Carbonate ion concentrating device and carbonate ion concentrating method

Abstract

To provide a carbonate ion concentration device and a carbonate ion concentration method which can concentrate carbon dioxide in the air as carbonate ions in the water at low energy, as a technique for solving environmental problems accompanying the increase in carbon dioxide concentration in the air.SOLUTION: A carbonate ion concentration device and a carbonate ion concentration method include a hydrogen ion exchange membrane for selectively permeating hydrogen ions, a cathode electrode and an anode electrode arranged so as to sandwich the hydrogen ion exchange membrane, and a first solution which is arranged on the cathode electrode side and contains carbon dioxide, and short-circuit the cathode electrode and the anode electrode. Thereby, the device and the method can concentrate carbon dioxide in the air as carbonate ions in the water at low energy.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for concentrating carbonate ions in water, and more particularly to an apparatus and method for concentrating carbonate ions that can dissolve carbon dioxide in air in water and then concentrate it as carbonate ions with low energy. [Background technology]

[0002] In recent years, reducing carbon dioxide emissions into the environment has become an urgent issue, as it is believed to have a major impact on environmental problems such as global warming. To address this issue, research is being conducted into technologies to reduce carbon dioxide emissions themselves, as well as technologies to capture and fix emitted carbon dioxide.

[0003] In particular, various methods are being considered as technologies for capturing and immobilizing carbon dioxide. For example, methods for capturing carbon dioxide from carbon dioxide-containing gases include the chemical absorption method, in which carbon dioxide is dissolved in an absorbent such as monoethanolamine, the physical adsorption method, in which carbon dioxide is adsorbed onto an adsorbent with gas adsorption capacity, and the membrane separation method, which uses a membrane. In addition to these methods, from the perspective of reducing the carbon dioxide concentration in the atmosphere, a method related to ocean storage is being considered, in which carbon dioxide is supplied to the ocean, stored in the ocean, and then isolated from the atmosphere.

[0004] For example, Patent Document 1 describes a carbon dioxide fixation system in which deep seawater is pumped up to near the sea surface and carbon dioxide is absorbed into the pumped seawater. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-262888 Summary of the Invention [Problem to be solved by the invention]

[0006] As described in Patent Document 1, when carbon dioxide is absorbed into seawater, carbon dioxide from the atmosphere can be temporarily dissolved in the seawater, but due to the difference in partial pressure of carbon dioxide with the atmosphere, the carbon dioxide dissolved in the seawater will be released back into the atmosphere. Therefore, it is necessary to effectively dissolve carbon dioxide in seawater and increase the amount of carbon dioxide stored in the ocean.

[0007] An object of the present invention is to provide a carbonate ion concentrating device and a carbonate ion concentrating method that can concentrate carbon dioxide in the atmosphere as carbonate ions in water with low energy, as a technology for solving environmental problems associated with an increase in the concentration of carbon dioxide in the atmosphere. [Means for solving the problem]

[0008] As a result of intensive research into the above-mentioned problems, the inventors have found that by using a hydrogen ion exchange membrane to allow hydrogen ions to permeate from seawater containing carbon dioxide, the chemical equilibrium reaction shifts in the direction of carbon dioxide forming carbonate ions, and carbon dioxide is converted into carbonate ions (bicarbonate ions (HCO3 - ), carbonate ions (CO3 2- The present inventors have found that the chemical equilibrium reaction of forming carbonate ions can be accelerated with low energy by short-circuiting the cathode and anode electrodes, and have completed the present invention. That is, the present invention provides the following carbonate ion concentrating device and carbonate ion concentrating method.

