Water electrolysis apparatus and method capable of removing suspended substances and producing fresh water using nanoelectrokinetic ion concentration polarization phenomenon

Abstract

To provide a method of removing suspended substances from saltwater by utilizing ion concentration polarization phenomenon, desalinating the saltwater simultaneously, minimizing contamination of a water electrolysis apparatus, and increasing energy efficiency.SOLUTION: An apparatus for desalinating saltwater and transporting hydrogen ions using ion concentration polarization phenomenon, comprising: a channel part including a channel into which saltwater is introduced, an ion-selective membrane connected to the channel, and a cathode part and an anode part capable of applying a voltage to both ends of the channel; a fresh water production part configured to obtain fresh water from the saltwater with ionic substances removed by ion concentration polarization phenomenon in a first region adjacent to the anode part of the ion-selective membrane; and a hydrogen gas production part in which the ionic substances are concentrated in a second region adjacent to the cathode part of the ion-selective membrane, and hydrogen ions (H+) contained in the ionic substances are reduced.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The technical idea of the present invention relates to a water electrolysis device and method capable of removing suspended matter and producing fresh water by using ion concentration polarization (ICP) in a water electrolysis device.

[0002] [Statement Regarding Support Research or Support Development] The present invention has received funding from the Ministry of Science and ICT (MSIT) and support from the National Research Foundation of Korea (NRF) under Project Specific Number 1711200490 and Project Number RS-2023-00302600.

Background Art

[0003] The shortage of clean water and the shortage of energy are the most important survival issues faced by humanity. Since energy is required for the supply of clean water and clean water is required for the production of energy, the two are closely related to each other. For carbon neutrality and the sustainable development of humanity, it is essential to understand such a linkage called the "water-energy nexus" and to have technologies that can efficiently utilize resources.

[0004] Among the desalination processes for producing clean water, evaporation and reverse osmosis currently dominate the market. However, due to their high fossil fuel consumption and plant construction costs, electromembrane desalination technology using ion exchange membranes is being actively researched as an alternative. However, this method is still energy-intensive. Among hydrogen gas production technologies that obtain energy from water, electrolysis is the most suitable method from the perspective of mass production and economic efficiency. Similar ion exchange membrane-based technologies are being widely researched, but their efficiency decreases when using highly saline water, such as seawater. In particular, naturally obtained water, such as seawater and brackish water, contains various impurities, microorganisms, and small suspended particles. If water is used as is, these impurities can adhere to the electrolysis membrane and electrodes, reducing the efficiency and shortening the lifespan of the water electrolysis device.

[0005] In addition, the ion exchange membrane, which is the core of the water electrolysis device, + However, when other salt ions are present in high concentrations in seawater, the selective permeability of the ion exchange membrane decreases, resulting in a decrease in current efficiency. For this reason, it is technically challenging to directly use seawater as influent in a water electrolysis device. Therefore, desalinated water, purified pure water, or an acidic aqueous solution used as a proton source is typically used, and in order to use seawater or brackish water, it is necessary to purify the seawater through a pretreatment system before using it. Summary of the Invention [Problem to be solved by the invention]

[0006] The technical problem to be achieved by the technical concept of the present invention is to provide a method for removing suspended solids from saltwater and desalination using ion concentration polarization, while minimizing contamination of a water electrolysis device and increasing energy efficiency, but this is merely an example and the technical concept of the present invention is not limited thereto. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a device for desalination of salt water and hydrogen ion transport using the ion concentration polarization (ICP) phenomenon.

[0008] The device includes a channel into which salt water is injected, an ion-selective membrane connected to the channel, and a cathode part and an anode part to which a voltage can be applied to both ends of the channel, a channel part; a fresh water generation part in which fresh water from which ionic substances have been removed from the salt water is obtained by the ion concentration polarization phenomenon in a first region adjacent to the anode part of the ion-selective membrane; a hydrogen gas production part in which the ionic substances are concentrated in a second region adjacent to the cathode part of the ion-selective membrane and hydrogen ions (H + ) contained in the ionic substances are reduced; and may include.

[0009] According to one embodiment, the first region may include an ion depletion zone, and the second region may include an ion enrichment zone.

[0010] According to one embodiment, the channel may include a first microchannel coupled to one side of the anode part and a second microchannel coupled to one side of the cathode part and connected to a ground voltage.

[0011] According to one embodiment, the ionic substance includes hydrogen ions (H + ) and may further include at least one of sodium ions (Na+), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ), and combinations thereof.

[0012] According to one embodiment, the ion-selective membrane may be a cation exchange membrane.

[0013] According to one embodiment, the potential applied to the first microchannel may be 100 mV to 300 V.

[0014] According to one embodiment, the first microchannel may include: a first injection channel having an inlet for injecting the brine at one end; a first discharge channel from which fresh water is discharged and a second discharge channel from which the remaining brine is discharged, which branch from the other end of the first injection channel.

[0015] According to one embodiment, the second microchannel may include a third discharge channel from which concentrated brine containing the ionic substance transmitted from the first microchannel is discharged.

[0016] According to another aspect of the present invention, there is provided a method for desalinating brine and transporting hydrogen ions using the ion concentration polarization (ICP) phenomenon.

