Seawater electrolysis enables scalable mineralization of atmospheric CO2

Abstract

Disclosed herein is a method for recovering CO2 from a gas source using electrochemically enhanced amine recovery to form a concentrated CO2 vapor, followed by sequestration of CO2 from the concentrated vapor in a sequestration step that includes contacting the concentrated vapor with an aqueous sequestration solution that includes ions capable of forming insoluble carbonates, such that the aqueous sequestration solution includes CO2 (electrochemically basifying the sequestration solution), thereby precipitating carbonate solids, and separating the carbonate solids from the surface of the aqueous sequestration solution or mesh.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 215,853, filed June 28, 2021, the entire contents of which are incorporated herein by reference.

[0002] Statement regarding government support This invention was made with Government support under Contract No. DE-FE0031705 awarded by the U.S. Department of Energy. The Government has certain rights in this invention. [Background technology]

[0003] Conversion technologies capable of capturing gigatons (Gt) of CO2 are important to mitigate environmental change. Various CO2 capture, sequestration, and storage processes (CCSS) are being considered to manage CO2 emissions from various sources. Current technology for carbon capture using amines relies on a thermal swing cycle where CO2 is absorbed in a bubbling flow column followed by regeneration of the CO2-rich amine solution in a packed distillation column at temperatures above 140 °C. This process has been used for post-combustion capture in power generation, but suffers from the high energy intensity (1.2 MWh / tonne of CO2 for power generation and 5.0 MWh / tonne of CO2 for DAC) required to desorb only a portion (~50%) of the CO2 captured in the amine solution. The low amine regeneration range leads to low effective CO2 absorption capacities (e.g., about 0.05 and 0.25 moles CO2 per mole MEA for DAC and power generation, respectively (see E Sanz-Perez, et al., Direct Capture of CO2 from Ambient Air, 116 Chem. Rev. 11840-76 (2016)). Furthermore, the high temperatures (>140°C) required for amine regeneration result in solvent loss due to chemical decomposition and evaporation.

[0004] The use of caustic solutions (e.g., KOH / K2CO3) for direct air capture also suffers from the high energy intensity required to generate mineral reagents for the pH swing process (e.g., 4.5 MWh per tonne of CO2 for chlor-alkali to generate NaOH and HCl). Adsorption using solid materials has also been proposed for direct air capture, but these processes also have high energy requirements for desorption (>2.0 MWh per tonne of CO2).

[0005] Strategies for indirect recovery via seawater have also been proposed, but these require either complex electrochemical cells (e.g., electrodialysis) and / or mineralization strategies that rely on slow precipitation kinetics. For example, precipitation of Mg-carbonate species from seawater requires elevated carbonate concentrations (>100 mM) over long timescales (weeks to months). (See IMPower, et al., Room Temperature Magnesite Precipitation, 17 Cryst. Growth Des. 5652-59 (2017)). Therefore, there is great interest in more efficient, less energy intensive processes for direct air capture of CO2. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] ESSanz-Perez,et al.,Direct Capture of CO2 from Ambient Air,116 Chem.Rev.11840-76(2016) [Non-Patent Document 2] IMPower,et al.,Room Temperature Magnesite Precipitation,17 Cryst.Growth Des.5652-59(2017) Summary of the Invention [Means for solving the problem]

[0007] In some embodiments, the disclosure relates to a method of recovering CO from a gas source, the method comprising: (a) concentrating CO from the gas source in a concentrating step, the concentrating step comprising: (i) contacting the gas source with an absorption solution having a solvent and a solute, the solvent and / or solute comprising an amine, thereby forming a solution comprising an amine-CO complex; (ii) electrochemically adjusting a pH of the absorption solution to less than about 7, thereby releasing the CO as an enriched vapor; (iii) collecting the enriched vapor; and (b) sequestering CO from the enriched vapor in a sequestration step, the sequestration step comprising: (iv) contacting the enriched vapor with an aqueous sequestration solution comprising ions capable of forming an insoluble carbonate, thereby causing the aqueous sequestration solution to comprise CO; (v) contacting the aqueous sequestration solution comprising CO with an electroactive surface to basify the aqueous sequestration solution comprising CO, thereby precipitating carbonate solids; and (vi) separating the carbonate solids from the aqueous sequestration solution or the electroactive surface.

[0008] In some embodiments, the anionic complex comprises a carbamate ion.

[0009] In some embodiments, the solvent comprises an amine, while in others the solute comprises an amine, and in still other embodiments the solvent and solute comprise an amine. The amine may be a primary amine, a secondary amine, a tertiary amine, or a mixture thereof. Preferably, the amine is a primary or secondary amine.

[0010] In some embodiments, the amine has the structure of Formula I: R x NH 3-x ,(I); wherein R is selected from optionally substituted alkyl, ether, and hydroxyalkyl, or two R together with the nitrogen atom to which they are attached form a nitrogen-containing heterocycle; x is 1, 2, or 3.

[0011] In some embodiments, the amine is monoethanolamine, 2-ethylaminoethanol, 2-methylaminoethanol, ethylenediamine, benzylamine, diethanolamine, pyrrolidine, morpholine, 2,6-dimethylmorpholine, monoisopropanolamine, piperazine 2-(dimethylamino)ethanol, N-tert-butyldiethanolamine, 3-dimethylamino-1-propanol, 3-(dimethylamino)-1,2-propanediol, 2-diethylaminoethanol, 3-diethylamino-1,2-propanediol, 3-diethylamino-1-propanol, triethanolamine. amine, 1-dimethylamino-2-propanol, 1-(2-hydroxyethyl)pyrrolidine, 1-diethylamino-2-propanol, 3-pyrrolidino-1,2-propanediol, 2-(diisopropylamino)ethanol, 1-(2-hydroxyethyl)piperidine, 2-(dimethylamino)-2-methyl-1-propanol, 3-piperidino-1,2-propanediol, 3-dimethylamino-2,2-dimethyl-1-propanol, 3-hydroxy-1-methylpiperidine, N-ethyldiethanolamine, 1-ethyl-3-hydroxypiperidine, and any combination thereof.

[0012] In some embodiments, the solvent comprises water.

[0013] In some embodiments, the gas source comprises about 0.4 to about 25% (v / v) CO. The gas source may be a gas source such as effluent from an industrial source, atmospheric air, or a combination thereof.

[0014] In some embodiments, the pH adjustment step is performed via water electrolysis. In some embodiments, the gas source is an effluent from an industrial feedstock or ambient air. In some embodiments, the pH adjustment step is performed at a temperature below 100° C. In some embodiments, the regenerated solvent is collected and reused in the same process. In some embodiments, the gas source is an atmospheric source (e.g., ambient air).

[0015] In some embodiments, the concentrated steam comprises about 2-99% (v / v) CO. In some embodiments, the concentrated steam comprises 2-15% (v / v) CO.

[0016] In some embodiments, the absorbent solution is regenerated with a strong base anion exchange resin.

[0017] In some embodiments, the isolating aqueous solution is in thermal equilibrium with the gas stream. In some embodiments, the isolating aqueous solution is not in thermal equilibrium with the gas stream.

