Methods for material recycling and a co2 supply chain

Abstract

Synthesis of multi-cation oxide utilizing recycled carbonate-containing material. Also provided is a method of capturing carbon dioxide and releasing it as needed.

Description

METHODS FOR MATERIAL RECYCLING AND A CO2 SUPPLY CHAIN CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No.63 / 608,699, filed December 11, 2023. The disclosure set forth in the reference application is incorporated herein by reference in its entirety. STATEMENT REGARDING FEDERAL FUNDING

[0002] This invention was made with government support under DE-AR0001399 awarded by the U.S. Department of Energy, and N00014-12-0524 awarded by the U.S Department of Defense Office of Naval Research. The government has certain rights in the invention. FIELD OF THE INVENTION

[0003] The present invention is directed to a method for recycling and refining multi- cation oxide compounds. A related method provides an efficient approach for carbon dioxide capturing, storing, transporting, and dispensing carbon dioxide. BACKGROUND

[0004] Traditional material synthesis techniques have many inefficiencies and negative consequences (e.g., solid-state, sol-gel, mechano-chemical, hydrothermal). Hydrothermal chemistries have been studied and manipulated over several decades to enable crystal growth technologies and kinetically drive chemical reactions. Current hydrothermal synthesis techniques, such as liquid-phase hydrothermal synthesis (LPH), vapor-phase hydrothermal synthesis (VPH), supercritical water synthesis (SCW), and vapor-assisted solid-state synthesis (VS), also suffer from a variety of disadvantages.

[0005] In traditional hydrothermal systems such as “liquid-phase hydrothermal” synthesis (LPH), the liquid water is used as the solvent and reaction medium, and any reactants are always dispersed or submerged. Additives such as mineralizers are typically added to the water to enhance its solvation properties. The water liquid-vapor equilibrium phase boundary governs the pressure within the hydrothermal autoclave. This means that the liquid and gaseous water always coexist. However, certain products, such as CaSiO3(calcium silicate), cannot be synthesized using LPH reactions.

[0006] Like LPH, “vapor-phase hydrothermal” synthesis (VPH) is also conducted below 374oC and 3200 psi (22 MPa). Once again, this means that both liquid and gaseous water are in equilibrium throughout the reaction progression. The difference, however, is in the precursor configuration. The precursors are suspended above the liquid phase and solely interact with water vapor or liquid water that condenses on a reactor surface and falls onto the powder mixture. This configuration allows precursor interactions with a gaseous atmosphere but is limited in versatility since an arbitrary pressure cannot be maintained constant over various temperatures. Instead, the pressure is fixed by Gibb’s phase rule. The pressure can remain constant if a “bleed-out” valve is implemented. Still, liquid-vapor equilibrium will no longer be maintained, which could create a need for water replenishment and significant variations in pressure.

[0007] Supercritical water synthesis (SCW), which reacts with precursors at supercritical temperature and pressure, typically requires thick-walled corrosion-resistant autoclaves. The cost of this vessel increases dramatically when approaching or exceeding the supercritical limit of water due to the corrosive properties of supercritical water.

[0008] Other methods, such as vapor-assisted solid-state reactions, are kinetically controlled rather than thermodynamically controlled. Further, these vapor-assisted reactions operate under equilibrium-controlled reaction conditions (pressure is fixed at 1 atm) and, therefore, are limited in versatility due to Gibb’s phase rule.

[0009] Thus, a need exists for a versatile, thermodynamically controlled, low- temperature method to produce inorganic oxides from readily available materials. Such a method will also minimize undesirable environmental impact. SUMMARY OF THE DISCLOSURE

[0010] The present invention meets such a need. Described herein are methods of recycling multi-cation oxide, hydroxide, carbonate, hydroxy carbonate inorganic compounds through hydrothermal vapor synthesis (HVS), such as HVS methods disclosed by US Patent No.11,332,847, the disclosure of which is incorporated herein by reference. The methods apply to recycling and refining materials, including hydraulic and carbonate cement comprising calcium silicates, calcium carbonate, calcium silicate hydrates, and any additional materials that do not participate in the HVS reaction. Other materials include but are not limited to advanced materials such as dielectric materials (e.g., barium titanate), battery materials (e.g.,lithium manganese oxide, lithium cobalt oxide), optical materials (e.g., lutecium silicate), magnetic materials (e.g., strontium ferrite), and superconductors (yttrium barium cuprate).

[0011] According to one aspect of the invention, a method is provided for recovering from a waste product a material containing an inorganic single or multi-cation compound, or a blend of single or multi-component compounds, wherein the method exposes the waste product to CO2in the presence of water with heating to obtain a carbonate mixture, and then exposes the carbonate mixture to an unsaturated water vapor with a partial pressure of between about 2 atm and about 80 atm at a temperature of between about 300°C and about 1000°C for a sufficient period of time to recover and recycle said material. In one embodiment, the material includes a product that was originally formed by reacting an alkaline earth or iron, manganese, or lithium carbonate with a scrap single- or scrap multi-cation non-alkaline earth oxide.

[0012] According to one embodiment, a method for recycling a multi-component oxide waste product by taking the following 3 steps: (1) Chose a multicomponent oxide material synthesized by reacting a single- or multi-cation carbonate element or with a single- or multi- cation non-alkaline earth oxide to form said multicomponent oxide. (2) Expose the multicomponent oxide waste product to CO2vapor in the presence of water with or without heating to obtain a multi-phase mixture either by (a) single- or multi-cation carbonates blended with (b) a single or multi-cation oxide or solely a mixture of 1 or more metal carbonates having at least 1 cation in each carbonate phase (3) De-carbonate the mixture by exposure to an unsaturated water vapor using a partial pressure of between about 1.01 atm and about 80 atm at a temperature of between about 300°C and about 1000°C for a sufficient time to recover the multicomponent oxide as a recycled material. A recycled material is one whose chemistry in the initial state as waste is the same multicomponent oxide as the one formed after the above three steps are performed. In another embodiment, the waste multicomponent oxide is upcycled. Upcycling is a situation where the waste multicomponent oxide differs from the multicomponent oxide formed after exposure to water vapor and heat, as mentioned above. For example, a mixture of various calcium silicate hydrates and calcium hydroxide could upcycle to form Ca5Si2O9•H2O. In some embodiments, the carbonation step (step 2) is unnecessary. The initial multicomponent oxide is upcycled to create a new multicomponent oxide by exposure to unsaturated water vapor with a partial pressure between about 1.01 atm and about 80 atm at a temperature of between about 300°C and about 1000°C for a sufficient time to recover and upcycle the material. Recovered materials include, but are not limited to, CaSiO3,Ca2SiO4, Ca3SiO5, Mg2SiO4, (Mg,Ca)SiO3, Fe2SiO4, Mn2SiO4, MgSiO3, FeSiO3, LiMn2O4, BaTiO3, CaTiO3, (Ba,Ca)TiO3, PbTiO3, PbZrO3, Pb(Zr,Ti)O3, FeTiO3, LiCoO2, and Ca5Si2O9•H2O, and multiphasic mixtures of calcium silicate hydroxides, calcium silicate hydrates, magnesium silicate hydroxides, and magnesium silicate hydrates, etc. The recovered materials may include one or more phases from Figures 6, 7, or 8.

[0013] In step 2, elements that form metal carbonates, also termed “carbonates,” cover nearly all of the elements from the periodic table, including alkali, alkaline earth, main group transition metal, rare earth, and actinide elements. Carbonates can have multiple cations and non-carbonate anions, such as, but not limited to, OH-, Cl-, and SO4-2. Carbonates can be amorphous, crystalline, or a mixture of both. Carbonates can also be comprised of multiple carbonate phases, whether they are polymorphic forms such as but not limited to aragonite, vaterite, or calcite or phases that have differences in cation chemistry such as, but not limited to MgCO3, CaCO3, or (Fe, Mn)CO3. Elements that remain as stable oxides at a CO2partial pressure of 1 atm or less in the absence of solution complexing agents are far scarcer, which include main group and transition metal elements, such as but not limited to B, Ga, Si, Ti, Ta, and Nb. The term “multicomponent oxides” or the term “oxide” can be a metal-oxide, -hydrous oxide, -hydroxide, or -hydrates; the “oxide” can be crystalline, amorphous, or a mixture of those mentioned above. Also, multiple metal cations can comprise the “oxide.” The “oxide” can also be multi-phasic in crystal structure, and the cations comprising each phase can be the same or different.

[0014] The recycling treatment method generally includes (a) subjecting a waste product containing a material originally formed by an alkaline earth carbonate with a single- or multi-cation non-alkaline earth oxide to HVS. The oxides may comprise oxide, hydroxide, carbonate, hydroxy-carbonate, and various adsorbed species. For example, a waste product containing a material formed from an alkaline earth carbonate of M and a non-alkaline earth oxide of A is exposed to heated unsaturated water vapor with a partial pressure between about 1.01 atm and about 80 atm in a reaction vessel, wherein the oxide of A is an oxide that is thermodynamically favored to react with the carbonate of M. These oxides may comprise any metal or metalloid-oxide, hydroxide, -carbonate, or -hydroxy-carbonate. More broadly, these oxides may also comprise various multi-cation oxide, hydroxide, and carbonate systems. For example, these oxides may comprise Fe2O3, Fe3O4, SiO2, TiO2, MnO, and CoO.

[0015] In another aspect of the invention, the oxides may comprise various calcium silicate hydrates.

[0016] The method continues by (b) heating the reaction vessel to a temperature between about 300°C and about 500°C, up to 1000oC for a sufficient period to recover and recycle the material.

[0017] The unsaturated water vapor can be generated by heating the reaction vessel filled with a predetermined amount of water. Alternatively, a stream of water vapor can be introduced to the preheated, partially pre-heated, or unheated vessel. Alternatively, the water vapor can be added as a hydroxide salt, for example, calcium hydroxide, where the hydroxide salt decomposes to release the appropriate amount of water as water vapor. Alternatively, a mixture using the methods above for adding water vapor can be utilized. The heating of the reaction system can be sustained with any energy source. In some embodiments, the heat is provided by a molten salt solution that is heated, for example, by solar radiation or an electricity power source. In some embodiments, unsaturated water vapor can be introduced into the vessel to remove evolved gaseous species from the reaction atmosphere.

[0018] The recycled material is preferably comprised of or milled to an average particle size of less than 150 µm. In other embodiments, the recycled material may be monolithic, dense, and not in powder form.

[0019] A low-energy recycling process is thus provided that does not involve a melting step. The process makes concrete a recyclable material like steel and aluminum.

[0020] Another variant of the recycling invention recycles waste material mixtures containing species that can form carbonates (a.k.a., a carbonatable oxide or species). According to one embodiment, a method is provided for recovering a metal oxide, hydroxide, or silicate phase from a carbonated and / or hydrated waste product mixture, in which the carbonated mixture is exposed to unsaturated water vapor with a partial pressure of between about 1 atm and about 80 atm at a temperature of between about 100°C and about 1000°C for a sufficient period to recover and recycle said metal oxide, hydroxide or silicate phase from the carbonated mixture.

[0021] In one embodiment, the method exposes a waste product mixture containing a carbonatable metal oxide, hydroxide or silicate phase being recycled to gaseous carbon dioxide to conduct a carbonation reaction. This reaction creates metal carbonates from the oxides, hydroxides, silicates, or any other phase in the material mixture that is carbonatable. Recoveredmaterials include, but are not limited to, CaSiO3, Ca2SiO4, Ca3SiO5, Mg2SiO4, Fe2SiO4, Mn2SiO4, MgSiO3, FeSiO3, LiMn2O4, BaTiO3, CaTiO3, FeTiO3, LiCoO2, Ca5Si2O9•H2O, calcium silicate hydroxides, calcium silicate hydrates, magnesium silicate hydroxides, and magnesium silicate hydrates. The recovered materials may also include a phase from Figs.6, 7 or 8.

[0022] In some embodiments, the metal carbonate is obtained from recycled materials.

[0023] In some embodiments, the metal carbonate is derived from a precursor non- alkaline earth oxide, which reacts with CO2 to form the metal carbonate and an oxide. The precursor compound can be collected from a recycled source, such as cured cement, hydrated cement, hydrated concrete, battery cathodes, and dielectric materials. The carbonation step proceeds at a temperature between about 80°C and about 100°C, and the pressure of the CO2ranges from about 10 to about 30 psig, up to 2000 psig. The pressure of CO2can also be as low as atmospheric concentrations (100 – 500 ppm).

[0024] The metal carbonate is preferably comprised or milled to an average particle size of less than about 150 µm. In other embodiments, the metal carbonate may be monolithic, dense, and not in powder form.

[0025] Another aspect of the invention relates to a method of capturing CO2. The method includes exposing a carbonatable material, optionally a metal silicate, a metal oxide, a metal hydroxide, or any of these phases with physically adsorbed- or chemically adsorbed species, or any combination thereof to CO2of various purity levels to form a metal carbonate. The CO2is in a gas phase comprising more than about 100 ppm concentration in a humid atmosphere that ranges from 0 – 99.99% relative humidity. Alternatively, the CO2is dissolved in an aqueous solution comprising a CO2-absorbing agent, and the solution can be heated to speed up the carbonation reaction kinetics. The method thus provides a low-cost and low energy means to capture CO2from the atmosphere, store (sequester) it as a carbonate, transport it as carbonate(s), and then heat the carbonated mixture in unsaturated steam to release the CO2as a gas mixture of water and CO2, condense the water phase and use the remaining CO2as a high purity commercial source of CO2. At the same time, the remaining oxide product, such as calcium monosilicate, resulting from the heated unsaturated steam treatment can be reused to capture additional CO2species at room temperature and atmospheric pressure, or other temperatures or other temperatures and pressures suited for CO2capture, and the entire process can be repeated as means to create a CO2supply chain.

[0026] Alternatively, the calcium silicate for other purposes, such as cement, soil amendment or nutritional supplement.. In either of these situations, a means to recycle cement or repeatedly capture, store, transport, and dispense CO2is established. Alternatively, the above cycle can be an upcycle process instead of a recycle process. For example, a mixture of calcium silicate hydrates can capture, store, and transport CO2by conversion to calcium carbonate, followed by treatment with heated unsaturated steam to form Ca5Si2O9•H2O or other calcium silicates. The formation of this upcycled oxide will release a gas mixture of CO2 and water and condense the water to provide a high-purity stream of CO2. Alternatively, Ca5Si2O9•H2O then be used to capture, store, and transport CO2 as carbonates, and again subjected to heated, unsaturated steam to release CO2, as mentioned earlier. This heating process could create Ca5Si2O9•H2O or make a mixture of different oxides, that have utility for a CO2supply chain. Alternatively, the upcycled Ca5Si2O9•H2O could be used as a cement or a soil amendment. Either way, the process of carbonation and decarbonation can create a closed loop supply chain of CO2, or the availability of low carbon footprint cementitious materials. This is feasible for recycling, where monocalcium silicate can be recycled repeatedly without composition change or other kinds of calcium silicates, such as a mixture of different hydrates are upcycled with a composition change taking place at least during one cycle or more.

[0027] The non-exclusive list of examples of silicates used for capturing CO2includes CaSiO3,Ca2SiO4, Ca3SiO5, Mg2SiO4, Fe2SiO4, Mn2SiO4, MgSiO3, FeSiO3, Ca5Si2O9•H2O. The Ca5Si2O9•H2O phase may also be written as Ca5Si2O9•H2O or Ca5(SiO4)2(OH2). This phase can also be referred to as “521”. The non-exclusive list also includes phases in the following groups: calcium silicate hydrates, magnesium silicate hydrates, and any combination thereof. Also, non-exclusively, other calcium silicates and calcium silicate hydrates with Ca:Si ratios ranging from 0 – 4 can also be used. The CO2can be collected from a concentrated 92% CO2stream from a biosynthesis process, a less concentrated, 15 %CO2stream from a power or heat generation source, a dilute 1000 ppm CO2ocean source, or a dilute 400 ppm CO2atmospheric source. A non-exclusive list of calcium silicates and calcium silicate hydrates is displayed in Figures 6, 7, and 8.

[0028] The captured CO2can be readily transported and released if needed. The captured CO2can be released by the procedure similar to the recycling invention described above: which involves exposing a mixture of the metal carbonate and SiO2or other metal or metalloid oxide to an unsaturated water vapor with a partial pressure of between about 1 atmand about 80 atm; and heating the reaction vessel to a temperature of between about 300°C and about 500°C, up to 1000°C for a sufficient period of time to release CO2. This de-carbonated mixture can now be used for carbon capture once again. Methods according to this aspect of the invention need not use waste materials, although they can. The utility of unsaturated water vapor for the decarbonation prevents any sintering and coarsening effects of the materials and allows the material to be cycled numerous times between the carbonated and de-carbonated form without any performance loss (i.e., degradation in ability to carbonate). This has value for the process of “looping”. Looping is used in power plants, industrial manufacturing, and direct capture of carbon from air (DAC). A typical looping process captures carbon, using CaO to react with CO2to form CaCO3. Once the CaO is reacted substantially, the CaCO3is heated to a high temperature, typically 850-1000˚C, to release the CO2for compression and burial underground or compression and storage as a liquid in insulated tanks. The problem with this process is substantial energy is required to release the CO2. More importantly, during each cycle the CaO particle size increases, which reduces the carbonation kinetics and amount of CO2that can be stored each cycle. The situation is rectified by using comminution to reduce the CaO particle size. Comminution is a very inefficient and energy intensive process. The recycling and upcycling processes outlined here solve this problem because each time the carbonated mixture is reacted with heated unsaturated steam, the resulting particle size small and reactive. We believe this results because the heated unsaturated steam induces hydrothermal vapor synthesis, which is a reactive crystal growth process that produces small particles. This reactive crystallization process contrasts with the conventional high temperature calcination process that induces CaO sintering, which is well known to reduce surface area and create large particles while the reactive crystallization process does not increase the crystal size to the extent where its ability to capture and store CO2is compromised. Resultantly, the use of this recycling or upcycling process will be able to loop CO2for substantially more cycles without the need to comminute or discard the material. In addition, the lower temperatures (200-500˚C) for the hydrothermal vapor synthesis process will conserve energy to an extent where renewable energy sources could be used to power the process instead of fossil fuels. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 illustrates the recycling process of carbonate concrete.

[0030] Figure 2 illustrates the recycling process of hydraulic concrete.

[0031] Figure 3 illustrates chemistry examples of recycling through carbonation and synthesis (closed-loop).

[0032] Figure 4 illustrates chemistry examples of recycling through carbonation and synthesis (semi-closed-loop).

[0033] Figure 5 illustrates potential materials for carbon capture, storage, transport, and delivery.

[0034] Figure 6 Illustrates potential calcium silicates that can be used as carbon capture media, as well as feedstocks and products in the recycling invention.

[0035] Figure 7 Illustrates additional potential calcium silicates that can be used as carbon capture media, as well as feedstocks and products in the recycling invention.

[0036] Figure 8 Illustrates yet additional calcium silicate subclasses that can be used as carbon capture media, as well as feedstocks and products in the recycling invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0037] Various embodiments of the present invention disclose the synthesis of multi- cation compounds suitable for a variety of applications. In particular, the processes described herein provide an efficient approach for the recycling and refining of materials. Material synthesis techniques (e.g., Hydrothermal Vapor Synthesis (HVS) as disclosed in the above- referenced U.S. Patent No. 11,332,847) are utilized to convert a functional material (e.g., battery cathode, cured cement, etc.) to its initial material constituents or other forms of raw material. This recycling technique can be applied to both monolithic or powdered materials with any degree of agglomeration or aggregation. Examples of multi-cation compounds include but are not limited to calcium silicate, magnesium silicate, calcium-magnesium silicate. Additional examples include all oxides that may contain one or more alkaline earth cations combined with any suitable cation, and alkaline cations combined with any suitable cation. Suitable cations include non-alkaline earth cations, i.e., cations that are not alkaline earth cations.

[0038] The multi-cation oxide compounds such as calcium silicate also find applications in the capture, storage, transport, and supply of carbon dioxide. Specifically, a silicate material can react with gaseous carbon dioxide to produce a mixture of silica and metal carbonate. The carbon dioxide is now permanently stored in carbonate form within this mixture and can be transported to the desired location. Additionally, this mixture can be treated (e.g.,thermally, hydrothermally, hydrothermal vapor (HVS), water-assisted solid-state reaction (WASSR)) to reverse the carbonation reaction and produce a silicate material once again. The biproduct of this reaction is high purity, commercially useful gaseous carbon dioxide that can be utilized for the desired reaction chemistry or other applications where an inert gas is used. This CO2is produced in a low temperature, low energy process without amine separation.

[0039] Additionally, once the CO2is produced and contained in a tank, the temperature can be adjusted to achieve a desired pressure. This would eliminate the need for a compressor and pressure regulation.

[0040] While the following text may reference or exemplify specific elements of a composite or a method of utilizing the composite, it is not intended to limit the scope of the invention to such particular reference or examples. Various modifications may be made by those skilled in the art, in view of practical and economic considerations, such as the temperature and pressure of the reaction conditions and the molar ratio between the calcium and silicon.

[0041] The articles "a" and "an" as used herein refers to "one or more" or "at least one," unless otherwise indicated. That is, reference to any element or component of the present invention by the indefinite article "a" or "an" does not exclude the possibility that more than one element or component is present.

[0042] The term "about" as used herein refers to the referenced numeric indication plus or minus 10% of that referenced numeric indication.