[0009] The carbonate ion concentrating device of the present invention, which solves the above-mentioned problems, comprises a hydrogen ion exchange membrane that selectively allows hydrogen ions to permeate, a cathode electrode and an anode electrode that are arranged on either side of the hydrogen ion exchange membrane, and a first solution that is arranged on the cathode electrode side and contains carbon dioxide, and is characterized in that the cathode electrode and the anode electrode are short-circuited. According to this carbonate ion concentrating device, a hydrogen ion exchange membrane is provided between the electrodes, and a first liquid containing a high concentration of carbon dioxide is placed on the cathode side, so that hydrogen ions in the first liquid move to the anode side due to the hydrogen ion concentration gradient. As a result, the hydrogen ion concentration in the first liquid decreases, and the chemical equilibrium reaction shifts in the direction of forming carbonate ions from carbon dioxide, resulting in the concentration of carbonate ions. Furthermore, the movement of hydrogen ions generates a potential difference between the cathode electrode and the anode electrode. In the device for concentrating carbonate ions of the present invention, the cathode electrode and the anode electrode are short-circuited, so that electrons move from the cathode electrode to the anode electrode, and the electrons are supplied to the hydrogen ions of the anode electrode, thereby generating hydrogen gas. As a result, the hydrogen ion concentration on the anode electrode side decreases without using electrical energy such as applying a voltage, and therefore the movement of hydrogen ions from the cathode electrode side can be promoted. Through the above reaction, the device for concentrating carbonate ions of the present invention can concentrate carbonate ions in the first liquid on the cathode electrode side with low energy.

[0010] Moreover, one embodiment of the carbonate ion concentrating device of the present invention is characterized in that the first solution is open to the atmosphere. According to this feature, excess carbon dioxide dissolved in the first solution is gradually released into the atmosphere, making it possible to increase the pH of the first solution without using chemicals. When the pH of the first solution increases, the solubility of carbonate ions (carbonate ions) becomes supersaturated, allowing them to react with divalent cations such as calcium ions and magnesium ions and precipitate. This makes it possible to fix the carbonate ions as carbonate salts.

[0011] Moreover, one embodiment of the carbonate ion concentrating device of the present invention is characterized in that the first liquid is seawater. Seawater contains divalent cations such as calcium ions and magnesium ions, as well as carbonate ions dissolved in a supersaturated state, so the carbonate ions concentrated in the first liquid can be quickly fixed as carbonate. In addition, because seawater can be obtained from nature, it is possible to fix atmospheric carbon dioxide as carbonate at low cost.

[0012] The method for concentrating carbonate ions of the present invention for solving the above-mentioned problems is characterized by comprising the steps of: arranging a cathode electrode and an anode electrode with a hydrogen ion exchange membrane between them; arranging a first solution containing carbon dioxide on the cathode electrode side; and short-circuiting the cathode electrode and the anode electrode. According to this method for concentrating carbonate ions, like the above-mentioned apparatus for concentrating carbonate ions, carbonate ions can be concentrated in the first liquid on the cathode electrode side with low energy. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a carbonate ion concentrating device and a carbonate ion concentrating method that can concentrate carbon dioxide in the atmosphere as carbonate ions in water using low energy. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic explanatory view of an apparatus for concentrating carbonate ions according to a first embodiment of the present invention. [Figure 2] 2 is a schematic explanatory view showing an example of the state of a substance in the carbonate ion concentrating device according to the first embodiment of the present invention, which shows the state from the initial state until the start of short-circuiting. [Figure 3] 3 is a schematic explanatory diagram showing an example of the state of substances in the carbonate ion concentrating device according to the first embodiment of the present invention, which shows the state from the early stage of short circuit until the substances in the first liquid and the second liquid reach concentration equilibrium. [Figure 4]4 is a schematic explanatory diagram showing an example of the state of substances in the carbonate ion concentrating device according to the first embodiment of the present invention, which shows the state from when the substances in the first liquid and the second liquid reach concentration equilibrium to when the carbon dioxide concentration in each solution reaches equilibrium with the atmosphere. [Figure 5] 5 is a schematic explanatory diagram showing an example of the state of a substance in the carbonate ion concentrating device according to the first embodiment of the present invention, in which the carbon dioxide concentrations in the first solution and the second solution are equilibrated with those in the atmosphere and then fixed as carbonate. [Figure 6] 1 is a graph showing an example of the abundance ratio of carbonate ions in seawater with changes in pH (1 atmosphere, 25° C.). [Figure 7] 3 is a graph showing changes in pH of the first liquid and the second liquid in the carbonate ion concentrating device according to the first embodiment of the present invention. [Figure 8] FIG. 2 is a schematic explanatory view of a carbonate ion concentrating device according to a second embodiment of the present invention. [Figure 9] FIG. 1 is a schematic explanatory view of a carbonate ion concentrating device according to a third embodiment of the present invention. [Figure 10] FIG. 10 is a schematic explanatory view of a carbonate ion concentrating device according to a fourth embodiment of the present invention. [Figure 11] FIG. 10 is a schematic explanatory view of a carbonate ion concentrating device according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the carbonate ion concentrating device according to the present invention will be described in detail with reference to the drawings. The description of the carbonate ion concentrating method according to the present invention can be replaced with a description of the operation of the carbonate ion concentrating device according to the present invention. The carbonate ion concentrating device and the carbonate ion concentrating method described in the embodiments are merely exemplified to explain the carbonate ion concentrating device and the carbonate ion concentrating method according to the present invention, and are not limited thereto.

