Alkaline cation enrichment and water electrolysis for CO2 mineralization and global scale carbon management

Abstract

Provided herein is a method for removing carbon dioxide from an aqueous or gaseous stream by contacting the gaseous stream containing carbon dioxide when present with an aqueous solution containing ions capable of forming insoluble carbonates; contacting the aqueous solution containing carbon dioxide with an electroactive grid that induces its alkalization, thereby forcing carbonate solids to precipitate from the solution and thereby removing dissolved inorganic carbon by electrolysis; and removing the precipitated carbonate solids from the solution or from the surface of the grid where the carbonate solids may be deposited. Also provided herein is a flow-through electrolysis reactor, the flow-through electrolysis reactor comprising: an intake device connected to a rotating cylinder fluid comprising an electroactive grid, and a scraping device and / or a liquid spray-based device for separating solids from the surface of the grid.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 861,848, filed on June 14, 2019, the entire contents of which are incorporated herein by reference.

[0003] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0004] This invention was made with government support under Grant Nos. DE-FE0029825, DE-FE0031718, and DE-FE0031705 awarded by the U.S. Department of Energy. The government has certain rights in this invention. Background Art

[0005] Existing atmospheric CO2 and continued CO2 emissions need to be managed to mitigate increases in global average temperatures and reduce the impacts of climate change. To achieve this realistically, approximately 10-20 gigatonnes (Gt) of CO2 must be removed from the atmosphere each year over the next century, so carbon management strategies that can be implemented at scale are needed.

[0006] Comparisons of carbon capture and storage are adjusted in terms of handling CO2 in a fluid state (e.g., gas, liquid, or supercritical). Such fluid state handling adds limitations and complexities in terms of access, process, and disposal pathways for CO2, including expensive and energy-intensive separation, large energy requirements for compression, and high costs of pressurized vessels with the potential for leaks.

[0007] Injection of CO2 captured from point sources or the atmosphere into geological formations (including: (depleted) oil and gas reservoirs, unrecoverable coal seams and saline aquifers) could store up to 22,000 Gt of CO2 in North America. While the theoretical capacity is very large, in practice, the pressure limits required to prevent rock fractures or reactivation of existing faults and / or the presence of residual hydrocarbons result in a more modest storage capacity of about 700 Mt per year over 50 years of injection. Although the possible capacity of geological storage sites is expected to exceed capacity sufficient to accommodate current (and future) levels of CO2 emissions, the risks of CO2 migration and leakage and the management and verification of the injection process require extensive monitoring of wells, subsurface and surface over time. Furthermore, conventional approaches to carbon management based on carbon capture, storage, and storage (CCSS) are subject to (i) thermodynamic penalties associated with the entropy of separating CO2 from air or flue gas streams and the need to subsequently satisfy the enthalpy of desorbing CO2 from solid or liquid substrates, and (ii) the need for a vast logistics and transportation infrastructure (e.g., pipelines) for transporting CO2 to geological storage sites. Specifically, in conventional adsorption / desorption-based CO2 capture, energy consumption is associated with the separation of CO2 from a gas mixture, including the reduction of the entropy of the system, the desorption step that allows CO2 concentrations to reach levels sufficient for pipeline transportation, and subsequent geological storage. In summary, while technical challenges remain and are being gradually addressed, the actual realization of CCSS depends largely on supportive policies that can provide global mandates for pending best practices and time-limited monitoring, reduce risks, and in extreme cases protect developers of CCSS projects from damage.

[0008] In addition to geological sequestration and storage, changes in land use, agricultural practices, marine geoengineering, and chemical conversion of CO2 to building materials offer alternative large-scale pathways that constitute a combination of approaches for ensuring carbon management (e.g., emissions reductions and atmospheric carbon removal). While some progress has been made in the development of negative (CO2 / carbon) emission technologies (NETs), more substantial "exponential" advances are needed to achieve the necessary CO2 removal rates and durable carbon storage in a cost-effective / feasible manner.

[0009] It is against this background that the embodiments described in this disclosure were developed. Summary of the invention

[0010] Some embodiments of the present disclosure include methods for removing carbon dioxide from an aqueous or gaseous stream by: contacting a gaseous stream containing carbon dioxide when present with an aqueous solution containing ions capable of forming insoluble carbonates; contacting an aqueous solution containing carbon dioxide with an electroactive grid that induces its alkalization, thereby forcing one or more carbonate solids to precipitate from the solution; and removing the precipitated carbonate solids from the solution or from the surface of the grid where the carbonate solids may be deposited. In some embodiments, there is a gaseous stream. In some embodiments, the gaseous stream contains CO2 between 0.04% by volume and 100% by volume. In some embodiments, the gaseous fluid is atmospheric air. In some embodiments, the gaseous fluid is flue gas emitted from a natural gas power plant, a coal-fired power plant, an iron plant, a steel plant, a cement plant, an ethanol plant, and a chemical manufacturing plant. In some embodiments, the aqueous solution contains a certain amount of dissolved carbon dioxide in equilibrium with the gaseous stream. In some embodiments, the aqueous solution is in thermal equilibrium with the gaseous stream. In some embodiments, the aqueous solution is not in thermal equilibrium with the gaseous stream. In some embodiments, there is no gaseous stream. In some embodiments, the ions capable of forming insoluble carbonates include ions including one or more of the following: Ca, Mg, Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu and Al. In some embodiments, the aqueous solution has a NaCl concentration of about 1,000 ppm or more. In some embodiments, the aqueous solution has a NaCl concentration of about 30,000 ppm or more. In some embodiments, the aqueous solution comprises seawater. In some embodiments, the electroactive grid comprises a mesh cathode comprising a metal or non-metallic composition. In some embodiments, the method utilizes an end-to-end energy intensity of about 2.5 MWh or less per ton of mineralized carbon dioxide. In some embodiments, the aqueous solution comprises a certain amount of dissolved carbon dioxide buffered to atmospheric abundance. In some embodiments, the electroactive grid generates increased alkaline conditions in situ in an electroactive grid of about 2 μm to 20000 μm in an aqueous solution. In some embodiments, the alkalinizing conditions are a pH of 9 or more. In some embodiments, the electroactive grid is composed of a metal or carbon-based grid. In some embodiments, the electroactive grid comprises stainless steel, titanium oxide, carbon nanotubes, polymers and / or graphite, or other mixed compositions of these materials. In some embodiments, the electroactive grid comprises pores having a diameter ranging from about 0.1 μm to about 10,000 μm. In some embodiments, inducing precipitation of carbonate solids comprises rotating a cylinder consisting of the electroactive grid in the solution while applying suction to draw the solution onto the outer surface of the grid. In some embodiments, the solution is a saline solution. In some embodiments, the solution is an alkali metal-containing solution.In some embodiments, inducing precipitation of carbonate solids comprises inducing precipitation of at least one carbonate having Ca, Mg, Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu, or Al.

[0011] Some embodiments of the present disclosure include a flow-through electrolysis reactor, which includes: an inhalation device connected to a rotating cylinder fluid including an electroactive grid, and a scraping device and / or a liquid spray-based device for separating solids from a surface or solution. In some embodiments, the reactor is also equipped with an aqueous solution containing carbon dioxide, Ca ions and Mg ions. In some embodiments, the electroactive grid is capable of inducing the removal of dissolved inorganic carbon by precipitating carbonate solids from an aqueous solution containing carbon dioxide and ions that can form insoluble carbonates. In some embodiments, the electroactive grid comprises a metal or carbon-based grid. In some embodiments, the electroactive grid comprises stainless steel, titanium oxide, carbon nanotubes, polymers and / or graphite, or a mixed composition of these materials. In some embodiments, the reactor includes a plurality of electroactive grids. In some embodiments, a plurality of electroactive grids are arranged into a series of parallel planar units or parallel cylindrical units. In some embodiments, the reactor is fluidly connected to the desalination device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 An embodiment of a carbon dioxide mineralization and disposal method is shown. The heating element and diffuser are optional components.

[0013] Figure 2 (a) shows a representative calculation, which demonstrates that the limits of calcite precipitation are affected by Ca, CO2, or alkalinity for solutions of the following composition: [Ca] = 10 mM, [Cl] = 20 mM, [CO2] = 10 mM (about 30% CO2; 300,000 ppm), pH = 4.16 (dashed curve). The maximum CaCO3 yield is 10 mmol / kg water. If [Ca] is reduced to 3 mM or 5 mM (dark blue curve) ([Cl] is 6 mM or 10 mM), [CO2] = 10 mM, pH = 4.17, the maximum CaCO3 yield is reduced to 3 mM and 5 mM. Similarly, [CO2] is reduced to 3 mM (light blue curve) (about 9% CO2, pH = 4.42) or 5 mM (about 15% CO2, pH = 4.31) ([Ca] = 10 mM, [Cl] = 20 mM) will reduce the maximum CaCO3 yield. Interestingly, for equal CaCO3 yield, decreasing [Ca] leads to increased NaOH consumption, whereas decreasing [CO2] decreases NaOH consumption. Figure 2(b) The following two cases are compared: (i) the initial pCO2 is 5%, corresponding to 1.73 mM CO2 (thick curve) and allowed to decrease with precipitation, and (ii) the pCO2 of the solution is kept constant (e.g., by continuous equilibration with a 17300 ppm gaseous CO2 stream) at 5% (thin curve). Figure 2 (a) In (i), CaCO3 precipitation is rapidly induced by the addition of NaOH and is limited by total dissolved CO2. In (ii), continuous supply of CO2 enables CaCO3 precipitation with a yield of about 7 mM (limited by [Ca]). (c) NaOH consumption for calcite precipitation of solutions in equilibrium with CO2 at different pCO2 levels (vol %) as specified by Henry's law.