[0017] The method includes: (a) preparing a device including a channel part including a channel into which salt water is injected, an ion-selective membrane connected to the channel, and a cathode part and an anode part to which a voltage can be applied to both ends of the channel; a fresh water generation part in a first region adjacent to the anode part of the ion-selective membrane, where fresh water from which an ionic substance is removed from the salt water by the ion concentration polarization phenomenon is obtained; and a hydrogen gas production part in a second region adjacent to the cathode part of the ion-selective membrane, where the ionic substance is concentrated and hydrogen ions contained in the ionic substance are reduced; (b) supplying salt water to the first region; and (c) between the anode part located in the first region and the cathode part located in the second region, a coefficient (X) calculated based on the following formula 1 is 0.05 to 5 mA / (cm 2Applying a current to reach (·mM) to transport hydrogen ions in the first region to the second region, and (d) obtaining fresh water with impurities removed in the first region while collecting hydrogen gas in the second region can be included.

[0018] [Formula 1] X = I / AC (where I: current (mA), A: area of the ion exchange membrane (cm 2 ), C: concentration of the brine (mM))

[0019] In one embodiment, the step (c) can be characterized in that a current is applied such that the coefficient (X) is 0.2 - 2 mA / (cm 2 ·mM).

[0020] In one embodiment, the step (c) can be characterized in that a current is applied such that the coefficient (X) is 0.5 - 1 mA / (cm 2 ·mM).

[0021] In one embodiment, the first region can include an ion depletion zone, and the second region can include an ion enrichment zone.

[0022] In one embodiment, the ion exchange membrane may be a cation exchange membrane.

[0023] In one embodiment, it can be characterized that the higher the current, the lower the pH of the second region.

[0024] In one embodiment, the step (c) may be a step of actively controlling the magnitude of the applied current based on the concentration of the brine and the concentration of the fresh water (C desalted ) obtained in the step (d).

[0025] In one embodiment, the step (b) may be a step of actively controlling the supply flow rate of the brine based on the concentration of the brine and the concentration (C desalted ) of the fresh water obtained in the step (d).

Advantages of the Invention

[0026] According to one embodiment of the present invention made as described above, it is possible to simultaneously produce fresh water and hydrogen gas, minimize the contamination of the electrodes and the ion exchange membrane generated in the ion transport process through the ion exchange membrane, increase the current efficiency and improve the hydrogen gas generation efficiency, thereby contributing to improving the performance, durability and long-term stability of the water electrolysis device.

[0027] The effects of the present invention described above are described exemplarily, and the scope of the present invention is not limited by such effects.

Brief Description of the Drawings

[0028]

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Figure 7A

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Figure 8C

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Figure 10B

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Figure 13

Best Mode for Carrying Out the Invention

[0029] Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more fully explain the present invention to those with ordinary knowledge in the relevant technical field. The following embodiments can be modified into various other forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to further enrich and complete the present disclosure and to fully convey the idea of the present invention to those skilled in the art. Also, in the drawings, the thickness and size of each layer are exaggerated for convenience of explanation and clarity.

[0030] FIG. 1 is a diagram for explaining a system for simultaneous production of hydrogen and fresh water through electrohydrodynamic ion transport according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a method for desalination of salt water and hydrogen ion transport using the ion concentration polarization (ICP) phenomenon according to an embodiment of the present invention.

[0031] Referring to FIGS. 1 and 2, a system 1 in which a method for desalination of salt water and hydrogen ion transport is realized can include a channel section 10, a hydrogen gas production section 20, and a fresh water production section 30.

[0032] The channel section 10 is a passage through which salt water flows. An ion exchange membrane is provided between the channel sections 10 to induce the ion concentration polarization (ICP) phenomenon. When an electric current flows through the channel section 10, an ion concentration polarization phenomenon occurs in the vicinity adjacent to the ion exchange membrane, whereby particles are separated and flow out from the salt water. At the same time, hydrogen ions are transported and reduced in the hydrogen gas production section 20, and desalination is performed in the fresh water production section 30 to obtain fresh water.

[0033] In the field of desalination technology, it is expected that the higher the salt ions pass through the ion-selective permeable membrane, the better the desalination efficiency. However, in the case of electrolytic hydrogen production, the hydrogen production efficiency will not be good unless a large amount of hydrogen ions pass through. Therefore, the present invention aims to provide an apparatus capable of desalination while hydrogen ions pass through the ion-selective permeable membrane and at the same time utilizing the ion depletion region around the membrane.

[0034] FIG. 3 is a diagram for explaining the channel portion of FIG. 1 in more detail. Referring to FIG. 3, the channel portion 10 can include a microchannel 11, an ion-selective permeable membrane 12, an anode portion 13, and a cathode portion 14.

[0035] The microchannel 11 may be configured in the form of a tube or a pipe with a diameter on the μm scale. Salt water is injected into and transferred through the microchannel 11. In one embodiment, the microchannel 11 can have a shape that extends long in one direction so that the salt water has a structure that is easy to move along the path.

[0036] Salt water (salt water) means various solutions containing sodium ions (Na + ) and chloride ions (Cl - ), and can include, for example, seawater, brine, treated sewage effluent, or salt-concentrated wastewater.