[0043] The term “hydrothermal Vapor Synthesis” (HVS) refers to a method for facilitating the production of a phase from a mixture of selected inorganic or organic precursors in a water vapor-phase reaction medium (i.e., unsaturated water vapor, super-heated steam at desired pressures). Exemplary processes are disclosed in U.S. Patent No, 11,332,847, previously incorporated by reference. By adjusting the temperature and the partial pressures of water and monitoring and in some cases modifying any relevant partial pressures of other gases (e.g., CO2), phases can be selectively partitioned out. The reaction can proceed for example at a temperature above 100oC with higher than 1 atm psig pressure and the water is in the vapor phase (unsaturated vapor).

[0044] The term “inorganic material” or “inorganic precursor” includes a material represented by the formula AaBbCcZzYyXx(α)f(β)g(γ)h∙ i(δ) ∙ j(ε) ∙ k(θ), wherein A, B, C aresingle or multi-elemental cations, Z, Y, X are single or multi-elemental anions, α, β, γ are charged molecules, and δ, ε, θ are neutral molecules. The material can be either crystalline (ordered), amorphous (disordered), or a mixture of both. (A), (B), and (C) can comprise of a single or multi elemental cation (positively charged alkali, alkali-earth, transition metal, semi- metal, non-metal, halogen, noble gas, lanthanide, or actinide species) with a concentration of [a], [b], and [c] between ppb (parts per billion) and 100%. (Z), (Y), and (X) can comprise a suitable single or multi elemental anion (negatively charged elemental species, e.g., Oxygen, nitrogen, carbon, fluorine, chlorine, etc) with a concentration of [Z], [Y], and [X] between ppb and 100%. (α), (β), and (γ) can comprise of a variety of charged molecules and ligand groups (organic or / and inorganic) with concentrations of [f], [g], and [h] between ppb and 100%. These molecules could be positively or negatively charged (e.g. OH-, CO3-, NH4+, NR4+). (δ), (ε), and (θ) can comprise of a variety of neutral molecules and ligand groups (e.g., H2O) with concentrations of [i], [j], and [k] between ppb and 100%.

[0045] The inorganic material may be the feedstock (i.e., precursor) material for HVS and thus, the material being recycled. The inorganic material instead may be the HVS reaction product. In either case, the reaction can be driven forwards and backwards by either utilizing CO2as a feedstock during the carbonation step or by emitting CO2as a product during the final step in the recycling procedure. This cycle is based on chemical equilibrium-controlled reactions that can be propagated in the forward and reverse directions an infinite number of times. This type of chemical process is similar to the recycling of steel, aluminum, or glass, in that it can be repeated an infinite number of times, hence referred to as a closed loop process. The invention here is unique in that it does not involve a melting-solidification step but instead uses carbonation and decarbonation steps where melting and solidification is not an essential part of the process. That being said, the temperatures can be chosen so the reactants or products could also include a melt-solidification step, but this is not essential for the invention. Instead, it is being able to conduct carbonation and decarbonation processes at low temperatures. While carbonation is well known to proceed at low temperatures, this invention is able to perform the decarbonization step at temperatures lower than those previously reported in the literature. These temperatures can be 3-4 times lower than typical temperatures reported for decarbonation.

[0046] The term “carbonatable” as used herein refers to any material that can form a carbonate upon exposure to carbon dioxide. This term is also referred to as “RIM”, which refersto a “Reactive Inorganic Material”. The phase of carbon dioxide could be solid, liquid, gas, supercritical, or any combination. “Inorganic material that can carbonate” as used herein refers to an inorganic material that comprises of at least one phase that is carbonatable and forms a metal carbonate upon exposure to carbon dioxide. Nonlimiting examples of anionic moiety of the metal carbonate include bi-carbonate, simple carbonate, H2O-bearing carbonates, OH- bearing carbonates, O-bearing carbonates, OH-and-H2O-bearing carbonates, Chloride-bearing carbonates, sulfate-bearing carbonate, fluoride-bearing carbonate, borate-bearing carbonates, phosphate-bearing carbonates, arsenate bearing carbonates, silicate-bearing carbonates, and carbonates with two or three other anions. The metal moiety of carbonatable materials may be for example rare-earth elements, alkali metals, alkaline earth metals, and other transition metals. Further nonlimiting examples include metals of groups 3-12 on the periodic table: scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium, darmstadtium, roentgenium, aluminum, gallium, indium, thallium, ununtrium, germanium, tin, lead, ununquadium, antimony, bismuth, ununpentium, polonium, and ununhexium. The metal may also be lanthanide and actinide including lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium.

[0047] The terms “vapor” and “gas” are used interchangeably throughout this document. When referring to the solvothermal or hydrothermal vapor atmosphere, this means the vapor is unsaturated gas. This unsaturated gas can also be referred to as superheated gas.

[0048] The term “liquid” refers to a material that is above its melting temperature and pressure, but below its boiling temperature and pressure.

[0049] The term “gas” refers to a material that is above its boiling temperature and pressure, but below its supercritical temperature and pressure.

[0050] The term “recycled” material refers to a used or waste product or product identified as requiring a transformation. Examples of recycled material include, but are not limited to, cured cement, used battery cathode, and used dielectric material. A recycled material may contain a precursor multi-cation oxide which can be converted via reaction withCO2to a carbonate compound, which can then be used in the regeneration of a multi-cation oxide product via a hydrothermal vapor synthesis process of the present invention.

[0051] The term “contactor” refers to the following: In some embodiments, the metal oxide, hydroxide, or silicate is placed into direct contact with a CO2-containing amine. The CO2-containing amine serves as the contactor that transfers CO2from low concentrations to high concentrations to enable carbonation reactions to occur. That is, to enable the formation of a carbonate phase. As such, this manner of CO2-solid interaction is referred to as one with a contactor.

[0052] The term “contactor-free” refers to the following: In some embodiments, the metal silicate is exposed to a humidified stream of CO2in dilute or concentrated concentrations. This method of contact does not include an organic or inorganic intermediate that serves as the transport medium for CO2between the gas-source and the metal silicate. As such, since the only contactor in this scenario is liquid water, this manner of CO2-solid interaction is referred to as contactor-free.

[0053] The term “Calcium-Looping” refers to the following: A process by which CO2is cycled between gaseous and carbonate form for the purpose of generating a higher concentration of CO2 gas.

[0054] The term “RIM” or “Reactive Inorganic Material” refers to the following: for example, a metal, or metal oxide, or metal hydroxide can react with carbon dioxide (liquid, gaseous, solid, ionic) to form a metal carbonate.

[0055] The term “CR” or “Concrete Rubble” refers to the following: Any type of demolition waste that is comprised of a cement that was hydraulically cured or cured via carbonation, or both. It may also consist of kiln dust or any other material that was disposed along the cement and concrete production and supply chain. It may also consist of all phases present in the following non-exclusive list of cements, Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate-sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate-sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, TypeHS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0056] The term “waste cement” refers to the following: Any type of cement (used or new) that has been identified as an end-of-life product that is comprised of materials that were hydraulically cured or cured via hydration or both. It may also consist of all phases present in the following non-exclusive list of cements, Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate-sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate-sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0057] The term “Cured Hydraulic Portland Cement” or “CHPC” refers to any waste cement that has been cured via a hydration process. There may also be carbonates present within the CHPC. CHPC consists of a mixture comprising CaCO3, Ca(OH)2, SiO2, Ca3SiO5, Ca2SiO4, and Calcium Silicate Hydrate (CSH) phases, among other phases. There are other phases present as well. These comprise of various calcium aluminate (and hydrated and carbonated forms) and calcium aluminoferrite phases (and hydrated and carbonated forms). If the material being recycled is cured concrete, then aggregate is present as well.

[0058] The term “sponge” refers to a material that can be used for carbonate capture. In other words, a material that can react with CO2to form a carbonate phase.

[0059] The following abbreviations are used: HVS: Hydrothermal Vapor Synthesis; LPH: Liquid-phase hydrothermal; VPH: Vapor-phase hydrothermal; SCW: Supercritical water.

[0060] Unlike LPH, VPH, and SCW synthesis, HVS is conducted at any temperature (> 100oC) and pressure where liquid water no longer exists. The pressurized water vapor atmosphere acts as a reaction catalyst for the synthesis of inorganic materials at relatively low temperatures (<500oC). This means that HVS enhances the kinetics of a thermodynamically favorable reaction between the selected precursors. Specifically, the main equation governingwhether a reaction between precursors is thermodynamically favorable is the Gibb’s freeenergy of reaction:

[0061] If the ∆Gorxnis negative, positive, or zero, then the reaction will proceed, not proceed, or remain in equilibrium respectively. The “o” refers to standard state conditions: i.e., Total Pressure = 1 atm. The pressure increase inside a hydrothermal vessel is dictated by the water liquid-vapor equilibrium curve and also by any volatile substance that could be adding gaseous products to the mix. Accordingly, any gaseous reactant or product can also contribute to the overall thermodynamics of the reaction system via the following non-standard-staterelationship:

[0062] where R is the molar gas constant (8.314 J / mol∙K), T is the temperature (Kelvin), K is the reaction equilibrium constant, a is the activity component of the reactants and products, and P is the partial pressure (atm) of the present gases (subscripts p= product, r= reactant, s = solid, g = gas). If the ∆Gtotal(non-standard-state change in Gibb’s free energy for a particular reaction) is negative, positive, or zero, then the reaction will proceed, not proceed, or remain in equilibrium respectively. The present disclosure details how to apply the thermodynamics of a system in the solvothermal vapor environment to predict product formation. In particular, one or more of the temperature, unsaturated vapor pressure, and partial pressure of any gases added or produced are selected to reduce the non-standard state change in Gibb’s free energy of the reaction system to less than or equal to zero. In some embodiments, the non-standard state change in Gibb’s free energy of the reaction system may be equal to zero, reduced to below zero, or below -10, or below -100, or below -1,000 kJ / mol. In some embodiments, the non-standard state change in Gibb’s free energy may be reduced down to -10,000 kJ / mol. The non-standard state change in Gibb’s free energy may also be reduced by the addition of a gaseous, liquid, or solid species, or by the production of a gaseous, liquid, or solid species within the reaction system. The non-standard state change in Gibb’s free energy may also be reduced by removal of any of these species from the reaction system. In some embodiments, there may be other compounds that can form alongside the desired product that are metastable, that is a non-standard state change in Gibb’s free energy that isless than zero, but not more negative than another more stable phase. In some embodiments, the compound being formed is metastable. In some embodiments the metastable and stable phases can be selected and partitioned out by changing the non-standard state change in Gibb’s free energy via the addition of a gaseous, liquid, or solid species, or by the production of a gaseous, liquid, or solid species within the reaction system

[0063] The solvothermal method deviates from the liquid-vapor equilibrium by eliminating the vessel liquid volume fraction. The utilization of unsaturated vapor increases the versatility of this process by introducing another synthesis variable and one additional degree of freedom; where any pressure (P) can be selected at a given temperature by control of the amount of reaction medium (water) added to the vessel. Tuning this variable can optimize reaction kinetics, and the reaction product’s physical and chemical characteristics, such as phase-purity, crystallite size, morphology, degree of agglomeration, and degree of aggregation.

[0064] In the case of water being the reaction medium, the reaction method is labeled “Hydrothermal Vapor Synthesis.” However, methods of the present disclosure may utilize other reaction mediums such as organic or inorganic species, or mixtures thereof. In some embodiments, the reaction medium may be one or more of ammonia, ethanol, methanol, acetone, toluene, and benzene. It may also be a deep eutectic liquid or an ionic liquid. If the reaction medium comprises more than one species, then at least one the species may in an unsaturated vapor state at the temperature and pressure of the reaction conditions. In some embodiments, the other species may be saturated, subcritical, or critical pressures.

[0065] The reactions observed in the CaO:SiO2:CO2:H2O system are excellent examples of the capabilities of HVS. The partial pressure of water throughout the reaction can be pre-selected by adjusting the reactor fill percentage or introducing pressure water vapor into the reaction vessel. Thus, HVS is a new synthetic method where low pressure reactions can be engineered provided the reaction thermodynamics can be calculated for the solid – water vapor equilibria and the kinetics are rapid enough to enable thermodynamic equilibrium to be achieved. These calculations enable systematic selection of the processing variables that include vessel volume, mass of solid component, amount of water and temperature. Thermodynamic calculations enable determination of the water and CO2 partial pressures that enable formation of the desired reaction product.

[0066] The range of temperature, pressure and compositions enabling the formation of a desired reaction product is defined as the “processing variable space (PVS). By operatingwithin PVS, the kinetic role of thermodynamic variable such as composition (e.g., water), temperature and pressure (e.g., water partial pressure and total pressure) reaction conditions that favor a labile reaction can be found while forming the product of interest. Without this knowledge and instrumentation that monitors pressure and temperature, continuously, both model validation and leak detection would not be possible. These technical issues thwart an investigator from being able to successfully make a reaction product using a combinatorial grid of variable settings because the number of experiments required are too numerous to perform, forcing the investigator to select only some of the variable settings.

[0067] In addition, without an understanding of the non-ideal thermodynamic behavior of chemical components such as water, the investigator is not able to determine if the pressures measured during the experiment are equilibrium values or those of a non-equilibrium system. Not knowing this makes it difficult to differentiate between experiments whose results are reproducible versus those that cannot be reproduced unless they repeat their experiments multiple times. This lack of reproducibility is abundant in the literature where investigators examining similar reaction conditions get different reaction products.

[0068] There are several considerations that make the HVS method possible and unique: (1) Achieving pressure control within an autoclave by avoiding leaks and knowing how much water to add to achieve a desired pressure and (2) Understanding the reaction thermodynamics between selected precursors so the HVS phase partitioning behavior is determined. The following section outlines both.

[0069] The complexity of HVS resides in fully understanding the water liquid-vapor phase equilibrium and the relationship between temperature (T), pressure (P), volume (V), and concentration (n) for non-ideal gasses. Accurate data for the water liquid-vapor equilibrium, e.g., from IAWPS (International Association for the Properties of Water and Steam), may be helpful in designing hydrothermal reactions (LPH, VPH, and SCW). To eliminate the liquid phase within an autoclave, equations that govern the relationship between T, P, V, and n are: (1) Ideal gas Law, (2) Van der-Waals equation, and the (3) Redlich-Kwong equation. These equations are designed to predict the pressure increase of a gas, with (2) and (3) considering non-ideal gas behavior. By simply utilizing (1), an incorrect calculation that doesn’t take into the proportionality constants associated with gaseous H2O would occur. The differences between (1), (2) and (3) can be identified for the following temperatures: 400, 374, 350, and 250oC. In each case, the ideal gas law fails to determine the correct pressure increase withinthe reactor at fill percentage’s > 2.5. Once the pressure at a pre-determined fill percentage is determined, then the water liquid-vapor phase equilibrium may be considered to ensure that the set temperature and resulting pressure create a single vapor phase as opposed to a coexistent vapor-liquid system. Knowing this methodology is critical; otherwise, the investigator will be unable to distinguish a reactor leakage problem from non-ideal gas behavior.

[0070] In some embodiments, the reaction vessel may be a batch, continuous, semi- batch, or semi-continuous reaction vessel. Where a continuous, semi-continuous, or semi- batch reaction vessel is used, unreacted reactants may be removed and recycled back into the reaction vessel. METHOD FOR MATERIAL RECYCLING & REFINING

[0071] Material carbonation is a process by which a Reactive Inorganic Material (RIM), for example, a metal, or metal oxide, or metal hydroxide can react with carbon dioxide (liquid, gaseous, solid, ionic) to form a metal carbonate. It is typically known to be an exothermic reaction process that is spontaneous at room temperature. It is important to note, that not all materials have equivalent carbonation conditions. For example, CaSiO3 can carbonate (from CaCO3and SiO2) at room temperature given the correct particle size, surface area, and humidity content, while Mg2SiO4requires temperatures for example >100oC along high water and CO2partial pressures to carbonate. These conditions are based on thermodynamic and kinetic studies. In addition, identical materials can be carbonated under completely different conditions. For example, CaO carbonate at room temperature in a wet (humid) environment in the presence of gaseous CO2, but it can also carbonate under elevated temperature conditions (for example ~650oC) solely in the presence of gaseous CO2(without any water content). Further, a spontaneous process might be kinetically limited (e.g., diffusion limited) and resultantly not achieve thermodynamic equilibrium.

[0072] The invention provides a method for recycling a multi-component oxide waste product by taking the following 3 steps: (1) Choose a multi-component oxide material synthesized by reacting a single- or multi-cation carbonate element or with a single- or multi- cation non-alkaline earth oxide to form said multicomponent oxide. (2) Expose the multicomponent oxide waste product to CO2 vapor in the presence of water with or without heating to obtain a multi-phase mixture either by (a) single- or multi-cation carbonates blended with (b) a single or multi-cation oxide or solely a mixture of 1 or more metal carbonates having at least 1 cation in each carbonate phase (3) De-carbonate the mixture by exposure to anunsaturated water vapor using a partial pressure of between about 1.01 atm and about 80 atm at a temperature of between about 300°C and about 1000°C for a sufficient time to recover the multicomponent oxide as a recycled material.

[0073] A recycled material is one whose chemistry in the initial state as waste is the same multicomponent oxide as the one formed after the above three steps are performed. In another embodiment, the waste multicomponent oxide is upcycled. Upcycling is a situation where the waste multicomponent oxide differs from the multicomponent oxide formed after exposure to water vapor and heat, as mentioned above. For example, a mixture of various calcium silicate hydrates and calcium hydroxide could upcycle to form Ca5Si2O9•H2O. In some embodiments, the carbonation step (step 2) is unnecessary. The initial multicomponent oxide is upcycled to create a new multicomponent oxide by exposure to unsaturated water vapor with a partial pressure between about 1.01 atm and about 80 atm at a temperature of between about 300°C and about 1000°C for a sufficient time to recover and upcycle the material. Recovered materials include, but are not limited to, CaSiO3, Ca2SiO4, Ca3SiO5, Mg2SiO4, (Mg,Ca)SiO3, Fe2SiO4, Mn2SiO4, MgSiO3, FeSiO3, LiMn2O4, BaTiO3, CaTiO3, (Ba,Ca)TiO3, PbTiO3, PbZrO3, Pb(Zr,Ti)O3, FeTiO3, LiCoO2, and Ca5Si2O9•H2O, and multiphasic mixtures of calcium silicate hydroxides, calcium silicate hydrates, magnesium silicate hydroxides, and magnesium silicate hydrates, etc. The recovered materials may include one or more phases from Figures 6, 7, or 8.

[0074] In step 2, elements that form metal carbonates, also termed “carbonates,” cover nearly all of the elements from the periodic table, including alkali, alkaline earth, main group transition metal, rare earth, and actinide elements. Carbonates can have multiple cations and non-carbonate anions, such as, but not limited to, OH-, Cl-, and SO4-2. Carbonates can be amorphous, crystalline, or a mixture of both. Carbonates can also be comprised of multiple carbonate phases, whether they are polymorphic forms such as but not limited to aragonite, vaterite, or calcite or phases that have differences in cation chemistry such as, but not limited to MgCO3, CaCO3, or (Fe, Mn)CO3. Elements that remain as stable oxides at a CO2partial pressure of 1 atm or less in the absence of solution complexing agents are far scarcer, which include main group and transition metal elements, such as but not limited to B, Ga, Si, Ti, Ta, and Nb. The term “multicomponent oxides” or the term “oxide” can be a metal-oxide, -hydrous oxide, -hydroxide, or -hydrates; the “oxide” can be crystalline, amorphous, or a mixture of those mentioned above. Also, multiple metal cations can comprise the “oxide.” The “oxide”can also be multi-phasic in crystal structure, and the cations comprising each phase can be the same or different.

[0075] The invention also provides a method for recovering from a waste product, a material containing an inorganic single or multi-cation compound, or a blend of single or multi- component compounds. Wherein the waste product is subjected to the following steps:

[0076] a) exposing said waste product to CO2 in the presence of water with heating to obtain a carbonate mixture; and

[0077] b) exposing the carbonate mixture to an unsaturated water vapor with a partial pressure of between about 2 atm and about 80 atm at a temperature of between about 300°C and about 1000°C for a sufficient period of time to recover and recycle said material.

[0078] Tin one embodiment, the material comprises a product that was originally formed by reacting an alkaline earth or iron, manganese, or lithium carbonate with a scrap single- or scrap multi-cation non-alkaline earth oxide.

[0079] Material carbonation enables recycling by carbonating a RIM to create a phase mixture comprised of a metal carbonate, and other reaction products, which include but are not limited to oxides and hydroxides. The material being recycled is comprised of any carbonatable inorganic material. Equation 1 exemplifies a carbonation reaction where “M” is the first Cation, “A” is the second cation, “C” is carbon, “O” is oxygen, “m” refers to the molar quantity of “M”, “a” refers to the molar quantity of “A”, “b” refers to the molar quantity of “O”, “c” refers to the molar quantity of product “M”, and “d” refers to the molar quantity of product “A”. The subscripts “a”, “b”, “c”, and “d” can be any value greater or equal to 0. Additionally, “W” refers to the molar quantity of the first reactant, “X” refers to the molar quantity of the second reactant, “Y” refers to the molar quantity of the first product, and “Z” refers to the molar quantity of the 2ndproduct. This implies that material carbonation is suitable for metals, non-metals, inorganic oxides, and inorganic non-oxides, and any combination thereof. WMmAaOb(s) + XCO2(g) ⇌ YMcCO3(s) + ZAdO2(s) (1)

[0080] Note, the above reaction is not balanced, and requires adequate balancing to represent an actual chemical reaction. For example, if CaSiO3was the material being carbonation, coefficients would be: W = 1, M = Ca, m = 1, A = Si, a = 1, O = O, b = 3, X = 1,Y = 1, M = Ca, c = 1, Z = 1, A (product) = Si, d = 1: producing the following balanced calcium silicate carbonation reaction: CaSiO3(s) + CO2(g)⇌ CaCO3(s) + SiO2(s).