[0016] (carbonate ion concentrator) The carbonate ion concentrating device of the present invention is for concentrating carbonate ions in water. Specifically, the carbonate ions are concentrated in the first liquid (carbonated water) by transferring hydrogen ions generated by ionization equilibrium in the first liquid (carbonated water) through a hydrogen ion exchange membrane. Here, the carbonate ion concentrating device of the present invention short-circuits a cathode electrode and an anode electrode disposed on either side of the hydrogen ion exchange membrane, so that electrons are supplied from the anode electrode to hydrogen ions that have flowed into the anode electrode side, thereby generating hydrogen. Therefore, the hydrogen ion concentration on the anode electrode side decreases, thereby facilitating the transfer of hydrogen ions from the first liquid.

[0017] The carbonated water that can be used as the first liquid of the present invention is not particularly limited in terms of its origin, as long as it is an aqueous solution containing dissolved carbon dioxide. It may be raw water into which carbon dioxide has been artificially dissolved, or it may be water that already contains dissolved carbon dioxide. Examples of raw water that can be used include natural resources such as river water, lake water, groundwater, rainwater, and seawater, as well as tap water, pure water, industrial wastewater and effluent, and leachate from landfills. Seawater is preferred. Seawater contains divalent cations such as calcium ions and magnesium ions, and concentrated carbonate ions (carbonate ions) can be fixed as carbonate salts such as calcium carbonate and magnesium carbonate.

[0018] In carbonated water, when carbon dioxide (CO2) is dissolved in water (H2O), a chemical equilibrium equation such as that shown in Equation 1 generally holds.

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[0019] As shown in Equation 1, when carbon dioxide dissolves in water, it reaches equilibrium with carbonic acid (H2CO3), and then some of the carbonic acid dissolves into hydrogen ions and bicarbonate ions (HCO3 - ) and bicarbonate ions are ionized into hydrogen ions and carbonate ions (CO3 2-In the present invention, the term "carbonate ions" refers to "bicarbonate ions (HCO3 - ) and carbonate ions (CO3 2- ) is a general term for

[0020] Since hydrogen is contained in an ionic state in the aqueous solution containing dissolved carbon dioxide, hydrogen ions can be transferred through the hydrogen ion exchange membrane. After the hydrogen ions have transferred, the chemical equilibrium shown in Equation 1 is reached by the carbonate ions (CO3 2- The reaction proceeds in the direction of producing hydrogen ions, so carbonate ions are concentrated in the first liquid. Carbonic acid (H2CO3) also passes through the hydrogen ion exchange membrane in small amounts due to osmotic pressure. Furthermore, in the carbonate ion concentrating device of the present invention, the cathode electrode and the anode electrode, which are disposed on either side of the hydrogen ion exchange membrane, are short-circuited, so that electrons flow from the cathode electrode to the anode electrode, generating hydrogen on the anode electrode. This reduces the hydrogen ion concentration on the anode electrode side, further promoting hydrogen ion migration and generating carbonate ions. At this time, an increase in pH due to the migration of hydrogen ions is observed in the first liquid. Thereafter, the migration of substances through the hydrogen ion exchange membrane reaches equilibrium, limiting the migration of hydrogen ions in the first liquid. Next, when the mass transfer reaches equilibrium, the carbon dioxide dissolved in the first liquid is released into the air, causing the pH to gradually rise. Through this process, the first liquid contains a high concentration of carbonate ions, causing the pH to rise, creating a state of supersaturation of carbonate ions.

[0021] Another feature of the carbonate ion concentrating device of the present invention is its low power consumption. Simply by short-circuiting the cathode electrode and anode electrode, which are arranged on either side of the hydrogen ion exchange membrane, the movement of hydrogen ions can be promoted.

