Dual-path system and method for capturing carbon dioxide from seawater

Abstract

This system provides a dual-pathway system that captures CO2 from both the acidified and basicified streams. The system can be implemented in a standalone offshore facility, making marine CO2 capture operations more efficient and cost-effective. By containing all intermediate acidic and alkaline solutions in a closed system, the effluent discharged into the ocean maintains the same pH and salinity as the seawater supply, with only CO2 removed, maintaining high environmental standards. The acid and base generated by the electrodialysis unit are used to remove gaseous CO2 and decarbonize oceanwater by removing solid CaCO3 precipitates. The system is configured so that only a small portion of the total intake seawater needs to be treated in the acid-base generation process.

Description

[Technical Field]

[0001] [Statement on government support] This invention was made with government support under Grant No. DE-AR0001407 awarded by the Department of Energy. The government has certain rights in this invention.

[0002] The present disclosure relates to a dual-path system and method for capturing carbon dioxide from seawater. [Background technology]

[0003] As atmospheric carbon dioxide (CO2) concentrations continue to rise beyond record high levels, capturing and converting CO2 from anthropogenic emissions is becoming an increasingly important societal responsibility. CO2 from the atmosphere, ocean waters, and point sources such as coal-fired power plants or cement factories is considered the primary feedstock for the subsequent capture and conversion process. Currently, atmospheric CO2 concentrations are about 400 ppm, or 0.00079 kgm -3 As a result, large volumes of air need to be treated in direct air capture processes. In contrast, the world's oceans constitute the largest carbon sink, absorbing approximately 40% of anthropogenic CO2 since the start of the industrial era. The effective CO2 concentration in seawater is 2.1 mmol kg -1 , i.e. 0.095 kgm -3 , which is 120 times higher than that in the atmosphere. Thus, CO2 extraction from seawater offers a unique alternative approach in the global carbon removal technology landscape compared to direct air capture (DAC). Summary of the Invention

[0004] The present embodiments are directed to a dual-path system and method for capturing carbon dioxide from seawater.

[0005] Many embodiments of the present disclosure provide a dual-path system for CO2 capture, comprising: a platform located adjacent to a source of seawater; an acid-base generator in fluid communication with the source of seawater, a purification unit configured to convert a first portion of the seawater into a source of NaCl; at least one electrodialysis device in fluid communication with the purification device and incorporating a bipolar membrane configured to convert the NaCl source into a source of HCl and a source of NaOH; an acid-base generating device comprising: an acidic CO2 removal system in fluid communication with the source of seawater, an acidification element in fluid communication with the HCl feedstock and configured to produce an acidified seawater feedstock from the seawater; a catalyst-bound membrane contactor in fluid communication with the acidification element and a vacuum system, the catalyst-bound membrane contactor extracting gaseous CO from the acidified seawater feed and outputting a decarbonized acidified seawater output at an output port; an acidic CO2 removal system comprising: an alkaline CO removal system in fluid communication with a source of CO2-loaded fluid and further in fluid communication with the NaOH source, the alkaline CO2 removal system configured to produce a CO2-lean effluent and carbonate; In a dual path system comprising: The output is directed to a dual-path system for CO2 capture that combines the decarbonized acidified seawater effluent and at least one effluent from the alkaline CO2 removal system to produce a combined seawater effluent for environmental release.

[0006] Further, in many embodiments of the present disclosure, the alkaline CO2 removal system is in fluid communication with the source of seawater; the alkaline CO2 removal system includes a basifying element in fluid communication with the NaOH feedstock and configured to produce a basified seawater feedstock from the seawater; a precipitation element in fluid communication with the basification element for recovering precipitate of inorganic carbonates from the basified seawater feed and outputting a decarbonized basified seawater output to the output; Equipped with The output combines the decarbonized acidified seawater effluent and the decarbonized basicified seawater effluent to produce a combined seawater effluent for environmental release, the combined seawater effluent having a pH approximately equivalent to the pH of the seawater source.

[0007] Further, in many embodiments of the present disclosure, the alkaline CO removal system is in fluid communication with the CO2-loaded fluid, including a source of CO2-containing gaseous feed; the alkaline CO2 removal system comprises a direct air recovery element in fluid communication with the NaOH source and the CO2-containing gaseous source and configured to produce a CO2-lean gaseous effluent and a carbonate solution; The output mixes the decarbonized acidified seawater effluent and the carbonate solution, and incorporates the CO2 in the carbonate into the decarbonized acidified seawater effluent for environmental release.

[0008] Furthermore, in many embodiments of the present disclosure, the acidified seawater feedstock has a pH range of about pH 4 to about pH 7.

[0009] Further, in many embodiments of the present disclosure, the basified seawater feedstock has a pH of approximately 10 and the inorganic carbonate is CaCO.

[0010] Additionally, in many embodiments of the present disclosure, the seawater and mixed seawater effluent have a pH of approximately 8.

[0011] Additionally, in many embodiments of the present disclosure, the system further comprises at least one pretreatment element disposed between the source of seawater and the acid-base generator, the acidic CO2 removal system, and the alkaline CO2 removal system, for screening the seawater.

[0012] Additionally, in many embodiments of the present disclosure, the pretreatment element comprises a drum screen filter.

[0013] Additionally, in many embodiments of the present disclosure, the purification device comprises one or more selected from the group consisting of a dissolved air suspension clarifier, a micro / ultra filter, a cartridge filter, and a water softening ion exchanger.

[0014] Further, in many embodiments of the present disclosure, the purification device comprises at least a clarifier and an ion exchanger, the clarifier being in fluid communication with the HCl source and the ion exchanger being in fluid communication with the NaOH source.

[0015] Furthermore, in many embodiments of the present disclosure, the electrodialysis device has a current of 250 mA / cm 2 to 1000mA / cm 2 The current density is configured to operate at a current density between .

[0016] Additionally, in many embodiments of the present disclosure, the bipolar membrane comprises a catalyst ion layer directly bonded to either the cation exchange membrane or the anion exchange membrane.

[0017] Furthermore, in many embodiments of the present disclosure, the ionic layer has a thickness between 5 and 50 μm.

[0018] Furthermore, in many embodiments of the present disclosure, the bipolar membrane is a three-layer structure comprising at least three elements selected from the group consisting of a porous solid electrolyte, a cation exchange membrane, and an anion exchange membrane.

[0019] Furthermore, in many embodiments of the present disclosure, the catalyst ion layer has a pK a at least one buffering group where M is about 7.

[0020] Additionally, in many embodiments of the present disclosure, the catalyst ion layer includes at least one buffering group covalently attached to the polymer backbone.

[0021] Furthermore, in many embodiments of the present disclosure, the polymer backbone is selected from the group consisting of polyethylene oxide, polypropylene, and polyethylene.

[0022] Furthermore, in many embodiments of the present disclosure, the at least one buffering group is selected from the group consisting of phosphonates and metal oxide nanomaterials.

[0023] Additionally, in many embodiments of the present disclosure, the system includes an electrodialysis stack.

[0024] Additionally, in many embodiments of the present disclosure, the catalyst-bound membrane contactor comprises one or more gas-liquid membrane contactor materials having a buffering catalyst bound thereto.

[0025] Additionally, in many embodiments of the present disclosure, the gas-liquid membrane contactor material comprises one or more hollow fibers.

[0026] Furthermore, in many embodiments of the present disclosure, the one or more hollow fibers are a material selected from the group consisting of polypropylene and polyethylene.

[0027] Additionally, in many embodiments of the present disclosure, the buffering group catalyst is a synthetic carbon anhydrase mimic.

[0028] Furthermore, in many embodiments of the present disclosure, the catalyst-bound membrane contactor comprises a baffle structure disposed externally of the one or more hollow fibers, and the flow of the acidified seawater feed is introduced at one or more angles relative to the one or more hollow fibers.

[0029] Furthermore, in many embodiments of the present disclosure, at least the portion of the catalyst-bound membrane contactor proximate the water intake does not contain the buffer group catalyst.

[0030] Additionally, in many embodiments of the present disclosure, the system further comprises one or more electrically interconnected renewable power sources that power the dual path system.

[0031] Furthermore, in many embodiments of the present disclosure, one or more of the renewable power sources are photovoltaic devices, which collect infrared radiation and use it to generate heat that heats the catalytically coupled membrane contactor.

[0032] Additionally, in many embodiments of the present disclosure, the precipitation element is further provided with at least one seeding growth material selected from the group consisting of vaterite, calcite, and salt solutions thereof.

[0033] Further, in many embodiments of the present disclosure, the first portion comprises approximately 0.5% of the seawater introduced into the dual-path system.

[0034] Furthermore, in many embodiments of the present disclosure, the catalyst-bound membrane contactor is in fluid communication with the HCl source.