[0081] The carbonated product consists of a material that consists of a metal carbonate and in some cases also comprises the corresponding oxide. This material can be considered “recycled” if it was previously used for a particular application and will now be re-purposed as a carbonate. For example, cured Portland Cement Concrete (PCC), viz. Concrete Rubble (CR), initially consists of calcium silicate hydrates, some unreacted cement, unreacted precursor minerals and aggregate. It may also consist of all phases present in the following non-exclusive list of cements, Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate-sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate-sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0082] By crushing, milling, packing, then carbonating the mixture, products compris- ed of CaCO3, amorphous SiO2, amorphous hydrated silica form. Aside from being a solidifica- tion process, this carbonation step is also a step in a CR recycling process. In this case, the concrete is not packed prior to carbonation but instead is subjected to another unit operation to create a cement. Such a unit-operation, such as, high-temperature treatment, decomposes the CaCO3to form CaO to readily react with the silica to form calcium silicates or simply remain as mixtures of CaO and SiO2, which we refer to as material synthesis material de-carbonation processes, respectively.

[0083] Material de-carbonation is a process by which CO2is removed from the carbonated material and produce an oxide, hydrous oxide, hydroxide, or hydrates of the aforementioned, hereon referred to as an “oxide.” The “oxide” can be crystalline, amorphous, or a mixture of the aforementioned. This can be achieved by various treatments, for example, high-temperature calcination, high-temperature steam calcination2, hydrothermal treatment, and hydrothermal vapor treatment. For example, magnesium carbonate (MgCO3) can be de- carbonated by a 600oC heat treatment and resultantly transform into magnesium oxide with a gaseous CO2byproduct. It can also be de-carbonated by a 400oC hydrothermal vapor treatmentand resultantly form either MgO or Mg(OH)2depending on the partial pressure of water, along with a gaseous CO2byproduct. Additional ways of de-carbonation could also consist of acid- washing the carbonate to completely or partially transform the carbonate into an aqueous species and gaseous carbon dioxide. If this product (de-carbonated) can now be employed within an application, it is considered “recycled”.

[0084] Equation 2 exemplifies a material de-carbonation reaction where (1) The reactant comprises of: “M” is the cation corresponding to the precursor carbonate, “a” is the molar quantity of precursor “M”, “C” is carbon, “b” is the molar quantity of the carbon precursor, “O” is oxygen, “c” is the molar quantity of the oxygen precursor, and (2) The product comprises of : “M” is the cation corresponding to the product oxide, “a” is the molar quantity of product “M”, “O” is oxygen corresponding to cation “M”, “d” is the molar quantity of the product oxygen, “Z” is the molar quantity of produced carbon dioxide. The subscripts “a”, “b”, “c”, and “d” can be any value greater or equal to 0. MaCbOc(s) ⇌ MaOd(s) + ZCO2(g) (2)

[0085] Material synthesis is a process by which one or more materials are chemically reacted to form a new phase of material. The materials being reacted can be a carbonate and an oxide for the purpose of forming a multi-cation oxide and a gaseous CO2 byproduct. The method of chemical reaction can be high-temperature calcination (solid-state synthesis), high- temperature steam calcination (steam-assisted solid-state reaction), water-assisted solid-state reaction (WASSR4), hydrothermal / solvothermal / supercritical treatment, and hydrothermal vapor treatment (HVS). The materials being chemically reacted can be a carbonate and an oxide for the purpose of forming a multi-cation oxide and a gaseous CO2byproduct.

[0086] Equation 3 exemplifies a material synthesis reaction where “M” is the cation corresponding to the precursor carbonate one of the product phases, “c” is the molar quantity of precursor “M”, “C” is carbon, “O” is oxygen, “A” is the cation in the second precursor (carbonate or non-carbonate), “d” is the molar quantity of precursor “A”, “m” refers to the molar quantity of product “M”, “a” refers to the molar quantity of product “A”, “b” refers to the molar quantity of “O”. The subscripts “a”, “b”, “c”, and “d” can be any value greater or equal to 0. Additionally, “W” refers to the molar quantity of the first reactant, “X” refers to the molar quantity of the second reactant, “Y” refers to the molar quantity of the first product, and “Z” refers to the molar quantity of the 2ndproduct.WMcCO3 (s) + XAdO2 (s) ⇌ YMmAaOb (s) + ZCO2 (g) (2)

[0087] Note, the above reaction is not balanced, and requires adequate balancing to represent an actual chemical reaction. For example, if CaSiO3 was the material being synthesized, coefficients would be: W = 1, M = Ca, m = 1, A = Si, a = 1, O = O, b = 3, X = 1, Y = 1, M = Ca, c = 1, Z = 1, A (product) = Si, d = 1: producing the following balanced calcium silicate carbonation reaction: CaCO3+ SiO2(s) ⇌ CaSiO3(s) + CO2(g). If this product (new- phase) is now employed within an application, it is considered “recycled”. The material synthesis reaction can be achieved by a variety of treatments, for example, high-temperature calcination, high-temperature steam calcination, hydrothermal treatment, and hydrothermal vapor treatment.

[0088] This disclosure combines (1) material carbonation, (2) material de- carbonation, and (3) material synthesis to enable a material recycling solution. In some embodiments, an individual process (1, 2, or 3) can sufficiently recycle material for an end-use application. Any combination of (1), (2), and (3) may be used to recycle a material. The invention can be used in a closed-loop or semi-closed loop fashion. Closed-loop refers to a complete reuse of the material being recycled. For example, a closed-loop recycling process for carbonate cement would proceed as follows: the carbonate cement (CaSiO3) during curing transforms into a mixture of CaCO3and SiO2. This mixture can be recycled back (transformed) into the original CaSiO3material by a Hydrothermal Vapor Synthesis (HVS) reaction. At this point, the CaSiO3material is transformed back into the original CaSiO3material that is ready to once again be used as carbonate cement. Semi-closed loop refers to a carbon capture cycle in which the material being used is not recycled back into its original form. For example, recycling used (cured) Portland Cement that is composed of calcium hydroxide, calcium silicate hydrate gel, and other phases by transforming it into a carbonate cement (e.g., CaSiO3) would result in a semi-closed loop. Figures 3 and 4 detail examples of closed- (Figure 3), and semi-closed (Figure 4)-loop examples. This invention focuses on pathways making cement and concrete materials using considerably less energy and emitting little to no CO2,

[0089] One aspect of the invention provides a method of synthesizing a multi-cation oxide utilizing the HVS technique. The compound has a cation of M and a cation of A. M is selected from the group consisting of alkaline earth metals, Fe, Mn, and Li. A can be any non- alkaline earth metal, including Si, Ti, Mn and Co. The method generally includes: (a) exposing a mixture comprising a carbonate of M and an oxide of A to an unsaturated water vapor with apartial pressure of between about 40 atm and about 80 atm in a reaction vessel; and (b) heating the reaction vessel to a temperature of between about 300°C and about 500°C for a sufficient period to form the multi-cation oxide. The pressure can be any partial pressure greater than 1 atm. A temperature up to 1000˚C may be utilized.

[0090] More broadly, recyclable multi-cation oxides include any element that forms a carbonate. Railsback has shown that most of the cations on the periodic table can form carbonates (Carbonates & Evaporites, 14(1), 1999, p. 1-20). Thus, almost any compound occurring in nature or made synthetically is likely to be recyclable via the 3-pathways outlined above. For example, Examples include but are not limited to CaSiO3, Ca2SiO4, Ca3SiO5, Mg2SiO4, Fe2SiO4, Mn2SiO4, MgSiO3, FeSiO3, LiMn2O4, BaTiO3, CaTiO3, FeTiO3, LiCoO2, Ca5Si2O9•H2O, calcium silicate hydroxides, calcium silicate hydrates, magnesium silicate hydroxides, and magnesium silicate hydrates. Examples of the oxide of A include SiO2, TiO2, MnO, and CoO. The oxide can also be in the form of a hydroxide, carbonate, or hydroxy- carbonate.

[0091] The HVS technique requires unsaturated water vapor. The partial pressure of the unsaturated water vapor can be regulated via the initial fill of liquid water in the reactor. The amount of liquid water ranges from about 0.1 to about 40 vol %, all subunits and sub-ranges included, of the total volume of the reaction vessel. In non-limiting exemplary embodiments, the water content is about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40% of the total volume of the reaction vessel. For example, in the case of a reaction at 374oC, the water fill percent may be less than 15.6% to achieve an all-gas (steam) reaction medium. All other cases can be numerically computed and experimentally confirmed. The numeric computation involves equating the pressure values obtained by surveying concentration of water in the Vander-Waals or Redlich-Kwong equations with the pressure in the water liquid-vapor equilibrium curve. One or more additional inert organic solvent may be added to further fine tune the total or partial-gas pressure in the vessel. The partial pressure of unsaturated water vapor can also be regulated via (1) injection of liquid water that is subsequently vaporized, (2) injection of unsaturated and / or saturated water vapor that is subsequently vaporized, (3) dehydration of oxides or other water-containing compounds, (4) decomposition of hydroxides of other water-containing compounds or any combination of (1), (2), (3) and (4).

[0092] The partial pressure of other gases present inside the reaction zone may also be preferentially increased or decreased by creating a flow-through gaseous system. Such a flow- through system may comprise of a steam generator constantly providing a pressurized stream of unsaturated water vapor at a pressure greater than the set value on a relief valve. This would create a continuous flow of steam within the reactor, flushing out all other produced gases (for example, the partial pressure of any gas produced as a result of a reaction would never increase beyond a certain limit due to the continuous flushing of unsaturated water vapor). This continuous flow of steam could also be utilized to minimize unwanted gaseous species inside the reactor vessel. For example, a gaseous byproduct may be produced throughout the reaction that may thermodynamically limit and resultantly halt the reaction. This gaseous byproduct can be removed, if necessary, by the continuous flow of steam. The flow of steam can also be semi- continuous.

[0093] In some embodiments, the unsaturated water vapor in the reaction vessel has a partial pressure of between about 40 atm and about 80 atm. Depending on the temperature insider the reaction vessel, the partial pressure of the unsaturated water vapor can be for example, between about 40 atm to about 50 atm, between about 50 atm to about 60 atm, or between about 60 atm to about 70 atm. The temperature can be controlled for example between about 300°C and about 350°C, between about 320°C and about 390°C, between about 350°C and about 400°C, between about 400°C and about 450°C, or between about 450°C and about 500°C. The temperature can be up to 1000°C. Depending on the reaction substrates and the temperature, the heating can continue for more than about 1 hour, more than about 2 hours, more than about 3 hours, or more than about 5 hours.

[0094] In some embodiments, the partial pressure of water in the reactor ranges from about 10 to 50000 psi or higher, all subunits and sub-ranges included. Non-limiting ranges include from about 10 psi to about 500 psi, from about 500 psi to about 700 psi, from about 700 psi to about 1000 psi, from about 1000 to about 1500 psi, from about 1500 to about 2000 psi, from about 2000 psi to about 2500 psi, from about 2500 psi to about 3000 psi, from about 2500 psi to 5000 psi, from about 2500 psi to 10000 psi, from about 2500 psi to 20000 psi, from about 5000 psi to 20000 psi and from about 2500 psi to 20000 psi. In other exemplary embodiments, the lower limit of the pressure range is about 150, about 200, about 250, about 300, about 350, about 400, about 450, about 500, about 550, about 600, about 650, about 700, about 750, about 800, about 850, about 900, about 950, about 1000, about 1200, about 1400, about 1600, about 1800, about 2000,about 3000, about 4000, about 5000, about 6000, about 8000, about 10000, about 12000, or about 14000 psi. In some embodiments, the upper limit of the pressure range is about 1000, about 1200, about 1400, about 1600, about 1800, about 2000, about 2200, about 2400, about 2600, about 2800, about 3000, about 3200, about 3400, about 4000, about 5000, about 6000, about 8000, about 10000, about 15000, about 20000, about 25000, or about 30000 psi. In some embodiments, the partial pressure of water in the reactor vessel is about 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, 3000, 3200, 3400, about 4000, about 5000, about 6000, about 8000, about 10000, about 12000, about 14000, about 16000, about 20000, or about 25000 psi.

[0095] Due to the low reaction temperatures (e.g., less than about 100°C for carbonation and less than about 500°C for HVS of multi-cation oxides), the described methodology also benefits from sources of renewable energy obtained from currently available solar energy (thermal radiation and electricity) while more conventional high temperature pyrothermal methods cannot be powered by currently available renewable energy source. These low temperatures associated with HVS processes allow for the use of high temperature phase change materials and molten salts heated solely by solar radiation and electricity.

[0096] Specifically, the utilization of “High Temperature Phase Change materials” to efficiently supply the energy required to carbonate and de-carbonate materials allows for low energy consumption. Solar energy provides the heat required to heat up the high temperature phase change material. This material is typically a salt (e.g., NaCl, KCl, LiCl, LiF) that has a specific melting point, a high heat of fusion, and offer favorable characteristics such as high working temperatures (over 500°C), low vapor pressure, good thermal and physical properties, low corrosivity and toxicity, and low cost. The material is heated past its melting temperature and energy is stored as the “heat of fusion”. Upon cooling, the material releases this energy.

[0097] The utilization of electricity generated by photovoltaic cells (i.e., solar panels) can also significantly reduce the carbon footprint of material recycling. By utilizing solar energy (direct electricity and heating phase change materials), material recycling can become a carbon neutral process. Solar energy can also be harnessed in the form of heat for the direct production of water vapor needed to power the material synthesis reactions based on the HVS process.

[0098] In some embodiments, the unsaturated water vapor is generated by heating liquid water prefilled in the reaction vessel. The amount of the water is calculated based onthe temperature and the volume of the reaction vessel. For example, to achieve a partial pressure of about 58 atm at 350°C, the amount of water can be chosen to be about 3% of the total volume of the reaction vessel. In some embodiments, the reaction vessel can be heated and then pressured with unsaturated water vapor, which is produced by a steam generator, water boiler, or other preheating systems and introduced into the vessel.

[0099] In some embodiments, the oxide of A is SiO2. To ensure the maximum conversion of the carbonate material into the corresponding silicate, the molar ratio between M and Si should be about 3:1, about 2:1, about 2.5:1, about 1.5:1, or about 1:1. In some embodiments, the molar ratio between M and Si is about 1:1. In some embodiments, additional SiO2 more than the required molar amount is used to drive the reaction to completion.

[0100] The carbonate of M can be obtained from a recycled material. For example, cured cement is a source of CaCO3, which can be converted to multi-cation oxide CaSiO3. The temperature of the reaction vessel can be adjusted to obtain one or more phases of α-CaSiO3, β-CaSiO3, Ca3Si2O7, Ca3SiO5, Ca5Si2O9•H2O, and Ca2SiO4.Other phases that can be produced are listed in a non-exclusive fashion in Figures 6, 7, and 8.

[0101] Starting materials (e.g., CaCO3) in monolithic or powder form can be processed to reduce the particle size before subsequent reactions. Preferably, a reactant has a particle size of less than about 200 µm, less than about 150 µm, or less than about 100 µm.

[0102] The particle size and surface area of a multi-cation oxide compound can be modified with techniques of the present invention. Generally, the particle size of a material is reduced through a milling process in which media physically impacts the material and causes breakage. The surface area of these materials increases with decreasing particle size. The process described herein chemically reduces the particle size without any mechanical grinding. Specifically, a multi-cation oxide compound (e.g., CaSiO3) can be cycled between its carbonate and silicate form several times, with each iteration decreasing the particle size and increasing the surface area. For example, a precursor CaSiO3can be first taken to a carbonation step to form a mixture of CaCO3and SiO2, which is then converted to a product CaSiO3with procedure described above. Such a cycle reduces the particle size of CaSiO3and hence increases its overall surface area. The cycle can be repeated 1, 2, 3 or more times.

[0103] The process of the present invention can be used in the recycling of various types of materials. Specifically, the process involves a carbonation step to convert a precursor multi-cation oxide in the recycled material to a corresponding carbonate, followed by a reactionbetween the carbonate with a respective oxide of A to regenerate the multi-cation oxide via a material synthesis reaction. The recycled material can be for example, used battery cathode and dielectric materials.

[0104] Additional examples of chemical components in the recycled material include CaSiO3, Ca2SiO4, Ca3SiO5, Mg2SiO4,Fe2SiO4, Mn2SiO4,MgSiO3, FeSiO3, LiMn2O4, BaTiO3, CaTiO3, FeTiO3, and LiCoO2and any polymorph of these components. The recycled material can be a mixture of different devices on a circuit board, where the devices are converted to powder, isolated from the circuit board, then separated by conventional means such air cyclones, hydrocyclones, froth flotation, magnetic separation, and dielectric separation. Such a mixture could include the following oxides: CaSiO3, Ca2SiO4, Ca3SiO5, Mg2SiO4,Fe2SiO4, Mn2SiO4, MgSiO3, FeSiO3, LiMn2O4, BaTiO3, CaTiO3, FeTiO3, and LiCoO2, which are subsequently converted to their respective carbonates and oxides via a material carbonation process to produce phases such as CaCO3, MgCO3, FeCO3, MnCO3, LiCO3, Mn2O3, and TiO2. Other gases can be added to CO2, such as H2, H2O, CO2, and others to control cation valence states to control the partitioning of certain oxides and carbonates, such as those associated with transition metals such as Co, Mn, and Fe.

[0105] In the material synthesis reaction, the produced carbonates are reacted with the co- produced oxides to re-synthesize the original or new oxide species. In the reactions that involve carbonates, the partial pressure of CO2in the reactor vessel is regulated to fine tune the reaction outcome. The regulation of the partial pressure of other gases may be accomplished by the introduction or removal of CO2from the reaction vessel through, e.g., outgassing the reaction vessel. In some embodiments, the partial pressure of CO2added or produced are independently between 0.0000001 and 10,000 atm, all subranges and subunits included. In some embodiments, the partial pressure of carbon dioxide ranges from about 0.00000001 to about 1000, from about 0.0000001 to about 0.00001, from about 0.000001 to about 0.0001, from about 0.00001 to about 0.001, from about 0.0001 to about 0.01, from about 0.001 to about 0.1, from about 0.01 to about 0.1, from about 0.1 to about 1, from about 0.1 to about 10, from about 1 to about 10, from about 1 to about 20, from about 1 to about 50, from about 1 to about 100 psi, all subranges and subunits included.

[0106] Non-limiting examples of the partial pressure of CO2include about 0.0005, about 0.001, about 0.005, about 0.01, about 0.05, about 0.1, about 0.5, about 1, about 5, about 10, about 15, about 20, about 25, about 30, about 40, about 50, about 80 and about 100 psi. In someembodiments, the amount of CO2ranges from about 50 ppm to about 1000 ppm, from about 100 ppm to about 800 ppm, from about 200 ppm to about 800 ppm, from about 400 ppm to about 800 ppm or from about 200 ppm to about 600 ppm in the reactor. In some embodiments, the CO2is in the supercritical state. In some embodiments, CO2is in a meta-stable or equilibrium state such as a 2-phase liquid-gas state, solid-gas, or 3-phase mixture of liquid, solid and gas. In some embodiments, CO2is completely in the gaseous state.

[0107] Also provided in the present invention is a multi-cation oxide compound prepared according to the above-described methods. This compound is synthesized through methods of the present invention are of crucial importance to anyone that has interest in the field of calcium silicate synthesis, carbon dioxide emissions, and manipulation of hydrothermal reactions for the synthesis of inorganic oxide materials.

[0108] In some embodiments, the material carbonation step generally proceeds at a temperature between about 80°C to about 100°C, between about 80°C to about 90°C, between about 85°C to about 90°C, and between about 90°C to about 95°C. The pressure of the CO2is controlled at a range of between about 10 psi and about 30 psi, between about 15 psi and about 25 psi, between about 15 psi and about 20 psi, between about 20 psi and about 25 psi.

[0109] Generally, the CO2is bubbled through an aqueous solution to create a humid gas stream. Alternatively, the reaction vessel can be humidified by introducing water vapor, which produces a relative humidity of for example between about 10% to about 90%, between about 10% to about 50%, or between about 10% to about 30%. The carbonation step is allowed to continue for more than about 5 hours, more than about 10 hours, or more than about 20 hours. CARBON CAPTURE, STORAGE, TRANSPORT, AND SUPPLY

[0110] Another aspect of the invention provides a method of capturing CO2which can be readily stored and transported in the form of a solid carbonate phase. If needed, the CO2can be released through processes such as HVS (treatment with unsaturated water vapor pressure). The by-product of this reaction is high purity gaseous carbon dioxide that can be utilized for desired applications, including commercial applications. Additionally, the gaseous carbon dioxide may be produced directly as a high-pressure gas if a pressurized reaction vessel is used, for example the HVS material synthesis route. Additionally, once the CO2is produced and contained in a tank and a desired pressure has not yet been achieved, the temperature can be adjusted to achieve a desired pressure. This advantageously eliminates the need for acompressor. This CO2is produced without amine separation. In some embodiments, the partial pressure of water vapor and / or CO2is regulated as described in the above section on material recycling & refining.