[0022] [First embodiment] FIG. 1 is a schematic explanatory view showing the structure of an apparatus 1A for concentrating carbonate ions according to a first embodiment of the present invention. As shown in Fig. 1, the carbonate ion concentrating apparatus 1A in this embodiment has a treatment tank 10, which is provided with a hydrogen ion exchange membrane 12. The hydrogen ion exchange membrane 12 is provided with a pair of electrodes (a cathode electrode 11a and an anode 11b). As shown in Fig. 1, the treatment tank 10 is divided by the hydrogen ion exchange membrane 12 into a first chamber 13a (cathode electrode side) for introducing a first solution containing carbon dioxide, and a second chamber 13b (anode electrode side) for introducing a second solution into which hydrogen ions in the first solution flow. The treatment tank 10 is also connected to a line L1 for introducing raw water S0 and a line L2 for introducing carbon dioxide (CO2) into the first chamber 13a.

[0023] The arrangement of lines L1 and L2 is not limited to this. For example, the raw water S0 may be introduced through line L1 only to the first chamber 13a, and pure water or an electrolytic solution, such as a sodium hydroxide solution, a potassium chloride solution, or a sodium chloride solution, may be introduced into the second chamber 13b. This advantageously results in ion migration based on the principles of electrodialysis, increasing the rate of hydrogen ion migration through the hydrogen ion exchange membrane 12 and shortening the time required for the pH of the solution to increase. The configuration and manner of carbon dioxide introduction are also not limited. For example, the first chamber 13a may be pressurized or depressurized to adjust the concentration of carbon dioxide dissolved in the raw water S0 according to the target pH of the solution. Furthermore, the first chamber 13a may be configured to generate fine carbon dioxide bubbles from the bottom, thereby maintaining a uniform carbon dioxide solubility at all times.

[0024] Here, the carbon dioxide supply source (or generation source) is not particularly limited. Specific examples of carbon dioxide supply sources include gases containing carbon dioxide emitted from various facilities (power generation facilities, factories, ordinary households, etc.) and transportation means associated with daily life and industrial activities, as well as naturally occurring gases containing carbon dioxide such as the atmosphere and volcanic gases. Note that if the raw water SO initially contains enough dissolved carbon dioxide to obtain a solution with the desired pH, the step of introducing carbon dioxide can be omitted.

[0025] The treatment tank 10 may be made of any material or shape as long as it is equipped with a hydrogen ion exchange membrane 12 and is capable of storing the raw water S0. For example, the material and shape used in structures known as electrolytic cells or electrodialysis cells may be used. In addition, it is preferable that the top of the treatment tank 10 is open. By opening the top of the treatment tank 10, carbon dioxide can be released from the first liquid into the atmosphere.

[0026] The cathode electrode 11a and the anode electrode 11b are provided on or near the surface of the hydrogen ion exchange membrane 12 and are electrically connected to each other using conductors. In this embodiment, the cathode electrode 11a and the anode electrode 11b are used to short-circuit the first liquid and the second liquid.

[0027] The material and shape of the cathode electrode 11a and the anode electrode 11b are not particularly limited. Examples of materials for the cathode electrode 11a and the anode electrode 11b include carbon and metals (gold, platinum, silver, palladium, gallium, stainless steel, copper, etc.) that are widely used as electrode materials in the field of electrochemistry. Examples of shapes for the cathode electrode 11a and the anode electrode 11b include a flat plate, a rod, a mesh, or an electrode substrate formed by coating a conductive substrate with metal particles. The cathode electrode 11a and the anode electrode 11b are preferably provided on or near the surface of the hydrogen ion exchange membrane 12. When providing the electrodes on or near the surface of the hydrogen ion exchange membrane 12, they are preferably shaped so as not to impede mass transfer to the hydrogen ion exchange membrane 12. Therefore, the shapes of the cathode electrode 11a and the anode electrode 11b in this embodiment include, for example, a mesh or a thin rod such as a wire. Another example of the cathode electrode 11a and the anode electrode 11b is one in which an electrode pattern is formed directly on the surface of the hydrogen ion exchange membrane 12 by a technique such as plating. In this case, the shape of the electrode pattern is not particularly limited, but it is preferable that the shape does not hinder the mass transfer to the hydrogen ion exchange membrane 12.