[0035] Furthermore, in many embodiments of the present disclosure, at least one electrodialysis device further outputs a dilute low-salinity effluent, which is reintroduced into the electrodialysis device as a feedstock.

[0036] Various embodiments of the present disclosure include a method for producing an acid-base generator comprising: introducing a first portion of seawater into an acid-base generator; converting the first portion of the seawater into a source of NaCl; Electrodialysis of the NaCl using a bipolar membrane to obtain an HCl raw material and an NaOH raw material; introducing a second portion of seawater into an acidification element in fluid communication with the HCl feedstock to produce an acidified seawater feedstock from the seawater; extracting gaseous CO2 from the acidified seawater feed through a catalyst-bound membrane contactor and outputting a decarbonized acidified seawater output; introducing a source of CO2-loaded fluid into an alkaline CO2 removal system in fluid communication with the NaOH feedstock and configured to produce a CO2-lean effluent and carbonate; combining the decarbonized acidified seawater effluent and at least one effluent from the alkaline CO2 removal system to produce a combined seawater effluent for environmental release; This document covers dual-route methods for capturing CO2, including:

[0037] Further, in many embodiments of the present disclosure, the source of CO2 loaded fluid includes a third portion of seawater, and the dual-path method for CO2 capture further comprises: introducing the third portion into a basifying element in fluid communication with the NaOH feedstock to produce a basified seawater feedstock from the seawater; recovering inorganic carbonate precipitate from the basified seawater feed and outputting a decarbonized basified seawater output; mixing the decarbonized acidified seawater effluent and the decarbonized basicified seawater effluent to produce a mixed seawater effluent for environmental release, the mixed seawater effluent having a pH approximately similar to the pH of the seawater source; Includes.

[0038] Further, in many embodiments of the present disclosure, the source of the CO2-loaded fluid comprises a CO2-containing gaseous feed, and the dual-path method for CO2 capture further comprises: introducing the CO2-containing gaseous feed to a direct air recovery element in fluid communication with the NaOH feed and configured to produce a CO2-lean gaseous effluent and a carbonate solution; The output mixes the decarbonized acidified seawater effluent and the carbonate solution, and incorporates the CO2 in the carbonate into the decarbonized acidified seawater effluent for environmental release.

[0039] Furthermore, in many embodiments of the present disclosure, the acidified seawater feedstock has a pH range of about pH 4 to about pH 7.

[0040] Further, in many embodiments of the present disclosure, the basified seawater feedstock has a pH of approximately 10 and the inorganic carbonate precipitate is CaCO.

[0041] Furthermore, in many embodiments of the present disclosure, the first portion comprises approximately 0.5% of the seawater introduced into the dual-pass system.

[0042] Additional embodiments and features are set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by practice of the present disclosure. The nature and advantages of the present disclosure may be better understood by reference to the other parts of the specification and the drawings which form a part of this disclosure. [Brief explanation of the drawings]

[0043] The description can be more fully understood by reference to the following figures and data graphs, which are presented as various embodiments of the present invention and should not be construed as the complete scope of the present disclosure.

[0044] [Figure 1A] FIG. 1 is a schematic diagram of a hybrid electrochemical pH CO2 capture system according to embodiments of the present disclosure. [Figure 1B] FIG. 1 is a schematic diagram of a hybrid electrochemical pH CO2 capture system incorporating a direct air capture system according to embodiments of the present disclosure. [Figure 1C] FIG. 10 shows a data plot of the effect of regeneration on CO2 extraction efficiency in gas-liquid contactors according to embodiments of the present disclosure. [Figure 2A] FIG. 1 is a schematic diagram of an acid pathway portion of a marine CO2 removal system according to embodiments of the present disclosure. [Figure 2B] 1 is a schematic diagram of a prior art bipolar membrane electrodialysis process. [Figure 3] Figure 3A shows a data plot of high current density from a BPM in 0.5 M NaCl aqueous solution according to the prior art, and Figure 3B shows a data plot of greater than 0.5 A cm from a BPM with a 10 μm thick AEM in 1 M KCl aqueous solution according to embodiments of the present disclosure. [Figure 4]BPM structures having a thin layer of cations according to various embodiments of the present disclosure, and BPM structures having a three-layer structure [Figure 5] Figure 5A shows the results of numerical modeling of 0.5 M of two buffer groups (two pKa values) at pH 7 according to embodiments of the present disclosure, demonstrating that the WDF achieves the highest zero-bias current density (50 mA / cm) in one buffer (dashed line) or several combinations of two buffers (lightest colors) with pKa = 7. Figure 5B shows a plot of experimental data for a series of novel trilayer BPMs with a PPO-Pi interlayer (pKa ≈ 7) when splitting a 0.5 M salt solution, demonstrating that at low overpotentials (<0.4 V), BPMs according to embodiments of the present disclosure (circles) outperform state-of-the-art commercial Fumatech FBMs and graphene oxide (open squares). [Figure 6A] FIG. 1 is a schematic diagram of a catalyst-bonded membrane in a gas-liquid contactor according to aspects of the present disclosure. [Figure 6B] FIG. 10 shows plots of modeling results of achievable CO removal rates at different pH values ​​for acidified seawater that would otherwise have a pH of about 8.1, according to embodiments of the present disclosure. [Figure 7] 1 shows mass spectrometry data of CO (m / z=44) before and after adding sodium phosphate WDF / BDF catalyst to NaHCO solution (pH 7) according to embodiments of the present disclosure. [Figure 8] FIG. 1 shows a table of major component concentrations of major components of natural seawater according to the prior art. [Figure 9] FIG. 1 is a schematic diagram of an apparatus for assessing sedimentation velocity and particle size in a basified stream according to aspects of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0045] It will be readily understood that the components of the embodiments as generally described herein and illustrated in the accompanying drawings could be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of various embodiments as illustrated in the drawings is not intended to limit the scope of the disclosure, but is merely representative of various embodiments. While various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0046] The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics, and the described embodiments are to be considered in all respects only as illustrative and not restrictive.

[0047] Throughout this specification, references to features, advantages, or similar language do not imply that all of the features and advantages that may be realized in the present invention should or will be present in any single embodiment of the present invention. Rather, language referring to features and advantages is understood to mean that the particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, throughout this specification, discussions of features and advantages, and similar language, may, but do not necessarily, refer to the same embodiment.

[0048] Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. Those skilled in the relevant art will recognize, in light of the description herein, that the invention may be practiced without one or more particular features or advantages of a particular embodiment. In other instances, certain embodiments may exhibit additional features and advantages that may not be present in all embodiments of the invention.

[0049] Throughout this specification, references to "one embodiment," "an embodiment," or similar language mean that a particular feature, structure, or characteristic described in connection with the illustrated embodiment is included in at least one embodiment. Thus, throughout this specification, "in one embodiment," "in an embodiment," and similar language may, but do not necessarily, all refer to the same embodiment.

[0050] Embodiments of the present disclosure are directed to a dual-pathway system for CO2 capture from seawater. In various embodiments, such systems are intended for offshore, standalone facility applications, enabling more efficient and cost-effective marine CO2 capture operations. Embodiments of the system minimize seawater intake costs by using an offshore floating platform that directly intakes seawater. In many embodiments, the systems contain all acidic and alkaline intermediate solutions in a closed system, ensuring that the effluent discharged into the ocean has a mild pH and salinity similar to the source seawater, with only CO2 removed, maintaining high environmental standards. Embodiments also include the combined use of acid and base generated by an electrodialysis device to decarbonize the oceanwater by removing gaseous CO2 and solid CaCO3 precipitates. According to embodiments, the system may be configured to treat only a small portion of the total treated seawater in the acid-base generation process. Each embodiment contemplates a dual-path system in which CO2 can be captured from seawater in both the acidified and basicified streams, reducing the overall cost of large-scale CO2 emission abatement.

[0051] Traditional seawater recovery involves acidifying seawater via electrodialysis, thereby shifting the CO2 / bicarbonate equilibrium toward dissolved CO2. The acidified stream is then passed through a liquid-gas membrane contactor, which captures gaseous CO2 from the dissolved CO2 in the aqueous stream. These traditional seawater recovery systems face challenges, including the high cost of seawater intake and pretreatment, and limited opportunities for co-location.

[0052] In a land-based marine CO2 removal system, seawater intake and pretreatment constitute the majority of the cost. Based on current and projected costs for desalination plants, seawater intake, pretreatment, and discharge for a land-based standalone CO2 capture plant would cost approximately $1.4 million per million gallons per day, corresponding to a best-case cost of $1,839 / t-CO2. While these costs may be reduced as the technology scales up, achieving a realistic cost target of less than $100 / t-CO2 in the long term with such an approach is nearly impossible. Reducing the long distances required for seawater intake, transportation, and pretreatment is key to reducing the cost of marine CO2 removal.