[0018] 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 sequestration solution has a NaCl concentration of about 1,000 ppm or greater. In some embodiments, the aqueous sequestration solution has a NaCl concentration of about 30,000 ppm or greater. In some embodiments, the aqueous sequestration solution comprises seawater. In some embodiments, the aqueous sequestration solution is a brine solution. In some embodiments, the aqueous sequestration solution is an alkali metal-containing solution.

[0019] In some embodiments, the electroactive surface comprises a cathode comprising a metal or non-metallic composition. In some embodiments, the electroactive surface is a mesh that generates, in situ, increasing alkaline conditions in an isolated aqueous solution within about 2-20,000 μm of the electroactive mesh. In some embodiments, the alkaline conditions are pH 9 or greater. In some embodiments, the electroactive mesh comprises a metal or carbon-based mesh. In some embodiments, the electroactive mesh comprises metals (such as steel, stainless steel, titanium oxide, nickel and nickel alloys), carbon nanotubes, polymers, and / or graphite, or other hybrid compositions of these materials. In some embodiments, the electroactive mesh comprises pores having diameters ranging from about 0.1 μm to about 10,000 μm.

[0020] In some embodiments, inducing precipitation of carbonate solids includes inducing precipitation of at least one carbonate having Ca, Mg, Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu, or Al.

[0021] In some embodiments, removing precipitated carbonate solids from the surface of the isolation solution or mesh includes rotating a rotating disk cathode having a mesh on a surface thereof past a scraper, which removes precipitated carbonate solids from the surface of the mesh. [Brief description of the drawings]

[0022] [Figure 1A] FIG. 1 is a schematic diagram of a CO2 capture and mineralization process according to the present disclosure. [Figure 1B] FIG. 1 is a schematic diagram of a CO2 absorption process according to the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram of an exemplary electrochemical cell 200 useful for amine-based CO2 capture, including a cathode 201, an anode 202, a second cation exchange membrane 203, an anion exchange membrane 204, a first cation exchange membrane 205, a base solution 206, a salt solution 207, an amine solution 208, and an acid solution 209. [Diagram 3] 1 is a plot of pH values ​​(circles) and the extent of CO2 desorption (triangles) at various solution proton:MEA ratios for a 22 vol.% MEA solution with a CO2 loading of 0.25 (red) and 0.5 (black) moles CO2 per mole of MEA. [Figure 4A] FIG. 1 is a cross-sectional view of an exemplary scalable carbon dioxide mineralization reactor, where an online pH monitoring system controls the applied current to achieve a constant catholyte pH that enables atmospheric CO2 capture and mineralization. The reactor uses a rotating disc cathode (316L stainless steel mesh) that is rotated past a scraper for product removal and collection. [Figure 4B] FIG. 1 shows a cross-sectional view of a laboratory-scale single-compartment CSTR. [Figure 5A] We present the pH evolution during the carbon dioxide mineralization process (150 min.HRT and 10-min.HRT, respectively), which was demonstrated using air, seawater, and reactor designs (shown in Figure 4B). [Figure 5B] We present the pH evolution during the carbon dioxide mineralization process (150 min.HRT and 10-min.HRT, respectively), which was demonstrated using air, seawater, and reactor designs (shown in Figure 4B). [Figure 5C] We show Ca2+ removal during the carbon dioxide mineralization process (150-min.HRT and 10-min.HRT, respectively), which was demonstrated using air, seawater, and reactor designs (shown in Figure 4B). [Figure 5D] We show Ca2+ removal during the carbon dioxide mineralization process (150-min.HRT and 10-min.HRT, respectively), which was demonstrated using air, seawater, and reactor designs (shown in Figure 4B). [Figure 5E]The resulting inorganic carbon effluent (IC) for the carbon dioxide mineralization process is shown (150 min.HRT and 10-min.HRT, respectively), which was demonstrated using air, seawater, and reactor designs (shown in FIG. 4B). The insets in FIG. 5E and FIG. 5F are scanning electron images showing a thick layer of aragonite (CaCO3) formed on the PP mesh. [Figure 5F] The resulting inorganic carbon effluent (IC) for the carbon dioxide mineralization process is shown (150 min.HRT and 10-min.HRT, respectively), which was demonstrated using air, seawater, and reactor designs (shown in FIG. 4B). The insets in FIG. 5E and FIG. 5F are scanning electron images showing a thick layer of aragonite (CaCO3) formed on the PP mesh. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The process according to the present disclosure is based on a series of electrochemically enhanced reactors that utilize water electrolysis to generate the protons and / or hydroxide ions necessary for energy-efficient CO2 concentration and storage. The first step in the overall process involves separation of CO2 from air (e.g., absorption of CO2) using an absorption solution (e.g., an aqueous amine solution). Such processes include, but are not limited to, those disclosed in PCT Application No. PCT / US22 / 25028, filed April 15, 2022, which is incorporated herein by reference in its entirety. The second step in this process involves releasing the absorbed carbon species into the concentrated CO2 gas stream. The third step in the process involves sequestration of the CO2 separated from the amine-based CO2 absorption process by mineralization in an aqueous solution (e.g., seawater or brine). Such processes include, but are not limited to, those disclosed in PCT Publication No. WO2021 / 061213, filed June 12, 2020, which is incorporated herein by reference in its entirety.

[0024] FIG. 1B shows the overall CO2 capture process according to the present disclosure. Briefly, CO2 is absorbed from one or more gas sources (e.g., air or industrial process gases) into an aqueous amine solution via the formation of anionic complexes (e.g., carbamate complexes). The CO2 is then desorbed from the amine via electrochemically induced acidification. The amine solution is regenerated for further absorption using a strong base anion exchange resin that is regenerated using alkaline catholyte from the electrochemical step.

[0025] This process uses an amine solution (pH>10) to absorb CO2 from a gas source. However, the CO2-rich amine is regenerated in an electrochemical cell where protons are generated from the aqueous solution at the anode (and hydroxide ions at the cathode). These protons diffuse into the rich amine solution, causing a drop in the pH of the amine solution (pH<7), decomposition of the carbamate ions, and release of CO2 (e.g., as a concentrated vapor containing CO2). The CO2 can be released as a gas stream containing 1-99% CO2. A salt bridge provides anions to maintain charge neutrality in the amine solution and cations to the cathode solution.

[0026] 1B, after the CO2 is released, the amine solution is restored to high pH via ion exchange with a strong base anion exchange resin. The basic solution from the cathode is used to regenerate the ion exchange resin, thereby recovering salt for recycle to the salt bridge solution.

[0027] This electrochemically induced pH-swing process has the advantage of replacing hazardous, expensive, and carbon-intensive reagents (e.g., mineral acids) with abundant and benign sources (e.g., water) while leveraging renewable energy to facilitate the process. Thus, the technology disclosed herein aims to incorporate water electrolysis into the amine absorption process to induce pH swing via electrochemically generated protons and hydroxide ions, thereby achieving higher adsorption-desorption working capacity in an energy-efficient and low-carbon intensity manner. This pH-swing process occurs at ambient temperature, thus offering the following advantages: (1) simpler process equipment requirements; (2) complete amine regeneration (hence maximum adsorption-desorption working capacity); and (3) reduced solvent loss. Specific aspects of the electrochemically induced pH swing process, as disclosed in PCT Application No. PCT / US22 / 25028, filed April 15, 2022, are discussed below.