[0028] The hydrogen ion exchange membrane 12 is a membrane that is selectively permeable to hydrogen ions. In this embodiment, the hydrogen ion exchange membrane 12 may be any membrane capable of transmitting hydrogen ions but not carbonate ions. The specific components and structure of the membrane are not particularly limited, and known membranes can be used. For example, a perfluorocarbon material may be used, which is composed of a hydrophobic Teflon skeleton composed of carbon and fluorine and perfluoro side chains with sulfonic acid groups. Depending on the conditions for the carbonate ion concentration process, such as when it is clear that the monovalent cations contained in the raw water S0 are only hydrogen ions, the hydrogen ion exchange membrane 12 may be one that has been treated to selectively transmit monovalent cations (a so-called monovalent ion selective membrane) or a cation exchange membrane containing divalent cations. In this case, the specific components and structure of the monovalent ion selective membrane or cation exchange membrane are not particularly limited, and known membranes can be used.

[0029] The carbonate ion concentrating device 1A concentrates carbonate ions by selectively allowing hydrogen ions from a first liquid (carbonated water) obtained by dissolving carbon dioxide in raw water S0 to permeate through a hydrogen ion exchange membrane 12. More specifically, the carbonate ion concentrating device 1A introduces carbon dioxide (carbon dioxide-containing gas) into a first chamber 13a to which raw water S0 is supplied, and selectively allows hydrogen ions generated in the first chamber 13a to permeate through the hydrogen ion exchange membrane 12, thereby increasing the concentration of carbonate ions in the first liquid.

[0030] The process of concentrating carbonate ions in the carbonate ion concentrating apparatus 1A of this embodiment will be described with reference to FIGS. FIG. 2 is a schematic explanatory diagram showing the carbonate ion concentrating process in the carbonate ion concentrating apparatus 1A of this embodiment. FIG. 2 shows the state from the initial state of the carbonate ion concentrating process until the start of short-circuiting. The configuration inside the treatment tank 10 in FIG. 2 is the same as the configuration shown in FIG. 1, and seawater is introduced as raw water S0 into both the first chamber 13a and the second chamber 13b. Carbon dioxide (carbon dioxide-containing gas) is introduced into the first chamber 13a via line L2 (not shown), and the water is in a state in which carbon dioxide is sufficiently dissolved (carbonated water). Note that the numbers of each substance shown in the figure do not accurately indicate the quantitative ratios.

[0031] As shown in FIG. 2, the first chamber 13a is filled with a first liquid containing carbon dioxide, and the first liquid contains carbon dioxide (H2CO3) and hydrogen ions (H + ), bicarbonate ion (HCO3 - ) and calcium ions (Ca 2+ ) and magnesium ions (not shown). The pH of the first liquid is around 5 due to the inclusion of carbon dioxide. Figure 6 shows the pH of seawater and the abundance ratio of carbonate ions. At a pH of around 5, the carbonate ions (CO3 2- ) is almost completely absent.

[0032] The change in pH of the first liquid is shown in Figure 7, and the state shown in Figure 2 is [1] in the graph of Figure 7. The second liquid (seawater) introduced into the second chamber 13b has a pH of about 8.

[0033] FIG. 3 is a schematic explanatory diagram showing the carbonate ion concentrating process in the carbonate ion concentrating device 1A of this embodiment, showing the state from the initial stage of short circuit until the substances in the first and second liquids reach concentration equilibrium. Due to the gradient of hydrogen ion concentration between the first and second liquids, hydrogen ions (H + ) permeates from the first liquid through the hydrogen ion exchange membrane 12 into the second liquid.

[0034] In addition, hydrogen ions (H +) permeates through the first and second liquids, causing a potential difference between the first and second liquids, and electrons flow from the cathode electrode 11a toward the anode electrode 11b. Then, hydrogen ions (H + ) reacts with electrons to generate hydrogen. This reaction reduces the hydrogen ion concentration in the second liquid, facilitating the permeation of hydrogen ions from the first liquid.

[0035] As shown in Figure 7, the pH of the first liquid rises to about 6 due to a decrease in the hydrogen ion concentration, and the pH of the second liquid falls to about 6 due to an increase in the hydrogen ion concentration (see [2] in the graph in Figure 7). In this state, the substances reach concentration equilibrium, and the movement of substances is restricted. Furthermore, referring to Figure 6, the first and second liquids mainly contain carbonic acid (H2CO3) and bicarbonate ions (HCO3 - ) and carbonate ions (CO3 2- ) is almost completely absent.