[0053] Regarding desalination, co-locating ocean CO2 removal systems with desalination plants is not considered scalable. Although co-locating ocean CO2 removal systems with desalination plants can overcome the distance issue, techno-economic analysis suggests that the resulting best-case cost of a marine CO2 removal system ($373 / t-CO2) is far from the FOA target of less than $100 / t-CO2. Furthermore, reverse osmosis plants would remove all of the drinking water currently consumed worldwide (4.3 trillion m3). 3 / yr) and removing all the CO2 from the water, only 0.95 Gt-CO2 / yr can be achieved. This means that even co-locating marine CO2 removal systems with desalination plants does not provide a viable path to scale-up to cost targets above 1 Gt-CO2 / yr.

[0054] Embodiments of the present disclosure provide a "dual-pathway" CO2 capture system that produces both an acidified and an alkaline aqueous stream via an electrochemical pH swing. This system implements CO2 capture in both an alkaline pathway, where dissolved inorganic carbon is extruded to form CaCO3, and gaseous CO2 recovery from the acidified stream using an electrodialysis device at high current densities. Thus, alkaline system embodiments are directed to methods and systems for controlling CaCO3 precipitation kinetics in a basified seawater stream to promote calcite formation through control of pH, temperature, and crystallization kinetics for calcite (solid-phase CaCO3) growth. Acidification system embodiments incorporate a fast redox couple electrolyte for marine CO2 removal into a unique electrodialysis architecture. This fast redox couple electrolyte incorporates a single-cell voltage and minimal electrochemical energy requirements for electrodialysis. Electrodialysis device design embodiments enable gaseous CO2 recovery from the acidified stream at high current densities. Thus, the dual-path system combines the basification and acidification aspects of CO2 capture using alkaline electrolyte produced in the basification stream via CaCO3 formation, improving overall CO2 capture efficiency.

[0055] As shown in FIG. 1a, each dual-pathway system and method embodiment comprises a modular, surface-based, stand-alone system for marine CO2 removal. In various embodiments, the hybrid marine CO2 capture system (100) comprises, among other components, three main components: an acid-base generator (102), an acidification pathway (104) for gaseous CO2 production, and an alkaline pathway (106) for CaCO3 production. As shown, the acid (108) and alkaline (110) streams are then recombined, and the decarbonized seawater (112) is pH adjusted and returned to the ocean. Each of these system embodiments, their integration, and associated process methods are described in more detail below. Each system embodiment is directed to minimizing seawater intake costs by using an offshore, stand-alone design, and by containing all acid and alkaline intermediate solutions in a closed system, the effluent discharged into the ocean maintains high environmental standards by maintaining pH and salinity similar to the supply seawater, with only CO2 removed.

[0056] Accordingly, each embodiment of the dual-path system includes a generally floating platform located in a body of saltwater, such as the ocean, allowing the majority of the treated seawater to be pumped a short vertical distance from below the floating platform. In such embodiments, one or more water intakes (114) are provided that are configured to supply raw seawater (116) to the acidic and alkaline pathways. As shown, the water intakes may include a pre-treatment (117) embodiment, including, for example, screens or other filters to prevent unwanted contaminants from entering the CO2 extraction pathway. The water intakes, pre-treatment systems, pumps (118) that introduce water into the system, and the overall dimensions and structure of the floating platform may be of any suitable configuration capable of supporting the dual-path system and supplying seawater. In each embodiment, the dual-path system can be stably and continuously operated (e.g., with an initial CO2 removal rate of 70% or greater for 84 hours or more) using a feedwater consisting of seawater that has been filtered only through a drum screen filter at a typical CO2 removal pH (pH 5 or less), followed by reactivation to achieve an initial CO2 removal rate of 95% or greater. Thus, various aspects of the dual-path system allow for robust operation with inexpensive filtration methods, requiring minimal fouling that is renewable for long-life operation without extensive and expensive water pretreatment.

[0057] One key advantage of such floating pathways is that the raw water in the system only has to travel short distances (e.g., a few meters). Reducing the long distances required for seawater intake, transportation, and pretreatment is one aspect of the disclosed system that allows for reduced costs of ocean CO2 removal. As previously mentioned, seawater intake and pretreatment represent the majority of the cost of land-based ocean CO2 removal systems, and co-locating a desalination plant is not sufficiently scalable, making it nearly impossible to achieve the long-term goal of less than $100 / t-CO2 using such an approach.

[0058] In various embodiments, incoming seawater is directed to one of three paths in a dual path system: an acid path (104), an alkaline path (106), and an acid-base generator (102). Each aspect and element of each of these paths will be described in more detail, but it should be understood that these paths are exemplary and each may include additional treatment or conditioning elements to improve the process.

[0059] Each embodiment of the acidic pathway (104) decarbonizes feed seawater by "pushing" and "pulling" CO2 from bicarbonate via the following reactions: [ka] In this embodiment, to make the reaction proceed in the forward direction, Le Châtelier's principle requires that H + The increase in concentration of "pushes" the reaction to form water by mass action, p CO2 The reduction of CO "pulls" the reaction to form gaseous CO. Similarly, each embodiment of the alkaline pathway (106) similarly "pushes" and "pulls" the basified seawater to produce precipitation products including CaCO, Ca(OH), MgCO, Mg(OH), SrSO, CaF, and CaSO, decarbonizing the feedwater. Note that while not all of these precipitation products contribute equally to CO capture (e.g., precipitation product Mg(OH)), they can be used in other applications, such as cement production, and can be used in the process as beneficial by-products to lower overall system operating costs.

[0060] In each embodiment of the dual-pathway system and method, these reactions are efficiently driven by directing a portion (120) of the total treated seawater through an acid-base generator (102). The acid-base generator (102) uses multiple pretreatment steps (122) to produce a purified stream of salts (e.g., NaCl (124)), which is then fed to a high-current-density, low-voltage electrodialysis device (126) to produce HCl and NaOH, before being fed (128 / 130) to the acidification (132) and basification (134) components of the acid and alkaline pathways. These acidified (136) and basified (138) water feeds are then directed to the appropriate CO2 extraction components for the corresponding pathways. In the acid pathway, this extraction component consists of a catalyst-bound membrane contactor (140) and an appropriate vacuum pump (142) for exhausting gaseous CO2 (144). In the alkaline route, this extraction element consists of a suitable settling element (146) and any other equipment required for the extraction of the precipitate.

[0061] While a dual-path system implementation configured to treat multiple streams of ocean water has been described with reference to FIG. 1a, it will be understood that other configurations incorporating mixed feed streams may be implemented. As shown in FIG. 1b, various embodiments of a dual-path system may incorporate many of the same systems as those previously described (e.g., the acid-base generator (102) and acid pathway (104) as described in FIG. 1a), but may instead incorporate a gaseous feed (148) comprising a CO stream. In various such embodiments, the gaseous feed may include any suitable source of gas incorporating a sufficient concentration of CO (e.g., greater than 400 ppm), including, for example, atmospheric air or industrial waste gases or flue gases. Embodiments incorporating a gas extraction system may incorporate any suitable direct air capture system (150). While many such direct air capture systems may be incorporated, in various embodiments, the direct air capture system uses an aqueous basic solution (130) generated by an acid-base generator (102) and provided to the direct air capture system to form a CO2-lean gas stream and an output of a carbonate solution (152) (e.g., a NaCO3 solution). The carbonate solution (152) can then be reintroduced into the CO2-lean effluent (110) from the acid pathway, releasing and incorporating CO2 into the output seawater (112).

[0062] As also shown in FIG. 1b, various embodiments of the system incorporate a system regeneration path. For example, it will be appreciated that the catalyst-bound contactor membrane (140) of the acid path, and pretreatment elements (e.g., clarifier (154) and ion exchanger (156)) can become fouled over time. In conventional systems, regenerative acid and base must be periodically fed to these systems to clean them. However, this requires periodic resupply of the platform. In various embodiments of the dual-path system, these regenerative acid and base can be fed directly from an acid-base generator (102), thereby allowing for self-contained maintenance of the platform elements. In various such embodiments, for example, an acid stream may be fed to the CO2 extraction elements of the acid path to regenerate the catalyst contactor membrane elements. Similarly, in various embodiments, a base stream may be fed as a clarifier feed to remove dications (e.g., Mg) in the seawater. 2+ or Ca 2+ ) may be precipitated to hydroxides or carbonates. An acid stream may be provided to regenerate the resin used in the ion exchange step and achieve efficient and effective dication removal to sub-1 ppm levels as a feed solution to the electrodialysis system. Figure 1c is a series of data plots showing the effect of regeneration on the CO2 extraction efficiency of the system. As shown, by using acid and base streams from the electrodialysis device, it is possible to regenerate the CO2 efficiency of the system back to starting levels, thereby enabling a greater duty cycle for the overall dual-path system.