[0037] The ion-selective permeable membrane 12 can selectively allow only specific ionic substances to pass through and can be connected to the microchannel 11 at one or more contact points. The ion-selective permeable membrane 12 is preferably a cation-permeable membrane that can allow hydrogen ions to pass through. The ion-selective permeable membrane 12 may be a material containing Nafion, which is a porous nanomaterial.

[0038] The anode part 13 and the cathode part 14 can be formed at one end and the other end of the microchannel 11 respectively. When an electric field is applied to the anode part 13 and the cathode part 14 across the ion-selective permeable membrane 12, ions with the same polarity as the ion-selective permeable membrane 12 cannot pass through the membrane, and only ions with the opposite polarity can pass through the ion-selective permeable membrane 12. As a result, the electrolyte concentration rapidly decreases at both ends of the membrane to form an ion depletion region P and increases to form an ion excess region Q, which is called the ion concentration polarization phenomenon.

[0039] Figure 3 shows the ion concentration polarization phenomenon when the ion-selective permeable membrane 12 is a cation-selective permeable membrane. The cation-selective permeable membrane selectively allows cations to pass through and blocks anions.

[0040] Taking Figure 3 as an example, the cation-selective permeable membrane selectively allows cations such as hydrogen ions (H + ) and sodium ions (Na + ), which are alkali metal ions, to pass through, but chloride ions (Cl - ), which correspond to anions, cannot pass through the cation-selective permeable membrane.

[0041] As a result, ionic substances including hydrogen ions, sodium ions, etc. transmitted through the ion-selective permeable membrane 12 are concentrated in the ion excess region Q, and an ion depletion region P is formed at the interface of the ion-selective permeable membrane 12 in the direction of the anode part 13.

[0042] Between the ions that cannot pass through the ion-selective permeable membrane 12, a strong electrical repulsive force acts, affecting both cations and anions, thereby causing the ion concentration gradient phenomenon to appear. At this time, vortices are formed around the interface of the ion depletion region P, and charged particles, cells, droplets, etc. are also affected by the electrical repulsive force of the ions at the interface of the ion depletion region P and are pushed out around the ion-selective permeable membrane 12.

[0043] A fresh water generation unit 30 may be provided in a first region including an ion depletion region P, from which fresh water with ionic substances removed can be obtained. A hydrogen gas production unit 20 may be provided in a second region including an ion excess region Q, where the ionic substances are concentrated and hydrogen ions contained in the ionic substances can be reduced.

[0044] As the ionic substances concentrated in the ion excess region Q, in addition to hydrogen ions, it may further include at least any one of sodium ions (Na + ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ) and combinations thereof. However, since sodium ions (Na + ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ) etc. have a much more negative reduction potential than hydrogen ions, in the hydrogen gas production unit 20, hydrogen ions can be more easily reduced compared to other cations.

[0045] Thus, the desalination and hydrogen ion transport device 1 for brine according to the present invention can utilize such an ion concentration polarization phenomenon to extract fresh water from the ion depletion region P generated around the membrane in the direction of the oxidation electrode, and at the same time provide a platform for producing hydrogen at the reduction electrode.

[0046] FIG. 4 is a schematic diagram showing a desalination and hydrogen ion transport device for brine according to an embodiment of the present invention.

[0047] Referring to FIG. 4, the microchannel 11 may have a structure in which a first microchannel 111 and a second microchannel 113 are arranged in parallel.

[0048] The first microchannel 111 may include a first injection channel 1112 having an inlet for injecting brine at one end, a first discharge channel 1114 from which fresh water is discharged and a second discharge channel 1116 from which the remaining brine is discharged, which branch from the other end of the first injection channel 1112.

[0049] An ion-selective permeable membrane 12 can be interposed between the first microchannel 111 and the second microchannel 113. Specifically, the first microchannel 111 can be disposed in contact with one side of the ion-selective permeable membrane 12, and the second microchannel 113 can be disposed in contact with the other side of the ion-selective permeable membrane 12.

[0050] The second microchannel 113 can include a third discharge channel 1133 through which the brine (or the concentrated substance) containing the ionic substance transmitted from the first microchannel 111 is discharged.

[0051] When an electric field is applied, an ion concentration polarization (ICP) phenomenon occurs near the point where the first discharge channel 1114 and the second discharge channel 1116 branch, thereby forming an ion depletion region P, and an ion excess region Q can be formed in a region of the second microchannel portion 113 facing the ion depletion region P.

[0052] At this time, hydrogen ions are transported from the first microchannel 111 to the second microchannel 113, a part of which is discharged through the third discharge channel 1133, and the remaining part can be reduced and converted into hydrogen gas.

[0053] FIG. 5 is a diagram for explaining the desalination of brine and the electrohydrodynamic ion transport in the apparatus for desalination of brine and hydrogen ion transport according to an embodiment of the present invention.

[0054] The first microchannel 111 can be injected with brine [for example, seawater B] through the first injection channel 1112, and fresh water F from which salt has been removed can be discharged through the first discharge channel 1114. The remaining brine substance B' can be discharged through the second discharge channel 1116. The first microchannel 111 can be coupled to the anode portion 13. The first discharge channel 1114 and the second discharge channel 1116 can be physically separated and partitioned by a branching portion 170 such as a channel wall.