[0111] The method includes exposing a metal silicate, a metal oxide, or metal hydroxide, or any of these phases with physically adsorbed- or chemically adsorbed species, or any combination thereof to CO2to form a metal carbonate. The CO2is in a gas phase comprising more than about 3% of the CO2by volume and having a relative humidity of more than about 1%, 5%, 10%, 20% or 50%. In some embodiments, the CO2is in a gas phase and is bubbled through water to create a humidified gaseous stream before contacting the metal silicate. In some embodiments, the CO2is atmospheric CO2with a concentration ranging between 100-5000 ppm. In some embodiments, the metal silicate is exposed to a humidified stream of CO2in dilute or concentrated concentrations. This method of contact does not include an organic or inorganic intermediate that serves as the transport medium for CO2between the gas-source and the metal silicate. As such, this manner of CO2-solid interaction is referred to as contactor-free.

[0112] Alternatively, the CO2can be dissolved in an aqueous solution comprising a CO2absorbing agent. In some embodiments, the CO2, which is in concentrated (500 ppm +) or dilute (atmospheric, 100-500ppm) is dissolved in an aqueous solution having about 20%, 30%, 40% or more of monoethanolamine (MEA). The solution is heated to above 35°C, above 40°C, above 50°C, or above 60°C. The reaction can last for more than about 30 minutes, more than about 1 hour, or more than about 2 hours to capture CO2dissolved in the solution. Besides atmosphere sources, CO2can be collected from any place such as power or heat generation sources, including, but not limited to, a concentrated 92% CO2stream from a biosynthesis process, a less concentrated, 15 %CO2 stream from a power or heat generation source, a dilute 1000 ppm CO2ocean source, or a dilute 400 ppm CO2atmospheric source. In some embodiments, the metal oxide, hydroxide, or silicate is placed into direct contact with the CO2- containing amine. The CO2-containing amine serves as the contactor that transfers CO2from low concentrations to high concentrations to enable carbonation reactions to occur. That is, to enable the formation of a carbonate phase. As such, this manner of CO2-solid interaction is referred to as one with a contactor. The CO2absorbing agent is selected from the group consisting of Monoethanolamine (MEA), Aminoethylethanoloamine (AEEA), Piperazine (PZ), Methyldiethanolamine (MDEA), Sodium hydroxide (NaOH), Adenosine monophos-phate (AMP), Diethylenetriamine (DETA), Diethanolamine (DEA), Triethylamine (TEA), Triisopropanolamine (TIPA), Potassium hydroxide (KOH), and any combination thereof..

[0113] The method thus provides a low-cost and low-energy means to capture CO2from the atmosphere, store (sequester) it as a carbonate, transport it as carbonate(s), and then heat the carbonated mixture in unsaturated steam to release the CO2as a gas mixture of water and CO2, condense the water phase and use the remaining CO2 as a high purity commercial source of CO2. At the same time, the remaining oxide product, such as calcium monosilicate, resulting from the heated unsaturated steam treatment can be reused to capture additional CO2species at room temperature and atmospheric pressure, or other temperatures or other temperatures and pressures suited for CO2capture, and the entire process can be repeated as means to create a CO2supply chain. Alternatively, the calcium silicate for other purposes, such as cement, soil amendment or nutritional supplement.. In either of these situations, a means to recycle cement or repeatedly capture, store, transport, and dispense CO2is established. Alternatively, the above cycle can be an upcycle process instead of a recycle process. For example, a mixture of calcium silicate hydrates can capture, store, and transport CO2by conversion to calcium carbonate, followed by treatment with heated unsaturated steam to form Ca5Si2O9•H2O or other calcium silicates. The formation of this upcycled oxide will release a gas mixture of CO2and water and condense the water to provide a high-purity stream of CO2. Alternatively, Ca5Si2O9•H2O then be used to capture, store, and transport CO2as carbonates, and again subjected to heated, unsaturated steam to release CO2, as mentioned earlier. This heating process could create Ca5Si2O9•H2O or make a mixture of different oxides, that have utility for a CO2supply chain. Alternatively, the upcycled Ca5Si2O9•H2O could be used as a cement or a soil amendment. Either way, the process of carbonation and decarbonation can create a closed loop supply chain of CO2, or the availability of low carbon footprint cementitious materials. This is feasible for recycling, where monocalcium silicate can be recycled repeatedly without composition change or other kinds of calcium silicates, such as a mixture of different hydrates are upcycled with a composition change taking place at least during one cycle or more.

[0114] The metal silicate used for capturing CO2in contactor or contactor-free configuration include for example, one or more of CaSiO3,Ca2SiO4, Ca3SiO5, Mg2SiO4, Fe2SiO4, Mn2SiO4, MgSiO3, and FeSiO3. The metal silicate can be resourced from a recycled or a waste material. In some embodiments, the silicate is CaSiO3. In some embodiments, themetal silicate is CaSiO3, Ca2SiO4,or any other calcium silicate phase. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. In other embodiments, the metal silicate is sourced from calcium silicate hydrates present in demolition waste. Other possible calcium silicate phases are listed in the Figures 6, 7, or 8.

[0115] In any embodiments of the methods disclosed herein, a metal silicate may also contain hydroxide (e.g., Mg3Si2O5(OH)4,Ca6Si6O17(OH)2) or may be in the form of a hydrate. In any embodiments, the CO2absorbing agent (contactor) may not be necessary. Instead, the metal silicate may be directly exposed to atmospheric CO2and resultantly carbonated by atmospheric CO2.

[0116] The captured CO2can be regenerated with processes described above for the synthesis of multi-cation oxide compound via the HVS material synthesis technique. The procedure generally includes:

[0117] (a ) exposing a mixture of the metal carbonate and SiO2to an unsaturated water vapor with a partial pressure greater than 1 atm, and can be between about 40 atm and about 80 atm; (b) heating the reaction vessel to a temperature of between about 300°C and about 500°C, up to 1000°C for a sufficient period of time to release CO2.

[0118] The water vapor is generated by heating liquid water in the reaction vessel, and the amount of the liquid water is so controlled that the resulting water vapor is unsaturated. In some embodiments, the amount of liquid water is no more than about 3% of the volume of the reaction vessel and the temperature is about 350°C. The amount of water can vary depending on the temperature as explained above. The unsaturated water vapor can also be introduced into the heated reaction vessel. The unsaturated water vapor can also be introduced by the thermal decomposition of a hydroxide material present inside the reaction vessel: for example, magnesium hydroxide. Viz., reaction (4) Mg(OH)2⇌ MgO + H2O (4)

[0119] As explained above, the heat for promoting the reaction can be provided by a molten salt solution, which contain for example one or more agents selected from the group consisting of, but not limited to NaCl, KCl, LiCl, and LiF. In some embodiments, the heat for promoting the reaction can be from any of the following, or any combination of: resistive heating, solar thermal, geothermal, waste-heat, combustion heat, solar photo-voltaic.

[0120] In some embodiments of the carbonation step and / or decarbonation step in any of the methods disclosed herein, the temperature may range from about 101 ºC to 1000 ºC, all subunits and sub-ranges included. In some exemplary embodiments, the lower limit of the temperature range is about 50 ºC, 100 ºC, 150 ºC 200 ºC, 250 ºC, 300 ºC, 350 ºC, 400 ºC, 500 ºC, 600 ºC, 700 ºC, 800 ºC or higher, and the upper limit of the range is about 100 ºC, 150 ºC, 200 ºC, 250 ºC, 300 ºC, 350 ºC, 400 ºC, 500 ºC, 600 ºC, 700 ºC, 800 ºC, 900 ºC, 1000 ºC, 1200 ºC, 1400 ºC, 1600 ºC, 1800 ºC, or 2000 ºC. More non-limiting examples of temperature include about 50 ºC, 80 ºC, 100 ºC, 150 ºC, 200 ºC, 250 ºC, 300 ºC, 350 ºC, 400 ºC, 450 ºC, 500 ºC, 550 ºC, 600 ºC, 650 ºC, 700 ºC, 750 ºC, 800 ºC, 850 ºC, 900 ºC, 950 ºC and 1000 ºC.

[0121] In other embodiments, the captured CO2can be readily transported and released if needed. The captured CO2can be released by the procedure similar to the recycling invention described above: which involves exposing a mixture of the metal carbonate and SiO2or other metal or metalloid oxide to an unsaturated water vapor with a partial pressure of between about 1 atm and about 80 atm; and heating the reaction vessel to a temperature of between about 300°C and about 500°C, up to 1000°C for a sufficient period of time to release CO2. This de- carbonated mixture can now be used for carbon capture once again. Methods according to this aspect of the invention need not use waste materials, although they can. The utility of unsaturated water vapor for the decarbonation prevents any sintering and coarsening effects of the materials and allows the material to be cycled numerous times between the carbonated and de-carbonated form without any performance loss (i.e., degradation in ability to carbonate). This has value for the process of “looping”. Looping is used in power plants, industrial manufacturing, and direct capture of carbon from air (DAC). A typical looping process captures carbon, using CaO to react with CO2 to form CaCO3. Once the CaO is reacted substantially, the CaCO3is heated to a high temperature, typically 850-1000˚C, to release the CO2for compression and burial underground or compression and storage as a liquid in insulated tanks. The problem with this process is substantial energy is required to release the CO2. More importantly, during each cycle the CaO particle size increases, which reduces the carbonation kinetics and amount of CO2that can be stored each cycle. The situation is rectified by using comminution to reduce the CaO particle size. Comminution is a very inefficient and energy intensive process.

[0122] The recycling and upcycling processes outlined here solve this problem because each time the carbonated mixture is reacted with heated unsaturated steam, the resultingparticle size small and reactive. We believe this is the result because the heated unsaturated steam induces hydrothermal vapor synthesis, which is a reactive crystal growth process that produces small particles. This reactive crystallization process contrasts with the conventional high temperature calcination process that induces CaO sintering, which is well known to reduce surface area and create large particles while the reactive crystallization process does not increase the crystal size to the extent where its ability to capture and store CO2is compromised. Resultantly, the use of this recycling or upcycling process will be able to loop CO2 for substantially more cycles without the need to comminute or discard the material. In addition, the lower temperatures (200-500˚C) for the hydrothermal vapor synthesis process will conserve energy to an extent where renewable energy sources could be used to power the process instead of fossil fuels. Examples Example 1 Reducing the particle size and increasing the surface area of materials via the recycling process.

[0123] Generally, the particle size of a material is reduced through a milling process in which media physically impacts the material and causes breakage. The surface area of these materials increases with decreasing particle size. This example details a methodology to chemically reduce the particle size without any mechanical grinding. Specifically, the material is cycled between its carbonate and silicate form several times, with each iteration decreasing the particle size and increasing the surface area.

[0124] Commercially available mineral CaSiO3(NYAD400), has a particle size of 8 μm and a surface area of 1.8 m2 / g. Five grams of this mineral (powdered) was carbonated as described by the carbonation section above. The carbonated mixture was composed of CaCO3and SiO2phases. These materials were then exposed to unsaturated water vapor for 12 h (350°C, 58 atm) as described by the materials section above. The powder retrieved after the unsaturated vapor treatment is high purity CaSiO3. The newly formed CaSiO3has a submicron particle size (400 nm) and has a surface much higher than the mineral form (>10 m2 / g). Repeating the carbonation and synthesis process further reduces the CaSiO3particle size and increases the surface area. The novelty here is the use of HVS to effect size reduction instead of energy intensive milling. This is particularly important for particles with sizes below 10 µm where the energy to achieve a smaller size requires exponentially higher kinetic energy. In cases where submicron particles are desired, such as in cases where the oxide must react rapidly with dilute CO2concentrations, the energy to reduce the particle size can generate more CO2than the CO2captured and sequestered. This positive emission of CO2is the case because milling is a slow inefficient process, even with the most powerful systems, such as media, attrition or vibratory milling, frequently requiring hours to produce submicron powders. In this case, HVS can create the submicron particle oxides with renewable energy in less than 1 hour to create a product that captures and sequesters more CO2than is generated in manufacturing the oxide. Example 2

[0125] This example describes the procedure for recycling and re-purposing Cured Hydraulic Portland Cement (CHPC) concrete via (a) material carbonation of CHPC for the production of carbonate powder, (b) material carbonation of CHPC for the conversion of CHPC into carbonated cement monoliths, (c) material synthesis for the conversion of CHPC to carbonate cement (CaSiO3) powder, (d) a combination of material carbonation and material synthesis for the purpose of forming CaSiO3from CHPC, (e) material synthesis for the purpose of forming Ca2SiO4, Ca3SiO5, and Ca5Si2O9•H2O from CHPC, and (f) ) Recycling and Re- purposing unused (uncured) hydraulic cement (HPC) via Material Synthesis: Converting unused (uncured) hydraulic cement to Ca2SiO4, Ca3SiO5, and Ca5Si2O9•H2O powder.

[0126] This application refers to the following non-exclusive list of cements when referring to cements that can be recycled using this invention: ASTM C150 designates 10 types of cement: Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate-sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate-sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration. (a) Recycling and Re-purposing cured hydraulic cement via Material Carbonation: Converting CHPC to CaCO3and SiO2powder. CHPC ⇌ CaCO3+ SiO2 (1)

[0127] CHPC consists of a mixture comprising CaCO3, Ca(OH)2, SiO2, Ca3SiO5, Ca2SiO4, and Calcium Silicate Hydrate (CSH) phases, among other phases. There are other phases present as well. These comprise of various calcium aluminate (and hydrated andcarbonated forms) and calcium aluminoferrite phases (and hydrated and carbonated forms). If the material being recycled is cured concrete, then aggregate is present as well.

[0128] The recycling process proceeds as follows: The cured hydraulic cement is crushed into fine powder (particle size < 200 μm) by a combination of jaw-crushing, hammer milling, and ball milling. If present, and chemically incompatible, the aggregate is sieved out of the mixture prior to fine (ball) milling.

[0129] Ten grams of this mixture is placed into a carbonation chamber (i.e., autoclave) for material carbonation. Liquid water is placed on the inside base of the autoclave. The autoclave is then sealed according to manufacturer’s specifications and heated to 90oC. This temperature creates a wet and humid atmosphere. The humidity is created by heating water in the autoclave, it is between 0.1 – 100% humidity. Upon reaching 90°C, gaseous CO2(up to 20 psig) is introduced into the autoclave. The autoclave is then kept isothermally for 24 h. After 24 h, the autoclave is depressurized, and the material is removed and characterized. Note, another variation of material carbonation can consist of flowing humidified (wet) CO2gas at any pressure and temperature through the autoclave.

[0130] Thermogravimetric analysis was used to gain insight on the degree of recycling that occurred. An unreacted cured Portland cement thermal decomposition profile has a large mass loss that occurs after 100oC which corresponds to the decomposition of calcium silicate hydrate phases. There is also an obvious mass loss at around 430oC which corresponds with the decomposition of calcium hydroxide (Portlandite). After carbonation, these carbonatable phases are transformed into carbonate phases. Some of these carbonate phases, especially CaCO3, have a high decomposition temperature (>600oC). Thus, thermogravimetric analysis can be used to determine the degree of recycling by determining the degree of carbonation that occurred. The carbonated cement samples were heated from room temperature to 1000°C at a heating rate of 20°C / min in a flowing N2atmosphere (50 mL / min). In this example, thermogravimetric analysis reveals that the typical hydraulic cement phases were transformed into carbonate phases. This is shown by the difference between the CHPC and carbonated CHPC decomposition profiles, specifically, by the reduction of water-containing phases.

[0131] Further, if the unrecycled hydraulic cement has a known composition, a theoretical maximum carbonation extent can be determined by relating the mass-percent of carbonate decomposition with the theoretical value. Equation 10 below describes the relationship between thermogravimetric mass loss due to carbonate decomposition (ML) andthe extent of reaction (Y, %), which for this example is also referred to as the degree of recycling.

[0132] Modenotes the molar mass ratio between CO2and material being carbonated, which is the amount of CO2corresponding to a 100 mol% complete carbonation reaction (e.g., 0.379 for CaSiO3that was fully carbonated into CaCO3and SiO2).

[0133] X-ray diffraction identified the newly formed phases to be SiO2, and CaCO3. In some cases, the SiO2phase is partially or fully amorphous and cannot be identified in x-ray diffraction. This can be seen by comparing the pre- and post-carbonation x-ray diffraction patterns. These newly formed phases are now the recycled products of cured hydraulic cement and can now be used in any application CaCO3and SiO2are desired. For example, the CaCO3can be used as a pigment, or the combination of the products (CaCO3and SiO2) can be used as raw materials for cement production. These materials can also be used directly as a cement additive. These materials can also be used as Supplemental cementitious materials (SCM). There may also be other phases, such as Calcium aluminate, or other phases present in the waste cement blend being recycled. Some of these other phase may form metal carbonates. In some cases, these metal carbonates are Calcium Carbonates.

[0134] Further, material carbonation of the cured cement does not need to proceed to 100% reaction, rather the recycled mixture can be of desired purity. For example, the carbonation reaction can proceed to 20 mol % to create a mixture of 20 mol% CaCO3and SiO2,with the remainder being unreacted oxides, hydroxides, hydrates, hydrous oxides, and carbonates in the system, whether the aforementioned are amorphous or crystalline, or a mixture of the aforementioned structural states. (b) Recycling and Re-purposing cured hydraulic cement via Material Carbonation: Converting cured hydraulic cement to CaCO3and SiO2monoliths. CHPC ⇌ CaCO3 + SiO2 (monolithic product)

[0135] CHPC consists of a mixture comprising CaCO3, Ca(OH)2, SiO2, Ca3SiO5, Ca2SiO4, and Calcium Silicate Hydrate (CSH) phases, among other phases. There are other phases present as well. These comprise of various calcium aluminate (and hydrated and carbonated forms) and calcium aluminoferrite phases (and hydrated and carbonated forms). If the material being recycled is cured concrete, then aggregate is present as well. This applicationrefers to the following non-exclusive list of cements when referring to cements that can be recycled using this invention: ASTM C150 designates 10 types of cement: Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate- sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate- sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0136] The recycling process proceeds as follows: The cured hydraulic cement is crushed into fine powder (particle size < 200 μm) by a combination of jaw-crushing, hammer milling, and ball milling. If present, and chemically incompatible, the aggregate is sieved out of the mixture prior to fine (ball) milling.

[0137] Five grams of this mixture is uniaxially pressed into a 13-mm cylindrical pellet using 2 metric tonnes of force. This uniaxial pressing step is not required, but eases the powder handling process. This pellet is placed into a carbonation chamber (i.e., autoclave) for material carbonation. Liquid water is placed on the inside base of the autoclave. The autoclave is then sealed according to manufacturer’s specifications and heated to 90°C. This temperature creates a wet and humid atmosphere. The humidity is created by heating water in the autoclave, it is between 0.1 – 100% humidity. Upon reaching 90°C, gaseous CO2(up to 20 psig) is introduced into the autoclave. The autoclave is then kept isothermally for 24 h. After 24 h, the autoclave is depressurized, and the material is removed and characterized. Another variation of material carbonation can consist of flowing humidified (wet) CO2 gas at any pressure and temperature through the autoclave.

[0138] After removal, this pellet was weighed and dimensioned to determine whether a mass, size, or shape change occurred during carbonation. It was found that the pellet had gained ~10 wt % mass, retained its size, and retained its shape.

[0139] Afterwards, the pellet was crushed in compressive mode to determine its compressive strength. The strength was determined to be >70 MPa, which indicates that particle bonding occurred during the carbonation process. After crushing, the crushed particles are milled to fine powder for thermogravimetric and x-ray diffraction analysis.

[0140] Thermogravimetric analysis was used to gain insight on the degree of recycling that occurred. An unreacted cured Portland cement thermal decomposition profile has a large mass loss that occurs after 100°C which corresponds to the decomposition of calcium silicate hydrate phases. There is also an obvious mass loss at around 430oC which corresponds with the decomposition of calcium hydroxide (Portlandite). After carbonation, these phases are transformed into carbonate phases, which has a high temperature (>600oC) decomposition. Thus, thermogravimetric analysis can be used to determine the degree of recycling by determining the degree of carbonation that occurred. In this example, the carbonated cement samples were heated from room temperature to 1000°C at a heating rate of 20°C / min in a flowing N2atmosphere (50 mL / min). This analysis revealed that the typical hydraulic cement phases were transformed into carbonate phases.

[0141] Further, if the unrecycled hydraulic cement has a known composition, a theoretical maximum carbonation extent can be determined by relating the mass-percent of carbonate decomposition with the theoretical value. The equation below describes the relationship between thermogravimetric mass loss due to carbonate decomposition (ML) and the extent of reaction (α , %), which for this example is also referred to as the degree of recycling.

[0142] Modenotes the molar mass ratio between CO2and material being carbonated, which is the amount of CO2corresponding to a 100 mol% complete carbonation reaction (e.g., 0.379 for CaSiO3that was fully carbonated into CaCO3and SiO2).

[0143] X-ray diffraction identified some of the newly formed phases to be SiO2, and CaCO3. This can be seen by comparing the pre- and post-carbonation x-ray diffraction patterns. These newly formed phases indicate that cured hydraulic Portland cement can be used as a raw material for carbonate cement applications with minimal pre-recycling processing. In some cases, the SiO2phase is partially or fully amorphous and cannot be identified in x-ray diffraction.