[0063] While the above discussion has focused on certain aspects of the dual-path systems and methods according to the present disclosure, it will be understood that other aspects and elements may be incorporated that are necessary or advantageous for the operation of the systems and methods. For example, as shown in Figure 2a, in various embodiments, the platform (200) may receive power for running various elements of the systems and methods using an array of large-area commercial floating solar panels (201) or other renewable or grid-backed renewable sources, such as offshore wind, along with an energy storage system, thereby achieving a sufficient capacity factor (e.g., 90% or greater) for the system.

[0064] Detailed discussions of aspects of the acid-base generator, acidic pathway, and alkaline pathway are provided in the following sections, which should be read to incorporate the aspects and elements described in the above and following sections.

[0065] Acid-base generator Electrodialysis device Each embodiment of the dual-path system and method is capable of providing 250 mA / cm 2 to 1000mA / cm 2This requires a low-overpotential electrodialysis system operating between 0.25 and 1.5 M, which is not currently available in the prior art. Turning to the details of the acid-base generator (102), it will be understood that a small amount of the influent water is diverted to a pretreatment element (122) within the acid-base generator (102). While in FIG. 1 a the water is shown coming from the acid pathway, it will be understood that influent water from any pathway, combination of pathways, or a separate source (as shown in FIG. 1 b) may be used. According to various embodiments, the pretreatment element may include any components suitable for converting the screened seawater into a purified stream of NaCl for use in the electrodialysis system (126) and producing a stream of HCl (between 0.8 M and 2.5 M) and a stream of NaOH (between 0.8 M and 2.5 M) for the acid pathway and alkaline pathway. As shown in more detail in Figures 1b and 2a, the pretreatment elements may include, among other elements, a dissolved air suspension clarifier (202), a micro / ultra filter (204), a cartridge filter (206), and a water softening (ion exchanger) (208). Regardless of the particular element arrangement in each embodiment, the salt splitting process is configured to provide a purified stream of NaCl and HO to an electrodialysis device (210). The electrodialysis device then splits the aqueous stream using bipolar membranes to produce OH. - ions and H + ions, which form Na + ions and Cl - It recombines with the ions to form HCl (between 0.8M and 2.5M) and NaOH (between 0.8M and 2.5M), which are introduced into an acidification unit (214) and a basification unit (not shown) and used to drive the CO2 capture reactions in the acidic and alkaline pathways.

[0066] 1a / 1b and 2a are shown as producing acid and base outputs that can be used to implement various embodiments of the overall dual-path system. These systems also produce a dilute solution stream (e.g., dilute solution) with a low salt concentration (between 0.01 and 0.1 M) after the electrodialysis process. While this dilute solution is shown as an output that is output to the ocean along with the remaining effluent stream, in various embodiments (as shown in FIG. 1b), this dilute solution (already purified by the pretreatment system (122) of the acid-base generator (102)) can be reintroduced into the electrodialysis device, thereby further reducing the overall volume of seawater that needs to be processed through the system.

[0067] In various embodiments, as shown in FIG. 2a, a single cell of an electrodialysis device according to the present disclosure can be configured to operate at 250 mA / cm 2 to 1000mA / cm 2 The electrodialysis device may have an active surface area suitable for electrodialysis of purified seawater between temperatures exceeding 1000 volts. In such an embodiment, each cell of the electrodialysis device may comprise an anode compartment (218), a dilute salt compartment (220), an acid compartment (222), a base compartment (224), and a cathode compartment (226). Conductive plates (e.g., Pt-coated Ti plates) may be used as the cathode and anode, and solutions containing a one-electron electrochemically reversible redox couple may be used as the anolyte and catholyte. The membrane thickness and spacing, as well as the type and concentration of the redox couple, may be varied to achieve a target voltage for the system (e.g., 1.6 V).

[0068] The basic aspect of electrodialysis with bipolar membranes (EDBM) is the combination of electrodialysis for salt separation and electrodialytic water splitting, which converts salts into their corresponding acids and bases. The bipolar membrane facilitates the splitting of water into protons and hydroxide ions. This is shown diagrammatically in Figure 2b. Bipolar membranes are a special type of layered ion-exchange (IX) membrane, with two polymer layers, one permeable only to anions and the other permeable only to cations. Unlike membrane processes, EDBM is not applied for separation purposes but rather to drive reactions at the bipolar junction of the membrane, where the anion-permeable and cation-permeable layers are in direct contact. Water is split into hydroxide ions and hydrogen ions. The resulting hydroxide ions and hydrogen ions are separated by migration out of the membrane. [ka] Unlike water splitting at electrodes during electrolysis, this reaction does not produce or use gas as a by-product. Electrodialysis with bipolar membranes (EDBM) can replace electrolysis by water splitting at electrodes, allowing for a wider range of applications.

[0069] Despite the clear advantages of the EDBM system, conventional salt splitting technologies, such as those proposed for use in the acid-base generator of the present disclosure, suffer from a number of problems. The first of these is that electrodialysis devices for acid / base generation are generally very expensive to operate and maintain. Currently, the high cost of electrodialysis devices is primarily due to the high cost of membrane materials and the efficiency of water dissociation at the bipolar membrane (BPM) interface. Inefficient water dissociation rates necessitate high operating voltages (greater than 1.3 V / cell), while the diffusion mass transport limitations of water to the BPM interface result in low operating current densities (less than 200 mA cm). 2 Aspects of the dual-path system according to the present disclosure provide high current densities (less than 250 mA / cm 2 to 1000mA / cm 2An acid-base generator incorporating a low overpotential electrodialysis device operating at temperatures above 1000 K has been demonstrated. By significantly lowering the overpotential and increasing the current density, the size of the electrodialysis device can be reduced, lowering overall system costs, particularly the high associated costs of generating the acidic and basic solutions required to drive the CO2-releasing reaction in the acidic and alkaline pathways of a dual-pathway system.

[0070] In embodiments of the dual-path system and method, the implementation of tailored BPM materials allows for operating current densities of approximately 100 mAcm. 2 From 250mA / cm 2 to 1000mA / cm 2 The current density limit of BPM can be attributed to dehydration of the BPM interface when the rate of water dissociation (WD) is high. Studies have shown that thinning the membrane can mitigate this dehydration. As shown in Figure 3a, a membrane with a thickness of 116 μm achieves an operating current density of approximately 800 mA cm. 2 reported, and data using a 60 μm thick BPM with a thin AEM layer (approximately 10 μm) showed a value of 500 mAcm 2 Thus, in various embodiments of the low overpotential / high current density electrodialysis device according to the present disclosure, a BPM containing a covalently bound catalyst is provided to induce reversible water dissociation and generation (WDF: HO←→H + (aq)+OH - (aq)). In such electrodialysis devices, membrane-bound WDF catalysts within the BPM reduce the operating voltage of the electrodialysis device by increasing the WDF reaction exchange rate. In various embodiments, thin layers (5-50 μm) of cation (or anion) exchange membranes are synthesized and directly bonded onto robust, commercially available cation exchange membranes (CEMs) (or anion exchange membranes (AEMs)) to further improve water transport to the BPM interface, achieving currents of up to 250 mA / cm. 2 to 1000mA / cm 2A thin membrane layer can increase co-ion crossover and reduce electrodialysis efficiency. Therefore, in each embodiment, a three-layer BPM structure is implemented to prevent dehydration at the BPM interface. Specifically, a three-layer BPM (Figure 4) can be provided to minimize co-ion crossover, and an active water supply from a dilute salt can be used to hydrate the BPM interface. Studies performed on electrochemical architectures have been successful in achieving high rates of H2O2 production and CO2 reduction. Operating current densities limited by water transport to the BPM junction are typically around 200 mAcm 2 However, according to the BPM mentioned above, 250mA / cm 2 to 1000mA / cm 2 This allows for operating current densities between ultra-

[0071] Regarding the specific materials and configurations of BPMs used in dual-path systems according to the present disclosure, in various embodiments, BPMs incorporating thin layers of anions (cations) may include materials such as X37 or XA9 ionomers (e.g., Nafion or sulfonated polyphenylsulfone). Such BPMs may be attached to commercially available CEMs (AEMs) with a thickness of, for example, less than 50 μm. As mentioned above, one potential risk is increased ion crossover due to the potentially low selectivity of the formed thin layers, which reduces the efficiency of the electrodialysis device. In various embodiments, a three-layer BPM structure may incorporate a porous solid electrolyte, such as a polymeric ion conductor or a solidified gel, as shown in Figure 4. Such a porous solid electrolyte may be infiltrated by a stream of dilute brine or deionized water. In such embodiments, it will be understood that commercially available CEMs and AEMs with a thickness of approximately 50-100 μm used in BPM structures may ensure low crossover rates while implementing an active water supply at the BPM interface to avoid water loss. In various embodiments, the cation (H +Styrene-divinylbenzene copolymer microspheres functionalized with sulfonic acid groups for ionic conduction may be incorporated into the BPM interface. In such embodiments, the interconnected surface provides rapid ionic conduction, while the micrometer-scale pores allow sufficient hydration for high current density operation.