[0028] CO2 Absorption by Electrochemically Induced pH-Swing Process During a conventional amine scrubbing process, CO2-containing gas is contacted with a concentrated (20-50% v / v) aqueous amine solution. Under basic conditions (pH > 10), absorption occurs by reaction of CO2 with an amine (e.g., MEA; RNH2, where R = CH2CH2OH), producing the carbamate anion (RNHCOO - ,RNCOO 2- ), protonated amines (RNH3 + ), and proton / hydronium ion (H + / H3O + ) are formed according to Equations 1-3, while other gases such as N2 and O2 escape into the effluent. CO2 also forms carbonates at high pH (Equation 4) 4 . RNH2+CO2⇔H + +RNHCOO - (1) RNHCOO - +RNH2⇔RNH3 + +RNCOO2- (2) RNHCOO - +H2O⇔H3O + +RNCOO 2- (3) CO2+H2O⇔CO3 2- +2H + (4)

[0029] The existing approach to release CO2 and regenerate the amine is a thermal process, in which the solution is heated to high temperatures (>140 °C) where the carbamate decomposes to produce the original amine molecule and releases CO2 as a concentrated vapor. 3、5-6 However, large heat loads (e.g., >5 MWh per tonne of CO2 for a 0.05 mol / mol adsorption / desorption differential for DAC applications) 3 This makes thermal processes economically unattractive. Furthermore, the high temperatures required for amine regeneration can result in chemical decomposition and solvent loss by evaporation. 3 These factors can result in up to a 50% increase in CAPEX and up to a 25% increase in OPEX, which is compounded by the high cost of carbon capture (>$100 / tonne CO2). 7-8 and restricts the use of amine-based processes to point source emitters (e.g., fossil fuel-fired power plants).

[0030] An alternative to thermal amine regeneration is to shift the pH of the solution to acidic conditions (pH ≦ 7), which promotes the decomposition of carbamate ions (by acid hydrolysis) according to the inverse of equations (1) and (3). This pH-swing process occurs at ambient temperature and therefore offers the following advantages: (1) simpler process equipment requirements; (2) utilization of the maximum adsorption / desorption differential of the amine; and (3) reduced solvent loss. However, the requirement of an acid and a base as stoichiometric reagents to shift the pH makes the pH-swing process infeasible for widespread adoption. An alternative to mineral acids and bases is to use water electrolysis to generate the protons required for carbamate ion hydrolysis (e.g., to convert the rich amine solution to a lean solution) and to generate the hydroxide ions required to increase the pH of the lean solution for a subsequent cycle of CO2 absorption (Figure 1B (left side)).

[0031] Referring now to FIG. 2, in this approach, protons are generated in an electrochemical cell from an aqueous solution at the anode (with hydroxide ions generated at the cathode) according to equations (5) and (6) below. 2H2O(l) → O2(g) + 4H + (aqueous solution)+4e - ;E0=1.23V vs.SHE (5) 4H2O(l)+4e - →2H2(g)+4OH - (Aqueous solution);E0=-0.83V vs.SHE (6)

[0032] Protons diffuse through the cation exchange membrane (CEM) into the rich amine solution, resulting in a drop in pH, which leads to the decomposition of carbamate ions and the release of CO2. The CEM is included to prevent the diffusion of carbamate anions into the anode and cathode chambers, thereby preventing electro-oxidation of the carbamate / MEA. To maintain electrical neutrality, a concentrated salt solution (e.g., NaCl or NaNO3) is used to provide counter anions to the amine solution and cations to the catholyte. An anion exchange membrane (AEM) prevents the diffusion of salt solution cations into the MEA compartment. After the CO2 is released, the amine lean solution is restored to high pH using a strong base anion exchange resin (Figure 1B (right side)). This resin absorbs counter ions (e.g., Cl) from a salt reservoir (e.g., accumulated in the amine solution). - or NO3 - ) is exchanged for hydroxide ions, raising the pH of the dilute amine back to its basic value.

[0033] The anion exchange resin is regenerated using hydroxide-rich solution from the cathode compartment of the electrochemical cell, thereby recovering the anions used in the salt solution compartment. This regeneration process ensures efficient recycling of necessary reagents, minimizing operating costs and preventing waste generation. This electrochemically induced pH-swing process has the advantage of replacing hazardous, expensive, and carbon-intensive reagents (e.g., mineral acids) with abundant and benign sources (e.g., water), while utilizing renewable energy to facilitate the process.

[0034] Incorporation of electrochemical reactions for amine regeneration Some recent research has focused on utilizing electrochemistry for amine-based CO2 capture. 9-16 In these studies, metals (e.g., Cu 2+ ion) and amines, which decomposes the carbamate ion and releases CO2. 11-12、14-16 This complex formation reaction proceeds electrochemically at the anode (Cu metal oxidation leads to Cu2+ ions are produced), and at the cathode, the Cu-amine complex is regenerated to amine (Cu 2+ is reduced to Cu metal).

[0035] This work was extended to electrochemical CO2 capture on solid polyanthraquinone. 9、13 The system uses a Faradaic electroswing process to capture CO2 via a carboxylation reaction (reduction) with quinone (to which polyvinylferrocene is oxidized), followed by reversing the polarity of the cell to decompose the carboxyl-quinone compound (and reduce the polyvinylferrocene), thereby desorbing CO2 and regenerating polyanthraquinone. These electrochemical processes have demonstrated high adsorption / desorption differentials (as much as 0.62 moles of CO2 per mole of amine for a 12% v / v CO2 flow) and low energy requirements (theoretical minimum requirement of about 0.60 MWh per tonne of CO2), but they also require complex Cu-based redox chemistry with expensive diamines or quinones. Furthermore, the electrochemistry acts directly on the amines. These functions can accelerate degradation of the amines or electrodes, leading to higher capital expenditures / operating costs (CAPEX / OPEX). 17 Importantly, these studies also focused on the very high CO2 concentrations in power plants (~12%) rather than studies in direct air (DAC) applications (~400 ppm).

[0036] Integrating water electrolysis into amine regeneration has two major advantages. First, performing water electrolysis in separate anode / cathode chambers allows local generation of protons and hydroxides without the need for stoichiometric or expensive / exotic regents, catalysts, or materials, reducing the risk of electrochemical decomposition of the amines / electrodes. Second, water electrolysis at the cathode produces H2, thereby offering the opportunity for realistic energy requirements of 2.0 MWh / ton CO2 by capturing and using the evolved H2. An additional advantage of using electrochemical processing is that up to 100% of the required energy can be supplied from renewable sources. These innovations impact both process equipment and energy efficiency. Complete regeneration of amine molecules at ambient temperature can be achieved via acid-mediated carbamate decomposition. This impacts process equipment by (1) reducing the amount of amine required by an amount proportional to the increase in capacity, and (2) replacing complex distillation columns with simpler modular electrochemical cells and anion exchange columns. This simple process equipment reduces CAPEX (e.g., less than the >$60 million investment cost for an amine stripper column). 7 ), has the potential to increase the plasticity and modularity of the system, both of which would enable the use of the process in a wider array of applications (e.g., capture from industrial processes and direct air capture).