[0014] Figure 3 The total dissolved carbon content of a solution in equilibrium with a CO2 gaseous stream as a function of pH is shown over a range of gas phase concentrations. Total dissolved CO2 is equal to [H2CO3*] + [HCO3 - ]+[CO3 2- ]. For reference, 0.04% represents the concentration of CO2 in the air. For comparison, the CO2 content in the air is shown.

[0015] Figure 4 A representative equilibrium calculation using PHREEQC with the llnl.dat database is shown for a reference seawater composition, as given by Millero et al. (Deep Sea Research Part I: Oceanographic Research Papers 2008 55(1), 50-72). Simultaneous addition of CO2 and NaOH in a 1:2 molar ratio results in the precipitation of calcite and magnesite, with up to about 55 mmol magnesite and about 10 mmol calcite per kg water. The saturation concentration of CO2 at atmospheric pressure is about 34 mM. In an engineered approach, CO2 equilibrium can be maintained by simply bubbling air during carbonate precipitation (see Figure 2 b. Figure 2 c).

[0016] Figure 5 Shown is the use of Aspen Simulated amine-based method, energy requirements for CO2 capture and compression as a function of concentration (red solid curve). The thermodynamic minimum energy required to separate CO2 from the mixture and compress it from 1atm to 15MPa (red dotted curve) is calculated based on the entropy of the (separated) mixed gas phase CO2. The energy cost of CO2 mineralization (blue solid line) of NaOH (blue dotted line) produced by chlor-alkali under the thermodynamic minimum energy demand of production is also shown. The theoretical energy demand for producing NaOH from NaCl is obtained from Thiel et al. (ACS Sustainable Chem. Eng. 2017, 5 (12), 11147-11162). The energy costs of direct air capture and compression (DACC; magenta triangles) and integrated caustic amines (green circles) using KOH / K2CO3 methods are obtained from Keith et al. (Joule 2018, 2 (8), 1573-1594, Climatic Change 2006, 74 (1), 17-45). The vertical grey lines represent CO2 concentrations in the air, natural gas and coal-fired power plants, and cement plant flue gases. The shaded areas represent representative energy cost ranges for the following CO2 mitigation strategies: (red) capture and compression (range: 0.1 MWh (at the thermodynamic minimum) to 4.5 MWh per tonne CO2; depending on concentration), (blue) stoichiometric addition of electrosynthesized NaOH (range: 1.26 MWh (at the thermodynamic minimum) to 4.5 MWh per tonne CO2), and (yellow) electrolytic precipitation (single-step carbon sequestration and storage) (range: 0.07 MWh (at the thermodynamic minimum) to 2.3 MWh per tonne CO2; independent of concentration).

[0017] Figure 6 (a) shows the Figure 6 (b) OH is generated locally on the membrane cathode - Conceptual illustration of the use of rotary drum filtration solutions to remove material deposited on / near the membrane surface as a means of inducing carbonate precipitation. Figure 6 (c) shows the results of using COMSOL Using time-step adaptation, triangular mesh elements (173.21 μm 2 The pH of the electrolyte at different overpotentials after 1 s of polarization simulated by the mesh openings (with periodic boundary conditions). The breakdown potential of water is assumed to be 0 V. RHE (RHE: reversible hydrogen electrode) (see RSC Adv. 2019, 9(54), 31563-31571). The simulation considers a planar electrode (100 mm) made of 304L stainless steel immersed in an excess electrolyte (0.1 M NaCl). 2), where for the hydrogen evolution reaction (HER), the Tafel relationship [η=0.172+log(i / i0), where η is the overpotential (V), i is the current density (A / m 2 ), and i0 is the exchange current density (1.04x10 -7 A / m 2 )] means: pH(t)=14+log[{(10 η-1.2) / 0.172] )t} / 9.6485+10 -7 ], where pH is the average pH produced in the adjacent brine electrolyte within a 1 mm thick region, η is the overpotential (V), and t is the time (s). For example, an overpotential of about 0.5 V is required to produce a pH of 10 at the membrane surface, at which all inorganic carbon in solution is converted to CO3 2- It is expected that increasing the surface area of ​​the electrode (e.g., using a mesh) or its electrochemical activity will reduce the overpotential required to induce near-surface alkalization.

[0018] Figure 7 A conceptual diagram showing single-step carbon sequestration and storage for achieving CO2 mineralization and disposal.

[0019] Figure 8 (a) shows the cathodic polarization curve of 304L stainless steel in 0.1 M NaCl solution. The dashed line represents the Tafel fitting of hydrogen evolution reaction (HER): η = 0.172 + log (i / i0), where η is the overpotential (V) and i is the current density (A / m 2 ), and i0 is the exchange current density (1.04x10 -7 A / cm 2 )], indicating that the pH of the electrolyte in the 1 mm thick region at time t(s) is 14+log[{(10 [(η-1.2) / 0.172] )t} / 9.6485+10 -7 ]. Figure 8 (b) shows the simulated equilibrium pH between the anode and cathode of the toroidal reactor (inset) as a function of the overpotential (e.g., the difference between the cell potential and the water breakdown potential of 1.23 V). - and H + Ion generation and mass transfer and acid-base neutralization (OH - +H + →H2O) to control pH.

[0020] Fig. 9 (a) shows a cross-sectional view of an electrolytic precipitator with a planar geometry. Fig. 9(b) shows a cross-sectional view of an electrolytic precipitator with cylindrical geometry. In both configurations, an acidified (C, Ca, Mg)-depleted seawater outlet feed can be used for silicate weathering to increase the alkalinity and pH of the effluent.

[0021] Fig.10 (a) shows the COMSOL The simulated geometry of a 1 mm thick mesh with cylindrical holes (100 μm, radius), e.g. Fig.10 (b) Cross section of the cathode. Fig.10 (a) shows the pH of the pore solution at different current densities for a flow rate of 1 mm / s, and Fig.10 (c) shows the value for 1 mA / cm 2 Current density, pH of pore solution at different average flow rates.

[0022] Fig.11 (a) shows a carbon nanotube-polyvinyl alcohol (CNT-PVA) composite membrane showing surface morphology and pore size of about 125 nm. Fig.11 (b) shows an optical image (FOV of approximately 1 mm × 1 mm) of the anodic activated carbon (graphite) electrode surface (pore size 20 μm) exposed to a 10 mM CaCl2 solution after applying a 1 V (cell) potential in a flow reactor, showing a precipitate identified as CaCO3 by thermogravimetric analysis. The lower [Ca] at the outlet compared to the inlet further demonstrates that dissolved Ca 2 + removal. DETAILED DESCRIPTION

[0023] Certain embodiments of the present disclosure relate to methods of fixing CO2.

[0024] According to one aspect of some embodiments, a method includes: introducing carbon dioxide into a solution; and inducing carbonate solids to precipitate from the solution, wherein inducing the precipitation of carbonate solids includes electrolyzing the solution. In some embodiments, carbon dioxide is introduced into the solution via a gas diffuser. In some embodiments, the solution contains (dissolves) carbon dioxide via equilibrium with the atmosphere. In some embodiments, electrolyzing the solution includes increasing the pH of the feed solution. In some embodiments, electrolyzing the solution includes generating hydroxide ions. In some embodiments, inducing the precipitation of carbonate solids includes rotating a membrane drum in the solution while applying suction to draw the solution onto the surface of the membrane drum. In some embodiments, the solution is a salt water solution. In some embodiments, the solution is an alkali metal-containing solution. In some embodiments, inducing the precipitation of carbonate solids includes inducing the precipitation of at least one of calcium carbonate or magnesium carbonate or other carbonates (e.g., barium carbonate) or other related solids. In some embodiments, the method also includes enriching the alkali metal cations in the solution.

[0025] In another aspect according to some embodiments, a method includes: introducing carbon dioxide into a solution; and inducing carbonate solids to precipitate from the solution, wherein the precipitation of inducing carbonate solids includes rotating a membrane drum in the solution while applying suction to draw the solution onto the surface of the membrane drum. In some embodiments, carbon dioxide is introduced into the solution via a gas diffuser. In some embodiments, inducing the precipitation of carbonate solids includes electrolyzing the solution with water. In some embodiments, electrolyzing the solution with water includes increasing the pH of the feed solution. In some embodiments, electrolyzing the solution with water includes generating hydroxide ions. In some embodiments, the solution is a salt water solution. In some embodiments, the solution is an alkali metal-containing solution. In some embodiments, inducing the precipitation of carbonate solids includes inducing the precipitation of at least one of calcium carbonate or magnesium carbonate or other carbonates (e.g., barium carbonate) or other related solids. In some embodiments, the method also includes enriching the alkali metal cations in the solution.