[0072] In addition to high current density, as mentioned above, each embodiment of the electrodialysis device according to the present disclosure is directed to a bipolar membrane for low-voltage operation. In developing such a low-voltage electrodialysis device, each embodiment of the present disclosure considers electrostatics, chemical reactions, and the migration and diffusion of solution species. These are important for achieving high WDF catalytic rates at the BPM interface, combining electric field-promoted WD and acting as an additional driving force for ion transport to the BPM interface. As seen from previous experiments and calculations, the pK of the buffering group a The rate of chemically catalyzed WDF is fastest at pK = 7 and local pH = 7. This is explained by the Shockley-Read-Hall mechanism for the fastest rates of generation and recombination of mobile charges, which is maximized by half-filled midgap states: a = pH = 0.5 × (pK a (H2O(l))+pK a (H + (aq)) = 7. In each embodiment of the present disclosure, two buffering groups are used to achieve the desired pK a It can be seen that a certain degree of flexibility in the values ​​can be achieved (Figure 5a). These maximum current densities are for an experimentally feasible concentration of 1 M buffer group and can be further enhanced by the local electric field inherent in the presence of a pH gradient across the BPM. In a three-layer structure such as the one described above, which is more conducive to water transport, the pH gradient and electric field are necessarily smaller, necessitating effective chemical catalysis of the WDF.

[0073] Thus, in various embodiments of the low overpotential / high current density electrodialysis devices according to the present disclosure, pK a A modified BPM polymer containing approximately 7 buffering groups is implemented, which is most effective in catalyzing WD. As shown in Figure 5b, the pKa Initial experimental results obtained using poly(phenylene oxide)-modified polymers containing phosphonate groups at pH = 7 demonstrate improved WDF both in the absence (about 0 V) ​​and presence (above 0 V) ​​of an electric field, demonstrating a 10-fold improvement in WDF over prior art. Thus, in many embodiments, buffering groups, such as phosphonates, may be incorporated into BPMs to catalyze WDF in solutions between pH = 8.1 and pH = 4. In various embodiments, these chemical functional groups are covalently attached to the polymer backbone. In the same or other embodiments, polymers may be modified with polar and / or charged groups to enhance hygroscopicity to facilitate hydration and water transport. While much of the data presented pertains to PPOs, it should be understood that any polymer that is scalable, cost-effective, and amenable to large-scale production may be used in accordance with various embodiments, such as poly(propylene oxide), polypropylene, and polyethylene. In certain embodiments, BPMs may be fabricated from monolithically molded polymers to enhance robustness. In such embodiments, chemical modification may be performed from opposing directions using an H-cell. Additionally, membranes according to aspects of the present disclosure may be bonded to the catalyst layer using fluorinated ionomers to mitigate degradation due to water oxidation side reactions.

[0074] As summarized above, the studies performed (Figure 5a) show that the use of two buffering groups synergistically promotes WDF, thereby increasing the pK a This indicates that the stringent requirement of about 7 can be relaxed. Therefore, in various embodiments, buffering groups spanning more than 7 units may be used. Under significantly field-enhanced WD, the pK a Buffer groups with pK = 3.5 are particularly promising. a To alleviate the constraint of a single buffer group of about 7, various embodiments of catalytic BPMs were designed to have a pK (measured in solution) a The polymer is co-modified with two buffering groups with a pK of about 7. In some embodiments, metal oxide nanomaterials may be implemented, which are known to contain several protonatable groups. In embodiments of BPM using such nanomaterials, the pK measured in solution isa This can mitigate the risk associated with the value changing when incorporated into the polymer. In other embodiments, field facilitation of the WD may be incorporated, which is primarily beneficial for large field strengths that often correlate with large overpotentials, and has a small voltage dependence that does not adversely affect the dual-path system of the present disclosure.

[0075] The monolithic membrane structures with covalently attached buffering groups according to embodiments of the present disclosure are inherently more robust than prior art and support the formation of atomically thin space charge regions to maximize the electric field enhancement of WDs, which is critical to enable the long-term operation of these robust materials and achieve the FOA target of less than $100 / t-CO2.

[0076] Various embodiments of the electrodialysis device according to the present disclosure also implement cell and cell stack architectures to minimize polarization losses associated with WD of the BPM interface. Many electrodialysis devices according to the present disclosure can employ stacks of various configurations to minimize polarization losses and enable operation at high current densities. We make progress in three areas. Cell and multi-cell stacks can be optimized for channel width, flow rate, and salt composition of the input and output streams, all of which are highly dependent on the operating current density. In various embodiments, such cell parameters are optimized for the lowest possible polarization losses. In many embodiments, continuum-level multiphysics modeling can be used to identify conditions that minimize polarization losses and optimize high-current-density stack operation. In various embodiments, 2D multiphysics simulation tools can be used to optimize cell architectures for high-current-density operation. Such models can provide optimal flow rates and cell dimensions determined by chemical species concentrations, target pH, and membrane properties at high current densities. For example, in various embodiments, it may be necessary to increase the flow rate of the dilute-salt channel (AEM / CEM) to minimize resistive losses across the channel. This is Na + ions and Cl - This is because the cell resistance increases as ions begin to become depleted.

[0077] Aspects of the Acidic Pathway As discussed above with respect to Figures 1a / 1b and 2, in various embodiments, a dual-path system is implemented with an acid pathway comprising a source of screened seawater (116) (pH approximately 8.1) in fluid communication with an acidification element (132), which is supplied with an HCl source (128) to acidify the seawater to a pH below an initial pH of approximately 8.1. This acidified seawater (136) is then routed to a CO2 extraction element (140), which is a suitable catalyst-bound membrane contactor. The membrane contactor then produces a gaseous CO2 stream and a decarbonized acidified seawater stream, which can be extracted by a vacuum pump or other suitable device and subsequently routed to storage or processing as a feedstock, and which is mixed with an alkaline seawater stream and returned to the ocean.

[0078] While methods for extracting CO2 from acidified seawater are known, currently, acidified seawater with a pH of approximately 4 is required to facilitate gaseous CO2 removal. In these conventional systems, dissolved CO2 is present at a concentration of only approximately 2 mM in the acidified seawater, requiring a high-surface-area gas removal unit to efficiently produce gaseous CO2 from seawater by lowering the diffusive mass transport limitation of dissolved CO2. However, to achieve this, seawater with an approximate pH of approximately 8.1 must first be acidified to a pH of approximately 4 to increase the rate of bicarbonate and CO2 interconversion, which is not limiting the gaseous CO2 removal rate from membrane contactors commonly used for seawater gaseous CO2 removal. The problem is that using only acid generated in an electrodialysis device to adjust the pH to approximately 4, which is necessary for the effective use of conventional marine CO2 removal gas removal units, cannot achieve the long-term i-CO2 / year and thus the long-term cost target of less than $100 / t-CO2. This is because in such systems, the majority of the energy required by the system is used to power the electrodialysis device to produce the required pH swing.

[0079] Thus, embodiments of the dual-pathway system reduce the acid / base requirements for marine CO2 removal by implementing membrane contactors in the acid pathway that effectively remove CO2 from seawater with a pH of about 4 to about 7. As a result, the majority of the treated seawater is pumped a short vertical distance from below the floating platform, after which only a small amount of HCl is added to remove CO2 from significantly higher pH seawater (pH about 4 to 7) in the catalyst-containing gas-liquid contactor in the acid pathway, thereby improving the efficiency of the overall system.

[0080] Specifically, in various embodiments of the present disclosure, highly atom-efficient, tailored catalysts are coupled to the gas-liquid membrane contactor material (Figure 6a), resulting in a significant increase in the rate of bicarbonate and CO2 interconversion. Specifically, in various embodiments, the use of a WDF catalyst and a bicarbonate dehydration (BDF) catalyst as synthetic carbon dehydration enzyme mimics provides an efficient seawater CO2 membrane contactor operating at an effective pH of about 4 to about 7, significantly accelerating the inherently slow rate of bicarbonate and CO2 interconversion. In some of these embodiments, a gas-liquid membrane contactor using a catalyst-coupled hollow fiber membrane bundle (Figure 6a) may be implemented. In embodiments incorporating such a catalyst-coupled hollow fiber membrane bundle, the spatial location of the catalyst, the flow rate of acidified seawater within the hollow fiber material, the seawater pH, and the gas partial pressure within the membrane contactor all contribute to the overall system efficiency. Additionally, CO2 removal efficiency and mass transport within the bundled fiber material are also factors.

