A water electrolysis apparatus and method capable of removing suspended solids and producing fresh water using nanoelectrohydrodynamic ion concentration polarization phenomena.

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 solids 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 funds from the Ministry of Science and ICT (MSIT) and support from the National Research Foundation of Korea (NRF) under Project Identification 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 interconnected. In order to achieve carbon neutrality and 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] In the desalination process for producing clean water, the evaporation and reverse osmosis methods 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, although this is still energy-intensive. Among hydrogen gas production technologies that obtain energy from water, electrolysis is the most suitable method considering mass production and economic feasibility, and similar technologies using ion exchange membranes are being widely researched. However, 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 solids. If used as is, these impurities can adhere to the water electrolysis membrane and electrodes, reducing the efficiency and shortening the lifespan of the water electrolysis device.

[0005] Furthermore, the ion exchange membrane, which is the core of the water electrolysis device, contains protons (H + Only certain ions must be selectively allowed to pass through, but if other salt ions are present in high concentrations in seawater, the selective permeability of the ion exchange membrane decreases, which can reduce current efficiency. For this reason, using seawater directly as inflow water in a water electrolysis device is technically challenging. Therefore, typically, desalinated water, purified pure water, or acidic aqueous solutions used as a proton source are used, and in order to use seawater or brackish water, it is necessary to purify the seawater through a pretreatment system before use. [Overview of the project] [Problems that the invention aims to solve]

[0006] The technical problem that the present invention aims to solve is to provide a method for removing suspended solids from saltwater and desalinizing it by utilizing the ion concentration polarization phenomenon, while simultaneously minimizing contamination of water electrolysis equipment and improving energy efficiency. However, such problems are illustrative, and the technical concept of the present invention is not limited to them. [Means for solving the problem]

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

[0008] The apparatus includes a channel section comprising a channel into which saltwater is injected, an ion-selective permeable membrane connected to the channel, and a cathode section and an anode section to which a voltage can be applied to both ends of the channel; a freshwater generation section in which freshwater is obtained from which ionic substances have been removed from the saltwater by ion concentration polarization in a first region adjacent to the anode section of the ion-selective permeable membrane; and a second region adjacent to the cathode section of the ion-selective permeable membrane in which the ionic substances are concentrated, and hydrogen ions (H) contained within the ionic substances are extracted. + It may include a hydrogen gas production unit in which ) is reduced;

[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 portion; and a second microchannel coupled to one side of the cathode portion and connected to the ground voltage.

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

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

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

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

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

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

[0017] The method includes the steps of: preparing an apparatus comprising: (a) a channel section including a channel into which salt water is injected, an ion-selective permeable membrane connected to the channel, and a cathode section and an anode section to which a voltage can be applied to both ends of the channel; a freshwater generation section in which freshwater is obtained from which ionic substances have been removed from the salt water by ion concentration polarization in a first region adjacent to the anode section of the ion-selective permeable membrane; and a hydrogen gas production section in which the ionic substances are concentrated in a second region adjacent to the cathode section of the ion-selective permeable membrane and hydrogen ions contained in the ionic substances are reduced; (b) supplying salt water to the first region; and (c) between the anode section located in the first region and the cathode section 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 by applying a current such that the coefficient (X) is 0.2 - 2 mA / (cm 2 ·mM).

[0020] In one embodiment, the step (c) can be characterized by applying a current 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, step (b) is the concentration of the saline solution and the concentration of the fresh water obtained in step (d) (C desalted This may involve actively controlling the supply flow rate of saltwater based on the following: [Effects of the Invention]

[0026] According to one embodiment of the present invention as described above, simultaneous production of fresh water and hydrogen gas is possible, contamination of electrodes and ion exchange membranes generated during the ion transport process via the ion exchange membrane is minimized, and the hydrogen gas generation efficiency is improved by increasing the current efficiency, thereby contributing to improving the performance, durability, and long-term stability of the water electrolysis apparatus.

[0027] The effects of the present invention described above are illustrative and do not limit the scope of the invention. [Brief explanation of the drawing]