[0036] FIG. 4 is a schematic explanatory diagram showing the carbonate ion concentrating process in the carbonate ion concentrating device 1A of this embodiment, and shows the state from when the substances in the first liquid and the second liquid reach concentration equilibrium to when the carbon dioxide concentration in each solution reaches equilibrium with the atmosphere. As shown in Figure 4, the first and second liquids, whose movement of substances is restricted, release carbon dioxide into the atmosphere, causing the pH of the first and second liquids to gradually increase (see [3] in the graph in Figure 7).

[0037] FIG. 5 is a schematic explanatory diagram showing the carbonate ion concentrating step in the carbonate ion concentrating device 1A of this embodiment, and shows a state in which the carbonate ions in the first solution are fixed as carbonate salts after the carbon dioxide concentrations in the first solution and the second solution have reached equilibrium with the atmosphere. After the carbon dioxide is released, the solution reaches equilibrium with the atmosphere, and the pH of the first and second solutions rises to 8, the same level as the original seawater (see [4] in the graph in Figure 7). When the pH rises to around 8, carbonate ions (CO3 2-) will be present (see Figure 6). Here, because the first liquid contains concentrated carbonate ions, they react with the calcium ions contained in the seawater to form calcium carbonate. This makes it possible to fix carbon dioxide as calcium carbonate. In addition, the second liquid simply returns to the same concentration of carbonate ions as seawater, and almost no calcium carbonate is formed.

[0038] As described above, the carbonate ion concentrating device 1A of this embodiment can fix gaseous carbon dioxide as carbonates such as calcium carbonate with almost no energy consumption by going through the processes shown in FIGS. 2 to 5.

[0039] [Second embodiment] Fig. 8 is a schematic explanatory diagram showing an apparatus 1B for concentrating carbonate ions in a second embodiment of the present invention. Fig. 8 shows an apparatus provided with a dissolution tank 30 as a means for dissolving carbon dioxide in raw water S0 in the first embodiment.

[0040] As shown in FIG. 8, the carbonate ion concentrating apparatus 1B in this embodiment is configured such that a line L2 for introducing carbon dioxide (carbon dioxide-containing gas) is connected to a dissolution tank 30, and carbon dioxide can be dissolved in raw water S0 in advance as a pretreatment for the reaction in the treatment tank 10. Furthermore, by connecting the dissolution tank 30 to the first chamber 13a of the treatment tank 10, the raw water S0 with dissolved carbon dioxide can be converted into carbonated water and used for the reaction in the treatment tank 10. The manner in which the line L2 is connected to the dissolution tank 30 is not particularly limited, and the line L2 may be connected to the space above the dissolution tank 30, or may be configured to generate carbon dioxide bubbles from the bottom end of the dissolution tank 30. The provision of the dissolution tank 30 ensures the dissolution of carbon dioxide and also makes it possible to appropriately prepare uniform carbonated water as a pretreatment for use in the reaction.

[0041] Furthermore, the function and configuration of the dissolution tank 30 are not limited. The dissolution tank 30 may be configured to be pressurizable or depressurizable, or the temperature may be adjustable, so that the solubility of carbon dioxide in the raw water S0 can be adjusted. Furthermore, in addition to dissolving carbon dioxide, pretreatment may be performed to remove substances that are undesirable for the reaction in the treatment tank 10.

[0042] [Third embodiment] FIG. 9 is a schematic explanatory view showing an apparatus 1C for concentrating carbonate ions according to the third embodiment of the present invention. 9, in the apparatus 1C for concentrating carbonate ions of this embodiment, a line L4 is connected to the first chamber 13a so that the treated solution S containing calcium carbonate is discharged to the outside of the system. At the same time, raw water S0 can be appropriately replenished into the first chamber 13a as the treated solution S is discharged. Therefore, it is possible to repeatedly carry out a series of processes for concentrating carbonate ions. In addition, calcium carbonate may be recovered from the treated solution S discharged from the line L4 and used for other purposes.