[0055] The second microchannel 113 has brine [for example, seawater B] injected therethrough the second injection channel 1131, and an ionic substance is additionally transmitted from the first microchannel 111, and the concentrated brine T can be discharged through the third discharge channel 1133.

[0056] The second microchannel 113 is coupled to one side of the cathode portion 14 and can be connected to the ground voltage through the cathode portion 14. When an electric field is applied between the anode portion 13 and the cathode portion 14, an ion concentration polarization (ICP) phenomenon occurs, thereby forming an ion depletion region P and an ion excess region Q.

[0057] At this time, the applied potential is preferably 100 mV to 300 V. The size of the ion depletion region P can vary according to the potential difference. As an example, when the voltage V applied to the anode portion 13 anodic becomes small, the amount of cations transported from the first microchannel 111 to the second microchannel 113 through the ion selective permeable membrane 12 decreases, and the generation of the ion depletion region becomes weak, so the fresh water production efficiency may decrease.

[0058] Conversely, when the voltage V applied to the anode portion 13 anodic becomes large, the cations tend to move in the direction of the ion selective permeable membrane 12, and the amount of cations transported from the first microchannel 111 to the second microchannel 113 increases, but the power consumption increases, and the efficiency of the water electrolysis device may decrease. Therefore, the range of the voltage V applied to the anode portion 13 anodic is preferably 100 mV to 300 V.

[0059] FIG. 6 is a diagram exemplarily realizing a three-dimensional water electrolysis device having the systems of FIGS. 1 and 2.

[0060] Referring to FIG. 6, inside the housing 102, a first region 104 and a second region 106 separated by an ion exchange membrane 108 are provided. A salt water supply stream 110 is supplied inside the housing 102, the anode part 105 is disposed in the first region 104, and the cathode part 107 is disposed in the second region 106. The first region 104 can correspond to the fresh water generation part 30, and the second region 106 can correspond to the hydrogen gas production part 20.

[0061] At this time, the housing 102 and pipes, tubes, etc. connected to the housing 102 can be macro channels on the scale of mm, cm or more in diameter. Devices based on micro channels can exhibit high desalination and hydrogen gas production efficiency on a small scale, but may have limitations in expanding to an industrial scale. Therefore, it is preferable to form with macro channels that are advantageous for large-scale processing. However, the channel part 10 according to the present invention is not limited in size and can include both micro channels and macro channels.

[0062] Salt water means various solutions containing sodium ions (Na + ) and chloride ions (Cl - ), and may be, for example, a substance having a salt concentration of 0.1 to 35 g / L. Typically, it may be seawater.

[0063] The ion exchange membrane 108 is preferably a cation permeable membrane that selectively allows only specific ionic substances to pass through and allows hydrogen ions to pass through. The ion exchange membrane 108 may be a material containing Nafion.

[0064] Various suspended substances exist in the salt water supplied to the first region 104, and such suspended substances must be removed during the desalination process. The suspended substances in the salt water can include particulate substances, organic substances, inorganic substances, etc., and can be separated and removed into the suspended substance discharge stream 320 by ion concentration polarization when an electric current is applied.

[0065] Suspended matter in the brine is discharged through the suspended matter discharge stream 320, and by the salt ions moving along the ion exchange membrane 108 into the second region 106, a fresh water discharge stream 310 can be formed. The salt ions can include at least any one of sodium ions (Na + ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ), potassium ions (K + ), lithium ions (Li + ) and combinations thereof.

[0066] On the other hand, on the second region 106 side as well, in order to impart a certain electrical conductivity similar to that of the first region 104, it is preferable to use an electrolyte. Therefore, an electrolyte supply stream 220 can be injected into the second region 106. When sodium ions, hydrogen ions, etc. are transported from the first region 104 through the ion exchange membrane 108 into the second region 106, the amount of the transported ions can be measured by ion chromatography or the like. At this time, an electrolyte such as LiCl or KCl can play the role of a reference substance.

[0067] The hydrogen ions that have moved into the second region 106 can then be reduced to form a hydrogen gas discharge stream 210.

[0068] The method for desalinating brine and transporting hydrogen ions according to an embodiment of the present invention will be described as follows with reference to the apparatus in FIG. 6.

[0069] First, the ion exchange membrane 108 is disposed within the housing 102, dividing the housing 102 into a first region 104 and a second region 106.

[0070] Next, brine is supplied to the first region 104 and the second region 106. In an embodiment of the present invention, it is preferable to supply brine having a salt concentration in the range of 0.1 to 35 g / L. Since the average salt concentration of seawater is generally about 35 g / L, according to the embodiment of the present invention, it can be used in a water electrolysis device without pretreating seawater or adjusting the concentration through a separate circulation system.

[0071] The concentration of the brine, i.e., the salt concentration, can affect the hydrogen generation reaction (reduction of H + ) occurring in the cathode part 107. Since the brine contains electrolytes such as NaCl, the higher the salt concentration, the better the current can be transmitted. However, if the salt concentration is too high, the salt ions present in the brine may inhibit the mobility of hydrogen ions and may contaminate the ion exchange membrane in the water electrolysis device.

[0072] Conversely, if the salt concentration is too low, the electrical conductivity decreases and the current density decreases, which may reduce the rate at which hydrogen ions move to the electrode and the rate of the electrochemical reaction required for the generation of hydrogen gas.

