / or pyroxene-rich iron ores, typically found in mafic and ultramafic igneous rocks, through sequential carbonation and serpentinization / hydration reactions. Process improvements to the process described in U.S. Patent No. 12,006,212 are desired to increase efficiency, selectivity, and product quality while also reducing operating and capital costs.SUMMARY OF THE DISCLOSURE

[0006] In a first aspect of the invention, a method for extracting an iron oxide composition from a mafic and / or ultramafic rock comprises introducing a mafic and / or ultramafic rock and CO2 to a first reactor, reacting the mafic and / or ultramafic rock and CO2 in the first reactor thereby yielding a first reactor effluent comprising one or more iron silicate compounds and one or more products of the reaction in the first reactor; separating the first reactor effluent into a first stream comprising the one or more iron silicate compounds and a second stream comprising the one or more reaction products of the first reactor; introducing the first stream and water to a second reactor, and reacting the first stream and water in the second reactor thereby yielding a second reactor effluent comprising one or more iron oxide compounds, water, and silica.

[0007] In a second aspect of the invention, a method for separating one or more ironsilicate compounds from a mineralization reaction effluent before the mineralization reaction effluent is introduced to a serpentinization reaction comprises providing theAtty Docket No. 395 / 46 PCT mineralization reaction effluent, introducing the mineralization reaction effluent to one or more separators whereby a stream comprising one or more iron-silicate compounds is obtained from the mineralization reaction effluent, and introducing the stream comprising the one or more iron silicate compounds to the serpentinization reaction.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The foregoing aspects and other features of the disclosure are explained in the following description, taken in connection with the accompanying drawings, wherein:

[0009] FIG. 1 is a block process flow diagram of the process described herein.

[0010] FIG. 2 is a schematic flow diagram illustrating a first exemplary arrangement (Scenario 1 ).

[0011] FIG. 3 is a schematic flow diagram illustrating a second exemplary arrangement (Scenario 2).

[0012] FIG. 4 is a schematic flow diagram illustrating a third exemplary arrangement (Scenario 3).

[0013] FIG. 5 is a bar chart showing the total dry weight recovered from froth (concentrate) and pulp (tailings) fractions and the amount of each mineral present in each phase on a dry weight basis for Example 1 .

[0014] FIG. 6 is a bar chart showing the total dry weight recovered from froth (concentrate) and pulp (tailings) fractions and the amount of each mineral present in each phase on a dry weight basis for Example 2.

[0015] FIG. 7 is a bar chart showing the total dry weight recovered from froth and pulp (tailings) fractions and the amount of each mineral present in each phase on a dry weight basis for Example 3.

[0016] FIG. 8 is a bar chart showing the total dry weight recovered from froth (concentrate) and pulp (tailings) fractions and the amount of each mineral present in each phase on a dry weight basis for Example 4.Atty Docket No. 395 / 46 PCTDETAILED DESCRIPTION

[0017] To promote an understanding of the principles of the present disclosure, reference will now be made to preferred embodiments, and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alteration and further modifications of the disclosure as illustrated herein, being contemplated as would normally occur to one skilled in the art to which the disclosure relates.

[0018] Described herein is a process to upgrade iron-containing minerals obtained from mafic or ultramafic rock to high-grade iron (Fe) containing minerals. Exemplary mafic or ultramafic rocks include gabbro or basalt, which are rich in iron silicate- containing minerals, such as pyroxene or olivine. The process comprises two reaction steps and produces magnetite (FesO4) and other valuable byproducts, such as magnesium carbonate (MgCOa), hydrogen (H2), and silica (SiCk), from olivine. The process includes one or more separation steps between the two reaction steps to increase process efficiency, product purity, and yield, thereby enhancing economic viability.

[0019] Mafic rocks are igneous rocks that are high in magnesium and iron content. They comprise minerals like olivine, pyroxene, amphibole, and biotite. An ultramafic rock is an igneous rock with a very low silica content, typically composed of over 90% mafic minerals like olivine and pyroxene. Sources of mafic and ultramafic igneous rocks can be found in many locations and account for at least 10% of the Earth's continental crust.

[0020] In the process described herein, a source of olivine and / or other iron- containing minerals is introduced to a first reactor. For example, mafic and / or ultramafic rock can be introduced to a first reactor. In another example, rock containing a mixture of olivine and other minerals may be fed or introduced to the first reactor. Olivine is a solid solution comprising 82-92% forsterite and 8-18% fayalite. A person with ordinary skill in the art will understand that forsterite is also referred to as magnesium silicate (Mg2SiO4), and fayalite is also called iron silicate (Fe2SiO4).