[0144] Further, material carbonation of the cured cement does not need to proceed to 100% reaction, rather the recycled mixture can be of desired purity. For example, the carbonation reaction can proceed to 20 mol% to create a mixture of 20 mol% CaCO3and SiO2,with the remainder being unreacted oxides, hydroxides, hydrates, hydrous oxides, andcarbonates in the system, whether the aforementioned are amorphous or crystalline, or a mixture of the aforementioned structural states. (c) Recycling of cured hydraulic cement via Material Synthesis: Converting CHPC to CaSiO3powder. CHPC ⇌ CaSiO3

[0145] CHPC consists of a mixture comprising CaCO3, Ca(OH)2, SiO2, Ca3SiO5, Ca2SiO4, and Calcium Silicate Hydrate (CSH) phases, among other phases. There are other phases present as well. These comprise of various calcium aluminate (and hydrated and carbonated forms) and calcium aluminoferrite phases (and hydrated and carbonated forms). If the material being recycled is cured concrete, then aggregate is present as well. If the material being recycled is cured concrete, then aggregate is present as well.

[0146] This application refers to the following non-exclusive list of cements when referring to cements that can be recycled using this invention: ASTM C150 designates 10 types of cement: Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate-sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate-sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0147] The recycling process proceeds as follows: The cured hydraulic cement is crushed into fine powder (particle size < 200 μm) by a combination of jaw-crushing, hammer milling, and ball milling. If present, and chemically incompatible, the aggregate is sieved out of the mixture prior to fine (ball) milling. Afterwards, powdered silica (crystalline, semi- crystalline, amorphous, or a mixture of the aforementioned structural states) is added to the mixture to create a 1:1 molar ratio of calcium to silica. If silica is not added, then 100% conversion to CaSiO3 would not be possible since the molar quantity of calcium is greater than silica. Thus, depending on the material synthesis procedure, one or more calcium-rich phases might form (e.g., Ca2SiO4, Ca3Si2O7, Ca3SiO5, or any other calcium-rich calcium silicate phase, which may include a calcium silicate hydrate and a calcium silicate carbonate, and a calcium silicate carbonate hydrate).

[0148] This mixture (10 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have a volume fill-percent of 3% to achieve an unsaturated water partial pressure of about 65 atm at 500°C. The inorganic mixture is either dispersed in the liquid water of suspended above. The autoclave is kept isothermal at 500oC for 12 h; after which it is depressurized. After depressurization, the reactor is cooled to room-temperature. After cooling, the synthesized material is removed from the autoclave. X-ray diffraction (Fig. 8) identified the newly formed phase to be β-CaSiO3. These newly formed phases are now the recycled products of cured hydraulic cement and can now be used in any application β-CaSiO3is desired. For example, the β-CaSiO3is inherently carbonate cement and can be directly used in all carbonate cement applications.

[0149] Further, material synthesis of the cured cement does not need to proceed to 100% reaction, rather the recycled mixture can be of desired purity. For example, the synthesis reaction can proceed to 20 mol% to create a mixture of 20 mol% CaCO3and SiO2,with the remainder being unreacted oxides, hydroxides, hydrates, hydrous oxides, and carbonates in the system, whether the aforementioned are amorphous or crystalline, or a mixture of the aforementioned structural states.

[0150] Another embodiment of this recycling process could include replacing or supplementing the HVS reaction with, for example, a thermal treatment (>650oC), an unsaturated water vapor-based thermal treatment (>450oC). In all embodiments of this recyc- ling process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics.(d) Recycling of cured hydraulic cement via Material Carbonation and Material Synthesis: Converting cured hydraulic cement to CaSiO3powder. CHPC ⇌ CaSiO3

[0151] CHPC consists of a mixture comprising CaCO3, Ca(OH)2, SiO2, Ca3SiO5, Ca2SiO4, and Calcium Silicate Hydrate (CSH) phases, among other phases. There are other phases present as well. These comprise of various calcium aluminate (and hydrated and carbonated forms) and calcium aluminoferrite phases (and hydrated and carbonated forms). If the material being recycled is cured concrete, then aggregate is present as well. This application refers to the following non-exclusive list of cements when referring to cements that can be recycled using this invention: ASTM C150 designates 10 types of cement: Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate- sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate- sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0152] The recycling process proceeds as follows: The cured hydraulic cement is crushed into fine powder (particle size < 200 μm) by a combination of jaw-crushing, hammer milling, and ball milling. If present, and chemically incompatible, the aggregate is sieved out of the mixture prior to fine (ball) milling. Afterwards, powdered silica (crystalline, semi- crystalline, or amorphous, or a mixture of the aforementioned structural states) is added to the mixture to create a 1:1 molar ratio of calcium to silica. If silica is not added, then 100% conversion to CaSiO3would not be possible since the molar quantity of calcium is greater than silica. Thus, depending on the material synthesis procedure, one or more calcium-rich phases might form (e.g., Ca2SiO4, Ca3Si2O7, Ca3SiO5, or any other calcium-rich calcium silicate phase, which may include a calcium silicate hydrate and a calcium silicate carbonate, and a calcium silicate carbonate hydrate).

[0153] Ten grams of this mixture is placed into a carbonation chamber (i.e., autoclave) for material carbonation. Liquid water is placed on the inside base of the autoclave. The autoclave is then sealed according to manufacturer’s specifications and heated to 90oC. Thistemperature creates a wet and humid atmosphere. The humidity is created by heating water in the autoclave, it is between 0.1 – 100% humidity. Upon reaching 90oC, gaseous CO2(up to 20 psig) is introduced into the autoclave. The autoclave is then kept isothermally for 24 h. After 24 h, the autoclave is depressurized, the material is removed and characterized. Another variation of material carbonation can consist of flowing humidified (wet) CO2gas at any pressure and temperature through the autoclave. X-ray diffraction identified the newly formed phases to be SiO2, and CaCO3. In some cases, the SiO2 phase is partially or fully amorphous and cannot be identified in x-ray diffraction.

[0154] These newly formed phases are now the recycled products of cured hydraulic cement and can now be used as a raw material in carbonate cement production via material synthesis.

[0155] This new carbonated mixture (13.8 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have volume fill-percent of 3% to achieve an unsaturated water partial pressure of about 65 atm at 500°C. The mixture can be either dispersed in the liquid water of suspended above. The autoclave is kept isothermal at 500oC for 12 h; after which it is depressurized. After depressurization, the reactor is cooled to room- temperature.

[0156] After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be β-CaSiO3. These newly formed phases are now the recycled products of cured hydraulic cement and can now be used in any application β-CaSiO3is desired. For example, the β-CaSiO3is inherently carbonate cement and can be directly used in all carbonate cement applications. In all embodiments of this recycling process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca- Si-O-H-C equilibria system. All polymorphs of the CaSiO3 (amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g.,Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics.

[0157] Further, neither material carbonation nor material synthesis of the cured cement does not need to proceed to 100 mol% complete degree of reaction, rather the recycled mixture can be reacted and carbonated to different degrees of reaction. For example, the synthesis reaction can proceed to a degree of reaction of 20 mol% to create a mixture of 20 mol% CaCO3and SiO2,with the remainder being unreacted oxides, hydroxides, hydrates, hydrous oxides, and carbonates in the system, whether the aforementioned are amorphous or crystalline.

[0158] Another embodiment of this recycling process could include replacing or supplementing the HVS reaction with, for example, a thermal treatment (>650oC), an unsaturated water vapor-based thermal treatment (>450oC). In all embodiments of this recycling process, the formed phase does not have to be solely β-CaSiO3, but can also be α- CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non- exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics. (e) Recycling and Re-purposing cured hydraulic cement via Material Synthesis: Converting cured hydraulic cement to Ca2SiO4, Ca3SiO5, and Ca5Si2O9•H2O powder. CHPC ⇌ Ca2SiO4+ Ca3SiO5+ Ca5Si2O9•H2O

[0159] CHPC consists of a mixture comprising CaCO3, Ca(OH)2, SiO2, Ca3SiO5, Ca2SiO4, and Calcium Silicate Hydrate (CSH) phases, among other phases. There are other phases present as well. These comprise of various calcium aluminate (and hydrated and carbonated forms) and calcium aluminoferrite phases (and hydrated and carbonated forms). If the material being recycled is cured concrete, then aggregate is present as well.

[0160] This application refers to the following non-exclusive list of cements when referring to cements that can be recycled using this invention: ASTM C150 designates 10 types of cement: Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate-sulfate resistance, air entraining, Type II (MH): Moderate heatof hydration and moderate-sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0161] The recycling process proceeds as follows: The cured hydraulic cement is crushed into fine powder (particle size < 200 μm) by a combination of jaw-crushing, hammer milling, and ball milling. If present, and chemically incompatible, the aggregate is sieved out of the mixture prior to fine (ball) milling.

[0162] This mixture (10 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have volume fill-percent of 3% to achieve an unsaturated water partial pressure of about 68 atm at 500°C. The mixture can be either dispersed in the liquid water of suspended above. The autoclave is kept isothermal at 500oC for 12 h; after which it is depressurized. After depressurization, the reactor is cooled to room-temperature. After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be predominately Ca5(SiO4)2(OH)2, with a trace of Ca(OH)2. Thermogravi- metric decomposition of the formed phases confirms the presence of Ca(OH)2and also shows additional hydrate or carbonate presence at higher temperature. These newly formed phases are now the recycled product of cured hydraulic cement and can now be used in any application Ca5(SiO4)2(OH)2is desired.

[0163] For example, this phase can be carbonated and used in carbonate cement. This phase can also be hydrated and used as a replacement for hydraulic cement. A mixture of carbonation and hydration can also be used to create a hydrated and carbonated cement.

[0164] Further, material synthesis of the cured cement does not need to proceed to 100% reaction; rather the recycled mixture can be of desired purity. For example, the synthesis reaction can proceed to 20 mol% to create a mixture of 20 mol% CaCO3and SiO2,with the remainder being unreacted oxides, hydroxides, hydrates, hydrous oxides, and carbonates in thesystem, whether the aforementioned are amorphous or crystalline, or a mixture of the aforementioned structural states.

[0165] Another embodiment of this recycling process could include replacing or supplementing the HVS reaction with, for example, a thermal treatment (>450oC), an unsaturated water vapor-based thermal treatment (>450oC). In all embodiments of this recycling process, the formed phase does not have to be solely Ca5(SiO4)2(OH)2,but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non- exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics. (f) Recycling and Re-purposing unused (uncured) hydraulic cement (HPC) via Material Synthesis: Converting unused (uncured) hydraulic cement to Ca2SiO4, Ca3SiO5, and Ca5Si2O9powder. HPC ⇌ Ca2SiO4+ Ca3SiO5+ Ca5Si2O9•H2O

[0166] Unused or Uncured hydraulic Portland cement consists of a mixture comprising CaCO3, SiO2, Ca3SiO5, and Ca2SiO4 among other phases. These comprise of various calcium aluminate (and hydrated and carbonated forms) and calcium aluminoferrite phases (and hydrated and carbonated forms). If the material being recycled is cured concrete, then aggregate is present as well.

[0167] This application refers to the following non-exclusive list of cements when referring to cements that can be recycled using this invention: ASTM C150 designates 10 types of cement: Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate-sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate-sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High earlystrength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0168] The recycling process proceeds as follows: The unused cement powder is into a hydrothermal vapor synthesis chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of between 1 and 68 atm at 500°C. The mixture can be either dispersed in the liquid water of suspended above. The autoclave is kept isothermal at 500oC for 12 h; after which it is depressurized. After depressurization, the reactor is cooled to room-temperature. After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be predominately Ca5(SiO4)2(OH)2. This newly formed phase is now the recycled product of unreacted hydraulic cement and can now be used in any application Ca5(SiO4)2(OH)2is desired. For example, this phase can be carbonated and used in carbonate cement. They can also be hydrated and used as a replacement for hydraulic cement.

[0169] Further, material synthesis of the cured cement does not need to proceed to a degree of reaction of 100 mol % reaction, rather the recycled mixture is processed to a desired degree of reaction. For example, the synthesis reaction can proceed to 20 mol% to create a 20 mol% Ca5(SiO4)2(OH)2phase with the remainder being unreacted oxides, hydroxides, and carbonates in the system.

[0170] Another embodiment of this recycling process could include replacing or supplementing the HVS reaction with, for example, a thermal treatment (>450oC), an unsat- urated water vapor-based thermal treatment (>450oC). In all embodiments of this recycling process, the formed phase does not have to be solely Ca5(SiO4)2(OH)2,but can also be α- CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorph- ous, α-, β-, γ-, δ-, ε-) Ca2SiO4 (amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5 (amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicatecarbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics. Example 3 Recycling and Re-purposing cured carbonate cement via Material Synthesis: Converting cured carbonate cement to CaSiO3powder.

[0171] The following examples describe the procedure for recycling and re-purposing cured carbonate cement (CC) via (a) material synthesis. This procedure describes conversion of cured carbonate cement into uncured carbonate cement. CC ⇌ CaSiO3

[0172] As can be seen in the x-ray diffraction pattern, cured carbonate cement consists of a phase mixture of CaCO3, SiO2, and CaSiO3phases. Other phases may also exist within the cured carbonate cement blend. These phase may include reactive inorganic materials (“RIM”). These phases may non-exclusively include wollastonite, rankinite, belite, alite, and hatrurite in varying compositions. This material can be recycled by converting the carbonated phase blend that is comprised of calcium carbonate and silica mixture, back into a RIM. For example, back into CaSiO3. CaCO3 (s) + SiO2 (s) ⇌ CaSiO3 (s) + CO2 (g)

[0173] The closed-loop recycling process proceeds as follows: The cured carbonate cement is crushed into fine powder (particle size < 200 μm) by a combination of jaw-crushing, hammer milling, and ball milling. If present, and chemically incompatible, the aggregate is sieved out of the mixture prior to fine (ball) milling. If present and chemically compatible, the HVS reaction can proceed without the need to separate out the aggregate. In this case, concrete rubble (CR) can be reconstituted as a concrete formulation without any need to add additional aggregate or common cement synthesis precursors like calcium carbonate and silica.

[0174] If the cured cement mixture does not have a 1:1 molar ratio of calcium to silica, then the corresponding oxide (calcium or silicon) is added to the mixture to create a 1:1 molar ratio of calcium to silica. If silica is not added, then 100% conversion to CaSiO3would not be possible, since the molar quantity of calcium is greater than silica. Thus, depending on the material synthesis procedure and corresponding chemical thermodynamics, an excess calcium phase might be created (e.g., Ca2SiO4, Ca3Si2O7, Ca3SiO5).

[0175] This mixture (10 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 350oC for 12 h; after which it is depressurized. After depressurization, the reactor is cooled to room-temperature. After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be β-CaSiO3. These newly formed phases are now the recycled products of cured hydraulic cement and can now be used in any application β-CaSiO3is desired. For example, the β-CaSiO3is inherently carbonate cement and can be directly used in all carbonate cement applications.

[0176] Further, material synthesis of the cured cement does not need to proceed to 100 mol% reaction, rather the recycled mixture can be of desired purity. For example, the synthesis reaction can proceed to 20 mol% to create a mixture of 20 mol% CaCO3and SiO2,with the remainder being unreacted oxides, hydroxides, hydrates, hydrous oxides, and carbonates in the system, whether the aforementioned are amorphous or crystalline, or a mixture of the aforementioned structural states.

[0177] Another embodiment of this recycling process could include replacing or supplementing the HVS reaction with, for example, a thermal treatment (>650oC), an unsaturated water vapor-based thermal treatment (>450oC). In all embodiments of this recycling process, the formed phase does not have to be solely β-CaSiO3. Still, it can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5, or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4 (amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5 (amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non- exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics.Example 4

[0178] The following example describes the procedure for recycling and re-purposing Cured Hydraulic Portland Cement (CHPC) concrete and Cured Carbonate Cement Concrete.

[0179] The recycling process proceeds as follows: The cured hydraulic cement concrete is crushed into fine powder (particle size < 200 μm) by a combination of jaw-crushing, hammer milling, and ball milling. The fine mixture comprises cured cement phases (calcium silicate hydrates, calcium carbonates, etc), sand (dolomitic, silica, olivine), and gravel (limestone, dolomite, anorthite, recycled concrete). The Ca:Si molar ratio is determined by energy dispersive spectroscopy. The weight percent of remaining elements must not exceed 50 wt %. A Ca:Si ratio of 1 would enable production of CaSiO3for carbonate cement applications. A Ca:Si ratio of >1, up to 3 enables production of Ca2SiO4, Ca3SiO5and Ca5(SiO4)2(OH)2for carbonate and hydraulic cement applications. In all embodiments of this recycling process, the formed phase does not have to be solely β-CaSiO3. Still, it can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca- Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ- , δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ- , δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ- , δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics.

[0180] To enable this conversion, the fine mixture is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of between 1 and 68 atm at 500°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 500oC for 12 h; after which it is depressurized. After depressurization, the reactor is cooled to room-temperature. After cooling, the synthesized material is removed from the autoclave. In this example, X-ray diffraction identified the newly formed phase to be predominately Ca5(SiO4)2(OH)2. This newly formed phase is now the recycled product of crushed OPC concrete (without aggregate separation) and can now be used in any applicationCa5(SiO4)2(OH)2is desired. The same procedure can be used to create the recycled product of carbonate cement concrete (without aggregate separation). For example, this phase can be carbonated and used in carbonate cement. They can also be hydrated and used as a replacement for hydraulic cement.

[0181] Further, material synthesis reaction does not need to proceed to 100 mol% reaction, rather the resulting reaction product can be of desired purity. For example, the material synthesis reaction can proceed to create a 20 mol% Ca5(SiO4)2(OH)2phase with the remainder being unreacted oxides, hydroxides, and carbonates in the system. Example 5

[0182] The following examples describe the procedure for recycling and re-purposing used lithium cathodes via (a) material carbonation and material synthesis. This procedure describes conversion of used lithium cathodes into fresh (new) lithium cathodes. Recycling and Re-purposing advanced materials via Material Carbonation and Material Synthesis:

[0183] Lithium manganate battery materials are commonly made by various synthesis methods, such as hydrothermal, solid state, and sol-gel methods. For example, the solid-state method is used as follows: ½Li2CO3+ 2MnO + ¾O2⇌ LiMn2O4+ ½CO2

[0184] Conversely, LiMn2O4can be converted to the starting reactants by simply carbonating the battery material. The resulting mixture of carbonates of lithium and manganes can then be reacted to form new LiMn2O4. For example, a sheet of lithium cathode material (LiMn2O4) is shredded into 40 mm x 50 mm pieces. Afterwards, it is ball milled for 1 h into fine powder (<200 μm). Ten grams of this mixture is placed into a carbonation chamber (i.e., autoclave) for material carbonation. Liquid water is placed on the inside base of the autoclave. The autoclave is then sealed according to manufacturer’s specifications and heated to 90°C. This temperature creates a wet and humid atmosphere. The humidity is created by heating water in the autoclave, it is between 0.1 – 100% humidity. Upon reaching 90°C, gaseous CO2(up to 20 psig) is introduced into the autoclave. The autoclave is then kept isothermally for 24 h. After 24 h, the autoclave is depressurized, and the material is removed and characterized. Another variation of material carbonation can consist of flowing humidified (wet) CO2gas at any pressure and temperature through the autoclave. X-ray diffraction identified the newly formed phases to be Li2CO3and MnO. The newly formed phases are now the recycled products of used lithium cathodes and can be used in applicable applications. In this example, they are usedto synthesize the LiMn2O4cathode, using the same reaction used in the original synthesis. Thus, this is a closed loop process that can be cycled as many times as needed. More details are as follows:

[0185] The newly carbonated electrode material is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water of suspended above. The autoclave is kept isothermal at 350°C for 12 h; after which it is depressurized. After depressurization, the reactor is cooled to room- temperature. After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be LiMn2O4. This newly formed phase is now the recycled products of used lithium cathode and can be used in any desired applicable application, for example, lithium cathodes.

[0186] Further, neither material carbonation nor material synthesis of the LiMn2O4needs to proceed to 100 mol% reaction, rather the recycled mixture is processed to a desired level of purity. For example, the synthesis reaction can proceed to 20 mol% to create a mixture of 20 mol% LiMn2O4with the remainder being Li2CO3and MnO in the system. Example 6

[0187] The following examples describe the procedure for recycling a carbon capture and storage material via material synthesis. Specifically, this example describes the procedure for recycling and cycling a carbon capture filter that is in (a) monolithic brick (b) coating (c) thin film (d) membrane (e) fiber (f) platelet (g) whisker and (h) equiaxed powder form. This procedure describes conversion of used (fully carbonated) carbon capture material into a fresh (new) carbon capture material. This procedure resultantly also describes the method to release the stored carbon dioxide for utilization of the chemical carbon dioxide. (a) Recycling carbon capture and storage-material via Material Synthesis: Converting used CaCO3and SiO2Monolithic Brick to a fresh (new) CaSiO3brick.

[0188] A carbon capture and storage material (monolithic brick) is composed of a metal silicate that reacts with flowing carbon dioxide in a flue gas stream. The flue gas is comprised of a multi-gas mixture that contains about 5-25 vol % CO2. This brick is made by creating anapproximately 80 wt% water-based slurry of CaCO3and SiO2. The slurry is cast into a cube mold and dried at 80oC for 24 h. The dried cube is treated in hydrothermal vapor (500oC, 850 psi) for 24 h. After the treatment, the crystallographic composition of this cube is no longer CaCO3& SiO2, and is instead a high-surface area, sub-micron, CaSiO3microstructure. This CaSiO3brick is now used as a carbon-capture filter by absorbing CO2at any desired location where CO2concentrations are >1 vol %.

[0189] In all embodiments of this invention, the metal-silicate phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ- , ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite).