[0037] Realistic energy requirements for the electrochemically enhanced amine process can be estimated based on the number of protons required for CO2 desorption and current state-of-the-art electrolyzers operating at approximately 80% efficiency (e.g., assuming the thermodynamic demand for a stoichiometric hydrogen evolution reaction is 54.8 kWh / kg, as shown in equations (5) and (6)). 19 , 68kWh per 1kg of H2 generated 18 For example, titration of a 22% MEA solution with various CO loadings (see FIG. 3; 0.25 and 0.5 moles CO / mole MEA) revealed approximately 1.0 mole of H per mole of MEA. +is shown to be required for a pH decrease from 12 to 0.6 (the point at which all CO2 is desorbed). From this information, the energy requirements for two embodiments of the technology can be estimated: (1) A DAC with an initial MEA loading is 20 and (2) industrial effluent containing 1-12% CO (initial loading of 0.5 moles CO per mole MEA).

[0038] In some embodiments, for direct air capture ("DAC") applications, the proton to CO2 ratio is about 4 for complete desorption. Using current electrolyzers, the process requires 6.3 MWh / ton CO2 to be removed. With about 70% of the H2 energy recovered, this value decreases to 3.8 MWh / ton CO2 (removed). At 95% cell efficiency, the energy requirements can be 5.3 and 2.8 MWh / ton CO2 without and with H2 capture, respectively. In comparison to conventional thermal swing processes, the reboiler duty required to desorb CO2 from a loading of 0.30 to 0.25 moles of CO2 per mole of MEA is about 5.0 MWh / ton CO2. 3 , the load required for complete desorption is >25MWh / tonne of CO2. 3、21 This preliminary energy analysis indicates that not only can the process now be run with much lower energy requirements than conventional thermal swing processes (6.3 vs. 25.0 MWh / tonne CO2), but also that it could potentially achieve a five times higher coefficient of adsorption / desorption differential (0.25 vs. 0.05 moles CO2 / mole MEA).

[0039] For applications with effluents containing >1% CO2, the energy requirements are reduced. For example, assuming an initial MEA load of 0.5 moles of CO2 per mole of MEA, the proton to CO2 ratio for complete desorption is about 2. At 80% efficiency, the process requires 3.1 MWh / ton of CO2 to be removed. With about 70% of the H2 energy recovered, this value decreases to 1.9 MWh / ton of CO2 removed. At 95% cell efficiency, the energy requirements are 2.6 and 1.4 MWh / ton of CO2 without and with H2 recovery, respectively. In comparison to conventional thermal swing processes, the reboiler duty required to desorb CO2 from a load of 0.5-0.25 moles of CO2 per mole of MEA is about 1.3 MWh / ton of CO2. 5 This loading increases from >2.2 MWh / tonne of CO2 for desorption to less than 0.20 moles of CO2 per mole of MEA, and >5 MWh / tonne of CO2 for desorption from low concentration amines (e.g., 0.3-0.2 moles of CO2 per mole of MEA). 5 Based on these studies, the loading required for complete desorption is >25 MWh / tonne CO2, because CO2 desorption is thermodynamically unfavorable at low CO2 loadings. 5、32 This preliminary energy analysis indicates that the process is now viable with comparable energy requirements as conventional thermal swing processes (1.9 vs. 1.3 MWh / tonne CO2) and can potentially achieve a two-fold higher adsorption / desorption differential (0.5 vs. 0.25 moles of CO2 per mole of MEA).

[0040] In some embodiments, the disclosed method includes a method or step of absorbing CO2, comprising contacting a gas source including CO2 with this absorbing solution including a solvent capable of forming an anionic complex, electrochemically adjusting the pH of the absorbing solution to less than about 7, collecting the CO2 as a concentrated vapor released during or after the pH adjustment step, regenerating the solvent and / or solute, and optionally collecting the regenerated solvent and / or solute. In some embodiments, the anionic complex includes carbamate ions and / or hydroxides (e.g., sodium hydroxide, potassium hydroxide). In some embodiments, the solvent is an amine. In some embodiments, the amine is a amine having a structure such as R x NH 3-x where R is selected from optionally substituted alkyl, ether or alcohol.

[0041] In some embodiments, the pH adjustment step is performed via water electrolysis. In some embodiments, the CO2 source is an effluent from an industrial source (e.g., flue gas emitted from a natural gas-fired power plant, a coal-fired power plant, an iron or steel mill, a cement plant, an ethanol plant, or a chemical manufacturing plant). In some embodiments, the CO2 source is an atmospheric source (e.g., ambient air). In some embodiments, the pH adjustment step is performed at a temperature below 100° C. In some embodiments, the regenerated amine is recovered and reused in the same process.

[0042] In some embodiments, the amine is one or more primary amines (e.g., monoethanolamine (MEA), 2-ethylaminoethanol, 2-methylaminoethanol, ethylenediamine, benzylamine); one or more secondary amines (e.g., diethanolamine (DEA), pyrrolidine, morpholine, 2,6-dimethylmorpholine, monoisopropanolamine, piperazine (PZ)); one or more tertiary amines (e.g., 2-(dimethylamino)ethanol (DMAE), N-tert-butyldiethanolamine (tBDEA), 3-dimethylamino-1-propanol (DMA-1P), 3-diethylamino-1,2-propanediol (DMA-1,2-PD), 2-diethylaminoethanol (DEAE), 3-diethylamino-1,2-propanediol (DEA-1,2-PD), 3-diethylamino-1-propanol (DEA-1P) , triethanolamine (TEA), 1-dimethylamino-2-propanol (DMA-2P), 1-(2-hydroxyethyl)pyrrolidine [1-(2HE)PRLD], 1-diethylamino-2-propanol (DEA-2P), 3-pyrrolidino-1,2-propanediol (PRLD-1,2-PD), 2-(diisopropylamino)ethanol (DIPAE), 1-(2-hydroxyethyl)piperidine [1-(2HE)P P], 2-(dimethylamino)-2-methyl-1-propanol (DMA-2M-1P), 3-piperidino-1,2-propanediol (3PP-1,2-PD), 3-dimethylamino-2,2-dimethyl-1-propanol (DMA-2,2-DM-1P), 3-hydroxy-1-methylpiperidine (3H-1MPP), N-ethyldiethanolamine, 1-ethyl-3-hydroxypiperidine); and mixtures thereof.

[0043] In some embodiments, the CO2 absorbing solution has a basic pH (e.g., >7). In some embodiments, the pH of the CO2 absorbing solution is greater than about 7, greater than about 7.5, greater than about 8, greater than about 8.5, greater than about 9, greater than about 9.5, greater than about 10, greater than about 10.5, greater than about 11, greater than about 11.5, or greater than about 12, or any range or value therebetween. In some embodiments, the CO2 absorbing solution has a pH of about 7, about 7.5, about 8, about 8.5, about 9, about 9.5, about 10, about 10.5, about 11, about 11.5, about 12, about 12.5, about 13, about 13.5, or about 14, or any range or value therebetween.