[0026] In another aspect according to some embodiments, a method of removing carbon dioxide from an aqueous or gaseous stream by contacting a gaseous stream containing carbon dioxide, when present, with an aqueous solution containing ions capable of forming insoluble carbonates; contacting the aqueous solution containing carbon dioxide with an electroactive grid that induces alkalinization thereof, thereby forcing carbonate solids to precipitate from solution and removing dissolved inorganic carbon by electrolysis; and removing the precipitated carbonate solids from the solution or from the surface of the grid where the carbonate solids may be deposited. In some embodiments, a gaseous stream is present. In some embodiments, the gaseous stream comprises between about 0.04% and 100% by volume of CO2 (e.g., about 0.04%, 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 98%, 99%, 99.9% by volume of CO2, and ranges therebetween). In some embodiments, the gaseous fluid is atmospheric air. In some embodiments, the gaseous fluid is flue gas emitted from natural gas and coal-fired power plants, steel and iron plants, cement plants, ethanol plants, and chemical manufacturing plants. In some embodiments, the aqueous solution comprises a certain amount of dissolved carbon dioxide in equilibrium with the gaseous stream. In some embodiments, the aqueous solution is in thermal equilibrium with the gaseous stream, for example, at a temperature of 5°C≤T≤100°C. In some embodiments, the aqueous solution is not in thermal equilibrium with the gaseous stream, for example at a temperature of 5°C≤T≤100°C. In some embodiments, there is no gaseous stream. In some embodiments, the ions capable of forming insoluble carbonates include ions comprising one or more of the following: Ca, Mg, Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu and Al. In some embodiments, the aqueous solution has a NaCl concentration of about 1,000 ppm or more. In some embodiments, the aqueous solution has a NaCl concentration of about 30,000 ppm or more. In some embodiments, the aqueous solution has a NaCl concentration of about 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm, 10000 ppm, 20000 ppm, 30000 ppm, 40000 ppm, 50000 ppm, 60000 ppm and the range therebetween. In some embodiments, the aqueous solution comprises seawater or brackish water or brine. In some embodiments, the electroactive grid comprises a mesh cathode comprising a metal or non-metallic composition. In some embodiments, the method utilizes an end-to-end energy intensity of about 2.5 MWh or less per ton of mineralized carbon dioxide. In some embodiments, the aqueous solution comprises an amount of dissolved carbon dioxide buffered to atmospheric abundance.In some embodiments, the electroactive grid generates increased alkaline conditions in situ within the electroactive grid of about 2 μm to 20000 μm in aqueous solution. In some embodiments, the alkalinizing conditions are a pH of 9 or greater (e.g., a pH of about 9, 10, 11, 12, 13, 14, and ranges therebetween). In some embodiments, the electroactive grid comprises a metal or carbon-based grid. In some embodiments, the electroactive grid comprises stainless steel, titanium oxide, carbon nanotubes, polymers and / or graphite, or other mixed compositions of these materials (e.g., metal / polymer, metal / non-metal, metal / ceramic). In some embodiments, the electroactive mesh comprises pores having a diameter in the range of about 0.1 μm to about 10000 μm (e.g., about 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 1000 μm, 1500 μm, 2000 μm, 3000 μm, 4000 μm, 5000 μm, 6000 μm, 7000 μm, 8000 μm, 9000 μm, or 10000 μm). In some embodiments, inducing precipitation of carbonate solids comprises rotating a cylinder consisting of an electroactive mesh in a solution while applying suction to draw the solution onto an outer surface of the mesh. In some embodiments, the solution is an alkali metal-containing solution. In some embodiments, inducing precipitation of carbonate solids comprises inducing precipitation of at least one carbonate having Ca, Mg, Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu, and Al.

[0027] In another aspect according to some embodiments, a flow-through electrolysis reactor comprises: an inhalation device connected to a rotating cylinder fluid comprising an electroactive grid, and a scraping device and / or a liquid spray-based device for separating solids from the grid surface / solution. In some embodiments, the flow-through electrolysis reactor also includes an aqueous solution comprising carbon dioxide, Ca ions, and Mg ions. In some embodiments, the electroactive grid is capable of inducing the removal of dissolved inorganic carbon by precipitating carbonate solids from an aqueous solution comprising carbon dioxide and ions capable of forming insoluble carbonates. In some embodiments, the electroactive grid comprises a metal or carbon-based grid. In some embodiments, the electroactive grid comprises stainless steel, titanium oxide, carbon nanotubes, polymers and / or graphite, or other mixed compositions. In some embodiments, the reactor comprises a plurality of electroactive grids. In some embodiments, a plurality of electroactive grids are arranged into a series of parallel planar units or parallel cylindrical units. In some embodiments, the reactor is fluidly connected to the desalination device.

[0028] CO2 can be fixed in stable mineral carbonates. The strategy is based on the separation of gaseous CO2 from liquid and solid streams with Ca in aqueous media. 2+ and / or Mg 2+The combination of ions (or other ions capable of forming insoluble carbonates, such as Ba, Sr, Fe, Zn, etc.) precipitates solid calcium carbonate (CaCO3), magnesium carbonate (MgCO3) and their variants. The mineralized carbon can then be disposed of on the earth's surface or discharged into the ocean. The large carbon storage capacity, minimal environmental impact and low risk of late CO2 release support the feasibility of this scheme as a major route for long-term Gt-level CO2 waste management.

[0029] Alkaline CO2 mineralization method can be realized by adding a strong base such as NaOH to a near-neutral feed solution containing Ca and Mg similar to seawater (for example, pure water containing about 10 millimoles per liter (mM) CaCl2 and about 55mM MgCl2), as described below. The feed solution can also be composed of liquid streams such as groundwater rich in alkali metals, industrial wastewater, desalinated brine, etc. Alkaline cation enrichment constitutes an optional pretreatment stage to increase the aqueous concentration of Ca, Mg and other alkaline cations. Enrichment can be achieved by filtration, capacitance concentration or a combination thereof. Then, an aeration tank (such as those used in the activated sludge process for wastewater treatment) can be used to obtain effective mixing and CO2 balance to produce water rich in CO2. Alkali (for example, NaOH) can be blended into water rich in CO2 such as in the coagulation and flocculation process for water treatment, resulting in CaCO3 and MgCO3 precipitation. The precipitate can be separated by sedimentation, and the discharged solid can be further dehydrated to be landfilled or discharged into the ocean like the brine disposal in the desalination plant.

[0030] The thermodynamics and kinetics of carbonate mineralization can be further enhanced by local pH and temperature excursions induced on the membrane surface. Instead of adding depleting reagents, advanced CO2 mineralization methods involve CO2 mineralization and disposal equipment that generates hydroxide ions (OH) by water electrolysis (via a water electrolyzer). - ) and raise the temperature of the site (via a heating element). A more alkaline solution increases the driving force for carbonate precipitation and generates OH by water electrolysis. - The pH of the liquid is increased to promote carbonate precipitation. Similarly, higher temperatures increase the driving force for carbonate precipitation, and the use of a heating element increases the temperature of the liquid to promote carbonate precipitation. CO2 is optionally injected or otherwise introduced into the liquid via a gas diffuser and compressor; or may be present in the liquid at a level in equilibrium with its gaseous atmosphere. Figure 1As shown, the device is designed in the form of a rotating vacuum membrane drum that rotates in a CO2-rich and Ca / Mg-containing liquid (e.g., seawater or other saline solution) placed in a pool. The membrane drum includes a membrane (e.g., a metal membrane in the form of a mesh or screen) as a filtration medium surrounding a central pipe through which suction (or negative pressure) is applied. As the membrane drum rotates through the liquid, carbonates can form on the surface of the membrane. A vacuum pump is connected to the central pipe and applies suction to draw the liquid onto and through the membrane surface, wherein the Ca 2+ and Mg 2+ With CO3 2- The Ca- / Mg-depleted filtrate flows to the interior of the membrane drum and is pumped out. The carbonate solids adhere to the exterior of the membrane drum, which then passes over a blade to remove the solids from the membrane, thereby regenerating the membrane surface for subsequent carbonation as the drum rotates back into the liquid. This advanced method also offers the possibility of a method integrated with / within a desalination plant, simultaneously addressing the problem of climate change caused by CO2 and the scaling problem in membrane desalination plants (caused by Ca on the membrane surface). 2+ and Mg 2+ accumulation of compounds).

[0031] Example

[0032] The precipitation of calcium carbonate such as calcite is given by the formula:

[0033]

[0034] Where K sp is the solubility product (also called the equilibrium constant) and is equal to Ca 2+ and CO3 2- The product of the water activities at equilibrium. During the precipitation of calcite, HCO3 - or CO3 2- (Both are formed by the speciation of CO2 in water) can be adsorbed and bound to the growth surface. K of CaCO3 sp As the temperature decreases, the temperature of the calcite saturated solution increases from 25°C to 90°C, resulting in the precipitation of calcite with a yield of about 300 μmol / kg water. The morphological reaction and dissociation constant describing the CO2-H2O system are written as:

[0035]

[0036]

[0037] Where H2CO3* represents the total CO2 (aqueous solution) and H2CO3 0 The distribution of dissolved CO2 is disclosed by the Bjerrum diagram. In general, CO3 2-The activity of anions depends on pH (e.g., in water, CO3 2- is the main carbon species at pH>10.33), as does the degree of calcite precipitation. Higher salinity shifts K1 and K2 to larger values, so HCO3 - and CO3 2- The pH shifts to smaller values ​​when the ions dominate. The thermodynamic driving force for mineral precipitation is given by saturation Ω = IAP / K sp is given by, where IAP is the ionic activity product; for example, for calcite this is the Ca 2+ and CO3 2- This is relevant to typical natural waters containing divalent metal cations (e.g., groundwater, seawater, produced water) because their near-neutral pH requires the provision of supplemental alkalinity to induce carbonate precipitation. Because Ca and Mg are the most abundant divalent cations in natural waters and in typical industrial waters (e.g., produced water, thermally evaporated brines, etc.); these waters are represented as CaCl2 solutions because, to a large extent, Cl - Provides charge compensation for the cations in these systems.