[0190] The brick reaches the end of the carbon capture cycle once all of the metal silicate (CaSiO3) has been converted to calcium carbonate or the reaction rate is too slow to form substantial amounts of additional calcium carbonate. In other words, the formation of additional carbonate is kinetically limited (too slow) to capture and store the desired amount of CO2in the gas stream of interest in a specified timeframe.

[0191] The used carbon capture monolithic brick consists of a monolithic mixture of CaCO3, SiO2, and CaSiO3phases. In some cases, the CaSiO3may be in such low concentrations that this substance is not detected with commonly available methods such as x-ray diffraction. Nonetheless, this material can be recycled by converting the calcium carbonate and silica mixture back into CaSiO3(Reaction 8). CaCO3 (s) + SiO2 (s) ⇌ CaSiO3 (s) + CO2 (g)

[0192] The recycling process proceeds as follows:

[0193] A 13.8-gram monolithic brick is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of wateris chosen to be ~30 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The brick is suspended above. The autoclave is kept isothermal at 350oC for 12 h; after which it is depressurized. The outlet gas stream is collected, and the water vapor is condensed, and gaseous CO2is stored for future use (e.g., underground storage, application, sale). After depressurization, the reactor is cooled to room- temperature. After cooling, the synthesized brick is removed from the autoclave. The brick has lost approximately 3.8 grams of mass due to the evolved CO2. X-ray diffraction confirmed that the composition of the brick changed from CaCO3and SiO2(Fig. 15a) to the newly formed phase to be β-CaSiO3 (Fig. 15b). This new brick (β-CaSiO3) can be used in any desired application or reused as a carbon-capture filter.

[0194] Further, material synthesis of the used brick does not need to proceed to 100 mol% reaction, rather the material can be recycled to the desired purity. For example, the synthesis reaction can proceed to 20 mol% to create a mixture of 20 mol% CaSiO3with the remainder being unreacted CaCO3and SiO2in the brick.

[0195] In all embodiments of this process, the material synthesis reaction does not have to be solely producing the β-CaSiO3phase, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite).

[0196] Furthermore, when the synthesized product forms, the crystal size is very small, making it highly reactive to gases like carbon dioxide. This feature is novel as when conventional means, such as pyrothermal processing is used, the crystallite size of the CaSiO3is larger than that of the reactant CaCO3and SiO2, making it less reactive with CO2than in the prior cycle when the initial size of the CaSiO3was considerably smaller. This feature is possible because pyrothermal processes reduce surface area at the end its cycle while HVS processes increase surface area. This is because of the mechanism by which HVS operates where the use of water provides accelerates mass transport at low temperature while restricting the particle growth to very small particle sizes. This conservation of particle size makes this invention ideafor carbon capture, storage and release because this cycle can be maintained for an infinite number of cycles while conventional pyrothermal processes increase the particle size at a rapid rate, such that the material is no longer reactive to carbon dioxide flow streams. (b) Recycling carbon capture and storage-material via Material Synthesis: Converting used CaCO3and SiO2capture material (powder) to a fresh (new) CaSiO3powder.

[0197] A carbon capture and storage material (powder) is composed of a metal silicate that reacts with flowing carbon dioxide in a flue gas stream. The material can also be a (b) coating (c) thin film (d) membrane (e) fiber (f) platelet (g) whisker and (h) equiaxed powder form. The flue gas is comprised of a multi-gas mixture that contains about 5-25 vol % CO2. It reaches the end of the carbon capture cycle once all of the metal silicate has been converted to carbonate. Further, it can also reach the end of the carbon capture cycle if the formation of additional carbonate is kinetically limited (too slow) to capture and store the desired amount of CO2in the gas stream of interest. The used carbon capture material consists of a powder mixture of CaCO3, SiO2, and CaSiO3 phases. This material can be recycled by converting the calcium carbonate and silica mixture back into CaSiO3.

[0198] In all embodiments of this recycling process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-), Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics.

[0199] The recycling process proceeds as follows: A 13.8-gram powder mixture is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have volume fill- percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at350°C. The powder is suspended above the liquid water. The autoclave is kept isothermal at 350oC for 12 h; after which it is depressurized. The outlet gas stream is collected, and the water vapor is condensed, and gaseous CO2is stored for future use (e.g., underground storage, application, sale). After depressurization, the reactor is cooled to room-temperature. After cooling, the powder is removed from the autoclave. The powder has lost approximately 3.8 grams of mass due to the evolved CO2. X-ray diffraction confirmed that the composition of the brick changed from CaCO3 and SiO2 (Fig.15a) to the newly formed phase to be β-CaSiO3 (Fig. 15b). This new powder (β-CaSiO3) can be used in any desired application (cement, concrete, whiteners, carbon capture, etc.) or reused as a carbon-capture filter.

[0200] Further, material synthesis of the used powder does not need to proceed to 100 mol% reaction, rather the recycled mixture can be of desired purity. For example, the synthesis reaction can proceed to 20 mol% to create a mixture of 20 mol% CaSiO3with the remainder being unreacted CaCO3and SiO2in the powder. In all embodiments of this recycling process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca- Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics. Example 7

[0201] The following examples describe the procedure for recycling and re-purposing a dielectric material via (a) material carbonation and material synthesis. (a) Recycling and Re-purposing barium titanate via Material Carbonation and Material Synthesis: Converting used BaTiO3dielectric material to a fresh (new) BaTiO3powder.

[0202] This example details the recycling of the dielectric material present in a capacitor: A capacitor consists of a material with a high dielectric constant sandwiched between two electrodes. The dielectric ceramic material can exist in either a monolithic or rolled up film form. Nonexclusively, other forms such as coating, thin film, membrane, fiber, platelet, whisker and equiaxed powder form are also suitable form-factors. In both cases, the dielectricceramic is removed, crushed, and milled into powder form. The following procedure assumes the dielectric ceramic is composed of barium titanate (BaTiO3).

[0203] Ten grams of this mixture is placed into a carbonation chamber (i.e., autoclave) for material carbonation. Liquid water is placed on the inside base of the autoclave. The autoclave is then sealed according to manufacturer’s specifications and heated to 90oC. This temperature creates a wet and humid atmosphere. The humidity is created by heating water in the autoclave, it is between 0.1 – 100% humidity. Upon reaching 90oC, gaseous CO2 (up to 20 psig) is introduced into the autoclave. The autoclave is then kept isothermally for 24 h. After 24 h, the autoclave is depressurized, and the material is removed and characterized. Another variation of material carbonation can consist of flowing humidified (wet) CO2gas at any pressure and temperature through the autoclave. X-ray diffraction identified the newly formed phases to be Ba(OH)2, TiO2, and BaCO3. These newly formed phases are now the recycled products of used lithium cathodes and can be used in applicable application. In this example, they are used to synthesize fresh (new) BaTiO3powder.

[0204] This new carbonated mixture is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water of suspended above. The autoclave is kept isothermal at 350°C for 12 h; after which it is depressurized. After depressurization, the reactor is cooled to room-temperature. After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be BaTiO3. This newly formed phase is now the recycled products of used BaTiO3dielectric material and can be used in any desired applicable application, for example, lithium cathodes.

[0205] Further, neither material carbonation nor material synthesis of the cured cement does not need to proceed to 100 mol% reaction, rather the recycled mixture can be of desired purity. For example, the synthesis reaction can proceed to 20 mol% to create a mixture of 20 mol% BaTiO3with the remainder being Ba(OH)2, BaCO3, and TiO2in the system. Example 8

[0206] The following examples describe the procedure for recycling and re-purposing a non-oxide material via (a) material carbonation and material synthesis.Recycling and Re-purposing non-oxide material via Material Carbonation and Material Synthesis: Repurposing a CaB2material.

[0207] The CaB2 solid is first ball-milled into fine (<200 µm) powder. Ten grams of this powder is placed into a carbonation chamber (i.e., autoclave) for material carbonation. Liquid water is placed on the inside base of the autoclave. The autoclave is then sealed according to manufacturer’s specifications and heated to 90oC. This temperature creates a wet and humid atmosphere. The humidity is created by heating water in the autoclave, it is between 0.1 – 100% humidity. Upon reaching 90°C, gaseous CO2(up to 20 psig) is introduced into the autoclave.10 psi of oxygen is also introduced into the autoclave to have sufficient oxidation of the boron species. The autoclave is then kept isothermally for 24 h. After 24 h, the autoclave is depressurized, and the material is removed and characterized. Another variation of material carbonation can consist of flowing humidified (wet) CO2gas at any pressure and temperature through the autoclave. X-ray diffraction identified the newly formed phases to be CaCO3and B2O3. These newly formed phases are now the recycled products of used CaB2and can be used in applicable application. At this stage of the recycling process, the recycled products can be re-purposed for an application other than non-oxide ceramics.

[0208] For conversion back into a non-oxide ceramic, the following procedure is followed: This new carbonated mixture is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 1-L autoclave, the amount of water is chosen to be ~30 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water of suspended above. A reducing gaseous (e.g., carbon monoxide, CO, hydrogen, H2) or solid species (e.g., Aluminum metal, Al) is introduced to remove the oxygen from the B2O3species. The autoclave is kept isothermal at 350°C for 12 h; after which it is depressurized. After depressurization, the reactor is cooled to room-temperature. After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be CaB2. At this point, the high purity CaB2powder can be used for any desired application.

[0209] Further, neither material carbonation nor material synthesis of the non-oxide material does not need to proceed to 100% reaction, rather the recycled mixture can be ofdesired purity. For example, the synthesis reaction can proceed to 20% to create a mixture of 20wt% CaB2with the remainder being CaCO3and B2O3in the system.

[0210] The following examples are related to carbon capture. Example 9 Carbon (a) Capture, Storage, Transport and (b) Supply via a CaSiO3sponge at CO2concentrations greater than 50 vol %.

[0211] This example combines the recycling techniques described above to enable a carbon capture, storage, transport, and supply innovation:

[0212] A. CO2Capture. One hundred grams (100 g) of β-CaSiO3(metal silicate) powder is exposed to a gas stream that contains carbon dioxide gas. The >50 vol% carbon dioxide gaseous stream is humidified by bubbling through de-ionized water. The humidity is between 0.1 – 100% humidity. Another variation of material carbonation can consist of flowing humidified (wet) CO2gas at any pressure and temperature through the autoclave. Tap water, distilled, deionized, or even saline water can be utilized.

[0213] Upon exposure, the 100 g of CaSiO3reacts with the present CO2and forms a 138 g mixture of CaCO3and SiO2. It is worthwhile to note, that the form-factor of the silicate does not need to be a powder, but can also be a monolithic powder compact, as well as a monolithic material. The form-factor may also be a monolithic brick, coating, thin film, membrane, fiber, platelet, whisker and equiaxed powder form. The form-factor may also be a partial or full combination of all of the aforementioned form-factors. X-ray diffraction was used to confirm that the CaSiO3phase was consumed and a newly formed mixture of CaCO3and SiO2was formed. The produced CaCO3mineral acts as storage for the CO2gas for an infinite period (>100 years) at room temperature. (Note: Pure CaSiO3can store up to 38% of its mass in CO2. One tonne (1000 kg) of CaSiO3can store up to 380 kg of CO2. This powder is transported to the desired location by truck or any other mode of physical transportation, without the need for pressurization or refrigeration. (Note: A truckload carrying 100 tonnes of material (i.e., CaCO3mixed with SiO2) can produce 38 tonnes of CO2.) The truckload does not require refrigeration, as the CaCO3is stable at room temperatures.

[0214] Further, material carbonation of the silicate does not need to proceed to 100% reaction, rather the carbonation extent is selected based on numerous factors, including feasiblereaction kinetics. For example, the carbonation reaction can proceed to 20 mol% to create a mixture of 20 mol% CaCO3and SiO2with the remainder being unreacted silicate structures.

[0215] B. CO2Supply. For CO2gas supply, the 138 g carbon containing mixture (CaCO3:SiO2) produced during the capture process is now de-carbonated and converted back into the CaSiO3sponge via the following procedure: This mixture (138 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. To create the unsaturated water vapor pressure required to achieve HVS conditions, liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 10-L autoclave, the amount of water is chosen to be ~300 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 350°C for 1 h. Throughout the 1 h, the pressure in the reactor increases to ~63 atm due to the evolved carbon dioxide. After 1 h, the vessel is depressurized, and the gas is allowed to flow through a condenser. The water condensed (300 mL) and was collected. The remaining gaseous species is CO2gas. The purity of the collected CO2gas is determined to be >99%. At this stage, the gaseous CO2can be temporarily stored in compressed gas form and ready to be supplied for any desired application.

[0216] After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be β-CaSiO3. This newly formed phase is in the correct form-factor and has the same or similar chemical reactivity as the original β-CaSiO3used for carbon capture. Thus, it can once again be used as the carbon-capture sponge. In some embodiments, the HVS reaction vessel may be a batch, continuous, semi-batch, or semi- continuous reaction vessel.

[0217] Where a continuous, semi-continuous, or semi-batch reaction vessel is used, unreacted reactants may be removed and recycled back into the reaction vessel. It may also be possible to utilize a flow-through system that may comprise of a steam generator constantly providing a pressurized stream of unsaturated water vapor instead of vaporizing liquid water within. It may also be possible to inject steam at a pressure greater than the set value on a relief valve. This would create a continuous flow of steam within the reactor, flushing out all other produced gases (for example, the partial pressure of any gas produced as a result of a reaction would never increase beyond a certain limit due to the continuous flushing of unsaturated watervapor). This continuous flow of steam could also be utilized to minimize unwanted gaseous species inside the reactor vessel. For example, a gaseous byproduct may be produced throughout the reaction that may thermodynamically limit and resultantly halt the reaction. This gaseous by- product can be removed, if necessary, by the continuous flow of steam. The flow of steam can also be semi-continuous.

[0218] Additionally, material synthesis (or material de-carbonation) of the material does not have to proceed to 100 mol%, rather the created mixture of raw-materials can be of desired purity. For example, the de-carbonation reaction can proceed to 20 mol% to create a mixture of materials suitable for desired application. In all embodiments of this process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca- Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics. Example 10 Carbon (a) Capture, Storage, Transport and (b) Supply via a CaSiO3sponge at CO2concentrations greater than 100 ppm and less than 50 vol %.

[0219] This example combines the recycling techniques described earlier in this application to enable a carbon capture, storage, transport, and supply innovation:

[0220] A. CO2Capture. One hundred grams (100 g) of β-CaSiO3(metal silicate) powder is exposed to a gas stream that contains carbon dioxide gas. The carbon dioxide gaseous stream (greater than 3 and less than 50 vol %, for example, the flue gas stream from a coal fired powerplant) is humidified by bubbling through de-ionized water. The humidity is between 0.1 – 100% humidity. Another variation of material carbonation can consist of flowing humidified (wet) CO2gas at any pressure and temperature through the autoclave. It is worthwhile to note, that any water purity source can be utilized to generate the needed humidity. Tap water, distilled, deionized, or even saline water can be utilized.

[0221] Upon exposure, the 100 g of CaSiO3reacts with the present CO2and forms a 138 g mixture of CaCO3and SiO2. It is worthwhile to note, that the form-factor of the silicate does not need to be a powder, but can also be a monolithic powder compact, as well as a monolithic material. The form-factor may also be a monolithic brick, coating, thin film, membrane, fiber, platelet, whisker and equiaxed powder form. The form-factor may also be a partial or full combination of all of the aforementioned form-factors. X-ray diffraction was used to confirm that the CaSiO3 phase was consumed and a newly formed mixture of CaCO3 and SiO2was formed. The produced CaCO3mineral acts as storage for the CO2gas for an infinite period of time at room temperature. (Note: Pure CaSiO3 can store up to 38% of its mass in CO2. One tonne (1000 kg) of CaSiO3can store up to 380 kg of CO2. This powder is transported to the desired location by truck or any other mode of physical transportation, without the need for pressurization or refrigeration. (Note: A truckload carrying 100 tonnes of material (i.e., CaCO3mixed with SiO2) can produce 38 tonnes of CO2.) The truckload does not require refrigeration, as the CaCO3is stable at room temperatures.

[0222] Further, material carbonation of the silicate does not need to proceed to 100% reaction, rather the carbonation extent is selected based on numerous factors, including feasible reaction kinetics. For example, the carbonation reaction can proceed to 20 mol% to create a mixture of 20 mol% CaCO3and SiO2with the remainder being unreacted silicate structures.

[0223] B. CO2Supply. For CO2gas supply, the 138 g carbon containing mixture (CaCO3:SiO2) produced during the capture process is now de-carbonated and converted back into the CaSiO3sponge via the following procedure: This mixture (138 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. To create the unsaturated water vapor pressure required to achieve HVS conditions, liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 10-L autoclave, the amount of water is chosen to be ~300 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 350°C for 1 h. Throughout the 1 h, the pressure in the reactor increases to ~63 atm due to the evolved carbon dioxide.

[0224] After 1 h, the vessel is depressurized, and the gas is allowed to flow through a condenser. The water condensed (300 mL) and was collected. The remaining gaseous speciesis CO2gas. The purity of the collected CO2gas is determined to be >99%. At this stage, the gaseous CO2can be temporarily stored in compressed gas form and ready to be supplied for any desired application. In some embodiments, the HVS reaction vessel may be a batch, continuous, semi-batch, or semi-continuous reaction vessel. Where a continuous, semi- continuous, or semi-batch reaction vessel is used, unreacted reactants may be removed and recycled back into the reaction vessel. It may also be possible to utilize a flow-through system that may comprise of a steam generator constantly providing a pressurized stream of unsaturated water vapor instead of vaporizing liquid water within. It may also be possible to inject steam at a pressure greater than the set value on a relief valve. This would create a continuous flow of steam within the reactor, flushing out all other produced gases (for example, the partial pressure of any gas produced as a result of a reaction would never increase beyond a certain limit due to the continuous flushing of unsaturated water vapor). This continuous flow of steam could also be utilized to minimize unwanted gaseous species inside the reactor vessel. For example, a gaseous byproduct may be produced throughout the reaction that may thermodynamically limit and resultantly halt the reaction. This gaseous byproduct can be removed, if necessary, by the continuous flow of steam. The flow of steam can also be semi-continuous.

[0225] After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be β-CaSiO3. This newly formed phase is in the correct form-factor and has the same or similar chemical reactivity as the original β-CaSiO3used for carbon capture. Thus, it can once again be used as the carbon-capture sponge.

[0226] Additionally, material synthesis (or material de-carbonation) of the material does not have to proceed to 100 mol%, rather the created mixture of raw materials can be of desired purity. For example, the de-carbonation reaction can proceed to 20 mol% to create a mixture of materials suitable for desired application. In all embodiments of this process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5, or any other calcium silicate phase in the Ca- Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-) and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g.,Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics. Example 11 Carbon (a) Capture, Storage, Transport and (b) Supply via a MgO sponge at CO2concentrations between 100 ppm and 100 vol %.

[0227] This example combines the recycling techniques described above to enable a carbon capture, storage, transport, and supply innovation with an MgO Sponge.

[0228] A. CO2 Capture. Thirty-five (35) grams of magnesium oxide (MgO) powder is exposed to a gas stream that contains carbon dioxide gas. The carbon dioxide gaseous stream (e.g., ~10 vol% CO2gas in a flue gas stream from a coal fired powerplant) is humidified by bubbling through de-ionized water. Another variation of material carbonation can consist of flowing humidified (wet) CO2gas at any pressure and temperature through the autoclave. Tap water, distilled, deionized, or even saline water can be utilized.

[0229] Upon exposure, the 35 g of MgO reacts with the present CO2and forms a ~73 g powder mixture of MgCO3. It is worthwhile to note, that the form-factor of the MgO phase does not need to be a powder, but can also be a monolithic powder compact, as well as a monolithic material. The form-factor may also be a monolithic brick, coating, thin film, membrane, fiber, platelet, whisker and equiaxed powder form. The form-factor may also be a partial or full combination of all of the aforementioned form-factors. X-ray diffraction was used to confirm that the MgO phase was consumed and MgCO3phase was formed. The produced MgCO3mineral acts as storage for the CO2gas for an infinite period of time at room temperature. (Note: Pure MgO can store up to ~109% of its mass in CO2. One tonne (1000 kg) of MgO can store up to 1092 kg of CO2. This powder is transported to the desired location by truck or any other mode of physical transportation, without the need for pressurization or refrigeration. (Note: A truckload carrying 100 tonnes of material (i.e., MgCO3) can produce 109.2 tonnes of CO2.) The truckload does not require refrigeration, as the MgCO3is stable at room temperatures.

[0230] Further, material carbonation of the oxide does not need to proceed to 100% reaction, rather the carbonation extent is selected based on numerous factors, including feasible reaction kinetics. For example, the carbonation reaction can proceed to 20 mol% with theremainder being unreacted oxide structures. The reaction can proceed quickly (<1 month), without the need for gas concentration.

[0231] B. CO2 supply. For CO2 gas supply, the 73 g carbon containing mixture (MgCO3) produced during the capture process is now de-carbonated and converted back into the MgO sponge. The exposure of MgCO3 to unsaturated water vapor can lower the decomposition temperature of MgCO3by several hundred degrees. The water vapor pressure can be engineered to synthesize either MgO or Mg(OH)2. The following procedure to de- carbonate the mixture is used: This mixture (73 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material de- carbonation reaction. To create the unsaturated water vapor pressure required to achieve HVS conditions, liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 10-L autoclave, the amount of water is chosen to be ~300 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 350oC for 1 h. Throughout the 1 h, the pressure in the reactor increases to ~63 atm due to the evolved carbon dioxide. After 1 h, the vessel is depressurized, and the gas is allowed to flow through a condenser. The water condensed (300 mL) and was collected. The remaining gaseous species is CO2gas. The purity of the collected CO2gas is determined to be >99%. At this stage, the gaseous CO2can be temporarily stored in compressed gas form and ready to be supplied for any desired application.