[0021] The first reaction step is referred to as a mineralization step. In theAtty Docket No. 395 / 46 PCT mineralization step, the magnesium silicate portion of the olivine reacts with carbon dioxide introduced to the reactor to yield magnesium carbonate (MgCOs) and silica (SiCte). The other portions of the olivine, such as the iron silicate portion, do not react with the carbon dioxide. The mineralization reaction is shown in Equation 1 :

[0022] Mineralization: Mg2SiOi+ 2CO2-> 2MgCO2+ SiO2(Eq. 1 )

[0023] In the second reaction step, referred to as serpentinization, the iron silicate portion of the olivine is reacted with water to produce magnetite (FesO^, hydrogen (H2), and silica (SiCte). The serpentinization reaction is shown in Equation 2:

[0024] Serpentinization: SFe^SiO^ + 2H2O - ZFesO + 3SiO2 + 2H2 (Eq. 2)

[0025] After the first reaction step (i.e., the mineralization step) is completed, the effluent contains olivine components that were not reacted in the mineralization step. These unreacted components include portions of MgaSiCU that did not fully react with carbon dioxide and FeaSiCh, which does not react with carbon dioxide. MgCC , water, and SiCte may also be present in the first reaction effluent.

[0026] Since olivine contains only 8 to 18% FeaSiCU, the effluent from the mineralization reaction also contains a relatively small fraction of FeaSiCU. Accordingly, processing efficiencies can be realized by processing the effluent from the first reaction step to isolate the FeaSiCU before proceeding to the serpentinization reaction. Isolating the FeaSiCU prior to performing the serpentinization step enables using a reactor vessel that is smaller than would be needed for processing the entirety of the first reaction effluent and potentially avoids additional separation steps after the serpentinization reaction. Thus, separating an iron silicate-rich fraction from the mineralization reactor effluent can reduce the size of the serpentinization reactor.

[0027] The magnetite formed during the serpentinization reaction can be separated magnetically. The non-magnetic fraction can be combined with the effluent from the first reactor for further separation. This process allows unreacted iron silicate to be recycled back into the serpentinization reactor, enhancing overall process yields. Consequently, dividing the first reactor's effluent into distinct components offers multiple benefits.

[0028] In an embodiment, the claimed process is a method for extracting an ironAtty Docket No. 395 / 46 PCT oxide composition comprising a high percentage of iron (e.g., > 67wt% iron) from olivine. The method comprises introducing olivine and CO2 to a first reactor, reacting olivine and CO2 in the first reactor, thereby yielding a first reactor effluent comprising iron silicate and a product of the reaction in the first reactor, separating the first reactor effluent into a first stream comprising iron silicate and a second stream comprising the reaction product from the first reactor, introducing the first stream and water to a second reactor, and reacting the first stream and water in the second reactor thereby yielding a second reactor effluent comprising an iron oxide composition comprising > 67wt% iron.

[0029] A block flow diagram (BFD) of an embodiment of the process is provided in FIG. 1. In this embodiment, the first step in the process is the mineralization reaction. In the mineralization reaction, carbon dioxide interacts with magnesium in ores introduced to the reactor as a slurry (as shown in Eq. 1 ) to form MgCOa. The pH of the ore slurry can be adjusted to between 4 and 10 before it is fed into the mineralization reactor with compressed CO2, which may be recirculated and reintroduced to the mineralization reactor. Mg2SiO4 reacts with CO2 in the reactor according to the reaction shown in Eq. 1 , producing an effluent including Fe2SiC>4, MgCOs, and SiC>2. The effluent from the mineralization reactor is sent to one or more Stage 1 Separation froth flotation tanks where the Fe-rich phase comprising Fe2SiO4 is separated. The remainder (MgCOs and SiC ) is sent to one or more Stage 2 Separation froth flotation tanks to separate the two products from one another. The Fe2SiO4 stream from the Stage 1 Separation can be mixed with a pH-adjusting compound and sent to the serpentinization reactor. The pH-adjusting compound can be a sodium bicarbonate (NaHCOs) buffer solution, and the pH can be adjusted to between 8.5 and 10.5. The Fe2SiO4 can be hydrolyzed in the serpentinization reactor according to the reaction shown in Eq. 2.

[0030] After the serpentinization reaction, magnetic separation can be used to recover magnetite, while unreacted Fe2SiO4 and SiO2 can be returned to Stage 1 Separation for additional processing to improve product yields. H2 produced in the serpentinization reactor can be treated for use in various applications. Moreover, waterAtty Docket No. 395 / 46 PCT in slurry streams throughout the process can be separated from any of the process streams and recycled back into the process as one or more recycle streams. For example, water can be separated from slurry streams using commonly available particulate filters, such as sintered glass.