[0038] Adding NaOH increases the pH and Ω of the solution 方解石 , which eventually leads to the precipitation of calcite. For a solution with a fixed initial CO2 concentration (pCO2), calcite precipitation is limited by the abundance of Ca, CO2 or alkalinity (pH). Figure 2 (a) shows a CaCl2 solution with CO2 added at various concentrations of Ca, CO2, or alkalinity. Although less acidic solutions (e.g., with lower CO2 concentrations) require less NaOH to initiate calcite precipitation, the maximum CaCO3 yield limited by CO2 in this case may therefore be lower ( Figure 2 On the other hand, excess CO2 in solution can make Ca the limiting reactant. In the case where both the NaOH:CaCO3 and H2O:CaCO3 molar ratios are minimized, the Ca and CO2 molar concentrations are approximately equal, and NaOH (indicating alkalinity) is added until the maximum CaCO3 yield is achieved ( Figure 2 The dotted curve in a). The addition of NaOH leads to Na + With CO3 2- complexation; therefore, {CO3 2-} and {Ca 2+ The molar ratio of CO2 to Ca required to achieve an equivalent activity between the two reactions (where the brackets {} denote activity) is slightly higher than 1. The molar ratio of NaOH consumed to CO2 stored as CaCO3 is at least 2 (e.g., for each of reactions [2] and [3], which provides one mole of OH - ).

[0039] For liquid streams characterized by low CO2 concentrations, air can be bubbled through the aqueous feed relative to the CO2 consumption rate. To illustrate this, Figure 2 In (b) two cases are compared: in one case the initial CO2 concentration is fixed and the dissolved carbon is gradually depleted, in the other case the CO2 concentration of the solution is kept constant by balancing with a gaseous stream characterized by a fixed pCO2. In the first case CaCO3 precipitation is rapidly induced by the addition of NaOH and is limited by the total dissolved CO2, while in the second case CO2 supplementation causes calcite precipitation until Ca is depleted. In the second case precipitation is initially inhibited by excess acidity, e.g. CO2. For completeness, the different cases of CO2 balancing / supplementation for varying pCO2 levels are shown in Figure 2 (c). In the limit, the carbonate yield depends only on the [Ca] abundance of the feed and does not vary with CO2 concentration. The amount of CO2 soluble in water is controlled by its pH and salinity, as well as the temperature-dependent Henry's law constant. For a given solution, increasing the solution pH (pH>6) increases the total dissolved carbon ( Figure 3 ). This is because the pH-dependent form of CO2 (aqueous solution) is HCO3 - and CO3 2- , which reduces the concentration of CO2(aqueous solution), allowing further dissolution of CO2(gas) according to Henry's law. It is for this reason that the formation of cation-carbonate and cation-bicarbonate complexes in seawater increases its carbon storage capacity relative to freshwater at pH>6.

[0040] The carbonate precipitation reaction is characterized by a time scale. Under well-mixed conditions (e.g., no mass transfer limitations) at 25 °C and 1 atm, the equilibrium described by reaction [4] is t = 5.0 x 10 -11 Occurs within s.

[0041]

[0042] As described in reactions [5]-[7], the water-containing substances H2CO3, HCO3 - and CO3 2- In 10 -2 Equilibrium is reached within s.

[0043]

[0044]

[0045]

[0046] However, relative to Ca 2+The equilibrium (i.e., reactions [8] and [9]) is only 10 3 Reached within s.

[0047]

[0048]

[0049] In alkaline solution (pH>10), by reacting with OH - Reaction to form HCO3 - The alternative pathway for CO2 solvation is even better than the reaction with H2O (k = 6.6x10 -4 M -1 s -1 ) is faster (k=8.5x10 3 M -1 s -1 ). The calcite precipitation rate in concentrated solutions similar to seawater (≥0.5 M NaCl) is shown to be about 3.2x10 6 Ms -1 The precipitation rate constant of Figure 2 (c) Consistent. This rate constant was obtained by fitting the experimental (calcite precipitation) data using an equation of the form: R = k(Ω-1) n , where R is the -1 The precipitation rate in units of , k is the precipitation rate in units of Ms -1 is the rate constant with units of , Ω is the saturation relative to calcite, and n is the reaction order. 2+ The reaction (e.g., CaCO3 precipitation) is rate-limiting. This allows analysis of the mass and energy balance of the subsequent CO2 mineralization.

[0050] Establish a baseline. In general, the above analysis shows that alkalinity promotes carbonate precipitation. Therefore, it is most important to examine the typical method of adding a strong base such as NaOH to a nearly neutral solution containing Ca and Mg ( Figure 4). For reference, it should be noted that the CO2 concentration from point source emissions is about 3% for natural gas power plants, 15% for coal-fired power plants and steel plants, 20% for cement plants, and >90% (vol %) for ammonia, ethanol, and hydrogen plants. On the other hand, the atmospheric CO2 concentration is about 0.04%, while the purity of CO2 captured by amine scrubbing can be greater than 99%. Therefore, this analysis includes reference concentrations of 0.04%, 5%, 20%, and 100%. The CO2 mineralization envisioned in the baseline case is modeled by simulating a water treatment process. First, if a CO2 source other than air is used, an aeration tank similar to that used in activated sludge treatment can be simply used to achieve effective mixing and CO2 equilibration with brine. Thereafter, as in the coagulation and flocculation processes, NaOH can be mixed into the CO2-rich water, resulting in the precipitation of CaCO3 and MgCO3. The precipitate is then separated from the solution by sedimentation, and the discharged solids can be dewatered using a belt press or discharged into the ocean similar to the disposal of brine in desalination.

[0051] Determining calcium and magnesium sufficiency for carbonate mineralization. Ca and Mg are available in more than sufficient amounts to meet carbon management needs on a global scale. For example, removing 10 Gt CO2 per year requires 9.1 Gt Ca or 5.5 Gt Mg, equivalent to 0.0017% of the total Ca and 0.00032% of the total Mg contained in the global oceans ("seawater"). Alternatively, although at much smaller levels, calcium and magnesium can be derived from: (a) underground brines that can contain more than 1,000 mg / L total dissolved solids (TDS), with extraction rates reaching 3.2 billion m3 / year in 2015. 3 , corresponding to 0.6 Mt Ca and 0.3 Mt Mg (using typical Ca and Mg concentrations in brackish waters in the United States); (b) global precipitation is 50 billion m 3 Desalinated brine produced at a rate of 2.5 Gt / year could provide an additional 0.04 Gt Ca and 0.1 Gt Mg per year; and (c) the 2.23 Gt of produced water produced annually in the United States alone (assuming an average Ca concentration of 5,000 mg / L) could provide an additional 0.01 Gt Ca per year. Although alkaline byproducts produced by the manufacture of metals, alloys, and cement and by coal combustion are rich in Ca and Mg, their weathering is presumed to fix no more than 0.3 Gt CO2 per year. In summary, seawater remains the most viable and abundant source of divalent metal ions for mineralization methods.

[0052] From a stoichiometric point of view, 2 mol of NaOH are required to convert 1 mol of CO2 into 1 mol of CaCO3 (see Figure 2 a and Figure 4). Therefore, the mineralization of 10Gt of CO2 requires a minimum of about 18Gt of NaOH. However, the global production of NaOH is relatively small; about 70Mt in 2016, but based on its Na content alone, 3.2x10 7 Gt NaOH. To meet this demand, 6,000 large chlor-alkali plants would be needed, each producing 3Mt NaOH per year; but this is an unfeasible proposition. Sufficient NaOH dosage has the potential to convert 2.86 g CO2 per kg water into MgCO3 and CaCO3 ( Figure 4 ). Thus, to store 10 Gt of CO2 per year, about 3500 Gt of water would need to be treated per year; an amount similar to our global annual water withdrawal (about 4000 Gt). On the other hand, in the United States, 47 Gt of wastewater is treated annually in more than 14,700 treatment plants. If a single CO2 reduction facility treated 2000 Mt of seawater per year (e.g., the size of a large wastewater treatment plant), then 1760 such plants would need to be built worldwide, each supplying 10 Mt of NaOH per year. Because carbonate yield is limited by the divalent cation content in the feed, enriching the Ca and Mg concentrations in the feed stream (e.g., using membranes that can selectively separate divalent cations) would allow smaller amounts of water to be treated. Obviously, such pretreatment can only be achieved with seemingly impractical large energy costs; although it would result in an increase in carbonate yield.

[0053] Energy intensity analysis. For comparison with the geological CCSS strategy, the energy requirements of the mineralization process using seawater as the source of divalent cations and NaOH as a stoichiometric additive can be estimated. Unlike geological CCSS, CO2 reduction based on seawater mineralization does not require a CO2 capture step. Therefore, the energy requirements of the baseline process (although not practically feasible) are based on the following requirements: water treatment and processing, and NaOH production. Water treatment and processing include: (a) seawater intake, which requires about 1.3kWh / t CO2 mineralization, (b) chemical dispersion, which requires 2.8-7.7kWh / t CO2 mineralization, and (c) sedimentation, which requires 0.175-0.35kWh / t CO2 mineralization. Therefore, overall, assuming seawater feed, water processing and treatment can consume about 5kWh / t mineralized CO2. The synthesis of NaOH by the chlor-alkali process requires 2.5MWh / t NaOH. Therefore, the energy requirement for direct CO2 mineralization (using seawater as a source of divalent ions and (dissolved) CO2) is estimated to be approximately 4.5 MWh / t CO2 ( Figure 5). Thus, for NaOH produced by current best-in-class chlor-alkali, the CO2 removal cost estimated from an industrial-use electricity price of about $70 per MWh is $315 / t CO2. 2+ Mg 2+ ) and OH - ) carbonation, which can slightly reduce the need for NaOH. The energy input for this direct carbonation includes pretreatment costs, including grinding and in some cases thermal activation, (carbonate) product disposal, and operation of pumps and mixers, and is about 0.5MWh / t CO2 (all included). Unfortunately, this direct carbonation of industrial alkaline solids is expected to provide no more than 0.3Gt of CO2 reduction per year. A less energy-intensive NaOH production route can be achieved by bipolar membrane electrodialysis. Even if NaOH can be produced with a theoretical minimum energy requirement of 0.7MWh / t NaOH (45% NaOH with by-product HCl available for enhanced silicate dissolution), the costs of mineralization-based CO2 management will be associated with an energy intensity of at least 1.26MWh / t CO2 ( Figure 5 ); for example, corresponding to a cost of no less than $90 per tonne of CO2 converted into solid carbonate using divalent cations from seawater.