[0073] Therefore, it is important to balance the ion movement and the current density at an appropriate concentration in the range of 1 to 35 g / L. When the concentration of the brine is appropriate, it is possible to optimize the electrical conductivity and efficiently transmit the current while reducing the contamination of the electrodes and the ion exchange membrane.

[0074] Thereafter, the anode part 105 and the cathode part 107 are connected to the first region 104 and the second region 106, respectively, and a current is applied between the anode part 105 and the cathode part 107 so that hydrogen ions are transported from the first region 104 to the second region 106.

[0075] The current, which is an electrical property that affects the production of fresh water and the transport of hydrogen ions according to an embodiment of the present invention, is one of the most important factors determining the water electrolysis efficiency and performance.

[0076] Unlike two-dimensional water electrolysis devices that rely on planar designs, three-dimensional water electrolysis devices have a three-dimensional fluid flow and complex flow structures in various directions. Therefore, it is preferable to apply a current above a certain level for efficient ion transport. Here, the current plays a role in moving ions under an electric field at a given voltage. The greater the current, the more charge (i.e., the amount of ion transport through the ion exchange membrane) moves per hour.

[0077] The current in the water electrolysis process can vary depending on factors such as the area of the ion exchange membrane, the concentration of the brine, the distance between the electrodes, the flow rate, and the flow velocity. In particular, the current depends greatly on the area of the ion exchange membrane and the concentration of the brine.

[0078] When the area of the ion exchange membrane increases, even if the same current is applied, the current density per unit area decreases, which may lead to a decrease in the reaction rate. Therefore, the larger the area, the greater the current needs to be applied to maintain an appropriate current density. Also, with a larger area, more ions can pass through, so only by applying a larger current can sufficient ion movement be maintained.

[0079] On the other hand, when the concentration of the brine increases, the concentration of salt ions increases, so a current that can process more ions can be applied. It is necessary to appropriately adjust the current density to find the optimal current value at which the reaction occurs efficiently without burdening the ion exchange membrane and the electrodes.

[0080] Therefore, it is important to appropriately select the combination of the concentration of the brine, the area of the ion exchange membrane, and the current. In the examples of the present invention, a current in the range where the coefficient (X) calculated based on the following formula 1 is 0.05 - 5 mA / (cm 2 ·mM), preferably 0.2 - 2 mA / (cm 2 ·mM), more preferably 0.5 - 1 mA / (cm 2 ·mM) is applied.

[0081] [Formula 1] X = I / AC (Here, I: current (mA), A: area of the ion exchange membrane (cm 2 ), C: concentration of brine (mM))

[0082] When the coefficient (X) is lower than 0.05, polyvalent cations such as Ca 2+ , Mg 2+ in the brine may form hydroxides or carbonates and deposit on the surface of the ion exchange membrane or the electrode. For example, precipitates such as CaCO3 (calcium carbonate) and Mg(OH)2 (magnesium hydroxide) can induce membrane fouling and electrode corrosion, which may inhibit the hydrogen gas generation efficiency.

[0083] Conversely, when the coefficient (X) is higher than 5, the power consumption increases, which may prevent the efficient operation of the water electrolysis device. For example, when the current becomes excessively high, the resistance of the entire system requires a further higher potential, resulting in an increase in power consumption.

[0084] Therefore, in order to reduce unnecessary power consumption and efficiently maintain the production reactions of fresh water and hydrogen gas, it is important to apply an appropriate current that matches the area of the ion exchange membrane and the concentration of the brine.

[0085] Additionally, in the present invention, it is important to actively control the supply flow rate of the brine based on the concentration of the supplied brine (NaCl) and the concentration of the obtained fresh water. By appropriately controlling the supply flow rate of the brine, the quality and production volume of fresh water can be maintained above a certain level. For example, the salt concentration of fresh water is preferably 500 ppm or less as a general standard for fresh water. Therefore, when the salt concentration of the fresh water obtained in the present invention exceeds 500 ppm, it is preferable to control the concentration of the fresh water not only by changing the current value according to the formula 1 but also by actively controlling the supply flow rate of the brine.

[0086] Hereinafter, the present invention will be described with reference to production examples and examples. However, the scope of the present invention is not limited to such production examples and examples.

[0087] <Production Example 1> As shown in Fig. 7A, two linear microchannels were connected with a Nafion ion exchange membrane, which is a cation-permeable membrane. A 10 mM aqueous potassium chloride (KCl) solution containing a pH indicator and a fluorescent substance, Alexa Fluor, was continuously injected into the two channels with a syringe pump. A reduction electrode was connected to the upper channel, and the lower channel was grounded. Fig. 7B shows an experiment conducted in the same manner except that a hydrochloric acid (HCl) solution was used instead of the potassium chloride (KCl) in Fig. 7A.

[0088] <Production Example 2> A water electrolysis device as shown in Fig. 6 was fabricated, and a Nafion 211 membrane was installed with a size of 1 cm 2 Two platinum wire electrodes were positioned at an 8-mm interval with such a Nafion membrane sandwiched therebetween. 20 mM NaCl was injected into the chamber where the oxidation electrode was located at a rate of 0.2 mL / min using a syringe pump, and 20 mM LiCl was injected into the chamber where the reduction electrode was located at a rate of 0.2 mL / min using a syringe pump. A DC power supply equipped with a voltmeter and an ammeter was used to supply direct current.