[0031] Feed Preparation

[0032] In the process described herein, ores comprising iron-containing minerals, such as olivine, are introduced to a reactor, and components of the minerals react with carbon dioxide in an acidic or basic environment. In embodiments, the ores can undergo preparation processes before being introduced to the first reactor. For example, the ores may be introduced into a crusher or grinder, where the ore is reduced to smaller size fractions. In embodiments, a washer may be used to clean the ore with water or a mildly acidic solution to remove contaminants and prepare it for the mineralization reaction. The crushed or ground rock can be passed through a sieve or separator that sorts it into pre-selected particle size ranges. In at least one embodiment, the comminuted rock has a powder-like consistency. The prepared rock can be fed into a first reactor or can be combined with water to form a slurry.

[0033] In one embodiment, water can be combined with crushed or ground rock to create a slurry before it is introduced into the first reactor. Performing the reaction in a slurry form can be advantageous because (1 ) water solvent allows the dissolution of gas-phase CO2 to form the more reactive bicarbonate anion (HCO3-), which enhances reaction kinetics, and (2) complete mixing is easier to achieve with a slurry compared to a dry powder. In at least one embodiment, the pH of the water mixed with the ground rock ranges from about 3.5 to about 6.5. Water within this pH range improves the reaction between carbon dioxide and the magnesium silicate mineral. In another embodiment, the pH of the water mixed with ground rock ranges from about 7.5 to about 10.5. The pH of the water can be adjusted using various pH-adjusting compounds, including, for example, hydrochloric acid (HCI), acetic acid (CH3COOH), sulfuric acid (H2SO4), sodium or potassium hydroxide (NaOH, KOH), or sodium or potassium carbonate or bicarbonate (Na2COs, K2CO3, NaHCOs, KHCO3). We note that a person skilled in the art will also recognize that pH adjustments can beAtty Docket No. 395 / 46 PCT performed using various other compounds.

[0034] Mineralization Reaction

[0035] The ore slurry, which contains olivine minerals, is introduced into the mineralization reactor along with compressed CO2. At least a portion of the Mg2SiC>4 component of the olivine is mineralized in the first reactor according to the reaction shown in Equation 1 , thereby producing MgCOs and SiC>2. Fe2SiO4 is also present in the reactor but as a non-reactive component of the olivine. Unreacted Mg2SiO4, CO2, and water are also present in the reactor.

[0036] During the first reaction step, the reactor operates at a temperature and pressure selected to facilitate the mineralization of Mg2SiO4. In some embodiments, the reactor is operated at a temperature between about 200-350°C and pressures ranging from approximately 50-100 bar. As the skilled person will understand, operating the reactor at higher pressures can enhance the mineralization reaction, and conversely, operating the reactor at lower pressures may reduce the reaction rate.

[0037] The reaction between carbon dioxide and Mg2SiC>4 produces magnesium carbonate (MgCO3) and silica (SiO2). The carbon dioxide is converted to a more environmentally friendly material that can be used as a raw material in applications such as concrete manufacture or stored in a landfill, ocean, lake, or other storage location, with stable lifetimes of over a thousand years. By reacting Mg2SiO4 with carbon dioxide under favorable temperature, pressure, and pH conditions, Mg2SiO4 can be converted into magnesium carbonate.

[0038] Stage 1 Separation

[0039] MgCC and SiO2 are present in the first reactor effluent. Unreacted Fe2SiC>4, Mg2SiO4, CO2, and water are also present in the first reactor effluent. The first reactor effluent is sent to Stage 1 Separation, which is a series of one or more separators that produces a Fe-rich stream comprising Fe2SiC>4, which is fed to the serpentinization reactor. Stage 1 Separation also produces a stream comprising MgCOs, SiC>2, water, and additional components (e.g., unreacted ore components) that are sent to Stage 2 Separation.

[0040] Stage 1 Separation can include one or more froth flotation tanks. FrothAtty Docket No. 395 / 46 PCT flotation is a method for physically separating particles based on differences in the ability of air bubbles to selectively adhere to specific mineral surfaces in a mineral / water slurry. The particles with attached air bubbles are carried to the surface and removed (often via skimming), while the completely wet particles stay in the liquid phase. In froth flotation, chemical treatments can selectively modify mineral surfaces to have the necessary properties to be adhered to air bubbles and thus separated. In the process described herein, the one or more froth flotation tanks separate Fe- containing components using highly selective chemicals for chemisorbing onto Fe sites, including, for example, fatty acids and fatty amines. Exemplary fatty acid collectors include, for example, one or more of oleic acid, lauric acid, linoleic acid, rosin acid, unsaponifiable acid, and their sodium salts.