[0232] After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be MgO. This newly formed phase is in the correct form-factor and has the same or similar chemical reactivity as the original MgO used for carbon capture. Thus, it can once again be used as the carbon-capture sponge. In other em- bodiments, the remaining solid material was identified to be Mg(OH)2. In other embodiments, the remaining solid material was identified to be a mixture of MgO and Mg(OH)2.

[0233] In some embodiments, the HVS reaction vessel may be a batch, continuous, semi-batch, or semi-continuous reaction vessel. Where a continuous, semi-continuous, or semi-batch reaction vessel is used, unreacted reactants may be removed and recycled back into the reaction vessel. It may also be possible to utilize a flow-through system that may comprise of a steam generator constantly providing a pressurized stream of unsaturated water vapor instead ofvaporizing liquid water within. It may also be possible to inject steam at a pressure greater than the set value on a relief valve. This would create a continuous flow of steam within the reactor, flushing out all other produced gases (for example, the partial pressure of any gas produced as a result of a reaction would never increase beyond a certain limit due to the continuous flushing of unsaturated water vapor). This continuous flow of steam could also be utilized to minimize unwanted gaseous species inside the reactor vessel. For example, a gaseous byproduct may be produced throughout the reaction that may thermodynamically limit and resultantly halt the reaction. This gaseous byproduct can be removed, if necessary, by the continuous flow of steam. The flow of steam can also be semi-continuous.

[0234] Additionally, material synthesis (or material de-carbonation) of the material does not have to proceed to 100 mol%, rather the created mixture of raw materials can be of desired purity. For example, the de-carbonation reaction can proceed to 20 mol% to create a mixture of materials suitable for desired application. Example 12 Carbon Capture from Air using mineralization reactions.

[0235] CO2Capture is needed to address the threat of global warming. Two types of solutions currently exist. The first relies on capture of CO2from concentrated sources. These sources flue gas from power-plants and manufacturing factories (glass, cement, etc). The second relies on capture directly from the air. In both cases, the process is logistically complex and economically expensive due to the logistics associated with concentration, capture, transport, and storage. For example, state-of-the-art CO2air-capture relies on sparging air in large volumes into a potassium hydroxide (KOH) solution which results in a chemical conversion of gaseous CO2to a solution of potassium carbonate (K2CO3). This solution is then exposed to calcium oxide (Lime, CaO), which in-turn extracts the CO2 from the potassium carbonate solution and recrystallizes into calcium carbonate (CaCO3). This solid-carbonate is then calcined at high-temperature (>900oC) to remove the CO2 in high-purity form (>95 vol%). This CO2is now pipelined towards its end-of-line application: products or permanent underground storage. After the CO2is removed from CaCO3, the newly formed CaO needs re- activation for the process to restart. This process results in a CO2price of $200-800 / tonne. For reference, commercial CO2delivered to a CO2utilizer manufacturing a product needs a CO2price between 50-100 / tonne in order to compete with current CO2providers. This invention shortens the logistics supply chain associated with carbon capture, storage, delivery, and supplyand improves price competitiveness. This is because numerous calcium silicates made by HVS are highly reactive with CO2in air (concentration of CO2in air = 400 ppm) and these various calcium silicates store amounts of CO2at storage densities better than liquid solvents and are comparable to pure liquid CO2(we need a table here comparing our storage densities to these conventional means. The process steps of this invention are the following:

[0236] (1) directly reacting a slurry, compact, granule, or powder comprised of calcium silicates with atmospheric air or ocean water to directly extract CO2and convert into solid- carbonate form factor: Calcium Carbonate (CaCO3)

[0237] (2a) permanently disposing the slurry, compact, granule, or powder in a landfill or ocean; or

[0238] (2b) creating a product from the carbonated material, for example, concrete, electronic materials, and agricultural purposes such as soil pH management.

[0239] (3, optional) If economics allow, the CO2can be removed by thermal or hydrothermal treatments for any desired application. Hydrothermal vapor treatments (HVS) are described in other examples in this application as “Material De-carbonation and Material Synthesis”. For example, the extracted CO2can be used for concrete curing or fuel production or underground storage. Alternatively, the material itself can be stored underground instead of using high-pressure gas storage methods.

[0240] It is important to note that a configuration requiring a CO2pipeline can be envisioned, however it is not necessary, as the material is safely transported by vehicular means, which avoids the multimillion-dollar cost per mile and complex logistics and liability of creating land easements associated with pipelines. In the case that the economics allow for the disposal of carbonated product, the excellent thermodynamic stability of calcium or other metal carbonates under ambient and even elevated temperatures (<650˚C at 1 atm) but can be stable at temperatures exceeding 2000˚C at pressures up to 42 GPa: (https: / / agupubs.onlinelibrary.wiley.com / doi / full / 10.1002 / 2017GL076536) which allows for permanent and safe landfilling. A. CO2 Capture from Air - CaSiO3.

[0241] Atmospheric air that contains CO2in concentrations ~400 ppm is humidified by bubbling through de-ionized, tap, or ocean water. Humidification can take place via other methods as well, including humidifiers or naturally occurring humidity. One hundred grams(100 g) of β-CaSiO3(metal silicate) powder that was produced via hydrothermal vapor synthesis, is exposed to the humidified air.

[0242] Upon exposure, the 100 g of CaSiO3reacts with the present CO2and forms a 138 g mixture of CaCO3and SiO2. It is worthwhile to note, that the form-factor of the silicate does not need to be a powder, but can also be a monolithic powder compact, as well as a monolithic material. The form-factor may also be a monolithic brick, coating, thin film, membrane, fiber, platelet, whisker and equiaxed powder form. The form-factor may also be a partial or full combination of all of the aforementioned form-factors. X-ray diffraction was used to confirm that the CaSiO3phase was consumed and a newly formed mixture of CaCO3and SiO2was formed. The produced CaCO3mineral acts as storage for the CO2gas for an infinite period of time at room temperature. (Note: Pure CaSiO3can store up to 38% of its mass in CO2. One tonne (1000 kg) of CaSiO3can store up to 380 kg of CO2. This powder is transported to the desired location by truck or any other mode of physical transportation, without the need for pressurization or refrigeration. (Note: A truckload carrying 100 tonnes of material (i.e., CaCO3mixed with SiO2) can produce 38 tonnes of CO2.) The truckload does not require refrigeration, as the CaCO3is stable at room temperatures.

[0243] The kinetics of this reaction are governed by the surface area of the unreacted CaSiO3and the air flowrate. A powder with a specific surface area (SSA) of > 50 m2 / g can efficiently extract CO2from air and convert fully to CaCO3and SiO2in ~ 1 day at a flow rate of <5 SCFM. In addition, a powder with a particle size < 3 microns can efficiently extract CO2from air and convert fully to CaCO3and SiO2in < 1 month. A powder with a smaller particle size than 3 microns can reduce the conversion time to < 1 day. The produced CaCO3mineral acts as storage for the CO2gas for an infinite period at room temperature. (Note: Pure CaSiO3can store up to 38% of its mass in CO2. One tonne (1000 kg) of CaSiO3 can store up to 380 kg of CO2. This powder is transported to the desired location by truck or any other mode of physical transportation, without the need for pressurization or refrigeration. (Note: A truckload carrying 100 tonnes of material (i.e., CaCO3mixed with SiO2) can supply 38 tonnes of CO2.) The truckload does not require refrigeration, as the CaCO3is stable at all temperature ranges found on earth. Furthermore, by storing the inorganic material in square or rectangular geometries, at least 20% more storage is possible when compared to liquid or gas tank storage, which must be cylindrical. This is true regardless of whether the CO2was captured from flue gas, vehicle exhaust gas, or directly from air. Further, carbonation of the material does not haveto proceed to 100 mol%, rather the created mixture of raw materials can be of desired purity. For example, the carbonation reaction can proceed to 20 mol% to create a mixture of materials suitable for desired application.

[0244] If CO2supply is required for any desired reason, the following procedure can be used to extract the CO2from the carbonate silicate. For CO2gas supply, the 138 g carbon containing mixture (CaCO3:SiO2) produced during the capture process is now de-carbonated and converted back into the CaSiO3sponge via the following procedure: This mixture (138 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. To create the unsaturated water vapor pressure required to achieve HVS conditions, liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 10-L autoclave, the amount of water is chosen to be ~300 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 350°C for 1 h. Throughout the 1 h, the pressure in the reactor increases to ~63 atm due to the evolved carbon dioxide.

[0245] After 1 h, the vessel is depressurized, and the gas is allowed to flow through a condenser. The water condensed (300 mL) and was collected. The remaining gaseous species is CO2gas. The purity of the collected CO2gas is determined to be >99%. At this stage, the gaseous CO2can be temporarily stored in compressed gas form and ready to be supplied for any desired application. In some embodiments, the HVS reaction vessel may be a batch, continuous, semi-batch, or semi-continuous reaction vessel. Where a continuous, semi- continuous, or semi-batch reaction vessel is used, unreacted reactants may be removed and recycled back into the reaction vessel.

[0246] It may also be possible to utilize a flow-through system that may comprise of a steam generator constantly providing a pressurized stream of unsaturated water vapor instead of vaporizing liquid water within. It may also be possible to inject steam at a pressure greater than the set value on a relief valve. This would create a continuous flow of steam within the reactor, flushing out all other produced gases (for example, the partial pressure of any gas produced as a result of a reaction would never increase beyond a certain limit due to the continuous flushing of unsaturated water vapor). This continuous steam flow could also be utilized to minimize unwanted gaseous species inside the reactor vessel. For example, a gaseous by-product may be producedthroughout the reaction that may thermodynamically limit and resultantly halt the reaction. This gaseous byproduct can be removed, if necessary, by the continuous flow of steam. The flow of steam can also be semi-continuous.

[0247] After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be β-CaSiO3. This newly formed phase is in the correct form-factor and has the same or similar chemical reactivity as the original β-CaSiO3used for carbon capture. Thus, it can once again be used as the carbon-capture material.

[0248] Additionally, material synthesis (or material de-carbonation) of the material does not have to proceed to 100 mol%, rather the created mixture of raw materials can be of desired purity. For example, the de-carbonation reaction can proceed to 20 mol% to create a mixture of materials suitable for desired application. In all embodiments of this process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca- Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4 (amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5 (amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics. B. CO2 Capture from Ocean - CaSiO3

[0249] Ocean water containing CO2in concentrations ~400-800 ppm or greater are captured with the stated invention by mechanical convection-through a porous material composed of CaSiO3as well as many of the other calcium bearing silicates, including cement hydrate and any calcium silicates listed in the Figures 6, 7, and 8.

[0250] Upon exposure, CaSiO3reacts with soluble CO2and forms a mixture of CaCO3and SiO2. The kinetics of this reaction are governed by the surface area of the unreacted CaSiO3and the water flowrate. A powder with a specific surface area (SSA) of > 5 m2 / g can efficiently extract CO2from water and convert fully to CaCO3and SiO2in ~ 1 day. It is worthwhile to note, that the form-factor of the silicate does not need to be a powder, but can also be a monolithic powder compact, as well as a monolithic material. The form-factor may also be a monolithic brick, coating, thin film, membrane, fiber, platelet, whisker and equiaxed powderform. The form-factor may also be a partial or full combination of all of the aforementioned form-factors. The produced CaCO3mineral acts as storage for the CO2gas for an infinite period of time at room temperature. (Note: Pure CaSiO3can store up to 38% of its mass in CO2. One tonne (1000 kg) of CaSiO3can store up to 380 kg of CO2.

[0251] This material is transported to the desired location by truck or any other mode of physical transportation, without the need for pressurization or refrigeration. (Note: A truckload carrying 100 tonnes of material (i.e., CaCO3mixed with SiO2) can produce 38 tonnes of CO2.) The truckload does not require refrigeration, as the CaCO3is stable at room temperatures. Carbonated material can also be directly disposed in the ocean without any harmful effects.

[0252] Further, carbonation of the material does not have to proceed to 100 mol%, rather the created mixture of raw materials can be of desired purity. For example, the carbonation reaction can proceed to 20 mol% to create a mixture of materials suitable for desired application.

[0253] If CO2supply is required for any desired reason, the following procedure can be used to extract the CO2from the carbonate silicate. For CO2gas supply, the 138 g carbon containing mixture (CaCO3:SiO2) produced during the capture process is now de-carbonated and converted back into the CaSiO3sponge via the following procedure: This mixture (138 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. To create the unsaturated water vapor pressure required to achieve HVS conditions, liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 10-L autoclave, the amount of water is chosen to be ~300 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 350oC for 1 h. Throughout the 1 h, the pressure in the reactor increases to ~63 atm due to the evolved carbon dioxide.

[0254] After 1 h, the vessel is depressurized, and the gas is allowed to flow through a condenser. The water condensed (300 mL) and was collected. The remaining gaseous species is CO2gas. The purity of the collected CO2gas is determined to be >99%. At this stage, the gaseous CO2can be temporarily stored in compressed gas form and ready to be supplied forany desired application. In some embodiments, the HVS reaction vessel may be a batch, continuous, semi-batch, or semi-continuous reaction vessel.

[0255] Where a continuous, semi-continuous, or semi-batch reaction vessel is used, unreacted reactants may be removed and recycled back into the reaction vessel. It may also be possible to utilize a flow-through system that may comprise of a steam generator constantly providing a pressurized stream of unsaturated water vapor instead of vaporizing liquid water within. It may also be possible to inject steam at a pressure greater than the set value on a relief valve. This would create a continuous flow of steam within the reactor, flushing out all other produced gases (for example, the partial pressure of any gas produced as a result of a reaction would never increase beyond a certain limit due to the continuous flushing of unsaturated water vapor). This continuous flow of steam could also be utilized to minimize unwanted gaseous species inside the reactor vessel. For example, a gaseous byproduct may be produced throughout the reaction that may thermodynamically limit and resultantly halt the reaction. This gaseous byproduct can be removed, if necessary, by the continuous flow of steam. The flow of steam can also be semi-continuous.

[0256] After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be β-CaSiO3. This newly formed phase is in the correct form-factor and has the same or similar chemical reactivity as the original β-CaSiO3used for carbon capture. Thus, it can once again be used as the carbon-capture material.

[0257] Additionally, material synthesis (or material de-carbonation) of the material does not have to proceed to 100 mol%, rather the created mixture of raw materials can be of desired purity. For example, the de-carbonation reaction can proceed to 20 mol% to create a mixture of materials suitable for desired application. In all embodiments of this process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca- Si-O-H-C equilibria system. All polymorphs of the CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics.C. CO2 Capture from Air – Calcium Silicate Hydrate (Waste Cement)

[0258] Waste cement consists of a mixture comprising CaCO3, Ca(OH)2, SiO2, Ca3SiO5, Ca2SiO4, and Calcium Silicate Hydrate (CSH) phases, among other phases. There are other phases present as well. These comprise of various calcium aluminate (and hydrated and carbonated forms) and calcium aluminoferrite phases (and hydrated and carbonated forms). If the material being recycled is cured concrete, then aggregate is present as well. This application refers to the following non-exclusive list of cements when referring to cements that can be recycled using this invention: ASTM C150 designates 10 types of cement: Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate- sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate- sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0259] Waste cement (WC) is globally abundantly available, with annual availability increasing by at least additionally 1 GT / y. Their abundance, excellent distribution on a global scale combined with the low cost and carbon-footprint of a waste product nearing ~0$ / ton and 0 kg CO2, respectively, enables WC to be a prime candidate for CO2mineralization reactions. This example describes how the cement phases found in waste cement, namely calcium silicate hydrates and calcium hydroxide, reacts with atmospheric CO2to permanently sequester CO2.

[0260] The cured hydraulic concrete was crushed into fine powder (particle size < 200 μm) by a combination of jaw-crushing, hammer milling, and ball milling. This powder mixture was composed of calcium silicate hydrate (CSH), sand, and gravel. If determined to be chemically incompatible, the aggregate could be sieved out of the mixture prior to fine (ball) milling. Atmospheric air that contains CO2in concentrations ~400 ppm was humidified by bubbling through de-ionized, distilled, tap, or ocean water. One hundred grams (100 g) of Calcium Silicate Hydrate (CSH) powder (Ca:Si ~ 1 – 3), was exposed to the humidified air. For a Ca:Si ratio of 1, 100 g of CSH reacts with the present CO2, and forms >140 g mixture of CaCO3and SiO2. The kinetics of this reaction are governed by the surface area of the unreacted CSH and the air flowrate. The native SSA of CSH is sufficient to efficiently extract CO2 from air and convert fully to CaCO3and SiO2in ~ 1 day at a flow rate of <5 SCFM. This reactionwas monitored over a 24h period within an x-ray diffractometer to determine the kinetics of the reaction between atmospheric CO2and CSH at 30oC. The carbonation reaction proceeds rapidly and begins to saturate (slow down) at ~24 h.

[0261] The produced CaCO3mineral acts as storage for the CO2gas for an infinite period of time (>100 years) at room temperature. (Note: Pure CSH can store up to >40% of its mass in CO2. One tonne (1000 kg) of CaSiO3can store >400 kg of CO2. This powder is transported to the desired location by truck or any other mode of physical transportation, without the need for pressurization or refrigeration. (Note: A truckload carrying 100 tonnes of material (i.e., CaCO3mixed with SiO2) can produce >40 tonnes of CO2.) The truckload does not require refrigeration, as the CaCO3is stable at room temperatures. The carbonated CSH can also be directly disposed (landfill, ocean, etc.) for permanent CO2sequestration.

[0262] Further, carbonation of the material does not have to proceed to 100% capacity. Where capacity is defined by the maximum uptake possible by the phase blend in a given used cement. For example, the carbonation reaction can proceed to 20% to create a mixture of materials suitable for desired application.

[0263] If CO2 supply is required for any desired reason, the following procedure can be used to extract the CO2from the carbonated material.

[0264] The carbonated mixture (>100 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. The carbonate containing mixture produced during the capture process is now de-carbonated and converted back into a favorable phase. If the carbonated mixture was comprised of an equimolar ratio of CaCO3 and SiO2, then CaSiO3may be the favored phase during the CO2extraction reaction (material synthesis).

[0265] To create the unsaturated water vapor pressure required to achieve HVS conditions, liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 10-L autoclave, the amount of water is chosen to be ~300 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 350oC for 1 h. Throughout the 1 h, the pressure in the reactor increases to ~63 atm due to the evolved CO2.

[0266] After 1 h, the vessel is depressurized, and the gas is allowed to flow through a condenser. The water condensed (300 mL) and was collected. The remaining gaseous species is CO2gas. The purity of the collected CO2gas is determined to be >99%. At this stage, the gaseous CO2can be temporarily stored in compressed gas form and ready to be supplied for any desired application. In some embodiments, the HVS reaction vessel may be a batch, continuous, semi-batch, or semi-continuous reaction vessel. Where a continuous, semi- continuous, or semi-batch reaction vessel is used, unreacted reactants may be removed and recycled back into the reaction vessel. It may also be possible to utilize a flow-through system that may comprise of a steam generator constantly providing a pressurized stream of unsaturated water vapor instead of vaporizing liquid water within.

[0267] It may also be possible to inject steam at a pressure greater than the set value on a relief valve. This would create a continuous flow of steam within the reactor, flushing out all other produced gases (for example, the partial pressure of any gas produced as a result of a reaction would never increase beyond a certain limit due to the continuous flushing of unsaturated water vapor). This continuous flow of steam could also be utilized to minimize unwanted gaseous species inside the reactor vessel. For example, a gaseous byproduct may be produced throughout the reaction that may thermodynamically limit and resultantly halt the reaction. This gaseous byproduct can be removed, if necessary, by the continuous flow of steam. The flow of steam can also be semi-continuous.

[0268] Additionally, material synthesis (or material de-carbonation) of the material does not have to proceed to 100%, rather the created mixture of raw materials can be of desired purity. For example, the de-carbonation reaction can proceed to 20 % to create a mixture of materials suitable for desired application. In all embodiments of this process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of CaSiO3(amorphous, α-, β-, γ-, δ-, ε-) Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics.D. CO2 Capture from Ocean - Calcium Silicate Hydrate (Waste Cement)

[0269] Waste cement consists of a mixture comprising CaCO3, Ca(OH)2, SiO2, Ca3SiO5, Ca2SiO4, and Calcium Silicate Hydrate (CSH) phases, among other phases. There are other phases present as well. These comprise of various calcium aluminate (and hydrated and carbonated forms) and calcium aluminoferrite phases (and hydrated and carbonated forms). If the material being recycled is cured concrete, then aggregate is present as well.

[0270] This application refers to the following non-exclusive list of cements when referring to cements that can be recycled using this invention: ASTM C150 designates 10 types of cement: Type I: Normal, Type IA: Normal, air entraining, Type II: Moderate-sulfate resistance, Type IIA: Moderate-sulfate resistance, air entraining, Type II (MH): Moderate heat of hydration and moderate-sulfate resistance, Type II (MH)A: Moderate heat of hydration, and moderate-sulfate resistance, air entraining, Type III: High early strength, Type IIIA: High early strength, air entraining, Type IV: Low heat of hydration, Type V: High sulfate resistance, ASTM C1157 describes six types of cement: Type GU: General use, Type HE: High early strength, Type MS: Moderate-sulfate resistance, Type HS: High sulfate resistance, Type MH: Moderate heat of hydration, Type LH: Low heat of hydration.