[0089] <Example 1> Figs. 7 to 10 show the experimental results of confirming whether hydrogen and fresh water were simultaneously produced according to Production Example 1 of the present invention.

[0090] In Figs. 7A and 7B, it was observed that the cations contained in the solution moved from the lower channel to the upper channel where the reduction electrode was located, and the color of the pH indicator near the ion excess region (IEZ) around the Nafion membrane in the upper channel changed to red. Through this, it was commonly confirmed that hydrogen ions had moved through the Nafion membrane.

[0091] In Fig. 7A, the color of the pH indicator changed to blue in the lower channel to which the oxidation electrode was connected, which means that after hydrogen ions passed from the lower channel to the upper channel, the remaining hydroxide ions (OH -) is a change due to this, which can also serve as evidence of the movement of hydrogen ions through the Nafion membrane.

[0092] In contrast, in Fig. 7(b), no change in the color of the pH indicator could be observed in the lower channel to which the oxidation electrode was connected. This is judged to be because, instead of potassium chloride (KCl), which is a neutral salt, a hydrochloric acid (HCl) solution, which is acidic, was used, so that although hydrogen ions moved, the brine did not become basic.

[0093] Thus, it was demonstrated that acidic brine for hydrogen production is generated in the ion-excess region (IEZ) around the cation exchange membrane, and fresh water is produced in the ion-depletion region (IDZ).

[0094] In Fig. 8A, acidification of the solution (red change by the pH indicator) was observed due to the movement of hydrogen ions toward the reduction electrode. In Fig. 8B, after the movement of hydrogen ions, basification of the solution in the channel on the oxidation electrode side (blue change by the pH indicator) was confirmed. And in Fig. 8C, the ion-depletion region (black region where fluorescence does not appear) was confirmed.

[0095] That is, simultaneously with the movement of hydrogen ions, an ion-depletion region (IDZ) where the fluorescence signal disappeared near the Nafion membrane was confirmed in the lower channel on the oxidation electrode side (Fig. 8(c)), and fresh water can be extracted from this part.

[0096] Summarizing the above results, as shown in Fig. 9, using the ion concentration polarization phenomenon in the microchannel, the generation of fresh water and the generation of gas were simultaneously confirmed.

[0097] In Fig. 9, when a reduction potential of +200 V was applied to the upper channel and ground was applied to the lower channel, bubbles were continuously generated at the reduction electrode (cathode) and flowed to the right together with the fluid flowing in from the left side. Simultaneously with the generation of such gas, an ion depletion region could be confirmed near the cation exchange membrane (nafion). Through this, it was shown that it is possible to implement a system for simultaneous production of fresh water and hydrogen using the electrohydrodynamic ion concentration polarization phenomenon.

[0098] To confirm the components of the bubbles generated at the reduction electrode (cathode), argon (Ar), which is a carrier gas, was injected into the device of Fig. 7, and the discharged gas was collected and analyzed by gas chromatography.

[0099] Fig. 10 shows the results of such gas chromatography analysis. Fig. 10A is a graph comparing the peak of hydrogen (H2) with the peaks of other gases (reference gases), and Fig. 10B is a graph with the peak of hydrogen enlarged.

[0100] In Fig. 10A, it can be seen that hydrogen gas was generated at the reduction electrode from the X region, which is the peak region of hydrogen. Through the generation of such hydrogen gas, it was shown that it is possible to implement a system for producing hydrogen using the nanoelectrohydrodynamic ion concentration polarization phenomenon. For reference, the Y part can be regarded as the baseline that appears when a large amount of argon or air is injected, rather than the peak of a specific substance.

[0101] <Example 2> Fig. 11 is a graph showing the production results of fresh water and hydrogen gas according to the magnitude of the current in the water electrolysis device according to Production Example 2.

[0102] In Fig. 11, it can be seen that when currents of 4 mA, 10 mA, and 20 mA were applied for 1 hour, the amount of hydrogen gas generated (ΔH2) increased as the current value increased.

[0103] In addition, fresh water was generated by ion concentration polarization at all currents. However, when the current was 4 mA, it was found that the concentration of fresh water exceeded 500 ppm (about 8.56 mM) of the salt concentration, which was not preferable. In comparison, when the current values were 10 mA and 20 mA, it was found that the concentration of fresh water (C desalted ) decreased and the quality of fresh water was improved. However, since the concentrations of fresh water at 10 mA and 20 mA were shown to be almost the same, it was found that it was most preferable to apply a current of 20 mA, which was more advantageous for the hydrogen gas generation reaction.

[0104] Through this, it can be seen that it is important to actively control the magnitude of the applied current based on the concentration of salt water (NaCl) and the concentration of fresh water (C desalted ).

[0105] <Example 2> FIG. 12 is a graph showing the competitive transport of hydrogen ions and salt ions through an ion exchange membrane in the water electrolysis apparatus according to Production Example 2.