[0044] In some embodiments, the CO2 absorption step is carried out at a temperature of less than about 100°C, less than about 95°C, less than about 90°C, less than about 85°C, less than about 80°C, less than about 75°C, less than about 70°C, less than about 65°C, less than about 60°C, less than about 55°C, less than about 50°C, less than about 45°C, less than about 40°C, less than about 30°C, or less than about 25°C, or any range or value therebetween. In some embodiments, the CO2 absorption step is carried out at a temperature of about 100°C, about 95°C, about 90°C, about 85°C, about 80°C, about 75°C, about 70°C, about 65°C, about 60°C, about 55°C, about 50°C, about 45°C, about 40°C, about 30°C, or about 25°C, or any range or value therebetween. In some embodiments, the CO2 absorption step is carried out under ambient conditions (e.g., room temperature and pressure).

[0045] In some embodiments, the pH of the solution is electrochemically adjusted to release CO2 as concentrated vapor. In some embodiments, the pH of the solution is adjusted to less than about 7.5, less than about 7, less than about 6.5, less than about 6, less than about 5.5, less than about 5, less than about 4.5, less than about 4, less than about 3.5, less than about 3, less than about 2.5, less than about 2, less than about 1.5, or less than about 1, or any range or value therebetween. In some embodiments, the pH of the solution is adjusted to about 7.5, about 7, about 6.5, about 6, about 5.5, about 5, about 4.5, about 4, about 3.5, about 3, about 2.5, about 2, about 1.5, or about 1, or any range or value therebetween.

[0046] In some embodiments, the pH adjustment step is performed at a temperature of less than about 100° C., less than about 95° C., less than about 90° C., less than about 85° C., less than about 80° C., less than about 75° C., less than about 70° C., less than about 65° C., less than about 60° C., less than about 55° C., less than about 50° C., less than about 45° C., less than about 40° C., less than about 30° C., or less than about 25° C., or any range or value therebetween. In some embodiments, the pH adjustment step is performed at a temperature of about 100° C., about 95° C., about 90° C., about 85° C., about 80° C., about 75° C., about 70° C., about 65° C., about 60° C., about 55° C., about 50° C., about 45° C., about 40° C., about 30° C., or about 25° C., or any range or value therebetween. In some embodiments, the pH adjustment step is performed under ambient conditions (e.g., room temperature and pressure).

[0047] In some embodiments, the concentrated vapor is from about 2% to about 99% CO2, from about 2% to about 95% CO2, from about 2% to about 90% CO2, from about 2% to about 85% CO2, from about 2% to about 80% CO2, from about 2% to about 75% CO2, from about 2% to about 70% CO2, from about 2% to about 65% CO2, from about 2% to about 60% CO2, from about 2% to about 55% CO2, or from about 2% to about 60% CO2, or from about 2% to about 6 ... O2, about 2% to about 50% CO2, about 2% to about 45% CO2, about 2% to about 40% CO2, about 2% to about 35% CO2, about 2% to about 30% CO2, about 2% to about 25% CO2, about 2% to about 20% CO2, about 2% to about 15% CO2, about 2% to about 10% CO2, about 2% to about 5% CO2, or any range or value therein. In some embodiments, the concentrated vapor comprises (v / v) about 2% CO2, about 5% CO2, about 10% CO2, about 15% CO2, about 20% CO2, about 25% CO2, about 30% CO2, about 35% CO2, about 40% CO2, about 45% CO2, about 50% CO2, about 55% CO2, about 60% CO2, about 65% CO2, about 70% CO2, about 75% CO2, about 80% CO2, about 85% CO2, about 90% CO2, about 95% CO2, about 96% CO2, about 97% CO2, about 98% CO2, about 99% CO2, or more, or any range or value therebetween.

[0048] A proof of concept electrochemical pH swing system is disclosed in PCT International Application No. PCT / US22 / 25028, filed April 15, 2022, which is incorporated by reference in its entirety.

[0049] CO2 Sequestration through Mineralization In some embodiments, the method according to the present disclosure includes a method or step of sequestering CO2 from the concentrated vapor generated in the CO2 absorption step discussed above. In some embodiments, the method or step of sequestering CO2 from the concentrated vapor generated in the CO2 absorption step includes contacting the concentrated vapor containing CO2 with a sequestration aqueous solution containing ions capable of forming insoluble carbonates to produce an aqueous solution containing carbon dioxide; contacting the aqueous solution containing carbon dioxide with an electroactive mesh that induces alkalization thereof to force precipitation of carbonate solid(s) from the sequestration solution; and removing the precipitated carbonate solids from the sequestration solution or from the surface of the mesh (where the carbonate solids may accumulate).

[0050] In some embodiments, the isolating aqueous solution is in thermal equilibrium with the gas stream. In some embodiments, the isolating aqueous solution is not in thermal equilibrium with the gas stream.

[0051] In some embodiments, the ions capable of forming insoluble carbonates include one or more of Ca, Mg, Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu, and Al, hi some embodiments, the aqueous solution comprises seawater or brine. In some embodiments, the aqueous solution has a NaCl concentration of about 1,000 ppm or more, about 2,000 ppm or more, about 3,000 ppm or more, about 4,000 ppm or more, about 5,000 ppm or more, about 6,000 ppm or more, about 7,000 ppm or more, about 8,000 ppm or more, about 9,000 ppm or more, about 10,000 ppm or more, about 15,000 ppm or more, about 20,000 ppm or more, about 25,000 ppm or more, or about 30,000 ppm or more, about 35,000 ppm or more, about 40,000 ppm or more, about 45,000 ppm or more, about 50,000 ppm or more, about 55,000 ppm or more, or about 60,000 ppm or more, or more, or any range or value therebetween.

[0052] In some embodiments, the electroactive mesh comprises a mesh cathode comprising a metallic or non-metallic composition. In some embodiments, the electroactive mesh comprises, consists essentially of, or consists of a metallic or carbon-based mesh. In some embodiments, the electroactive mesh comprises steel, stainless steel, titanium oxide, nickel and nickel alloys, carbon nanotubes, polymers, and / or graphite, or other hybrid compositions of these materials. In some embodiments, the electroactive mesh comprises pores having diameters ranging from about 0.1 μm to about 10,000 μm (e.g., about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 1000, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, or 10,000 μm).

[0053] 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 contains an amount of dissolved carbon dioxide, which is buffered to an atmospheric amount.

[0054] In some embodiments, the electroactive mesh produces increased alkaline conditions in situ in an isolated aqueous solution within about 2-20,000 μm of the electroactive mesh. In some embodiments, the alkaline conditions are a pH of 7 or greater, 7.5 or greater, 8 or greater, 8.5 or greater, 9 or greater, 9.5 or greater, 10 or greater, 10.5 or greater, 11 or greater, 11.5 or greater, or 12 or greater, or any range or value therebetween. In some embodiments, the alkaline conditions are a pH of about 7, about 7.5, about 8, about 8.5, about 9, about 9.5, about 10, about 10.5, about 11, about 11.5, about 12, about 12.5, about 13, about 13.5, or about 14, or any range or value therebetween.

[0055] In some embodiments, inducing precipitation of carbonate solids includes rotating a cylinder of electroactive mesh in the solution while applying suction to draw the solution onto the outer surface of the mesh, hi some embodiments, the method uses a rotating disc cathode.

[0056] In some embodiments, the solution is a brine 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 comprising Ca, Mg, Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu, or Al. In some embodiments, inducing precipitation of carbonate solids comprises inducing precipitation of at least one carbonate comprising Ca and / or Mg.