[0054] The energy intensity of the conventional CCSS pathway was estimated by considering a monoethanolamine (MEA)-based process consisting of an absorber, a stripper, a cooler, and a four-stage compressor using Aspen and the eRNTL thermodynamic properties method (see Figure 5 ). In this paper, it is assumed that the CO2-depleted gas is extracted from the top of the absorber, while the CO2-rich solvent stream is extracted from the bottom. In order to release the CO2, the CO2-rich amine is heated to achieve the desorption enthalpy. The overhead condenser provides a reflux liquid stream to the column and the CO2-rich gas is purified to nearly 100% CO2. The nearly pure CO2 stream released from the stripper is compressed and transmitted for geological storage. Considering an inlet stream with 3% CO2 (e.g., corresponding to flue gas emitted from a natural gas power plant), an energy intensity of about 1.5 MWh / t CO2 is estimated for amine-based CO2 capture (heat load for amine regeneration of 1.3 MWh / ton) and for pressurization of the recovered CO2 stream (0.2 MWh / ton) from atmospheric pressure to pipeline specifications at 14 MPa (see Figure 5; solid red curve). As the concentration of CO2 in the inlet stream increases to about 12%, this energy intensity decreases to 0.8MWh / ton CO2 (for a coal-fired power plant; 0.6MWh for carbon capture and 0.2MWh for compression per ton CO2); it remains constant thereafter. However, at inlet CO2 concentrations below 3% CO2, the energy intensity of the amine-based process increases dramatically. The low capacity of the amine in contact with air (about 0.25mol / mol) would require a reboiler duty of greater than 5.0MWh / ton CO2 to achieve a workload of less than 0.05mol / mol. This suggests that for situations where the CO2 feed stream is unusually dilute, such as when removing CO2 from the atmosphere or water in atmospheric balance, the distinct advantage of the alternative mineralization method is that it is less energy intensive to operate.

[0055] Single-step carbon sequestration and storage (sCS 2 ): The above discussion shows that the energy consumption of mineralization-based CO2 management is mainly related to the need to provide alkalinity for the process. An ideal carbon sequestration method would not require consumable chemical inputs, which incur manufacturing, transportation, handling, and storage costs. Ideally, the method could be powered using zero-carbon electrons (e.g., from photovoltaics). Single-step carbon sequestration and storage (sCS) without chemical inputs 2 ) method is shown in Figure 6 and Figure 7 Here, water (e.g., seawater) containing dissolved CO2 (in equilibrium with air) flows over a porous metal membrane / cathode. Application of a cathode potential results in water electrolysis and localized elevation of OH at the membrane / water interface. - concentration, which promotes rapid binding of carbonate anions and metal cations while minimizing transport limitations and providing a substrate for heterogeneous nucleation. Specifically, the electrolyte is flowed through the pores of the membrane so that all ionic species (OH - 、CO3 2- and Me 2+ ) to minimize the diffusion length scale (to the pore radius) while providing surface sites for nucleation and growth of metal carbonates. Finite element analysis (FEA) shows that at a reasonable overpotential (≈0.5 V; see Figure 6 c), superalkaline conditions can indeed be generated near the surface of the electroactive membrane ("electrode"). In fact, the electrolyte volume within 200 μm of the electrode / membrane surface (e.g., much larger than the pore size of the electroactive membrane envisioned for such applications) experiences superalkaline conditions within 1 s of electrical polarization, sufficient to induce carbonate precipitation to Figure 5For reference, in this article, 304L stainless steel electrodes are represented as flat sheets; however, a coarse mesh with openings of approximately 20 μm is envisioned for practical applications. This analysis confirms that the application of a mild potential can rapidly generate the alkalinity required for carbonate precipitation. Although this analysis ignores electromigration and gas evolution that lead to convective mixing, it provides a lower estimate of the overpotential required to induce rapid alkalinization and thus carbonate precipitation.

[0056] Based on electrochemical OH - The actual energy requirements of the resulting electrolytic mineralization process can be estimated based on a prior art electrolyzer operating at 79% efficiency (e.g., assuming a thermodynamic requirement of 39.4 kWh / kg for the stoichiometric hydrogen evolution reaction, 50 kWh of electricity to produce 1 kg of H2). 1 kg of H2 produced via the electrolysis of water produces 1000 moles of OH - ion, which on a stoichiometric basis would sequester 22 kg CO2 for an energy intensity of 2.3 MWh / ton CO2. If the calorific value of the co-produced hydrogen is taken into account, assuming a conversion efficiency (e.g. for burning hydrogen and producing electricity) of about 60%, e.g. similar to natural gas combustion, the process yields an energy intensity of 1.2 MWh / ton mineralized CO2. This analysis considers 2 mol OH - The stoichiometric amount of 1 mol of CO2 mineralized into calcium carbonate (CaCO3). Based on this benchmark, 45 kg of low-pressure H2 will be generated per ton of mineralized CO2. 2(g) . This hydrogen is expected to provide a commercial value of approximately $3 / kg, resulting in a cost recovery of approximately $135 per ton of mineralized CO2. On the other hand, if a hydrogen fuel cell (HFC) is used to convert the produced low-pressure hydrogen into electricity, a conversion efficiency of approximately 80% can be achieved, resulting in an energy intensity of 0.84 MWh / ton of mineralized CO2. For an electrolyzer operating at 90% efficiency, the energy intensity is further reduced to 1.9 MWh / ton CO2 (without H2 recovery; $133 / ton CO2) and 0.38 MWh / ton CO2 (using HFC to recover and convert H2 at 90% efficiency; $27 / ton CO2). These values ​​limit the potential of sCS 2 The actual energy intensity (see Figure 5 In summary, this analysis shows that: (i) direct electrowinning can achieve carbon removal at ambient concentrations of CO2 at nearly twice the efficiency of typical chlor-alkali-based NaOH production and amine solvent-based processes (e.g., conservatively, <2.3 MWh / ton versus >4 MWh / ton), and (ii) if the energetic benefits of hydrogen byproducts are considered and / or zero-carbon energy inputs are used; in each case, sCS 2 The approach provides the basis for pioneering, true negative emissions technologies (NETs).

[0057] The significant advantage of using electroactive membranes for mineralization to generate alkalinity locally is that, due to the increase in pH, supersaturation (Ω; see Figure 4 and Figure 6 c) and the resulting temperature increase at the membrane surface due to Joule heating (up to 60 °C in solution), which enhances the precipitation kinetics (nucleation and growth). The electrolytic nature of the process requires a conductive (e.g., metal or composite) membrane that is mechanically and chemically stable under cathodic conditions. Such membrane surfaces are expected to scale during operation due to the formation of metal carbonates. sCS is expected to 2 The engineering design of the method will match the Reynolds number, Peclet number, and Damköller number within the electrolytic precipitation reactor; so that (reactant) mass transfer and chemical precipitation kinetics occur in correspondence with each other. Although this is unlikely to result in significant flux attenuation in a coarse grid structure as considered herein, the insulating properties of mineral carbonates can indeed compromise current density (e.g., thereby increasing the required overpotential) and energy efficiency. Therefore, it may be necessary to cyclically reverse the applied potential to generate O2 and H at the anode near the membrane surface. + , thereby removing the deposits. However, anodic conditions can lead to rapid corrosion, particularly where iron-based membranes are used. Another approach involves physical abrasion of the deposited carbonates in a manner similar to that used for continuous cleaning of rotary drum filters (see, for example, Figure 6 b. Figure 7 ). In these systems, the membrane surface is continuously scraped with a blade which removes the accumulated solids and exposes the membrane surface again. 2 The concept is characterized by high energy intensity for carbon reduction; this concept: (a) is more efficient than most other direct air capture (DAC) methods, (b) allows for direct use of carbon-free electricity; for example, especially when in excess, and (c) ensures end-to-end CO2 reduction. In addition, the electrolysis reactor envisioned herein can be simply modularly integrated with existing and future desalination plants without requiring the construction of new chlor-alkali plants, allowing for the removal and storage of CO2 while producing drinkable water and hydrogen that can be used as fuel. sCS 2 An additional benefit of the process is the production of softened water, which is an excellent feed for desalination plants. Currently, considering that seawater reverse osmosis (SWRO) requires 2-2.5 kWh / m 3 , and the pre-treatment step (e.g., substantially including water softening) consumes 0.3-1.0 kWh / m 3 Seawater, the energy cost of seawater desalination can be estimated at 3.5 kWh / t water. Combining CO2 mineralization-based pretreatment and SWRO desalination can result in 9% lower energy usage than the total energy consumption of both methods operating alone.