[0106] In FIG. 12, when 4 mA, 10 mA, and 20 mA were applied under constant current conditions, the ion transport amounts depending on the magnitude of the current were compared. When the total ion transport amount ΔQ was the sum of the transport amount of sodium ions (ΔNa + ), which accounted for the largest ratio among the salt ions present in the salt water, and the transport amount of hydrogen ions (ΔH + ), the ion concentration polarization phenomenon was shown differently depending on the magnitude of the current. When the current was supplied for 1 hour, the transport amount of sodium ions (ΔNa + / ΔQ) among the total ion transport amount passing through the ion exchange membrane was measured and shown in a graph.

[0107] As shown in FIG. 12, at a current of 4 mA, it can be seen that the transport of Na + ions is more dominant than that of H + (ΔNa + >ΔH +) This means that the movement of other cations in the brine is smoother compared to hydrogen ions. Also, the hydrogen ions that can neutralize the OH - ions generated after the production of hydrogen gas at the reduction electrode are transported less through the ion exchange membrane, so the probability that polyvalent cations such as Ca 2+ , Mg 2+ form hydroxides or carbonates and deposit on the surface of the ion exchange membrane or the electrode becomes higher.

[0108] When the current is 10 mA, the electric field becomes stronger and the ion separation phenomenon occurs, so it can be seen that the movement of H + ions is more dominant compared to Na + ions (ΔH + >ΔNa + ). The total ion movement amount (ΔQ) can increase as the current increases. Among the ions passing through the ion exchange membrane, hydrogen ions have a very small size and high mobility, so they can move even faster at the same current. As the current increases, hydrogen ions move even faster, and sodium ions also move, but their speed can be slower compared to hydrogen ions. As a result, the movement amount of hydrogen ions (ΔH + ) increases as the current increases, but the movement amount of sodium ions (ΔNa + ) increases less or hardly at all as the current increases, so the difference in the movement amounts of hydrogen ions and sodium ions can become more prominent as the current increases.

[0109] When the current reaches 20 mA, the movement amount of hydrogen ions (ΔH + ) increases compared to when it is 10 mA, and the movement amount of sodium ions (ΔNa + ) decreases, but the absolute value of the slope of the graph decreases.

[0110] When the current exceeds 20 mA, the resistance of the entire system requires a larger potential, so the power consumption may increase.

[0111] Therefore, in order to improve the amount of hydrogen ion transfer through the ion exchange membrane, prevent contamination of the ion exchange membrane and the electrodes, and reduce unnecessary power consumption, it is most preferable to apply a current value of 10 to 20 mA. In this case, the coefficient (X) calculated based on the above formula 1 corresponds to 0.5 to 1 mA / (cm 2 ·mM).

[0112] <Example 4> Figure 13 is a graph comparing the measured amounts of hydrogen gas generation (ΔH2) and pH changes when the charge amount (Q) was controlled to be the same in the water electrolysis device according to Production Example 2 above.

[0113] Here, the applied charge amount (Q) was controlled to be the same by applying a current of 4 mA for 2.5 hours, a current of 10 mA for 1 hour, a current of 20 mA for 0.5 hour, and a current of 40 mA for 0.25 hour. When using a Pt electrode, the Faradaic efficiency is close to 100%, and it was considered that almost all of the charge amount (Q) flowing through the electrode was used for hydrogen production. At this time, the purpose of controlling the charge amount was to control the amount of hydrogen gas production to be the same so that the consumption amount of H + on the reduction electrode side due to hydrogen production would be the same.

[0114] The concentration of the solution in the chamber where the reduction electrode was located was measured by ion chromatography, and the pH was measured with a pH meter.

[0115] The amount of hydrogen gas generation (ΔH2) shown on the y-axis of Figure 13 is a value obtained by quantitatively measuring the gas collected after the application of the current by gas chromatography. As a result, the amount of hydrogen gas generation showed a tendency to increase slightly as the current increased, but was almost the same.

[0116] Before the application of the current, the initial pH of the solution on the chamber side where the reduction electrode was located was 5.58, but after the production of hydrogen gas, H +Due to the consumption of [[ID=]], the pH became higher than 11 in all experimental examples. However, it can be confirmed that the higher the applied current, the lower the pH gradually becomes, despite almost the same hydrogen gas production amount. This means that the higher the applied current, the more the transport amount of hydrogen ions through the ion exchange membrane increases, and the concentration of OH - generated by the production of hydrogen gas at the reduction electrode decreases.

[0117] Also, when comparing the concentration ([OH - ) of OH in the solution on the y-axis, the concentration of OH - at 4 mA is about three times higher than the concentration of OH - under the condition of 40 mA. The higher the concentration of OH - , the more the production amount of cation precipitates can increase. -

[0118] Also, judging from the fact that the hydrogen gas production amount is almost the same as the current increases, it can be inferred that at currents exceeding 40 mA, the power consumption becomes excessive compared to the hydrogen gas production amount, which is not preferable.

[0119] Summarizing the results in Fig. 13, by increasing the applied current in the water electrolysis device of the present invention, the transport of hydrogen ions through the ion exchange membrane is improved, the supply of protons for hydrogen gas production is improved, and by reducing the increase in pH after hydrogen gas production on the reduction electrode side, the contamination of the electrodes due to the precipitation of other cations in the brine can be prevented, and the durability and stability of the water electrolysis device can be improved. Considering the power consumption, it is preferable to apply a current of 40 mA or less. Through this, the durability and long-term stability of the water electrolysis device can be improved.