[0271] Waste cement (WC) is globally abundantly available, with annual availability increasing by at least additionally 1 GT / y. Their abundance, excellent distribution on a global scale combined with the low cost and carbon-footprint of a waste product nearing ~0$ / tonne and 0 kg CO2, respectively, enables WC to be a prime candidate for CO2mineralization reactions. This example describes how the cement phases found in waste cement, namely calcium silicate hydrates and calcium hydroxide, reacts with CO2present in ocean water to permanently sequester CO2.

[0272] The cured hydraulic concrete was crushed into fine powder (particle size < 200 μm) by a combination of jaw-crushing, hammer milling, and ball milling. This powder mixture was composed of calcium silicate hydrate (CSH), sand, and gravel. If determined to be chemically incompatible, the aggregate could be sieved out of the mixture prior to fine (ball) milling. Ocean water that contains dissolved CO2in concentrations >400 ppm is flowed- through a porous material composed of waste cement. Upon exposure, the waste cement reacts with the dissolved CO2, and forms a mixture of CaCO3and SiO2and numerous other phases that may also carbonate. The kinetics of this reaction are governed by the surface area of the waste cement and the water flowrate. A powder with a specific surface area (SSA) of > 5 m2 / gcan efficiently extract CO2from water and convert fully to CaCO3and SiO2in ~ 1 day. (Note: Pure calcium silicate hydrate can store up to >40% of its mass in CO2. One tonne (1000 kg) of CaSiO3can store >400 kg of CO2). This powder is transported to the desired location by truck or any other mode of physical transportation, without the need for pressurization or refrigeration. (Note: A truckload carrying 100 tonnes of material (i.e., CaCO3mixed with SiO2) can produce >40 tonnes of CO2.) The truckload does not require refrigeration, as the CaCO3is stable at room temperatures. The carbonated CSH can also be directly disposed (landfill, ocean, etc.) for permanent CO2sequestration.

[0273] Further, carbonation of the material does not have to proceed to 100% capacity. Where capacity is defined by the maximum uptake possible by the phase blend in a given used cement. For example, the carbonation reaction can proceed to 20% to create a mixture of materials suitable for desired application.

[0274] If CO2supply is required for any desired reason, the following procedure can be used to extract the CO2from the carbonated material.

[0275] The carbonated mixture (>100 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. The carbonate containing mixture produced during the capture process is now de-carbonated and converted back into a favorable phase. If the carbonated mixture was comprised of an equimolar ratio of CaCO3and SiO2, then CaSiO3may be the favored phase during the CO2extraction reaction (material synthesis).

[0276] To create the unsaturated water vapor pressure required to achieve HVS conditions, liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 10-L autoclave, the amount of water is chosen to be ~300 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 350°C for 1 h. Throughout the 1 h, the pressure in the reactor increases to ~63 atm due to the evolved carbon dioxide. After 1 h, the vessel is depressurized, and the gas is allowed to flow through a condenser. The water condensed (300 mL) and was collected. The remaining gaseous species is CO2gas. The purity of the collected CO2gas is determined to be >99%. At this stage, the gaseous CO2can be temporarily stored in compressed gas form and ready to be supplied forany desired application. In some embodiments, the HVS reaction vessel may be a batch, continuous, semi-batch, or semi-continuous reaction vessel.

[0277] Where a continuous, semi-continuous, or semi-batch reaction vessel is used, unreacted reactants may be removed and recycled back into the reaction vessel. It may also be possible to utilize a flow-through system that may comprise of a steam generator constantly providing a pressurized stream of unsaturated water vapor instead of vaporizing liquid water within. It may also be possible to inject steam at a pressure greater than the set value on a relief valve. This would create a continuous flow of steam within the reactor, flushing out all other produced gases (for example, the partial pressure of any gas produced as a result of a reaction would never increase beyond a certain limit due to the continuous flushing of unsaturated water vapor). This continuous flow of steam could also be utilized to minimize unwanted gaseous species inside the reactor vessel. For example, a gaseous byproduct may be produced throughout the reaction that may thermodynamically limit and resultantly halt the reaction. This gaseous byproduct can be removed, if necessary, by the continuous flow of steam. The flow of steam can also be semi-continuous.

[0278] Additionally, material synthesis (or material de-carbonation) of the material does not have to proceed to 100%, rather the created mixture of raw materials can be of desired purity. For example, the de-carbonation reaction can proceed to 20 % to create a mixture of materials suitable for desired application. In all embodiments of this process, the formed phase does not have to be solely β-CaSiO3, but can also be α-CaSiO3, β-CaSiO3, amorphous CaSiO3, Ca3Si2O7, Ca3SiO4, Ca2SiO5,or any other calcium silicate phase in the Ca-Si-O-H-C equilibria system. All polymorphs of CaSiO3(amorphous, α-, β-, γ-, δ-, ε-), Ca2SiO4(amorphous, α-, β-, γ-, δ-, ε-), and Ca3SiO5(amorphous, α-, β-, γ-, δ-, ε-) are also possible. Additional possible calcium silicate phases are non-exclusively listed in Figures 6, 7, and 8. The produced phase(s) do not have to be solely anhydrous phases. In-fact, they can also be blend of calcium silicate hydrates (e.g., Foshagite) and calcium silicate carbonates (e.g., Spurrite), and calcium silicate carbonate hydrates (e.g., Scawtite). The produced phase is dependent on chemical thermodynamics and kinetics.Example 13 Carbon (a) Capture, Storage, Transport and (b) Supply via a Mg2SiO4sponge at high CO2concentrations ~ >90 vol %. A. CO2Capture.

[0279] This example describes the carbonation process of a metal silicate with the exception that the source of gaseous CO2is from a high pressure and high purity source, such as, an Allam Cycle power plant. For the case of high-pressure gaseous CO2, we can explore the possibility of using Mg2SiO4, a material that requires a higher pressure of CO2to sufficiently carbonate, as a carbon capture material:

[0280] One hundred (100 g) of Mg2SiO4(metal silicate) powder is exposed to a pressurized gas stream that contains >95% carbon dioxide gas. This gaseous exhaust stream has a CO2pressure > 1071 psi, so that the CO2in the stream is in the supercritical phase. If necessary, the stream is humidified by bubbling through de-ionized water. Upon exposure, the 100 g of Mg2SiO4reacts with the present CO2species, and forms ~ 163 g mixture of MgCO3and SiO2within 24h. It is worthwhile to note, that the form-factor of the Mg2SiO4phase does not need to be a powder, but can also be a monolithic powder compact, as well as a monolithic material. The form-factor may also be a monolithic brick, coating, thin film, membrane, fiber, platelet, whisker and equiaxed powder form.

[0281] The form-factor may also be a partial or full combination of all of the aforementioned form-factors. X-ray diffraction was used to confirm that the Mg2SiO4phase was consumed and MgCO3phase was formed. The produced MgCO3mineral acts as storage for the CO2gas for an infinite period of time at room temperature. (Note: Pure Mg2SiO4can store up to ~62.3% of its mass in CO2. One tonne (1000 kg) of Mg2SiO4 can store up to ~623 kg of CO2). This powder is transported to the desired location by truck, without the need for pressurization or refrigeration. (Note: A truckload carrying 100 tonnes of material (i.e., MgCO3mixed with SiO2) can produce 63 tonnes of CO2.) The truckload does not require refrigeration, as the MgCO3is stable at room temperatures.

[0282] Further, carbonation of the material does not have to proceed to 100 mol%, rather the created mixture of raw materials can be of desired purity. For example, the carbonation reaction can proceed to 20 mol% to create a mixture of materials suitable for desired application. Further, it is worthwhile to note that the carbonation reaction can proceedpassively via exposure to atmospheric CO2. The reaction can proceed quickly (<1 month), without the need for gas concentration. B. CO2 Supply

[0283] For CO2gas supply, the 163 g carbon containing mixture (MgCO3) produced during the capture process is now de-carbonated and converted back into the Mg2SiO4 sponge via the following procedure: This mixture (163 grams) is placed into a hydrothermal vapor chamber (i.e., autoclave) for conducting a hydrothermal vapor synthesis (HVS) material synthesis reaction. Liquid water is added to the inside (base) of the autoclave. The amount of water used is determined by the volume of the autoclave. In the case of a 10-L autoclave, the amount of water is chosen to be ~600 mL to have volume fill-percent of 3% in order to achieve an unsaturated water partial pressure of about 58 atm at 350°C. The mixture can be either dispersed in the liquid water or suspended above. The autoclave is kept isothermal at 350oC for 1 h. Throughout the 1 h, the pressure in the reactor increases to >64 atm due to the evolved carbon dioxide. After 1 h, the vessel is depressurized, and the gas is allowed to flow through a condenser. The water condensed (300 mL) and was collected. The remaining gaseous species is CO2gas. The purity of the collected CO2gas is determined to be >99%. At this stage, the gaseous CO2can be temporarily stored in compressed gas form and ready to be supplied for any desired application.

[0284] After cooling, the synthesized material is removed from the autoclave. X-ray diffraction identified the newly formed phase to be Mg2SiO4. This newly formed phase is in the original form-factor (sponge or monolith or powder) and has the same or similar chemical reactivity as the original Mg2SiO4used for carbon capture. Thus, it can once again be used as the carbon-capture sponge.

[0285] In some embodiments, the HVS reaction vessel may be a batch, continuous, semi-batch, or semi-continuous reaction vessel. Where a continuous, semi-continuous, or semi-batch reaction vessel is used, unreacted reactants may be removed and recycled back into the reaction vessel. It may also be possible to utilize a flow-through system that may comprise of a steam generator constantly providing a pressurized stream of unsaturated water vapor instead of vaporizing liquid water within. It may also be possible to inject steam at a pressure greater than the set value on a relief valve. This would create a continuous flow of steam within the reactor, flushing out all other produced gases (for example, the partial pressure of any gas produced because of a reaction would never increase beyond a certain limit due to the continuous flushingof unsaturated water vapor). This continuous flow of steam could also be utilized to minimize unwanted gaseous species inside the reactor vessel. For example, a gaseous byproduct may be produced throughout the reaction that may thermodynamically limit and resultantly halt the reaction. This gaseous byproduct can be removed, if necessary, by the continuous flow of steam. The flow of steam can also be semi-continuous.

[0286] Additionally, material synthesis (or material de-carbonation) of the material does not have to proceed to 100 mol%, rather the created mixture of raw materials can be of desired purity. For example, the de-carbonation reaction can proceed to 20 mol% to create a mixture of materials suitable for desired application. Example 14 Novel method for Calcium-looping for direct air capture applications.

[0287] This example is yet another embodiment to this invention that leverages the highly reactive calcium silicates produced via the HVS (material synthesis) process for large- scale CO2management efforts. Specifically, as described in this example, calcium silicates can be used to extract CO2 from the atmosphere, where it comprises 100-1000 ppm. During the extraction process, the calcium silicate converts to a mixture of calcium carbonate and silica. A material synthesis method is then used to remove the CO2locked in the carbonate phase and produce a high purity stream of CO2. The end result is a low-cost, low-energy method for converting CO2from low concentrations to high concentrations.

[0288] The most promising CO2direct-air-capture (DAC) and storage (DAC+s) solutions rely on looping technologies that are comprised of (1) mineral carbonation reactions for air-capture, and (2) calcination reactions for high-purity CO2supply to a CO2off- taker / utilizer or underground storage site. These processes have already been demonstrated to be scalable and capable of continuous operation (e.g., the Carbon Engineering company), but are cost-prohibitive (>>200$ / tonne CO2) for delivering the gigaton volumes needed to reduce CO2emissions in a significant manner. The primary energy and cost driver of these processes is the calcination unit-operation, in which a carbonate-phase, commonly calcium carbonate (CaCO3), is heat-treated at >1000oC to convert the captured CO2into high-purity gas-form (CaCO3(s) ⇌ CaO (s) + CO2(g)) for down-stream utilization or underground storage. This calcination reaction is very energy intensive due to the high temperatures required (~2 GJ / tonne CO2) and its endothermic nature (~4 GJ / tonne CO2). Furthermore, the high temperatures inhibit the capture performance of the calcined product (lime, CaO) after a handful of cycles, whichcreates an additional economic and logistical constraint in the air-capture loop. This inhibition arises from particle coarsening as a result of exposure to high temperatures. Finally, the temperatures required for calcination cannot be easily achieved with renewable energy sources, thereby, most calcination-based looping processes rely on fossil-fuel powered reactions that lower the effectiveness of the cycle by further increasing the carbon intensity.

[0289] The invention described in this example can navigate around the high energy requirements, the capture media de-activation, and could accommodate a wide-variety of sustainable fuels, could result in the lowest cost and carbon-intensity direct-air-capture system to date. This example utilizes pressurized steam to enable a dramatic reduction in calcination temperature from 1000°C to <500oC. The added benefits of this technology include a (1) reduction in energy from heating (>20% reduction), (2) a reduced calcination endotherm (>50% reduction), (3) zero cyclic performance loss, (4) direct production of high-pressure CO2that does not need additional compression for storage, shipping, utilization, or sequestration, and (5) decarbonated oxides that are highly reactive with atmospheric CO2. The overall thermodynamic energy reduction of this invention is at least 25%, without accounting for efficiency gains from (3), (4), and additional heat-cycle optimization operations.

[0290] Hydrothermal Vapor Synthesis (HVS) utilizes pressurized unsaturated water vapor (1-150 atm) to unlock the ability to decarbonate / calcine a carbonate precursor via the silicate crystallization reaction at low temperatures (<500oC, CaCO3(s) + SiO2(s) ⇌ CaSiO3(s) + CO2(g)). In this example, the HVS process was used to calcine CaCO3at temperatures <500oC via the silicate crystallization reactions of Ca2SiO4, CaSiO3, and other silicate phases. The methods described in the examples above for decarbonation and materials synthesis can be used to calcine / process the passively or actively carbonated calcium silicates. These silicate crystallization reactions provide an ideal analog to the production of CaO (lime) via calcination due to their reactivity with atmospheric (400 ppm) or aqueous CO2(e.g., K2CO3). Having the ability to reduce the reaction temperature below 500oC offers the following advantages: (1) clinker-free calcination (i.e., powder in, powder out), (2) larger variety of fuel, and (3) production of highly CO2reactive phases due to their submicron particle size and high surface area. This is in contrast with traditional calcination, which occurs >1000°C and sinters the reaction product, resulting in a low-activity, low-surface area phase. Thus, the low-temperature reactions enabled by HVS enables calcium looping to be a far more practical process.

[0291] The HVS technology can be applied to CaCO3looping in the following ways: (1) with a contactor, and (2) contactor-free. The contactor configuration refers to a continuous loop in which a CO2ionization medium absorbs CO2from air and ionizes it to a reactive form, for example, bicarbonate, in order to chemically react with the CaSiO3phase (CaSiO3(s) + CO2(g) ⇌ CaCO3(s) + SiO2(s)). This configuration is commonly used, in which an aqueous salt (potassium hydroxide, KOH) is used as the contactor to concentrate the atmospheric CO2in the form of aqueous K2CO3. This K2CO3solution then rapidly reacts with Ca(OH)2to form CaCO3. The formed CaCO3is then calcined at 1000°C in order to supply the concentrated CO2to the desired location, for example, for fuel production or underground storage.

[0292] A nearly identical approach can be used with the technology described here, with the difference being in the configuration of the calciner, the corresponding energy required (i.e., lower) and the precursor being used. In this invention, the calciner would be replaced with the HVS reactor, that would promote a decarbonation reaction via the reactive crystallization of a silicate phase at a temperature >500oC lower than the calciner, which equates to 25-50% energetic reduction. Additional energetic reductions should be expected when a full system (capture, calcination, storage, sequestration) is developed from the (1) avoidance of compression technologies, since the HVS evolved CO2 will be autogenously pressurized, (2) efficiency gains from the HVS heat cycle improvements, and (3) zero deterioration in cyclic performance between carbonation and decarbonation unit-operations.

[0293] In the contactor-free configuration, an environmental weathering approach would be taken, in which the CaSiO3phase is exposed to the atmosphere in uncontrolled (spreading on land outside) or controlled (container) humidity environments to passively absorb atmospheric CO2. A particle size < 3 micron can be weathered to 100% (fully converted to CaCO3and SiO2) within 1 month. This environmental weathering approach is popular amongst up-and-coming capture companies to passively convert atmospheric CO2into concentrated solid-state form (carbonate-form). This approach is followed by calcination in order to supply the CO2to the desired location. Technoeconomic analyses indicate that this approach will cost anywhere between $50-$150 / tonne CO2captured, without including storage and processing costs. In this invention, weathering can be performed in an identical manner, but the manner of CO2release utilizes HVS to crystallize a CaSiO3phase for simultaneous CO2removal (Eq.2). As with the case of the contactor approach, this technology is expected to reduce the energetics of calcination by 25-50%, thereby, creating the lowest cost pathway to direct-air-capture andutilization / storage. From literature evidence, the contactor-free approach is expected to have a lower overall cost.

[0294] This invention enables (1) rapid-calcination of CaCO3, (2) high-surface area oxides that can be rapidly carbonated via concentrated CO2sources, (3) high-surface area oxides that can be rapidly carbonated via atmospheric CO2, (4) and consistent cyclic performance for carbonation and decarbonation cycles. For (1), HVS can promote the calcination reaction (Eq. 2) at temperatures <500oC. Initially, this innovation required >12h of reaction time to obtain substantial calcination yield (>70 mol %). This was insufficient for designing an efficient looping process, as a rapid process is needed to scale a modular system. To overcome this limitation, a proprietary, ultra-low cost (~0$ kg) catalyst to enable a calcination time of <2 h. Catalyst may consist of any salt, including sodium chloride, sodium hydroxide, potassium chloride, potassium hydroxide, magnesium chloride, magnesium hydroxide, or other applicable salts. For (2), the formed calcium silicates can carbonate to >70 mol % completion within 90 minutes by using a concentrated CO2source (PCO2~ 10 psig).

[0295] The formed silicates can also react with atmospheric CO2to form carbonates within 1 week, up to 1 month. In addition, the formed silicates can react with aqueous carbonate salts (e.g., potassium carbonate, sodium carbonate), enabling a high carbonation reaction yield as well. For (3), the formed calcium silicates can react with atmospheric CO2 to a high carbonation yield at <4 weeks of exposure to a humidified airstream. For (4), The low temperature nature of the decarbonation process disable a coarsening effect (de-activation) experienced during traditional calcination. This enables a near-zero performance degradation when performing the CaSiO3(s) + CO2(g) ⇌ CaCO3(s) + SiO2(s) cycle numerous times. The cycle can be performed more than 100 times.

[0296] It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described. Rather, the scope of the present invention is defined by the claims which follow. It should further be understood that the above description is only representative of illustrative examples of embodiments. The description has not attempted to exhaustively enumerate all possible variations. The alternate embodiments may not have been presented for a specific portion of the invention and may result from a different combination of described portions, or that other un-described alternate embodiments may be available for a portion, is not to be considered a disclaimer of those alternate embodiments. It will be appreciated that many of those un-described embodiments are within the literal scope of the following claims, and others are equivalent.

Claims

AMENDED CLAIMS received by the International Bureau on 19 May 2025 (19.05.2025)CLAIMSWe claim:

1. A method of recovering an inorganic compound from a material, the method comprising: contacting the material with CO2 in the presence of water and heat; forming a carbonate mixture through a material carbonation reaction; contacting the carbonate mixture with an unsaturated water vapor; subjecting the carbonate mixture to a hydrothermal vapor synthesis, wherein the hydrothermal vapor synthesis reduces the particle size of the material; decarbonizing the material; and forming the inorganic compound.

2. The method of claim 1 wherein the material is a waste product.

3. The method of claim 1 wherein the material comprises a reactive inorganic material.

4. The method of claim 3 wherein the reactive inorganic material comprises a metal.

5. The method of claim 3 wherein the reactive inorganic material comprises a metal oxide.

6. The method of claim 3 wherein the reactive inorganic material comprises a metal hydroxide.

7. The method of claim 1 further comprising reacting a carbonate element with a non-alkaline earth oxide to form the material.

8. The method of claim 1 wherein the partial pressure of the unsaturated water vapor is between about 1 atm and about 80 atm.

9. The method of claim 1 wherein the temperature of the unsaturated water vapor is between about 100 °C and about 1000 °C.

10. The method of claim 1 wherein the inorganic compound comprises a calcium silicate hydroxide.

11. The method of claim 1 wherein the unsaturated water vapor is derived from a hydroxide salt.

12. The method of claim 1 further comprising milling the material.

13. The method of claim 1 wherein the material carbonation reaction occurs at a temperature of above about 80 °C.

14. The method of claim 1 wherein the material carbonation reaction occurs at a pressure of above about 10 psi.

15. The method of claim 1 wherein the CO2is at a concentration of about 100 ppm to about 500 ppm.

16. The method of claim 1 wherein the material comprises a particle size of less than about 150 μm.

17. The method of claim 1 wherein the hydrothermal vapor synthesis enhances the kinetics of a thermodynamically favorable reaction.

18. A method of recovering an inorganic compound from a material, the method comprising: contacting the material with CO2in the presence of a reaction medium and heat; forming a carbonate mixture through a material carbonation reaction; contacting the carbonate mixture with an unsaturated vapor state of the reaction medium; subjecting the carbonate mixture to a vapor synthesis to reduce the particle size of the material; decarbonizing the material; and forming an inorganic compound.

19. The method of claim 18 wherein the material is a waste product.

20. The method of claim 18 wherein the reaction medium comprises an organic species.

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