[0058] Importantly, however, even if cation replenishment / pH adjustment is required, this can be readily accomplished in electrochemical systems by exploiting the resulting acidity generation at the anode. Specifically, in an engineered system, electrolytic (re)alkalinization of a waste seawater stream can be accomplished by using a sCS 2 The acidity co-produced during the process dissolves mafic and ultramafic rocks and industrial solids including coal combustion and metal processing residues in a manner that enhances weathering. Significantly, the analysis showed that a greater amount of CO2 is stored as an aqueous solution than as a solid per unit of alkalinity. And for every mole of C stored as carbonate solids, 2 moles of OH are required. - , only 1.2 moles of OH are required per mole of C stored as dissolved ions - As a result, increasing the pH from 8 to 9 (e.g., 1 μM OH - to 10 μM OH - ) can dissolve 33mmol more CO2 per kg of water ( Figure 3 ). Thus, the discharged water can be designed to have a greater pH (e.g., higher [Ca] and / or [Mg]) than the extracted seawater; to provide further enhanced carbon reduction benefits. Therefore, strategies to remove atmospheric CO2 should be carefully combined with (re)alkalization of seawater to enhance its CO2 capacity driven by the ocean-atmosphere balance.

[0059] Fate of carbonate solids. Entrapment of CO2 within mineral carbonates can occur rapidly and provide stable and durable storage while eliminating any risk of post-storage release. Assuming stoichiometry and precipitation of calcite, the removal of 10 Gt of CO2 from the atmosphere (dissolved in seawater) can result in the production of about 20 Gt of solids per year. Some of these solids could replace the global limestone market across building materials (aggregates) and specialty applications. In the United States, 68% of crushed stone produced is composite carbonate rock; about 1 Gt of production is used in construction and as a raw material for cement production. Unusable solids can be disposed of via existing solid waste management strategies. In 2016, global municipal solid waste generation and industrial, agricultural, construction, and demolition waste totaled about 25 Gt. In the United States, the landfill cost of solid waste is about $45 / t, and landfill disposal of 10 Gt of carbonate solids requires about 6.8 km per year. 3 (6.8 billion m 3 ) space. Solids can be stored in abandoned mines instead of building new landfills. In 2017, 53Gt of metallic and non-metallic ore materials, 15Gt of fossil fuels and 24Gt of biomass were mined worldwide. However, off-site storage requires transporting solids at a cost of about $0.03 / m 3More realistically, especially if seawater is used as the alkalinity source, the precipitate could be redeposited in the ocean (e.g., in the form of desalinated brine; where these solids may remain stable and unreactive due to the ocean's supersaturation with calcite and magnesite), or used for land reclamation and erosion control purposes.

[0060] Under the London Protocol, as amended and implemented in 2006, dumping at sea is prohibited except for potentially acceptable wastes listed in the “reverse list” of Appendix 1. Calcium and magnesium carbonates can be considered “inert geological materials” allowing for disposal in the ocean, where they can remain stable because near-surface seawater is supersaturated with respect to both phases. If dissolved Ca and Mg are taken from sources other than seawater (e.g., saline groundwater), precipitated Ca and Mg carbonates can be used to buffer the decrease in ocean pH caused by atmospheric CO2 uptake or direct CO2 injection, through the addition and dissolution of limestone. Returning to land reclamation, a simple model of the migration of the southern California coastline approximates a retreat of about 30 m for a 1 m rise in sea level. Assuming an average depth of 50 m for the continental shelf, the generation of 20 Gt of solids over a 4500 km stretch of coastline could reverse this effect; about half the length of Florida’s Gulf Coast. Creating new land through solids derived from CO2 mineralization would not only address future CO2 emissions, it could also reverse one of the most significant effects of climate change. It can address the crisis of land and habitat loss due to sea level rise, while providing a permanent CO2 storage solution that does not require constant monitoring. 2 Methods An in-depth analysis of the mechanisms for subsidizing CO2 management, particularly the associated capital costs, is beyond the scope of this study. Nevertheless, the recent 45Q tax credits in the US and California’s Low Carbon Fuel Standard (LCFS) incentivize carbon reductions by implicitly pricing CO2 between $35-180 per ton. This incentive provides an important and potentially necessary pathway to achieving and enhancing CO2 reductions and mitigations on a global scale.

[0061] This sCS solution to the CO2 problem 2 The approach is different from traditional carbon capture and geological storage strategies. Unlike conventional sorbent-based CO2 capture methods, in which large amounts of energy consumption are associated with the energy consumption required to: (1) separate the CO2, which is usually in dilute concentration (less than 15 vol%) from the gas mixture, and (2) for CO2 desorption, sCS 2The method relies on electrolysis-facilitated precipitation of carbonate minerals in a process that can be operated entirely using renewable energy. However, major gaps in the supply of carbon-free electricity need to be bridged to achieve practical feasibility. Finally, by stabilizing solid carbonates, the method eliminates the need to monitor and verify CO2 sequestration and storage, while improving and ensuring the durability of CO2 storage. Given that carbon storage needs to last for thousands of years, the combination of electrolytic seawater CO2 mineralization can only provide us with a viable, environmentally friendly and potentially more acceptable solution to the global carbon crisis than traditional geological sequestration when combined with accelerated silicate / carbonate weathering; especially when NETs are deployed in the short to medium term (5 to 10 years).

[0062] In some embodiments, sCS 2 The methods include electroactive mesh compositions and their integration in "detachable and stackable" flow reactors to achieve scalable CO2 abatement in a strategy tailored for direct air capture (DAC) without the need for any stoichiometric reagents or additives (see Figure 7 ). Here, water (e.g., produced water, groundwater, or seawater) containing dissolved alkaline cations and dissolved CO2 in equilibrium with air flows over a porous conductive mesh / cathode. Application of a cathode potential results in electrolysis of the water and localized elevation of OH at the mesh / water interface. - concentration, which promotes the transport of carbonate anions and metal cations (e.g., Ca 2+ Mg 2+ )'s fast combination ( Figure 7 There are two basic principles for this hypothesis: (1) OH on the cathode surface - The electrochemical generation of OH and N&G of metal carbonates are fast reactions. Therefore, the crystal growth rate is limited by the transport of ions to the growth nuclei. - At the same time, the electrolyte flows through the pores of the mesh to minimize the total amount of ionic species (OH - 、CO3 2- , Ca 2+ and Mg 2 + ) and provide surface sites for N&G of metal carbonates, thereby increasing the reaction rate. (2) Heterogeneous nucleation is favored over homogeneous nucleation due to the lower energy barrier for crystal growth (e.g., 5 kJ / mol vs. 12.5 kJ / mol for CaCO3). Therefore, providing a surface (e.g., mesh / electrode) with the highest pH promotes the precipitation of carbonates while sequestering atmospheric CO2.

[0063] In support of this approach, experimental data and finite element analysis (FEA) indicate that ultraalkaline conditions (pH > 10) can be readily generated near the electroactive mesh / cathode surface (e.g., within 200 μm) at reasonable overpotentials (≈0.5 V). Although carbonate formation on the mesh surface can limit electron transfer reactions, sCS 2 Methods may include physical methods (e.g., scraping and / or water scrubbing) to remove sediment and renew the grid / cathode surface in a manner similar to that used in commercial drum filters. The sediment may be collected and / or discarded as suspended solids in a manner similar to desalinated brine ( Figure 7 ). Electrolytic (re)alkalinization of waste seawater streams by dissolving alkaline rocks and industrial solids (coal combustion residues) may allow for the uptake of more CO2 from the atmosphere in a manner that enhances weathering. Furthermore, the electroactive grid structures that can be developed herein have superior performance (e.g., based on energy per unit of CO2 captured, mineralized, or reduced) compared to existing adsorbents and membranes for DAC.

[0064] The method exploits the much higher CO2 concentration in water relative to air, which is regulated by the atmosphere-seawater balance. Seawater, with an average current pH of 8.1, contains 150 times more CO2 than an equal volume of air ( Figure 3 ), thus significantly reducing the volume of fluid to be treated. Although the relative density of seawater and air is greater than this concentration factor, pumping water is more efficient than air, and less water than air needs to be treated to remove the same amount of CO2. In addition, sCS 2 The method exploits the favorable thermodynamics of carbonate precipitation from alkaline solutions. The thermodynamic driving force for precipitation is given by Ω = IAP / K in the saturated state. sp is given by, where IAP is the ion activity product, and K sp is the solubility product. For calcite, this is the Ca 2+ and CO3 2- The Gibbs free energy difference is a function of the solution composition according to the following formula: ΔG = RT InΩ, where R is the gas constant and T is the temperature. CO2 (gas) (-394.3 kJ / mol), CO3 2- The standard Gibbs free energy of formation of CaCO3 calcite (-527.8 kJ / mol) and CaCO3 calcite (-1129.1 kJ / mol) Comparison of the results shows that carbonate precipitation ("CO2 mineralization") is thermodynamically downward. Electrochemical alkalization increases the pH and Ω 方解石 , thereby ensuring that calcite (and / or magnesite or other carbonates) precipitate ( Figure 4 and Figure 6). The reactions associated with the precipitation of carbonates in alkaline solutions are rapid. Under well-mixed conditions at 25°C and 1 atm (1 bar), The equilibrium described is at t = 5.0x10 -11 s. Water-containing substances H2CO3, HCO3 - and CO3 2- As described below: and In 10 -2 In alkaline solution (pH>10), it reacts with OH- to form HCO3 - The alternative pathway for CO2 solvation is even better than the reaction with H2O (k = 6.6x10 -4 M -1 s -1 ) is faster (k=8.5x10 3 M -1 s -1 ). Data on the precipitation rate of calcite in high saline water (≥0.5 M NaCl) indicate that the precipitation rate constant is 3.2x10 6 Ms -1 , the yield and Figure 4 is consistent with that obtained by fitting the experimental precipitation data to: R p =k(Ω-1) n , where R p is the precipitation rate, k is the rate constant, Ω is the saturation exponent, and n is the reaction order. Therefore, in a well-mixed system with low mass transfer resistance, CaCO3 precipitation is rate-limiting. The net reaction is: Ca 2+ +CO2+2OH - →CaCO3+H2O and Mg 2+ +CO2+2OH - →MgCO3+H2O. According to these stoichiometric quantities, 1 mol of CO2 is replaced by 1 mol of aqueous Ca 2+ or Mg 2+ capture, and requires 2 mol OH - To produce 1 mol CaCO0 or MgCO3. For typical seawater, in a cation-limited environment (relevant boundary conditions), 2.86 g CO2 ( Figure 4 ).