[0120] Finally, through the fresh water discharge stream 310 discharged from the first region 104, fresh water with impurities removed is obtained, and at the same time, hydrogen gas is collected through the hydrogen gas discharge stream 210 discharged from the second region 106.

[0121] ​The present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and it will be understood by those having ordinary knowledge in the relevant technical field that various modifications and equivalent other embodiments will be possible hereafter. Therefore, the true technical protection scope of the present invention must be determined by the technical idea of the appended claims.

Claims

1. A device for desalinating salt water and transporting hydrogen ions using the ion concentration polarization (ICP) phenomenon, comprising: a channel into which salt water is injected, an ion-selective membrane connected to the channel, and a cathode part and an anode part to which a voltage can be applied to both ends of the channel, a channel part; a fresh water generation part in a first region adjacent to the anode part of the ion-selective membrane, where fresh water from which ionic substances have been removed from the salt water is obtained by the ion concentration polarization phenomenon; A hydrogen gas production unit in which the ionic substance is concentrated in a second region adjacent to the cathode portion of the ion-selective permeable membrane, and hydrogen ions (H ＋ +) contained in the ionic substance are reduced, and a desalination and hydrogen ion transport device for brine.

2. The device for desalinating salt water and transporting hydrogen ions according to claim 1, wherein the first region includes an ion depletion zone and the second region includes an ion enrichment zone.

3. The channel of the device for desalinating salt water and transporting hydrogen ions according to claim 1 comprises: a first microchannel coupled to one side of the anode part; a second microchannel coupled to one side of the cathode part and connected to a ground voltage.

4. The ionic substances are: Hydrogen ions (H ＋ ) and Sodium ions (Na ＋ ), calcium ions (Ca ２＋ ), magnesium ions (Mg ２＋ ), and the desalination and hydrogen ion transport device for saline water according to claim 1, further comprising at least any one of combinations thereof.

5. The device for desalinating salt water and transporting hydrogen ions according to claim 1, wherein the ion-selective membrane is a Nafion membrane.

6. The potential applied to the first microchannel is 100 mV to 300 V for the device for desalinating salt water and transporting hydrogen ions according to claim 3.

7. The first microchannel of the device for desalinating salt water and transporting hydrogen ions according to claim 3 comprises: a first injection channel having an inlet for injecting the salt water at one end; a first discharge channel through which fresh water is discharged and a second discharge channel through which the remaining salt water is discharged, which branch from the other end of the first injection channel.

8. The second microchannel of the device for desalinating salt water and transporting hydrogen ions according to claim 7 comprises: a third discharge channel through which concentrated salt water containing ionic substances transmitted from the first microchannel is discharged.

9. A method for desalinating salt water and transporting hydrogen ions using the ion concentration polarization (ICP) phenomenon, comprising: Step of preparing a device including: a channel into which salt water is injected, an ion-selective membrane connected to the channel, and a cathode part and an anode part capable of applying a voltage to both ends of the channel, i.e., a channel part; a fresh water generation part where fresh water from which ionic substances are removed by an ion concentration polarization phenomenon is obtained in a first region adjacent to the anode part of the ion-selective membrane; and a hydrogen gas production part where the ionic substances are concentrated and hydrogen ions contained in the ionic substances are reduced in a second region adjacent to the cathode part of the ion-selective membrane. Step of supplying salt water to the first region. (c) A current is applied between the anode portion located in the first region and the cathode portion located in the second region such that the coefficient (X) calculated based on the following formula 1 is 0.05 to 5 mA / (cm ２ ·mM), to transport hydrogen ions in the first region to the second region; A method for desalination of salt water and hydrogen ion transport, including: step of obtaining fresh water from which impurities are removed in the first region and simultaneously collecting hydrogen gas in the second region. 【Number 1】 (Here, I: current (mA), A: area of the ion exchange membrane (cm ２ ), C: concentration of the brine (mM)) Claim 10 The step (c) is The step of applying a current such that the coefficient (X) is 0.2 to 2 mA / (cm ２ ·mM), characterized in that it is the method for desalination of salt water and hydrogen ion transport according to claim 9. Claim 11 The step (c) is The step of applying a current such that the coefficient (X) is 0.5 to 1 mA / (cm ２ ·mM), characterized in that it is the method for desalination of saline water and hydrogen ion transport according to claim 9. Claim 12 The method for desalination of salt water and hydrogen ion transport according to claim 9, wherein the first region includes an ion depletion zone and the second region includes an ion enrichment zone. Claim 13 The method for desalination of salt water and hydrogen ion transport according to claim 9, wherein the ion-selective membrane is a cation exchange membrane. Claim 14 The method for desalination of salt water and hydrogen ion transport according to claim 9, characterized in that the higher the current, the lower the pH of the second region. Claim 15 The step (c) is Based on the concentration of the brine and the concentration (C ｄｅｓａｌｔｅｄ ) of the fresh water obtained in the step (d), the method for desalination of brine and hydrogen ion transport according to claim 9, which actively controls the magnitude of the current to be applied. Claim 16 The step (b) is Based on the concentration of the brine and the concentration (C ｄｅｓａｌｔｅｄ ) of the fresh water obtained in the step (d), the method for desalinating brine and transporting hydrogen ions according to claim 9, which actively controls the supply flow rate of the brine.

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