[0041] In a froth flotation tank where fatty acids are used as collectors, the fatty acids adsorb on the surfaces of the iron oxide components through chemical bonding. For example, oleic acid and lauric acid chemisorb on iron oxide components. In addition to chemisorption, fatty acids can adsorb onto mineral surfaces through surface precipitation.

[0042] The iron oxide components with adhered fatty acids are made relatively more hydrophobic such that as air or other gases are bubbled through the flotation tank, the hydrophobic particles attach to the bubbles and float to the surface as froth and are removed from the flotation tank. The stream recovered from the froth phase is called the flotation concentrate. The hydrophilic components in the flotation tank have much less tendency to attach to air bubbles and thus remain in suspension. The components that do not float into the froth are called the flotation tailings or flotation tails. In embodiments, in Stage 1 Separation, the tails comprise MgCOs and SiOa.

[0043] Fatty acid collectors can be used for anionic froth flotation of Fe minerals under alkaline pH conditions. In some embodiments, the Stage 1 Separation comprises one or more froth flotation separators operated at a pH of from about 7 to about 10, the concentration of the fatty acid collectors can range from about 1 mM to about 10 mM, and the slurry solids content can range from about 2% to about 25%.

[0044] Amine collectors, such as dodecyl amine and its hydrochloride salt, can beAtty Docket No. 395 / 46 PCT used for anionic froth flotation of Fe minerals under acidic conditions. In some embodiments, one or more Stage 1 froth flotation separators are operated at a pH of from about 4 to about 7, the concentration of amine collectors ranges from about 1 mM to about 10 mM, and the slurry solids content ranges from about 2% to about 25%.

[0045] In exemplary embodiments, Stage 1 Separation can comprise two froth flotation tanks operating in series. A slurry comprising finely ground components (for example, FeaSiC MgCOs, and SiO ) mixed with water is introduced to the first flotation tank. An impeller or similar device within the tank creates vigorous mixing to generate air bubbles and facilitate particle-bubble collisions. Collectors (hydrophobic chemicals) are added to selectively coat the desired mineral particles (here FeaSiO), making them more likely to attach to air bubbles. As described above, the collectors for FeaSiC can include fatty acid collectors or amine collectors. If fatty acid collectors are used, typically, the pH of the flotation tank will be between about 7 and 10. If amine collectors are used, typically, the pH of the flotation tank will be between about 4 and 7. In embodiments, the first flotation tank and the second flotation tank use the same type of collectors and, therefore, operate at about the same pH.

[0046] As the skilled person will understand, it is possible to operate the first flotation tank with one type of collector at one pH range and operate the second flotation tank with a different type of collector at a different pH range. If this is the case, a pH-adjusting step can be used between the first and second flotation tanks to change the pH as needed.

[0047] The process can be tailored to selectively target specific minerals within the ore by selecting chemical reagents. For example, fatty acid or amine collectors can be used to target Fe2SiO4. In embodiments described herein, Fe2SiO4particles rise to the top of the flotation tank, forming a froth layer that is removed using a launder or skimming mechanism. The froth layer removed from the tank can be referred to as the concentrate. Meanwhile, heavier, non-floating particles, such as MgCO3and SiO2, settle at the bottom of the tank and are discharged as tailings.

[0048] Different operating arrangements are available when two flotation tanks are operated in series. FIG. 2 is a schematic flow diagram illustrating a first exemplaryAtty Docket No. 395 / 46 PCT arrangement (Scenario 1 ). In Scenario 1 , the tailings from the first flotation tank are introduced to a second flotation tank.

[0049] FIG. 3 is a schematic flow diagram illustrating a second exemplary arrangement (Scenario 2). In Scenario 2, the concentrate from the first flotation tank is introduced to a second flotation tank. Then, the tailings from Tank 1 are combined with those from Tank 2.

[0050] FIG. 4 is a schematic flow diagram illustrating a third exemplary arrangement (Scenario 3). In Scenario 3, the concentrate from the first flotation tank is introduced to a second flotation tank. Then, the tailings from Tank 2 are recycled for reintroduction to Tank 1 .

[0051] A person of ordinary skill in the art will recognize that flotation tanks arranged in series can be operated using various processing schemes to achieve specific outcomes. For instance, the tanks can be configured to optimize the recovery or yield of Fe2SiO4alternatively, to prioritize the recovery of MgCO3and SiO2.