[0065] For clarity, the pH distribution in the scaled reactor was simulated. The simulation considered the following electrode reactions: (1) At the anode: oxygen evolution reaction (OER): 2H2O → O2 + 4H + +4e -; (2) At the cathode, (2a) oxygen reduction reaction (ORR): O2+H2O+4e - →4OH - , and (2b) hydrogen evolution reaction (HER): 2H2O+2e-→H2+2OH - .

[0066] The electrochemical behavior of 304L stainless steel is shown in Figure 8 (a). Dissolved oxygen in the solution promotes ORR (relative to HER) at negative overpotentials and reaches 4x10 -7 A / cm 2 The ORR can generate local alkalinity up to pH 10 at the cathode, while the HER promotes higher pH production; albeit at higher cell potentials.

[0067] CS 2 A method consists of a main unit operation, such as Fig. 9 Herein, Ca- and Mg-rich water (e.g., seawater, produced water, groundwater) saturated with CO2 from air under atmospheric conditions (about 23°C, 1 bar total pressure and about 400 ppm CO2) is brought into an electrolytic flow reactor.

[0068] As non-limiting examples, two configurations are disclosed, using either: (A) planar electrodes ( Fig. 9 (a)) or (b) tubular electrode ( Fig. 9 (b)). In (a), a mesh cathode is placed in the center of a rectangular housing made of non-conductive material, thereby forming two chambers ( Fig. 9 (a)). The anode is inserted near the wall of one of the chambers. In (B), the anode and cathode are placed radially inside a non-conductive tube, similar to Figure 4 The configuration shown ( Fig. 9 (b)). Seawater (105 mg CO2 equivalent C / L, see Figure 3 ) flows through a precipitation reactor consisting of the grid / cathode-anode system described below. An oxygen selective material (e.g., MnO2) with 95%-100% OER efficiency can be used as a coating on the anode to allow the use of a single electrolyte (seawater), thereby suppressing the Cl at the anode caused by seawater electrolysis. 2(g) In the reactor, the application of cathode potential causes [OH - ] increases, leading to precipitation. This is shown in simulations of the pH distribution within the pores of the electroactive mesh ( Fig.10 Nearly neutral seawater enters the pores and becomes increasingly alkaline until pH 12 ( Fig.10 (a)), the current density depends on the Fig.10 (b)) and flow rate ( Fig.10 (c)) degree.

[0069] Taking advantage of the technical advantages of membrane-based water treatment systems and the fact that the amount of CO2 in seawater is significantly higher than that in air under ambient conditions, and taking advantage of thermodynamically favorable mineralization reactions, the electroactive grid composition and flow reactor make seawater-mediated DAC possible. Since membrane fouling does not affect sCS 2 method, and indeed its goal, so that it allows simple mechanical removal of solids and / or cycle polarity reversal as a means of membrane regeneration.

[0070] CS 2 The method is more energy-efficient than the existing direct air capture (DAC) method. First, by considering the absorber, stripper, cooler and four-stage compressor and using Aspen A monoethanolamine (MEA)-based approach was used to estimate the energy intensity of conventional carbon capture and storage (CCS). The energy requirement rises sharply at inlet CO2 concentrations < 3 vol% CO2, extrapolating to > 3MWh / t CO2 at 0.04%, mainly due to the increased thermal energy required to desorb CO2 from the solvent at low loads. sCS 2 The energy requirements are mainly related to water electrolysis. A state-of-the-art electrolyzer operating at 79% efficiency (e.g., assuming a thermodynamic requirement of HER of 39.4 kWh / kg and 50 kWh of electricity to generate 1 kg H2) produces 1000 moles of OH - ions, which on a stoichiometric basis can mineralize 22 kg CO2 for an energy intensity of 2.3 MWh / tonne CO2. For an electrolyzer operating at 90% efficiency, the energy intensity drops to 1.9 MWh / tonne CO2. Figure 4 The expected power requirement for the process (2 kg CO2 per day) is about 0.2 kW (about 4.6 kWh per day). Pumping water also requires energy: (i) through the mesh (≈10 psi for 40 μm mesh openings; 1.2 kWh / t CO2) and (ii) against gravity (e.g., 1 meter total dynamic head; 1.3 kWh / t CO2).

[0071] Table 1. State point data of the CO2 removal system based on electroactive grids

[0072]

[0073]

[0074] The methods disclosed in some embodiments herein are functionally similar to membrane-based DAC methods. However, removal is based on an electrically induced chemical reaction rather than size or charge repulsion. Metrics such as (1) processing capacity, (2) energy intensity, and (3) carbonate single-pass yield can provide relevant information similar to that sought in traditional membrane-based methods. The data indicate that the electrolytic precipitation reaction is rapid; k≈3.2x10 6 Ms -1 The yield is therefore limited by the amount of cations present. For the Ca, Mg limited reactions, 60% and 100% conversions were obtained as "measured" and "expected" metrics.

[0075] In some embodiments, using a hydrogen fuel cell (HFC) to convert the generated low-pressure hydrogen into electricity, a conversion efficiency of approximately 80% can be achieved, resulting in a net energy intensity of 0.84 MWh / t mineralized CO2.

[0076] The feasibility of (a) electroactive mesh materials and (b) flow reactors into which the mesh is integrated to allow water alkalization and promote ultrafast precipitation has been demonstrated for the treatment of chromium-containing water, where pH swings along the mesh surface / cathode enable rapid accumulation of Cr(OH)3 at the membrane / water interface ( Fig.11 ). The grids include: (a) baseline grids based on 316L stainless steel (SS) grid or perforated grid, (b) non-metallic carbon-based grids (carbon nanotube (CNT) / polymer / exfoliated graphite composites), and (c) SS grids with locally sintered titanium films (Magnelli phase sintered Ti4O7 materials). The latter two grid compositions were selected to provide: high conductivity and stability in seawater, especially under anodic conditions that can corrode iron-based materials (regular cleaning of the grid may be required). The selected materials have: low cost and ease of processing, which enables easy fabrication of many form factors, including porous (e.g., coarse grids with openings in the μm to mm range) structures. For example, porous Ti4O7 materials are easily fabricated by sintering and thermal reduction of TiO2 powders. It is also possible to: (i) apply doctor blade processing to rapidly produce samples spanning 100s in 2 and (ii) fabricating large CNT-based membranes by air brushing a percolating network of CNTs onto a porous polymer support followed by crosslinking with a polymer such as polyvinyl alcohol (PVA) (see Fig.11 ). These composites are stable and conductive, with variable pore sizes ranging from nm to mm.

[0077] A range of metal and carbon-based grids / electrodes suitable for inducing pH swings in saline solutions can be used. Specifically, the use of porous geometries (e.g., grids or nonwoven mats) is made of: stainless steel (SS) (sintered grids are about $12 / m 2, or about $0.05 / g), Magnelli phase sintered Ti4O7 materials (synthesized from TiO2, about $0.10-0.20 cents / g), and carbon nanotube (CNT) / polymer / exfoliated graphite (eG) composites (e.g., CNT costs about $3-30 / g, and eG synthesized from graphite is about $0.10 / g). Mesh materials (<5cm x 5cm) with various porosities (15%-40%) and pore sizes (0.1μm-100μm, corresponding to a pressure drop of <15psi) can be used (smaller pores allow higher pH and lower overpotentials, but require a larger driving force to push water through). For SS, commercially available mesh materials (e.g., made from 304 and 316L SS) and sintered metal sheets with pore sizes between 37μm (400 mesh) and 1μm (for sintered SS plates) can be used. To prepare Ti4O7-coated grids, TiO2 powder can be purchased, cast in a gel and sintered under flowing air at 1050°C, followed by reduction under flowing H2 gas at 1050°C; this is a condition that produces substoichiometric Ti4O7. An alternative synthesis method is via a combination of sol-gel and vacuum carbothermal methods. Carbon-based grids can be made by spraying CNT / eG suspensions onto porous polytetrafluoroethylene and stainless steel supports and cross-linked using PVA. The grid surface morphology and pore size can be evaluated using scanning electron microscopy (SEM); the grid roughness can be evaluated using atomic force microscopy (AFM); and the pore size can be evaluated using SEM. The composition of the grid can be determined using energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and quantitative X-ray diffraction using Rietveld analysis. The overall electrochemical properties can be characterized using a four-point conductivity probe, cyclic voltammetry, electrochemical impedance spectroscopy, and electrochemical microscopy. The long-term stability of the grid can be between 1 and 200 mA / cm 2 The results were evaluated in a dead-end filtration cell operated continuously for >168 hours at a current density of 1.5 Å / min, where the feed stream (seawater) was pressurized to flow through a mesh that can be used as a cathode. MnO2-coated Ti rods can be used as anodes.

[0078] In situ atomic force microscopy (AFM) can be performed on different grid materials to optimize current density and (water) flux for carbonate precipitation via seawater electrolysis. This can determine the best performing grid composition that makes the alkalization kinetics consistent with thermodynamic predictions; while maximizing solid precipitate formation. An electrochemical AFM equipped with a fluid cell and temperature control, a potentiostat, and a photothermal probe excitation module that allows high-speed imaging can be used for screening analysis.