[0043] [Fourth embodiment] Fig. 10 is a schematic explanatory view showing an apparatus 1D for concentrating carbonate ions in a fourth embodiment of the present invention. As shown in Fig. 10, the apparatus 1D for concentrating carbonate ions in this embodiment recovers hydrogen and carbon dioxide generated in the step of concentrating carbonate ions by connecting a line L5 to the upper part of the second chamber 13b.

[0044] The manner of recovery and utilization of the recovered hydrogen is not limited. For example, the generated hydrogen gas may be transported to a storage facility and stored therein, or may be transported directly to a use point and utilized as an energy source. Furthermore, methane gas may be produced by methanation from hydrogen and carbon dioxide.

[0045] It is also preferable that the cathode electrode 11a and the anode electrode 11b are provided near the hydrogen ion exchange membrane 12. This allows the hydrogen ions that have permeated the hydrogen ion exchange membrane 12 to be converted into hydrogen more efficiently, thereby improving the hydrogen recovery efficiency.

[0046] Fifth Embodiment FIG. 11 is a schematic explanatory view showing a carbonate ion concentrating apparatus 1E according to the fifth embodiment of the present invention. As shown in FIG. 11, in the carbonate ion concentrating apparatus 1E of this embodiment, raw water S0 is introduced only into the first chamber 13a via a line L1, the second chamber 13b is not provided, and the hydrogen ion exchange membrane and the anode electrode 11c are open to the atmosphere. The gas placed on the anode electrode 11c side is not limited to the air, but may be any gas that does not react with hydrogen and has a specific gravity greater than that of hydrogen.

[0047] The above-described embodiments show examples of the carbonate ion concentrating device and carbonate ion concentrating method. The carbonate ion concentrating device and carbonate ion concentrating method according to the present invention are not limited to the above-described embodiments, and the configurations of the carbonate ion concentrating device and carbonate ion concentrating method according to the above-described embodiments may be interchanged or modified as long as they do not change the gist of the claims.

[0048] For example, in the carbonate ion concentrating device and carbonate ion concentrating method according to the present embodiment, the number of hydrogen ion exchange membranes provided is not limited to one. For example, the number of membranes may be increased to increase the number of compartments corresponding to carbonate ion concentrating tanks, thereby increasing the scale of the carbonate ion concentrating process. Furthermore, hydrogen ion exchange membranes, cathode electrodes, and anode electrodes may be installed in the ocean, and carbonate ions may be concentrated in the ocean.

[0049] In the carbonate ion concentrating apparatus of this embodiment, the electrodes are not limited to being disposed at both ends of the hydrogen ion exchange membrane in the treatment tank. For example, they may be disposed at a certain distance from the hydrogen ion exchange membrane. Furthermore, a plurality of electrodes may be provided, and they may be evenly disposed so that the reaction occurs uniformly throughout the treatment tank. [Industrial Applicability]

[0050] The carbonate ion concentrating device and carbonate ion concentrating method of the present invention can concentrate carbonate ions with low energy, and therefore can be suitably used in a large-scale carbon dioxide fixation system. [Explanation of symbols]

[0051] 1A, 1B, 1C, 1D carbonate ion concentrator, 10 treatment tank, 11a cathode electrode, 11b, 11c anode electrode, 12 hydrogen ion exchange membrane, 13a first chamber, 13b second chamber, 30 dissolution tank, L1 to L5 lines, S0 raw water, S treated solution

Claims

1. a hydrogen ion exchange membrane that selectively allows hydrogen ions to pass through; a cathode electrode and an anode electrode disposed on either side of the hydrogen ion exchange membrane; a first solution containing carbon dioxide and disposed on the cathode electrode side; An apparatus for concentrating carbonate ions and / or bicarbonate ions, characterized in that the cathode electrode and the anode electrode are short-circuited, and carbonate ions are fixed as carbonate salts in the first solution.

2. The apparatus for concentrating carbonate ions and / or bicarbonate ions according to claim 1 , wherein the first solution is open to the atmosphere.

3. 3. The apparatus for concentrating carbonate ions and / or bicarbonate ions according to claim 1, wherein the first solution is seawater.

4. disposing a cathode electrode and an anode electrode with a hydrogen ion exchange membrane between them; Placing a first solution containing carbon dioxide on the cathode electrode side; a step of short-circuiting the cathode electrode and the anode electrode and fixing carbonate ions as carbonate salts in the first solution.

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