[0081] Thus, in many embodiments, common membrane / fiber materials, such as polypropylene hollow fibers, may be chemically grafted or blended into membrane contactors, allowing catalytic buffering groups (described above) to be incorporated into the shell side of the fiber material. Because of the short diffusion distances within membrane contactors and the rapid interconversion rates between bicarbonate and CO2, seawater can act as a reservoir for dissolved CO2 within the hollow membrane fiber material. Various embodiments of the present disclosure implement hollow fiber modules in which microporous hollow fibers are woven into a textile bundle. In such implementations, a catalyst layer may be coated on the shell side of the fiber material, allowing the acidified seawater to contact an increased surface area of ​​catalyst compared to planar structures (schematically shown in the inset of Figure 6b). While specific membrane and catalyst combinations are described above, it will be understood that other combinations may also be used in accordance with embodiments of the present disclosure.

[0082] For example, in various embodiments, a metal oxide nanomaterial catalyst (which, as previously described, can be used to enhance the water dissociation rate in BPM in an acid-base generator) may be added to the membrane / fiber material as a composite material to improve the BDF conversion rate. According to embodiments of the present disclosure, regeneration strategies including rapid pulse flushing using dilute brine and acid / base from the electrodialysis stack and solar heating to reactivate the membrane contactor may be implemented to extend the life of the catalyzed gas-liquid membrane contactor material. Furthermore, while flow through the system is shown as proceeding only in a straight line relative to the fiber bundle, it will be understood that in some embodiments, baffles may be incorporated external to the fibers to introduce flow counter to and perpendicular to the fibers to optimize gas-liquid contactor operation.

[0083] Regardless of the specific design, catalyst-coated membrane materials according to embodiments of the present disclosure improve the rate of bicarbonate-CO2 interconversion. As a result, CO2 can be efficiently removed from seawater, even with a small decompression airflow, using a much higher pH (pH 4 to 7) rather than a pH of about 4. As shown in Figure 6b, embodiments of the present invention increase the forward and reverse reaction rates of bicarbonate-CO2 interconversion by 106 By increasing the pH by 2.5, a maximum CO2 removal rate similar to that of seawater at a pH of 4 (natural seawater) can be achieved at pH values ​​of 6.1, 7.1, or 8.1 (natural seawater). As a result, much less acid and base need to be generated by the electrodialysis device to efficiently remove CO2 from high-pH seawater (above pH 4 to above pH 7). For example, using seawater at pH 7.1 requires pretreatment of only 1 / 360 of the seawater, significantly reducing the cost of the electrodialysis device. In various embodiments of dual-path systems, approximately 0.5% of the incoming water volume needs to be converted to a moderately concentrated acid / base (less than 0.5 M), requiring pretreatment of approximately 0.5% of the total treated seawater for use in the electrodialysis stack. Furthermore, as discussed above with respect to FIG. 1b, in various embodiments, the acid-base generator can be configured to recycle a dilute effluent from the electrodialysis device back to the electrodialysis device, further reducing the percentage of seawater that requires pretreatment, thereby further reducing the total energy input required to operate the electrodialysis device system.

[0084] For the buffer catalyst itself, in each embodiment of the present disclosure, the pK a values ​​range from approximately 3.5 to 10.0, and various buffer groups over a range of concentrations and pH conditions, as well as pK a It will be appreciated that combinations of 1–3 buffer groups, which have been shown to alleviate the constraints of CO2 absorption and achieve fast WDF, are contemplated (Figure 5a). Analyzing the kinetics of CO2 release from small volumes of aqueous solutions containing bicarbonate and different buffer groups may identify specific species. This allows for the identification of optimal combinations in terms of the trade-off between stability and efficacy in solution, followed by optimization for covalent attachment to water-soluble ionomers and small polymer groups, and ultimately for covalent incorporation into ion-exchange membranes and gas-liquid membrane contactors. The polarity of the polymer may be tuned by chemical modification to achieve specificity for CO2 by altering the equilibrium constant for CO2 absorption from seawater, thereby achieving the appropriate binding strength and enabling improved conversion rates of dissolved CO2 to gaseous CO2 under minimal vacuum or flow conditions.

[0085] In various embodiments, the inherently slow rate of CO dissolution to form bicarbonate may be overcome by using carbonic anhydrase. Carbonic anhydrase has a catalytic rate increase of 10 7 It is one of the most efficient biological catalysts known for any reaction, with a catalytic activity of the order of 1000 . The reaction proceeds via a hydroxylated intermediate, followed by a rate-determining step, WD, and finally OH. - The catalyst enhances the forward and reverse reaction rates, and thus various aspects of such carbonic anhydrase systems, according to the present disclosure, can be used to enhance the rate of CO removal in the ocean. a The buffer group = 7 exhibits the fastest catalytic activity for WDF, and the active site of carbonic anhydrase has a pK of the conjugate base. a The buffering groups (containing metal cations such as Zn(II)) and polymers developed for the study of WDF may therefore be used to catalyze BDF, according to embodiments of the present disclosure. Figure 7 shows the relationship between phosphate (pK a (Approximately 7,2) Experimental results are shown in which CO2 released from a 2 mM NaHCO3 solution was measured by in-line mass spectrometry after adding a WDF catalyst. As shown in the figure, the catalytic systems according to various embodiments of the present invention significantly improve the rate of bicarbonate-CO2 interconversion by BDF, even at target pHs of 4-7.

[0086] Additionally, catalytic BDF membranes may be used to incorporate other elements into system embodiments to enhance CO2 release. For example, a problem may arise in that the conversion of dissolved CO2 to gaseous CO2 can be slow. According to embodiments of the present disclosure, a BDF catalyst may be placed at the gas / liquid interface via covalent bonding to a polymer, which helps disrupt the interfacial water hydrogen-bonding network and reduce surface tension, leading to increased gaseous CO2 release. Furthermore, in embodiments of the present disclosure, the overall BDF catalytic rate may be further increased by increasing the local temperature, which further reduces CO2 solubility. Many system embodiments according to the present disclosure utilize high-efficiency photovoltaic devices (see description of Figure 2), and in such systems, infrared light may be transmitted through commercially available bifacial solar cells, collected by an infrared-absorbing photonic layer, and then used to locally heat the membrane contactor to further enhance CO2 release.

[0087] In various embodiments, as described in more detail below, the gaseous CO2 recovered from the gas-liquid contactor may be used as a feedstock for various industrial processes, thereby increasing the economic benefits of the system. However, the CO2 stream captured from the gas-liquid contactor may contain other impurities such as HO, O2, and N2, and may contain Cl2 in the seawater, depending on the pH swing required for effective CO2 release. -The resulting seawater may even contain small amounts of HCl due to the high concentration of CO. To separate dissolved gases other than CO, embodiments of the membrane contactor may be configured without a catalyst buffer near its intake, resulting in a rapid initial release of O and N. Initially, O can be purged by flowing seawater through a region of the membrane contactor that does not contain a BDF catalyst, so that in subsequent catalyst-containing regions, CO release will primarily involve the production of water vapor. Downstream of the catalyst-free region, the acidified, degassed seawater encounters a region coated with a buffer catalyst, promoting the release of CO as well as HO and HCl impurities. In various embodiments, these remaining impurities may be separated by modest temperature and / or pressure changes in a centralized location. Ultimately, as shown and described in connection with Figures 1a / 1b, the impurities are reintroduced into the flowstream with the addition of more alkaline seawater, so that the discharge will be decarbonized seawater alone. Additionally, in various embodiments, the duty cycle of the BDF membrane may be extended by using periodic gas purging processes and / or excess acid / base addition to antifoul and subsequently decontaminate the membrane.

[0088] Aspects of the alkaline pathway As discussed above and shown in FIG. 1a, the dual-path system in various aspects according to the embodiments further includes an alkaline path (106) in which the incoming screened seawater stream passes through a basification element (138). The basification element (138) receives the NaOH feedstock (130) produced in the acid-base generator (102) to raise the pH from about 8.1 to about 10. The basified water feedstock (138) is then introduced into a precipitation element (146) where the precipitation product is collected. The remaining alkaline water is then combined with the acidic water, and a water effluent with a natural pH of about 8.1 is reintroduced into the environment.