[0052] For example, in embodiments, the Stage 1 separation may include multiple froth flotation tanks. While it is not necessary to perform the Stage 1 Separation in multiple steps, in some embodiments, doing so increases the Fe2SiO4 ratio in the concentrate, and in some embodiments, doing so improves the overall recovery of Fe2SiO4.

[0053] In other embodiments, the froth flotation tailings from an individual Stage 1 froth flotation tank may be recycled to the inlet of the Stage 1 separation. The recycle stream may comprise a slurry rich in Fe2SiC>4. While it is not necessary to recycle the tailings from an individual Stage 1 froth flotation tank to the inlet of the separation process, doing so in some embodiments improves the overall recovery of Fe2SiC>4 for subsequent conversion to magnetite in the serpentinization reactor, thus rendering the process more economically feasible.

[0054] In embodiments, the Fe2SiO4 yield after Stage 1 Separation is > 80%, for example, > 90%; and the Fe recovery after the first stage separator is > 80%, for example, > 90%.

[0055] Stage 2 SeparationAtty Docket No. 395 / 46 PCT

[0056] The tailings from Stage 1 Separation are sent to a Stage 2 separation. In embodiments, the Stage 2 separation comprises one or more froth flotation tanks in which SiO2 is separated from MgCOs and MgaSiCk using an amine collector. An exemplary amine collector can include dodecylamine, oleylamine, and their corresponding hydrochloride salts. In embodiments, water from the Stage 2 separation process can be separated from the slurry with a particulate filter, for example, a sintered glass particulate filter. The separated water can be recycled back to the overall process at various points.

[0057] In embodiments, the one or more Stage 2 froth flotation tanks are operated at a pH of from about 4 to about 7, the concentration of the amine collectors ranges from about 1 mM to about 10 mM, and the slurry solids content ranges from about 2% to about 25%.

[0058] In exemplary embodiments, Stage 2 Separation can comprise two froth flotation tanks operating in series. While performing the Stage 2 separation in multiple steps is not required, in some embodiments, doing so increases product purity and the overall product yield.

[0059] In this embodiment of Stage 2 separation, a slurry comprising finely ground components (for example, MgCOs and SiOa) mixed with water is introduced to the first flotation tank. An impeller or similar device within the tank creates vigorous mixing to generate air bubbles and facilitate particle-bubble collisions. Collectors (hydrophobic chemicals) are added to selectively coat the desired mineral particles (here, SiOa), making them more likely to attach to air bubbles. The collectors for SiCk can include amine collectors. If amine collectors are used, typically, the pH of the flotation tank will be between about 4 and 7. In embodiments, the first flotation tank and the second flotation tank use the same type of collectors and, therefore, operate at about the same pH.

[0060] In embodiments, the SiOs yield after Stage 2 separation is > 80%, for example, > 90%, and the recovery of silica is at least 90%, for example at least 95% recovery of silica. In embodiments, the MgCOs yield after Stage 2 separation is > 80%, for example, > 90%, and the recovery of MgCOs is at least 80%, for example at leastAtty Docket No. 395 / 46 PCT90% recovery of MgCOs.

[0061] Serpentinization Reaction

[0062] Fe2SiO4 from Stage 1 separation is introduced to the serpentinization reactor. The reaction that takes place in the serpentinization reactor is illustrated in Equation 2. In embodiments, FeaSiC is mixed with an aqueous buffer solution to adjust the pH to between 8.5 and 10.5 before being introduced to the serpentinization reactor, in which Fe2SiO4 is hydrolyzed to produce magnetite. Exemplary aqueous buffer solutions include sodium or potassium bicarbonate, sodium or potassium acetate, or sodium or potassium bicarbonate. In some embodiments, the reactor is operated at a temperature between about 200-350°C and pressures ranging from approximately 1 -100 bar. As the skilled person will understand, operating the reactor at higher pressures can enhance the serpentinization reaction, and conversely, operating the reactor at lower pressures may reduce the reaction rate.

[0063] Separation After the Serpentinization Reaction

[0064] The reactor effluent from the serpentinization reactor contains SiC>2, magnetite, water, and unreacted Fe2SiO4. The effluent components can be separated magnetically using a wet drum separator. Other suitable separator types are known and can be selectively used by a person having ordinary skill in the art. Magnetite can be readily separated from other components in the reactor effluent using a magnetic separator. The other components can be recycled back to various stages of the overall process as suitable. Furthermore, a skilled person will understand that filtration devices can be incorporated into the process as needed, based on how recycled streams are reintroduced into the system.