[0057] Some embodiments of the present disclosure include a flow-through electrolytic reactor that includes a suction device in fluid communication with a rotating cylinder containing an electroactive mesh, and a scraping device and / or a liquid spray system for separating solids from a surface or solution.

[0058] Referring now to FIG. 4A, a membrane-less reactor 400 is shown to be capable of implementing a single-step carbon sequestration and storage (sCS) system based on electrochemically enhanced (Mg,Ca)-carbonate and / or hydroxide precipitation in seawater with the potential to capture several gigatons of CO. 2 ) strategy. As a non-limiting example, such a process is disclosed in PCT Publication No. WO2021 / 061213, filed June 12, 2020, which is incorporated herein by reference in its entirety.

[0059] The basic CO2 mineralization process can be achieved by alkalizing ambient neutral Ca and Mg-bearing solutions (e.g., seawater, alkali metal-rich groundwater, industrial wastewater, desalinated brines). The inventors evaluated the feasibility of the conceptualized multi-compartment reactor by using a single compartment continuous stirred tank reactor (CSTR). The operating parameters (e.g., voltage, current density, and hydraulic retention time ("HRT")) can also be selected to demonstrate the carbonation energy intensity of the design.

[0060] 4A, the reactor 400 includes an air pump 401 in fluid communication with one or more air inlets 404 for introducing atmospheric air and / or concentrated CO2 vapor into an isolation aqueous solution (e.g., seawater) contained within a reservoir 405. The reactor further includes a seawater inlet 403 and a seawater outlet 411. An electrode assembly 406 is in fluid contact with the isolation aqueous solution reservoir 405 and includes a rotating disk cathode 407 and an anode 409 separated by a barrier layer 408. The rotating disk cathode 407 (e.g., 316L stainless steel mesh) may be rotated about a shaft 402 to pass a scraper 410 for product removal and recovery. The reactor may further include a neutralization pool 412. O2 may be produced at the anode 409 and released at an O2 outlet 413. H2 may be produced at the rotating disk cathode 407 and released at an H2 outlet 414.

[0061] The electrolytes may be separated with a porous barrier for the following reasons: (1) minimizing neutralization reactions between the anolyte and catholyte allows for a stable catholyte pH for CO2 capture and mineralization; (2) the separated electrolytes facilitate higher energy efficiency of the reactor; (3) the gas streams (H2 and O2) may need to be split and collected separately; and (4) atmospheric CO2 mineralization is generally an acidification process, and the surplus of acid produced needs to be retained to avoid ocean acidification.

[0062] With further reference to FIG. 4A, the catholyte may be air purged and seawater flushed so that atmospheric CO2 reacts with the electrolytic alkalinity to produce mineral carbonates and hydroxides. An online pH monitoring system may be used to control the applied current to achieve a constant catholyte pH, for example, at 9.5-9.6. This pH advantageously maximizes the capture of atmospheric CO2 or from concentrated vapors containing CO2 (e.g., those produced in the absorption step described above). The stainless steel cathode 407 may be covered with a hydrophobic mesh (e.g., polypropylene (PP) mesh) as a carbonation catalyst.

[0063] The PP covered stainless steel cathode may be rotated past a scraper (e.g., metal brush, blade, or high pressure nozzle) to remove carbonates, thereby regenerating the cathode for subsequent carbonation as the disk rotates back into the liquid. A porous barrier 408 (e.g., cellulose or other polymer film) may be used to separate the anolyte (e.g., acid) from the catholyte (e.g., alkalized seawater) to prevent seawater acidification and CO2 degassing. The anolyte may then be circulated to a neutralization pool 412, where the acidity generated is consumed to dissolve mafic, ultramafic minerals, and rocks back to alkalinity. Ca-rich fly ash and minerals (e.g., gypsum) may be used to remove Ca in the anolyte. 2+ may be concentrated. EXAMPLES

[0064] Example 1: Proof-of-concept two-chamber reactor Referring now to FIG. 4B, to demonstrate the process according to the present disclosure, a two-chamber CSTR reactor 500 was used with a barrier layer (filter paper in this example) 512 to separate the anolyte reservoir 505 and catholyte reservoir 506. A 0.3 M Na2SO4 solution was used as the anolyte, and a solution simulating seawater composition (prepared using INSTANT OCEAN® salt) was used as the catholyte, introduced via inlet 502 and removed via outlet 503. A 316 stainless steel mesh covered with a PP mesh was used as the cathode 508, and a platinum coated titanium plate was used as the anode 509. In the CSTR setup, the flow rate of the catholyte was controlled by a programmable syringe pump (New Era Pump Systems, Inc.), while a peristaltic pump was used to control the flow rate of the anolyte. The catholyte pH was maintained at 9.5. Effective mixing and CO2 equilibration is enabled by aeration using an air pump 501, which introduces air via inlet 504. A pH controller 510 maintains a desired pH within the anode chamber 506 and the isolation aqueous solution reservoir 505. An anolyte pool 507 is in fluid communication with the anode chamber 506.

[0065] Referring now to Figures 5A-F, two sets of experiments (150 min-HRT and 10 min-HRT) were performed with different operating parameters. The barrier (filter paper) effectively separated the acidified and alkalized electrolytes, demonstrating the feasibility of the membrane-less setup. While about 30% Ca removal was achieved in the 150 min-HRT experiment (Figure 5C), the 10 min-HRT experiment achieved a similar, but lower Ca removal rate (about 25%, Figure 5D), although the reactor was compatible with a much faster flow rate.

[0066] Although the seawater effluents of both experiments were controlled at a pH of 9.5, the IC concentration is higher (2 mM) for the 10 min HRT (Figure 5F) compared to that observed in the 150 min-HRT experiment (1.5 mM, Figure 5E). Calculated from Ca removal and effluent IC, the 10 min-HRT experiment is much more efficient in terms of atmospheric CO2 mineralization (~0.09 g atmospheric CO2 / L seawater) compared to the 150 min-HRT experiment (~0.07 g atmospheric CO2 / L seawater). Furthermore, the high pH and abundance of IC in the effluents from both experiments confers additional CO2 capture potential when discharged into the ocean. As shown in the insets of Figures 5E and 5F, CO2 was mineralized as aragonite (CaCO3) that formed a thick but brittle scale on the PP mesh, allowing for easy removal by a simple scraping process.

[0067] The electric energy intensity (EEI) of the carbonation process was calculated using the following equation (7):

number

[0068] Example 2 (Prophetic): The reactor configuration described in Example 1 is useful for the formation of CaCO3 by air purging, but the formation of MgCO3 does not occur due to the kinetic limitations mentioned above. Without the formation of MgCO3, the CO2 removal capacity of the system is reduced by more than one-fifth. To address this limitation, the mineralization process described above is combined with a low-energy amine-based DAC process (e.g., similar to that disclosed in PCT Application No. PCT / US22 / 25028, filed April 16, 2021, which is incorporated by reference in its entirety). This process (schematically shown in FIG. 1B) uses an amine solution (pH>10) to absorb CO2 from a gas-phase stream. However, the CO2-rich amine is regenerated in an electrochemical cell where protons are generated from the aqueous solution at the anode (and hydroxide ions at the cathode). These protons diffuse into the rich amine solution, resulting in a decrease in the pH of the amine solution (pH<7), decomposition of the carbamate ions, and the release of CO2. (The salt bridge provides anions to maintain charge neutrality in the amine solution and cations to the cathode solution.) The CO2 is released as a gas stream containing 1-99% CO2, which can be absorbed into seawater to increase the dissolved inorganic carbon concentration to levels >>10 mM, which is sufficient for the mineralization of both CaCO3 and MgCO3.