[0079] The current density at the grid surface and the morphology of the carbonate overgrowth layer can be monitored while various overpotentials (0.0 V to 2.0 V) are applied to a 1 cm x 1 cm x ≤ 0.25 cm grid sample mounted in a fluid cell containing simulated seawater. The fluid cell features separate liquid and gas exchange ports. The aqueous environment to which the grid is exposed can be controlled in real time (e.g., during application of potential and data collection) by exchanging the solution or gas within the fluid cell using a programmable syringe pump. For example, to replenish dissolved Ca 2+ and Mg 2+ (e.g., it is extracted from solution by CaCO3 precipitation), simulated seawater is exchanged through a sealed unit at a flow rate that matches the rate at which it is exhausted from solution. On the other hand, in order to replenish dissolved atmospheric CO2 without replenishing cations, air can flow through the unit. The kinetics (e.g., rate, morphology) of carbonate growth can be evaluated by collecting time series images in a time period of seconds to hours. The morphology of the precipitate can be tracked by measuring aspect ratio, thickness and surface coverage, which can affect the progress of electrolytic precipitation by causing resistive loss / joule heating at the grid surface. Fixed solution composition and pCO2 can also be evaluated. Solution Ω can be estimated by modeling the pH evolution and gas / liquid exchange rate at the surface. Therefore, the electrolysis conditions (e.g., applied potential, flow rate, Ω) that maximize the growth rate can be identified. A grid that has the highest yield and rate of carbonate precipitation at the lowest overpotential and a carbonate growth rate that decreases over time can be selected, for example, due to resistive loss. The cycling performance of the selected grids can be tested within 10 s of polarization reversal while monitoring the surface morphology / current density.

[0080] definition

[0081] As used herein, the singular terms "a", "an", and "the" may include plural referents unless the context clearly indicates otherwise. Thus, for example, a reference to an object may include a plurality of objects unless the context clearly indicates otherwise.

[0082] As used herein, the term "group" refers to a collection of one or more objects. Thus, for example, a group of objects may include a single object or a plurality of objects. Individual objects in a group may also be referred to as members of the group. Individual objects in a group may be the same or different. In some instances, individual objects in a group may share one or more common features.

[0083] As used herein, the term "connected" refers to an operational connection or link. Connected objects can be directly connected to each other or indirectly connected to each other, such as via one or more other objects.

[0084] As used herein, the terms "substantially" and "approximately" are used to describe and illustrate small variations. When used in conjunction with an event or circumstance, the term may refer to instances where the event or circumstance occurs precisely as well as instances where the event or circumstance occurs approximately. When used in conjunction with a numerical value, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%.

[0085] In addition, amounts, ratios and other numerical values ​​are sometimes presented in this article in a range format. It should be understood that such a range format is used for convenience and brevity, and should be flexibly understood to include the numerical values ​​clearly specified as range limits, and also include all single numerical values ​​or subranges contained within the range, as if each numerical value and subrange are clearly specified. For example, a ratio within the range of about 1 to about 200 should be understood to include the clearly listed limits of about 1 and about 200, but also includes individual ratios such as about 2, about 3 and about 4, and subranges such as about 10 to about 50, about 20 to about 100, etc.

[0086] Additional Implementation

[0087] E1. A method comprising:

[0088] introducing carbon dioxide into the solution; and

[0089] Inducing precipitation of carbonate solids from the solution, wherein inducing precipitation of the carbonate solids comprises subjecting the solution to water electrolysis.

[0090] E2. A method as described in E1, wherein the carbon dioxide is introduced into the solution through a gas diffuser, or the solution may contain carbon dioxide at a level in equilibrium with its environment.

[0091] E3. A method as described in any of E1-E2, wherein water electrolyzing the solution includes increasing the pH of the feed solution.

[0092] E4. A method as described in any of E1-E3, wherein the water electrolysis of the solution includes producing hydroxide ions.

[0093] E5. A method as described in any of E1-E4, wherein inducing precipitation of carbonate solids includes rotating a membrane drum in the solution while applying suction to draw the solution onto the surface of the membrane drum.

[0094] The method as described in any one of E1-E5, wherein the solution is a saline solution.

[0095] E7. A method as described in any one of E1-E6, wherein the solution is a solution containing an alkali metal.

[0096] E8. The method of any one of E1-E7, wherein inducing precipitation of carbonate solids comprises inducing precipitation of at least one of calcium carbonate or magnesium carbonate.

[0097] E9. A method comprising:

[0098] introducing carbon dioxide into the solution; and

[0099] Inducing precipitation of carbonate solids from the solution, wherein inducing precipitation of the carbonate solids comprises rotating a membrane drum in the solution while applying suction to draw the solution onto a surface of the membrane drum.

[0100] E10. A method as described in E9, wherein the carbon dioxide is introduced into the solution via a gas diffuser.

[0101] E11. A method as described in any of E9-E10, wherein inducing precipitation of carbonate solids comprises performing water electrolysis on the solution.

[0102] E12. The method of any one of E9-E11, wherein the solution is a saline solution.

[0103] E13. A method as described in any one of E9-E12, wherein the solution is a solution containing an alkali metal.

[0104] E14. The method of any one of E9-E13, wherein inducing precipitation of carbonate solids comprises inducing precipitation of at least one of calcium carbonate or magnesium carbonate.

[0105] Although the present disclosure has been described with reference to its specific embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the present disclosure as defined in one or more of the appended claims. In addition, many modifications may be made to adapt specific circumstances, materials, compositions of matter, methods, one or more operations to the purpose, spirit and scope of the present disclosure. All of these modifications are within the scope of one or more of the appended claims. Specifically, although certain methods have been described with reference to specific operations performed in a specific order, it is understood that these operations may be combined, subdivided or reordered to form equivalent methods without departing from the teachings of the present disclosure. Therefore, unless expressly stated herein, the order and grouping of operations are not limitations to the present disclosure.

Claims

1. A method for removing carbon dioxide from a fluid, the method comprising: contacting a fluid comprising carbon dioxide with an aqueous solution comprising calcium and magnesium cations to form an aqueous solution comprising calcium cations, magnesium cations, and carbon dioxide; contacting the aqueous solution comprising calcium cations, magnesium cations and carbon dioxide with an electroactive grid to induce alkalinization by electrolysis of water, thereby inducing precipitation of calcium and magnesium carbonates from the aqueous solution comprising calcium cations, magnesium cations and carbon dioxide, wherein contacting the fluid comprising carbon dioxide with the aqueous solution comprising calcium and magnesium cations comprises continuously equilibrating the aqueous solution comprising calcium and magnesium cations with the fluid comprising carbon dioxide, and wherein contacting the aqueous solution with the electroactive mesh electrode comprises passing the aqueous solution through pores of the electroactive mesh, and The precipitated carbonate solids are removed from the surface of the grid on which the carbonate solids are deposited.

2. The method of claim 1, wherein the fluid is a gaseous fluid.

3. The method of claim 2, wherein the gaseous fluid comprises between 0.04 vol% and 100 vol% CO2.

4. The method of claim 2, wherein the gaseous fluid is atmospheric air.

5. The method of claim 2, wherein the gaseous fluid is flue gas emitted from a natural gas power plant, a coal-fired power plant, an iron plant, a steel plant, a cement plant, or a chemical manufacturing plant.

6. The method of claim 2, wherein the aqueous solution is in thermal equilibrium with the gaseous fluid.

7. The method of claim 1, wherein the fluid is a liquid fluid.

8. The method of claim 7, wherein the liquid fluid is an aqueous fluid.

9. The method of claim 8, wherein the gaseous stream is bubbled through the liquid fluid before the liquid fluid is contacted with the aqueous solution.

10. The method of claim 1, wherein the aqueous solution further comprises at least one additional cation capable of forming an insoluble carbonate selected from the group consisting of Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu, and Al.

11. The method of claim 1, wherein the aqueous solution has a NaCl concentration of 1,000 ppm or more.

12. The method of claim 1, wherein the aqueous solution has a NaCl concentration of 30,000 ppm or more.

13. The method of claim 1, wherein the aqueous solution comprises seawater.

14. The method of claim 1, wherein the method utilizes an end-to-end energy intensity of 2.5 MWh or less per ton of mineralized carbon dioxide.

15. The method of claim 1, wherein the aqueous solution comprises an amount of dissolved carbon dioxide buffered to atmospheric abundance.

16. The method of claim 1, wherein the electroactive grid is within a range of 2 μm to 20,000 μm of the electroactive grid in the aqueous solution. In situ Increasingly alkaline conditions are produced.

17. The method of claim 16, wherein the alkalinizing condition is a pH of 8 or greater.

18. The method of claim 1, wherein the electroactive grid comprises a metal or a carbon-based material.

19. The method of claim 18, wherein the electroactive grid comprises stainless steel, titanium oxide, carbon nanotubes, polymers, graphite, or any combination thereof.

20. The method of claim 1, wherein the electroactive grid comprises pores having diameters in the range of 0.1 μm to 10,000 μm.

21. The method of claim 1, wherein inducing precipitation of the carbonates of calcium and magnesium comprises rotating a cylinder containing the electroactive mesh in the solution while applying suction to draw the solution onto an outer surface of the mesh.

22. The method of claim 1, wherein the aqueous solution is a saline solution.

23. The method of claim 1, wherein the aqueous solution is an alkali metal-containing solution.

24. The method of claim 1, wherein inducing precipitation of the carbonates of calcium and magnesium further comprises inducing precipitation of a carbonate of at least one cation selected from the group consisting of Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu, and Al.

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