[0065] For example, in some embodiments, a stream comprising the Fe2SiO4-rich slurry that remains after magnetic separation can be recycled back to Stage 1 separation to recover some of the unreacted Fe2SiO4. In embodiments, the magnetite stream resulting from the magnetic separation comprises > 80% magnetite, for example, > 90% magnetite, and < 10% impurities, for example, < 7% impurities.

[0066] While it is not necessary to separate the iron-containing compounds from the effluent of the first reactor before introducing them to the second reactor,Atty Docket No. 395 / 46 PCT implementing such a separation step improves yields. By isolating Fe-containing species between the first and second reactors, the production of both magnetite and silica is enhanced. Additionally, this step reduces capital and operating costs, as it allows for the use of a smaller serpentinization reactor and decreases the demand for water and base.

[0067] Moreover, with fewer contaminants present during the magnetic separation process, the magnetite produced is less likely to contain impurities. Since the market value of magnetite is highly dependent on its purity, the separation process in Stage 1 increases the economic feasibility of the overall operation.

[0068] Recycling the Fe2SiO4-rich slurry exiting the magnetic separator by combining it with the first reactor effluent before the Stage 1 separation is not strictly necessary but significantly enhances the overall conversion of Fe2SiO4to magnetite. Achieving complete serpentinization of Fe2SiO4(100% conversion) in a single pass through the second reactor is unlikely. Recycling the unreacted Fe2SiO4establishes a multi-pass conversion process, thereby improving product yields.

[0069] The articles “a” and “an” are used herein to refer to one or to more than one (i.e. at least one) of the grammatical object of the article. By way of example, “a nanostructured silicon carbon composition material” means at least one nanostructured silicon carbon composition material and can include more than one nanostructured silicon carbon composition material.

[0070] Throughout the specification, the terms "about” and / or "approximately" may be used in conjunction with numerical values and / or ranges. The term "about" is understood to mean those values near to a recited value. For example, "about 40 [units]" may mean within + / - 25% of 40 (e.g., from 30 to 50), within + / - 20%, + / - 15%, + / - 10%, + / - 9%, + / -8 %, + / - 7%, + / - 6%, + / - 5%, + / - 4%, + / - 3%, +1-2 %, + / - 1 %, less than + / - 1 %, or any other value or range of values therein or there below. Furthermore, the phrases "less than about [a value]" or "greater than about [a value]" should be understood in view of the definition of the term "about" provided herein. The terms "about" and "approximately" may be used interchangeably.

[0071] Throughout the specification, numerical ranges are provided for certainAtty Docket No. 395 / 46 PCT quantities. It is to be understood that these ranges comprise all subranges therein. Thus, the range "from 50 to 80" includes all possible ranges therein (e.g., 51 -79, 52- 78, 53-77, 54-76, 55-75, 60-70, etc.). Furthermore, all values within a given range may be an endpoint for the range encompassed thereby (e.g., the range 50-80 includes the ranges with endpoints such as 55-80, 50-75, etc.).

[0072] As used herein, the verb "comprise" as is used in this description and in the claims and its conjugations are used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded.

[0073] Throughout the specification the word "comprising," or variations such as "comprises" or "comprising," will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The present disclosure may suitably "comprise", "consist of", or "consist essentially of", the steps, elements, and / or reagents described in the claims.

[0074] It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as "solely", "only" and the like in connection with the recitation of claim elements, or the use of a "negative" limitation.

[0075] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Preferred methods, devices, and materials are described, although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. All references cited herein are incorporated by reference in their entirety.

[0076] The following Examples further illustrate the disclosure and are not intended to limit the scope. It is to be understood that this disclosure is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.Atty Docket No. 395 / 46 PCTEXAMPLES

[0077] Example 1. Stage 1 froth flotation using lauric acid as a fatty acid collector

[0078] In an exemplary experiment, a mixture of 7.0 g magnesium carbonate, 1 .5 g iron silicate, and 1.5 g silica was prepared to represent the effluent from the mineralization reactor. 50 ml of a solution of lauric acid (5 mM) in aqueous potassium carbonate (pH 10.0) was added to the mixture to create a slurry. The slurry was then poured into a flotation cell, and nitrogen was used to froth the cell. After the froth phase reached a stable height, the froth phase and tailings were separated. After filtering and drying, the concentrate from the froth phase and the pulp from the tailings were weighed and characterized by ICP-AES. FIG. 5 is a bar chart showing the total dry weight recovered from froth (concentrate) and pulp (tailings) fractions and the amount of each mineral present in each phase on a dry weight basis. In this example, the Fe recovery in the froth was 92%, and the Mg recovery in the pulp was 40%.