[0069] After the CO2 is released, the amine solution is restored to high pH via ion exchange with a strong base anion exchange resin. The basic solution from the cathode is used to regenerate the ion exchange resin, thereby recovering salt for recycle to the salt bridge solution. This pH-swing process occurs at ambient temperature, thus offering at least the following advantages: (1) simpler process equipment requirements; (2) complete amine regeneration (hence maximum adsorption-desorption differential); and (3) reduced solvent loss. Importantly, this process requires approximately 2x lower energy (2.8 MWh per ton of CO2 captured) compared to the thermal swing process (>5.0 MWh per ton of CO2 captured).

[0070] As used herein, the singular terms "a," "an," and "the" 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 dictates otherwise.

[0071] As used herein, the term "set" refers to a collection of one or more objects. Thus, for example, a set of objects may include a single object or multiple objects.

[0072] As used herein, the terms "substantially" and "about" are used to describe and explain small variations. When used in conjunction with an event or circumstance, the term may refer to an event or circumstance occurring very close to, as well as an event or circumstance occurring in close proximity. For example, when used in conjunction with a numerical value, the term may encompass a variation range of ±10% or less of that numerical value, such as, for example, ±5% or less, ±4% or less, ±3% or less, ±2% or less, ±1% or less, ±0.5% or less, ±0.1% or less, or ±0.05% or less.

[0073] As used herein, the term "size" refers to a characteristic dimension of an object. Thus, for example, the size of a circular object may refer to the diameter of the object. In the case of a non-circular object, the size of the non-circular object may also refer to the diameter of a corresponding circular object that exhibits or has a particular set of derivable or measurable properties that are substantially the same as the diameter of the non-circular object. Alternatively, or in addition, the size of a non-circular object may refer to the average of the object's various orthogonal dimensions. Thus, for example, the size of an elliptical object may refer to the average of the object's major and minor axes. When referring to a set of objects having a particular size, it is contemplated that the objects may have a distribution of sizes around the particular size. Thus, as used herein, the size of a set of objects may refer to a typical size of a distribution of sizes, such as an average size, a median size, or a peak size.

[0074] Additionally, amounts, ratios, and other numerical values ​​may be presented herein in a range format. It is understood that such range formats are used for convenience and brevity, and include numerical values ​​explicitly specified as range limits, but should be flexibly interpreted to include all individual numerical values ​​or subranges subsumed within the range, as if each numerical value and subrange were explicitly specified. For example, a ratio range of about 1 to about 200 should be understood to include the explicitly stated limits of about 1 to about 200, but also individual ratios such as about 2, about 3, and about 4, as well as subranges such as about 10 to about 50, about 20 to about 100, etc.

[0075] Although the present disclosure has been described with reference to certain embodiments thereof, those skilled in the art will understand 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 the appended claims. Furthermore, many modifications may be made to adapt a particular situation, material, composition of matter, method, operation(s) to the objective, spirit and scope of the present disclosure. All such modifications are intended to be within the scope of the appended claims. In detail, certain methods are described in terms of specific operations performed in a specific order, but it will be understood that these operations may be combined, sub-divided or reordered to form equivalent methods without departing from the teachings of the present disclosure. Thus, unless expressly indicated herein, the order and classification of operations are not limitations of the present disclosure.

[0076] References 1.Keith,DW;Holmes,G.;St.Angelo,D.;Heidel,KA Process for Capturing CO2 from the Atmosphere.Joule 2018,2(8),1573-1594. 2.Keith,D.W.;Ha-Duong,M.;Stolaroff,J.K.Climate Strategy with CO2 Capture from the Air.Clim.Change 2006,74(1),17-45. 3.Sakwattanapong,R.;Aroonwilas,A.;Veawab,A.,Behavior of Reboiler Heat Duty for CO2 Capture Plants Using Regenerable Single and Blended Alkanolamines.Ind.Eng.Chem.Res.2005,44,4465-4473. 4.Feng,B.;Du,M.;Dennis,T.J.;Anthony,K.;Perumal,M.J.,Reduction of Energy Requirement of CO2 Desorption by Adding Acid into CO2-Loaded Solvent.Energy & Fuels 2010,24(1),213-219. 5.Dutcher,B.;Fan,M.;Russell,A.G.,Amine-Based CO2 Capture Technology Development from the Beginning of 2013--A Review.ACS Appl.Mater.Interfaces 2015,(7),2137-2148. 6.MacDowell,N.;Florin,N.;Buchard,A.;Hallett,J.;Galindo,A.;Jackson,G.;Adjiman,C.S.;Williams,C.K.;Shah,N.;Fennell,P.,An Overview of CO2 Capture Technologies.Energy Environ.Sci.2010,3,1645-1669. 7.Husebye,J.;Brunsvold,A.L.;Roussanaly,S.;Zhang,X.,Techno Economic Evaluation of Amine based CO2 Capture: Impact of CO2 Concentration and Steam Supply.Energy Procedia 2012,23,381-390. 8.Roussanalya,S.;Fua,C.;Voldsunda,M.;Anantharamana,R.;Spinellib,M.;Romanob,M.,Techno-economic analysis of MEA CO2 capture from a cement kiln - impact of steam supply scenario.Energy Procedia 2017,114,6229-6239. 9.Liu,Y.;Ye,H.-Z.;Diederichsen,K.M.;Van Voorhis,T.;Hatton,T.A.,Electrochemically mediated carbon dioxide separation with quinone chemistry in salt-concentrated aqueous media.Nat Commun 2020,11(1),2278-2278. 10.Rahimi,M.;Catalini,G.;Puccini,M.;Hatton,T.A.,Bench-scale demonstration of CO2 capture with an electrochemically driven proton concentration process.RSC Advances 2020,10(29),16832-16843. 11.Stern,M.C.;Hatton,T.A.,Bench-scale demonstration of CO2 capture with electrochemically-mediated amine regeneration.RSC Advances 2014,4(12),5906. 12.Stern,M.C.;Simeon,F.;Herzog,H.;Hatton,T.A.,Post-combustion carbon dioxide capture using electrochemically mediated amine regeneration.Energy & Environmental Science 2013,6(8),2505. 13.Voskian,S.;Hatton,T.A.,Faradaic electro-swing reactive adsorption for CO2 capture.Energy & Environmental Science 2019,12(12),3530-3547. 14.Wang,M.;Hariharan,S.;Shaw,R.A.;Hatton,T.A.,Energetics of electrochemically mediated amine regeneration process for flue gas CO2 capture.International Journal of Greenhouse Gas Control 2019,82,48-58. 15.Wang,M.;Herzog,H.J.;Hatton,T.A.,CO2 Capture Using Electrochemically Mediated Amine Regeneration.Industrial & Engineering Chemistry Research 2020,59(15),7087-7096. 16.Wang,M.;Rahimi,M.;Kumar,A.;Hariharan,S.;Choi,W.;Hatton,T.A.,Flue gas CO2 capture via electrochemically mediated amine regeneration: System design and performance.Applied Energy 2019,255,113879. 17.Adenier,A.;Chehimi,M.M.;Gallardo,I.;Pinson,J.;Vila,N.,Electrochemical Oxidation of Aliphatic Amines and Their Attachment to Carbon and Metal Surfaces.Langmuir 2004,20,8243-8253. 18.Ivy,J.Summary of Electrolytic Hydrogen Production;Milestone Completion Report NREL / MP-560-36734;2004. 19.Rau,G.H.;Carroll,S.A.;Bourcier,W.L.;Singleton,M.J.;Smith,M.M.;Aines,R.D.,Direct electrolytic dissolution of silicate minerals for air CO2 mitigation and carbon-negative H2 production.Proc Natl Acad Sci U S A 2013,110(25),10095-10100. 20.Arshad,M.W.;Fosbol,P.L.;von Solms,N.;Svendsen,H.F.;Thomsen,K.,Equilibrium Solubility of CO2 in Alkanolamines.Energy Procedia 2014,51,217-233. 21.Arshada,M.W.;Fosbola,P.L.;Nicolas von Solmsa,H.;Svendsenb,F.;Thomsena,K.,Equilibrium Solubility of CO2 in Alkanolamines.Energy Procedia 2014,51,217-223.