[0089] The conversion of CO2 to precipitated inorganic carbonates via the inorganic carbonation route is considered a promising option for carbon capture and storage (CCS) because the captured CO2 can be permanently stored. In the embodiments of this disclosure, this process is incorporated into the alkaline pathway of a dual-pathway system. All of the precipitation products that can be produced by seawater inorganic carbonate precipitation reactions, including CaCO3, Ca(OH)2, MgCO3, Mg(OH)2, SrSO4, CaF2, and CaSO4, are incorporated into the embodiments because these different precipitates can be available at various temperatures, pHs, and salinities. Figure 8 includes the major ions in seawater and their associated concentrations, demonstrating the availability of ions in seawater for various precipitation reactions.

[0090] In constructing an alkaline pathway according to each embodiment of the present invention, the kinetics of water dissociation, the CO2 / bicarbonate / carbonate acid-base reaction and its reaction rate, and the boric acid reaction in seawater are taken into consideration. For example, the following two reactions may be used to describe the CO2 / bicarbonate equilibrium: [ka] where k f and k b represent the forward and reverse rate constants for each reaction, respectively. The temperature and salt concentration dependence of all equilibrium constants must also be considered. For example, K for the dissociation of water w becomes: 2

number

[0091] Understanding the kinetics of various precipitation products from seawater is important because, although most of these products can be made easier to produce through adjustments, not all of them lead to the same level of CO2 capture efficiency. For example, an important characteristic of calcium carbonate precipitation is the polymorphism of the product. Under various experimental conditions, the formation of a mixture of orthorhombic calcite and spherical vaterite, as well as needle-like aragonite, has been reported. For the purpose of capturing and extracting CO2 in the form of solid precipitates, these precipitation products are equally excellent as long as the precipitation rate is fast enough to achieve high capture efficiency at a given seawater flow rate. On the other hand, other precipitation products, especially K, are not. sp is 1.8×10 -11 If preferentially precipitated, the very low Mg(OH)2 would consume hydroxide ions in the basified stream produced from the bipolar membrane-based electrodialysis device, thus reducing the overall energy efficiency and increasing the cost of CO2 capture from seawater.

[0092] Accordingly, embodiments of the present disclosure target operational conditions to optimize the formation of calcite crystals. According to various embodiments of the present disclosure, the pH of the basified water is approximately 10-11, which most efficiently results in CaCO3 precipitation. This may seem counterintuitive, since increasing the pH of the basified stream above approximately 10 increases the concentration of carbonate ions available for CaCO3 precipitation, but also increases the formation of Mg(OH)2. Accordingly, embodiments of the present invention incorporate thermodynamic calculations into the model described above, and an optimal pH range (e.g., pH approximately 10-11) for preferentially precipitating CaCO3 is implemented within the basification element.

[0093] Alkaline pathway embodiments may incorporate seeded crystal growth to control CaCO precipitation. Given the nature of large-scale seawater treatment, uniform seeding using molecular or polymeric additives is not feasible unless the seeds are reusable. Various embodiments of the present disclosure may accelerate the overall CaCO precipitation rate by implementing CaCO seeds, such as vaterite or calcite crystals or relatively concentrated salt solutions derived therefrom, all of which are produced within the hybrid system. Other heterogeneous seeding techniques, such as using fine mesh or sharp substrates, may also be implemented by various embodiments. Small amounts of dissolved organic matter present in natural seawater may also affect the rate of CaCO precipitation for CO capture; therefore, strategies to optimize the presence or absence of such organic matter may be implemented. In summary, dual-pathway system embodiments may optimize the kinetics of CaCO precipitation in the basified stream and the energy efficiency of CO capture through control of pH, temperature, and various seeding strategies.

[0094] Quantitative assessment of solids settling rate in the basified stream according to embodiments of the present disclosure may be made using an apparatus such as that shown in Figure 9. As shown, in the apparatus, electrochemical quartz crystal microbalance measurements are used for real-time monitoring of settling rate. An in-line particle size analyzer may be used to monitor the formation of suspended precipitate in the basified stream in real time. Additionally, the temperature, pH, and salinity of the basified stream in both the reactant and reaction chambers may be continuously monitored by temperature measurement, pH monitoring, and salinity measurement, respectively, while SEM and EDX may be used to further analyze the chemical composition of the precipitated product.

[0095] In addition to this carbonate precipitation pathway, as described with respect to FIG. 1b, in various other embodiments of the dual pathway system, the alkaline pathway uses a gaseous feed to produce an ion concentration of approximately 1.0 M OH. - , 0.5M CO3 2-, and 2.0M Na + In some embodiments, the direct air capture system may incorporate an aqueous solution of CO2 to capture CO2 from the gas feed stream. In such embodiments, the alkaline pathway produces an output stream of CO2-lean gas and a carbonate solution. The direct air capture system configuration may take any suitable form, but in various embodiments may include a contactor that contacts the feed gas with the alkaline capture solution. CO2 capture from the feed gas occurs at the surface of the solution, and any suitable structure may be used to increase the contact area (e.g., co-flowing the gas feed and solution through a high surface area element, etc.). It will be understood that each embodiment may include any suitable contactor design.

[0096] Economic aspects of dual-route systems Aspects of the present disclosure provide an efficient and cost-competitive offshore standalone system for CO2 removal from seawater. As explained in the sections above, three particular aspects of the system significantly reduce the cost of CO2 removal: i) co-location on or near a body of saltwater; ii) high current density (250 mA / cm 2 to 1000mA / cm 2and iii) a novel membrane contactor that exhibits unprecedented rates of CO2 removal from only slightly acidified seawater (pH ∼4 to 7). These embodiments minimize energy spent on i) water pumping, ii) salt splitting, in which approximately 0.5% of the water volume is converted to acid / base at moderate concentrations (<0.5 M), and iii) pretreatment of approximately 0.5% of the total treated seawater for use in the electrodialysis stack. Such a dual-path system enables the process to meet cost targets of less than $100 / t-CO2 at a planned scale of 100 Gt-CO2 per year. Design embodiments can also achieve unprecedented second-law efficiencies of 50% (or 0.46 MWh / t-CO2) and embodied emissions estimated at less than 2% of lifecycle captured emissions. Furthermore, in each aspect of the dual-pathway system, the acidification and subsequent basification of seawater is carried out in a closed system, making it environmentally and ecologically friendly, as the only effluent released into the ocean is decarbonized seawater at the same salinity level as when it was taken.

[0097] Although specific embodiments of the invention have been described and illustrated, the invention is not limited to the specific forms or arrangements of parts so described and illustrated, the scope of the invention being defined by the claims appended hereto and their equivalents.

[0098] Although the operations of the methods herein are shown and described in a particular order, the order of the operations of each method may be changed such that certain operations may be performed in reverse order or such that certain operations may be performed at least in part concurrently with other operations. Instructions or sub-operations of separate operations may be performed intermittently and / or alternately.

[0099] It should also be noted that at least some operations of the methods described herein may be implemented using software instructions stored on a computer usable storage medium for execution by a computer. As an example, a computer program product embodiment includes a computer usable storage medium for storing a computer readable program.

[0100] A computer-usable or computer-readable storage medium may be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device). Examples of non-transitory computer-usable and computer-readable storage media include semiconductor or solid-state memory, magnetic tape, removable computer diskettes, random access memory (RAM), read-only memory (ROM), rigid magnetic disks, and optical disks. Current examples of optical disks include compact disks with read-only memory (CD-ROM), compact disks with read / write (CD-R / W), and digital video disks (DVDs).

Claims

1. CO ２ A dual path system for recovery, comprising: a platform located adjacent to a source of seawater; an acid-base generator in fluid communication with the source of seawater, a purification unit configured to convert a first portion of the seawater into a source of NaCl; at least one electrodialysis device in fluid communication with the purification device and incorporating a bipolar membrane configured to convert the NaCl source into a source of HCl and a source of NaOH; an acid-base generating device comprising: an acidic CO 2 in fluid communication with said source of seawater; ２ 1. A removal system comprising: an acidification element in fluid communication with the HCl source and configured to produce an acidified seawater source from the seawater; a gaseous CO extractor in fluid communication with the acidification element and a vacuum system, the gaseous CO extractor from the acidified seawater feedstock; ２ and outputting the decarbonized acidified seawater effluent to an output port. Acidic CO ２ A removal system; CO ２ a source of fluid having a CO ２ Alkaline CO2 configured to produce lean exhaust and carbonates ２ Removal system and In a dual path system comprising: The output is the decarbonized acidified seawater effluent and the alkaline CO ２ mixing at least one effluent from the CO removal system to produce a mixed seawater effluent for environmental release; ２ Dual-path system for recovery.