[0079] Example 2. Stage 1 froth flotation using laurylamine as an amine collector

[0080] In a second exemplary experiment, a mixture of 7.0 g magnesium carbonate, 1 .5 g iron silicate, and 1 .5 g silica was prepared to represent the effluent from the mineralization reactor. A slurry with 50 ml of laurylamine (5 mM) solution in aqueous acetic acid (pH 4.0) was then prepared. The slurry was then poured into a flotation cell, and nitrogen was used to froth the cell.

[0081] After the froth phase reached a stable height, the froth phase and tailings were separated. After filtering and drying, the froth and pulp fractions were weighed and characterized by ICP-AES. FIG. 6 is a bar chart showing the total dry weight recovered from froth (concentrate) and pulp (tailings) fractions and the amount of each mineral present in each phase on a dry weight basis. In this example, the Fe recovery in the froth was 96% and the Mg recovery in the pulp was 48%.

[0082] Example 3. Stage 1 froth flotation using amine collectors and higherAtty Docket No. 395 / 46 PCT liquid :solid ratio

[0083] To demonstrate the effect of liquid:solid ratios, an exemplary experiment was conducted using a mixture of 7.0 g magnesium carbonate, 1 .5 g iron silicate, and 1.5 g silica that represents the effluent from the mineralization reactor. A slurry using 200 ml of a solution of laurylamine (5 mM) in aqueous acetic acid (pH 4.0) was then prepared. The amount of liquid in the slurry in this example was 200 ml, and the amount of liquid in the previous two examples was 50 ml. Thus, the slurry in this example has a higher liquid-to-solid ratio than the slurries in Examples 1 and 2.

[0084] The slurry was then poured into a flotation cell and frothed with nitrogen. After the froth phase reached a stable height, the tailings and the froth phase were separated. Both fractions were then filtered, rinsed with water, dried, and characterized both gravimetrically and by ICP-AES.

[0085] FIG. 7 is a bar chart showing the total dry weight recovered from froth and pulp (tailings) fractions and the amount of each mineral present in each phase on a dry weight basis. In this example, the Fe recovery in the froth was 70% and the Mg recovery in the pulp was 70%. In Example 3, which is the example with a higher liquid :solid ratio relative to Examples 1 and 2, the recovery of Fe in the concentrate was relatively lower, and the recovery of Mg in the tailings was relatively higher.

[0086] Example 4. Stage 2 froth flotation using amine collectors

[0087] In another exemplary experiment, a mixture of 8.0 g magnesium carbonate and 2.0 g silica was prepared to represent the feed to Stage 2. A slurry was prepared using 100 ml of a solution of laurylamine (5 mM) in aqueous acetic acid (pH 4.0). The slurry was then poured into a flotation cell, and nitrogen generated a froth. After the froth phase reached a stable height, the tailings and froth phase were separated. Both fractions were then filtered, rinsed with water, dried, and characterized both gravimetrically and by ICP-AES. FIG. 8 is a bar chart showing the total dry weight recovered from froth (concentrate) and pulp (tailings) fractions and the amount of each mineral present in each phase on a dry weight basis. In this example, the Si recovery in the froth was 66%, and the Mg recovery in the pulp was 61 %.

[0088] Any patents or publications mentioned in this specification are indicative ofAtty Docket No. 395 / 46 PCT the levels of those skilled in the art to which the invention pertains. These patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference.

Claims

Atty Docket No. 395 / 46 PCTCLAIMSThe invention claimed is:1 . A method for extracting an iron oxide composition from a mafic and / or ultramafic rock, the method comprising:- introducing a mafic and / or ultramafic rock and CO2 to a first reactor;- reacting the mafic and / or ultramafic rock and CO2 in the first reactor, thereby yielding a first reactor effluent comprising one or more iron silicate compounds and one or more products of the reaction in the first reactor;- separating the first reactor effluent into a first stream comprising the one or more iron silicate compounds and a second stream comprising the one or more reaction products of the first reactor;- introducing the first stream and water to a second reactor; and- reacting the first stream and water in the second reactor, thereby yielding a second reactor effluent comprising one or more iron oxide compounds, water, and silica.

2. The method of claim 1 , further comprising recycling unreacted CO2 from the first reactor back to the first reactor.

3. The method of claim 1 , wherein the second reactor effluent comprises one or more unreacted iron silicate compounds.

4. The method of claim 3, further comprising separating the second reactor effluent into a magnetic fraction and a non-magnetic fraction.