Claims

1. A method for recovering CO from a gas source ２ comprising: (a) (i) bringing the gas source into contact with an absorption solution having a solvent and a solute, wherein the solvent and / or the solute contains an amine, whereby a solution containing an amine-CO ２ complex is formed; (ii) electrochemically adjusting the pH of the absorption solution to less than about 7, thereby releasing CO ２ as concentrated vapor; (iii) collecting the concentrated vapor; in the concentration step including the above, concentrating CO from the gas source ２ and (b) (iv) contacting the concentrated vapor with an isolated aqueous solution containing ions capable of forming an insoluble carbonate, such that the isolated aqueous solution contains CO ２ ; and (v) CO ２ contacting the isolated aqueous solution containing CO with the electroactive surface to make the isolated aqueous solution containing CO ２ basic, thereby precipitating a carbonate solid; (vi) separating the carbonate solid from the isolated aqueous solution or the electroactive surface; isolating CO from the concentrated vapor in an isolation step comprising; ２ the method comprising.

2. The anionic complex contains carbamate ions; The solvent contains an amine; and / or The solute contains an amine, and optionally the amine is a primary amine, secondary amine, tertiary amine, or a mixture thereof, preferably the amine has the structure of formula I: R x NH 3−x, (I); wherein R is selected from optionally substituted alkyl, ether, and hydroxyalkyl, or two Rs together with the nitrogen atom to which they are attached form a nitrogen-containing heterocyclic ring; and x is 1, 2, or 3, The method according to claim 1.

3. The amine is selected from monoethanolamine, 2-ethylaminoethanol, 2-methylaminoethanol, ethylenediamine, benzylamine, diethanolamine, pyrrolidine, morpholine, 2,6-dimethylmorpholine, monoisopropanolamine, piperazine 2-(dimethylamino)ethanol, N-tert-butyldiethanolamine, 3-dimethylamino-1-propanol, 3-(dimethylamino)-1,2-propanediol, 2-diethylaminoethanol, 3-diethylamino-1,2-propanediol, 3-diethylamino-1-propanol, triethanolamine, 1-dimethylamino-2-propanol, 1-(2-hydroxyethyl)pyrrolidine, 1-diethylamino-2-propanol, 3-pyrrolidino-1,2-propanediol, 2-(diisopropylamino)ethanol, 1-(2-hydroxyethyl)piperidine, 2-(dimethylamino)-2-methyl-1-propanol, 3-piperidino-1,2-propanediol, 3-dimethylamino-2,2-dimethyl-1-propanol, 3-hydroxy-1-methylpiperidine, N-ethyldiethanolamine, 1-ethyl-3-hydroxypiperidine, and any combination thereof, The method according to claim 2.

4. The solvent contains water; Step (ii) includes water electrolysis; The gas source contains about 0.4 to about 25% (v / v) of CO 2; The gas source is an effluent from an industrial source; or Step (ii) is carried out at a temperature of less than about 100 °C; The gas source is an atmospheric source; The concentrated vapor contains about 2 to 99% (v / v) of CO 2; The concentrated vapor contains 2-15% (v / v) of CO₂; and / or The absorption solution is regenerated using a strong base anion exchange resin, The method according to any one of claims 1 to 3.

5. The method according to any one of claims 1 to 3, wherein the isolating aqueous solution is in thermal equilibrium with the gas stream.

6. The ions capable of forming an insoluble carbonate are selected from the ions of Ca, Mg, Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu, Al, and any combination thereof; The isolating aqueous solution contains NaCl at a concentration of about 1,000 ppm or more, and optionally the isolating aqueous solution contains NaCl at a concentration of about 30,000 ppm or more; and / or The isolating aqueous solution contains seawater, The method according to any one of claims 1 to 3.

7. The method according to any one of claims 1 to 3, wherein the electroactive surface includes an anode and / or a cathode containing a metal composition.

8. The method according to any one of claims 1 to 3, wherein the electroactive surface increases the basicity of the isolating aqueous solution in situ within a distance of about 2 to 20,000 μm from the electroactive surface.

9. The method according to claim 8, wherein the pH of the isolating aqueous solution is at least about 9, preferably about 9 to about 10.

10. The method according to any one of claims 1 to 3, wherein the electroactive surface is an electroactive mesh.

11. The method according to claim 10, wherein the electroactive mesh is a metal mesh, a carbon-based mesh, or a combination of both.

12. The method according to claim 11, wherein the electroactive mesh includes steel, stainless steel, titanium oxide, nickel and nickel alloys, carbon nanotubes, polymers, graphite, or any combination thereof.

13. The method according to claim 10, wherein the electroactive mesh includes pores having a diameter in the range of about 0.1 μm to about 10,000 μm.

14. The isolating aqueous solution is a brine solution; and / or The isolating aqueous solution is an alkaline earth metal-containing solution, The method according to any one of claims 1 to 3.

15. The method according to any one of claims 1 to 3, wherein precipitating the carbonate solid comprises precipitating a carbonate containing ions of Ca, Mg, Ba, Sr, Fe, Zn, Pb, Cd, Mn, Ni, Co, Cu, Al, or any combination thereof.

16. The method according to claim 10, wherein separating the solid carbonate(s) from the surface of the solution or the electroactive mesh comprises rotating a disk cathode having the electroactive mesh thereon beyond a scraper, the scraper removing the precipitated carbonate from the surface of the mesh.

17. The method according to any one of claims 1 to 3, wherein step (a) further comprises (iv) regenerating the solvent and / or the solute.

18. The method according to claim 17, wherein regenerating the solvent and / or the solute comprises adjusting the pH of the isolated aqueous solution to be greater than about 8.

19. The method according to claim 18, wherein step (a) further comprises optionally collecting the solvent and / or solute regenerated after step (iii).

20. The method according to claim 18, wherein the regenerated solvent is collected and reused in step (i) at least once.

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