2. The alkaline CO ２ a removal system in fluid communication with the source of seawater; The alkaline CO ２ the removal system comprising: a basifying element in fluid communication with the NaOH source and configured to produce a basified seawater source from the seawater; a precipitation element in fluid communication with the basification element for recovering precipitate of inorganic carbonates from the basified seawater feed and outputting a decarbonized basified seawater output to the output; Equipped with 10. The CO2 method of claim 1, wherein the output combines the decarbonized acidified seawater effluent and the decarbonized basicified seawater effluent to produce a combined seawater effluent for environmental release, the combined seawater effluent having a pH approximately similar to a pH of the seawater source. ２ Dual-path system for recovery.

3. The alkaline CO ２ The removal system is ２ the CO containing gaseous feedstock source. ２ in fluid communication with the entrained fluid; The alkaline CO ２ The removal system comprises a NaOH source and a CO ２ in fluid communication with the gaseous feedstock containing CO ２ a direct air recovery element configured to produce a lean gaseous exhaust and a carbonate solution; The output is a step of mixing the decarbonized acidified seawater effluent and the carbonate solution, and adding CO2 in the carbonate to the decarbonized acidified seawater effluent. ２ and releasing it into the environment. ２ Dual-path system for recovery.

4. 10. The CO 2 solution of claim 1, wherein the acidified seawater feedstock has a pH range of about pH 4 to about pH 7. ２ Dual-path system for recovery.

5. The basified seawater feedstock has a pH of approximately 10, and the inorganic carbonate is CaCO ３ 3. The CO according to claim 2, ２ Dual-path system for recovery.

6. 3. The CO2 method of claim 2, wherein the seawater and mixed seawater effluent have a pH of approximately 8. ２ Dual-path system for recovery.

7. The seawater source, the acid-base generator, and the acidic CO ２ Removal system and the alkaline CO ２ 10. The CO 2 treatment system of claim 1, further comprising at least one pretreatment element disposed between the CO 2 treatment system and the CO 2 treatment system, for screening the seawater. ２ Dual-path system for recovery.

8. 8. The CO 2 filter of claim 7, wherein the pretreatment element comprises a drum screen filter. ２ Dual-path system for recovery.

9. 10. The CO purifier of claim 1, wherein the purification device comprises one or more selected from the group consisting of a dissolved air suspension clarifier, a micro / ultra filter, a cartridge filter, and a water softening ion exchanger. ２ Dual-path system for recovery.

10. 10. The CO2 purification system of claim 9, wherein the purification system comprises at least a clarifier and an ion exchanger, the clarifier in fluid communication with the HCl feedstock and the ion exchanger in fluid communication with the NaOH feedstock. ２ Dual-path system for recovery.

11. The electrodialysis device is operated at 250 mA / cm ２ to 1000mA / cm ２ 10. The CO2 of claim 1, configured to operate at a current density between ２ Dual-path system for recovery.

12. 10. The CO2 separator of claim 1, wherein the bipolar membrane comprises a catalyst ion layer directly bonded to either a cation exchange membrane or an anion exchange membrane. ２ Dual-path system for recovery.

13. 13. The CO2 of claim 12, wherein the ionic layer has a thickness between 5 and 50 μm. ２ Dual-path system for recovery.

14. 13. The CO 2 separator of claim 12, wherein the bipolar membrane is a three-layer structure comprising at least three elements selected from the group consisting of a porous solid electrolyte, a cation exchange membrane, and an anion exchange membrane. ２ Dual-path system for recovery.

15. The catalyst ion layer has a pK ａ 13. The CO2 of claim 12, comprising at least one buffering group where ２ Dual-path system for recovery.

16. 16. The CO2 of claim 15, wherein the catalyst ion layer comprises at least one buffering group covalently attached to a polymer backbone. ２ Dual-path system for recovery.

17. 17. The CO of claim 16, wherein the polymer backbone is selected from the group consisting of polyethylene oxide, polypropylene, and polyethylene. ２ Dual-path system for recovery.

18. 17. The CO2 composition of claim 16, wherein the at least one buffering group is selected from the group consisting of phosphonates and metal oxide nanomaterials. ２ Dual-path system for recovery.

19. 10. The CO2 of claim 1 comprising an electrodialysis stack. ２ Dual-path system for recovery.

20. 10. The CO 2 method of claim 1, wherein the catalyst-bound membrane contactor comprises one or more gas-liquid membrane contactor materials having a buffer-based catalyst bound thereto. ２ Dual-path system for recovery.

21. 21. The CO 2 system of claim 20, wherein the gas-liquid membrane contactor material comprises one or more hollow fibers. ２ Dual-path system for recovery.

22. 22. The CO according to claim 21, wherein the one or more hollow fibers are made of a material selected from the group consisting of polypropylene and polyethylene. ２ Dual-path system for recovery.

23. 21. The CO2 of claim 20, wherein the buffering group catalyst is a synthetic carbon dehydratase mimic. ２ Dual-path system for recovery.

24. 22. The CO2 method of claim 21, wherein the catalyst-bound membrane contactor comprises a baffle structure disposed externally of the one or more hollow fibers, and the flow of acidified seawater feed is introduced at one or more angles relative to the one or more hollow fibers. ２ Dual-path system for recovery.

25. 21. The CO2 method of claim 20, wherein at least a portion of the catalyst-bound membrane contactor proximate to the water intake is free of the buffer group catalyst. ２ Dual-path system for recovery.

26. 10. The CO2 system of claim 1 further comprising one or more electrically interconnected renewable power sources that power the dual-path system. ２ Dual-path system for recovery.

27. 27. The CO2 system of claim 26, wherein one or more of the renewable power sources are photovoltaic devices, the photovoltaic devices collect infrared radiation, and the infrared radiation is used to generate heat that heats the catalytically coupled membrane contactor. ２ Dual-path system for recovery.

28. 3. The CO precipitation method of claim 2, wherein the precipitation element is further provided with at least one seeding growth material selected from the group consisting of vaterite, calcite, and salt solutions thereof. ２ Dual-path system for recovery.

29. 10. The CO 2 solution of claim 1, wherein the first portion comprises approximately 0.5% of the seawater introduced into the dual-path system. ２ Dual-path system for recovery.

30. 10. The CO 2 process of claim 1, wherein the catalyst-bound membrane contactor is in fluid communication with the HCl source. ２ Dual-path system for recovery.

31. 2. The CO 2 treatment method according to claim 1, wherein at least one electrodialysis device further outputs a dilute low-salinity wastewater, and the dilute low-salinity wastewater is reintroduced into the electrodialysis device as a feedstock. ２ Dual-path system for recovery.

32. introducing a first portion of seawater into an acid-base generator; converting the first portion of the seawater into a source of NaCl; Electrodialysis of the NaCl using a bipolar membrane to obtain a raw material for HCl and a raw material for NaOH; introducing a second portion of the seawater into an acidification element in fluid communication with the HCl source to produce an acidified seawater source from the seawater; and extracting gaseous CO from the acidified seawater feedstock through a catalyst-bound membrane contactor. ２ and outputting a decarbonized acidified seawater discharge; in fluid communication with the NaOH source; ２ Alkaline CO2 configured to produce lean exhaust and carbonates ２ The removal system ２ introducing a source of fluid incorporating the the decarbonized acidified seawater effluent and the alkaline CO ２ mixing at least one effluent from the removal system to produce a mixed seawater effluent for environmental release; CO ２ Dual-path method for recovery.

33. The CO ２ the source of fluid containing the CO 2 includes a third portion of seawater; ２ The dual path method for recovery further comprises: introducing the third portion into a basifying element in fluid communication with the NaOH source to produce a basified seawater source from the seawater; recovering inorganic carbonate precipitate from the basified seawater feed and outputting a decarbonized basified seawater output; mixing the decarbonized acidified seawater effluent and the decarbonized basicified seawater effluent to produce a mixed seawater effluent for environmental release, the mixed seawater effluent having a pH approximately similar to a pH of the seawater source; 33. The CO of claim 32, ２ Dual-path method for recovery.

34. The CO ２ The source of the fluid that absorbed CO ２ The CO ２ The dual path method for recovery further comprises: in fluid communication with the NaOH source; ２ a direct air recovery element configured to produce a lean gas effluent and a carbonate solution; ２ introducing a gaseous feedstock containing The output is a step of mixing the decarbonized acidified seawater effluent and the carbonate solution, and adding CO2 in the carbonate to the decarbonized acidified seawater effluent. ２ and released into the environment. ２ Dual-path method for recovery.

35. 33. The CO2 solution of claim 32, wherein the acidified seawater feedstock has a pH range of about pH 4 to about pH 7. ２ Dual-path method for recovery.

36. The basified seawater feedstock has a pH of approximately 10, and the inorganic carbonate precipitate is CaCO ３ 34. The CO of claim 33, ２ Dual-path method for recovery.

37. 33. The CO2 of claim 32, wherein the first portion comprises about 0.5% of the seawater introduced into the dual-path system. ２ Dual-path method for recovery.

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