5. The method of claim 4, wherein the magnetic fraction comprises magnetic iron oxides and the non-magnetic fraction comprises water, silica, and unreacted iron silicate compounds.

6. The method of claim 5, wherein the non-magnetic fraction from the second reactor effluent is introduced to the first reactor effluent before the first reactor effluent is separated.Atty Docket No. 395 / 46 PCT7. The method of claim 1 , wherein the product in the first reactor effluent comprises magnesium carbonate, silica, or a mixture thereof.

8. The method of claim 1 , wherein the first reactor effluent further comprises unreacted rock.

9. The method of claim 1 , wherein separating the first reactor effluent comprises one or more froth flotation devices.

10. The method of claim 9, wherein the one or more froth flotation devices comprise direct anionic flotation comprising an iron-component collector.

11. The method of claim 10, wherein the iron-component collector comprises one or more fatty acid or amine collectors.

12. The method of claim 10, wherein the iron-component collector comprises oleic acid, lauric acid, linoleic acid, rosin acid, unsaponifiable acid, and sodium salts thereof, or dodecylamine, oleylamine, and hydrochloride salts thereof.

13. The method of claim 1 , further comprising separating the second stream into a silica-containing stream and a magnesium carbonate-containing stream.

14. The method of claim 13, wherein separating the second stream comprises one or more froth flotation devices.

15. The method of claim 13, wherein the one or more froth flotation devices comprise direct anionic flotation comprising a magnesium-component collector.

16. The method of claim 15, wherein the magnesium-component collector comprises dodecylamine, oleylamine, and hydrochloride salts thereof.

17. The method of claim 13, further comprising filtering the magnesium carbonate- containing stream and recycling at least a portion of the filtrate to the first reactor.

18. The method of claim 1 , further comprising combining a pH-adjusting compound with the first stream and water before they are introduced to the second reactor.

19. The method of claim 18, wherein the pH-adjusting compound comprises sodium or potassium bicarbonate, sodium or potassium carbonate, sodium or potassium acetate, or mixtures thereof.Atty Docket No. 395 / 46 PCT20. A method for separating one or more iron-silicate compounds from a mineralization reaction effluent before the mineralization reaction effluent is introduced to a serpentinization reaction, the method comprising:- providing the mineralization reaction effluent;- introducing the mineralization reaction effluent to one or more separators whereby a stream comprising one or more iron-silicate-compounds is obtained from the mineralization reaction effluent; and- introducing the stream comprising one or more iron silicate compounds to the serpentinization reaction.21 . The method of claim 20, further comprising combining the mineralization reaction effluent with a non-magnetic fraction of an effluent from the serpentinization reaction prior to introducing the mineralization reaction effluent to the one or more separators.

22. The method of claim 20, wherein separating the iron-silicate containing stream from the mineralization reaction effluent comprises a froth flotation process.

23. The method of claim 22, wherein the pH during the froth flotation process ranges from about 4 to about 10.

24. The method of claim 22, wherein a solids content of a slurry in the froth flotation process ranges from about 2 to about 25%.

25. The method of claim 22, wherein the froth flotation comprises direct anionic or cationic flotation comprising an iron-component collector.

26. The method of claim 25, wherein the iron-component collector has a concentration of 1 to 10 mM.

27. The method of claim 25, wherein the iron-component collector comprises one or more fatty acid collectors or amine collectors.

28. The method of claim 25, wherein the iron-component collector comprises oleic acid, lauric acid, linoleic acid, rosin acid, and sodium salts thereof, or dodecylamine, oleylamine, and hydrochloride salts thereof.

29. The method of claim 20, further comprising a second separation stepAtty Docket No. 395 / 46 PCT comprising separating the stream remaining after the iron-silicate-containing stream is separated from the mineralization reaction effluent into a silicon oxidecontaining stream and a magnesium carbonate-containing stream.

30. The method of claim 29, wherein the second separation step comprises a froth flotation process.

31. The method of claim 30, wherein the pH during the froth flotation process ranges from about 7 to about 10.

32. The method of claim 30, wherein a solids content of a slurry in the froth flotation process ranges from about 2 to about 25%.

33. The method of claim 30, wherein the froth flotation comprises direct anionic flotation comprising a magnesium-component collector.

34. The method of claim 33, wherein the magnesium-component collector comprises dodecylamine or oleylamine.

35. The method of claim 33, wherein the magnesium-component collector has a concentration of 1 to 10 mM.

36. The method of claim 29, further comprising filtering the magnesium carbonate- containing stream and recycling at least a portion of the filtrate to the first reactor.

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