[0028] [Figure 1] This figure illustrates a system for the simultaneous production of hydrogen gas and fresh water via electrohydrodynamic ion transport according to an embodiment of the present invention. [Figure 2] This figure illustrates a method for desalination of brine and transport of hydrogen ions using the ion concentration polarization (ICP) phenomenon according to an embodiment of the present invention. [Figure 3] This diagram provides a more detailed explanation of the channel section in Figure 1. [Figure 4] This is a schematic diagram showing a brine desalination and hydrogen ion transport apparatus according to one embodiment of the present invention. [Figure 5] This figure illustrates the desalination of brine and electrohydrodynamic ion transport within a hydrogen ion transport apparatus according to one embodiment of the present invention. [Figure 6] Figure 2 illustrates an exemplary three-dimensional water electrolysis apparatus with the system shown in Figure 2. [Figure 7A] This is the result of confirming whether hydrogen, gas, and fresh water were produced simultaneously according to the examples of the present invention. [Figure 7B] This is the result of confirming whether hydrogen, gas, and fresh water were produced simultaneously according to the examples of the present invention. [Figure 8A] This is a photograph confirming the desalination of brine, the movement of hydrogen ions within a hydrogen ion transport device, and the ion depletion region according to an embodiment of the present invention. [Figure 8B] This is a photograph confirming the desalination of brine, the movement of hydrogen ions within a hydrogen ion transport device, and the ion depletion region according to an embodiment of the present invention. [Figure 8C] This is a photograph confirming the desalination of brine, the movement of hydrogen ions within a hydrogen ion transport device, and the ion depletion region according to an embodiment of the present invention. [Figure 9] This is an example of a saline desalination and hydrogen ion transport device according to an embodiment of the present invention. [Figure 10A] Figure 9 shows the results of gas chromatography analysis of the gas components generated through the apparatus. [Figure 10B] This is the result of analyzing the gas components generated through the apparatus shown in Figure 9 using a gas chromatograph. [Figure 11] Figure 6 is a graph showing the production results of fresh water and hydrogen gas depending on the magnitude of the current when the water electrolysis device is driven. [Figure 12] This graph shows the competitive transport of hydrogen ions and salt ions across an ion exchange membrane in an embodiment of the present invention. [Figure 13] This graph shows the changes in hydrogen gas production and pH change when the charge amount is controlled to the same level under constant current conditions according to an embodiment of the present invention. [Best Mode for Carrying Out the Invention]

[0029] Various embodiments of the present invention will be described in detail below with reference to the attached drawings. These embodiments are provided to further fully illustrate the invention to those ordinary skill in the art, and the embodiments described below can be modified into various other forms; the scope of the invention is not limited to these embodiments. Rather, these embodiments are provided to further enrich and complete this disclosure and to fully convey the idea of ​​the invention to those skilled in the art. Furthermore, the thicknesses and sizes of the layers in the drawings are exaggerated for illustrative purposes and clarity.

[0030] Figure 1 is a diagram illustrating a system for the simultaneous production of hydrogen and freshwater via electrohydrodynamic ion transport according to an embodiment of the present invention. Figure 2 is a diagram illustrating a method for desalination of brine and transporting hydrogen ions using the ion concentration polarization (ICP) phenomenon according to an embodiment of the present invention.

[0031] Referring to Figures 1 and 2, System 1, which realizes the desalination of brine and hydrogen ion transport method, can include a channel section 10, a hydrogen gas production section 20, and a freshwater generation section 30.

[0032] The channel section 10 is a passage through which saltwater flows, and an ion exchange membrane is provided between the channel sections 10 to induce an ion concentration polarization (ICP) phenomenon. When an electric current is passed through the channel section 10, an ion concentration polarization phenomenon occurs near the adjacent ion exchange membrane, causing particles to separate from the saltwater and flow out. At the same time, hydrogen ions are transported and reduced in the hydrogen gas production section 20, and desalting is performed in the freshwater generation section 30, thereby obtaining freshwater.

[0033] In freshwater technology, it is expected that the more salt ions that pass through the ion-selective permeable membrane, the better the freshwater efficiency. However, in the case of electrolytic hydrogen production, the hydrogen gas production efficiency will not improve unless a large amount of hydrogen ions pass through. Therefore, the present invention aims to provide a device that enables desalination by utilizing the ion-depletion region around the membrane while allowing hydrogen ions to pass through the ion-selective permeable membrane.

[0034] Figure 3 is a diagram illustrating the channel portion of Figure 1 in more detail. Referring to Figure 3, the channel portion 10 may 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 pipe with a diameter on the μm scale. Saltwater is injected into and transported through the microchannel 11. In one embodiment, the microchannel 11 may have a shape that extends long in one direction so that the saltwater can easily move along the path.

[0036] Saltwater contains sodium ions (Na + ) and chloride ions (Cl - This refers to various solutions containing ) and may include, for example, seawater, brine, sewage treatment effluent, or saline wastewater.

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

[0038] The anode portion 13 and the cathode portion 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 portion 13 and the cathode portion 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. The membrane is polarized into an ion-depletion region P where the electrolyte concentration decreases rapidly and an ion-excess region Q where it increases rapidly at both ends, a phenomenon called ion concentration polarization.

[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 while blocking anions.

[0040] Taking Figure 3 as an example, the cation-selective permeable membrane allows hydrogen ions (H) to pass through. + ) and alkali metal ions such as sodium ions (Na + It selectively allows cations such as ) to pass through, but chloride ions (Cl - Since ) is an anion, it cannot pass through a cation-selective permeable membrane.

[0041] As a result, ionic substances, including hydrogen ions and sodium ions, that have been transmitted through the ion-selective permeable membrane 12 are concentrated in the ion-rich region Q, and an ion-depleted region P is formed at the interface of the ion-selective permeable membrane 12 in the direction of the anode portion 13.

[0042] Between ions that could not pass through the ion-selective permeable membrane 12, a strong electrical repulsion force acts, affecting both cations and anions, resulting in the appearance of an ion concentration gradient phenomenon. At this time, a vortex is formed around the interface of the ion-depletion region P, and charged particles, cells, and droplets are also affected by the electrical repulsion force of ions at the interface of the ion-depletion region P, causing them to be pushed out around the ion-selective permeable membrane 12.

[0043] A freshwater generation unit 30 may be provided in a first region including an ion-depleted region P, from which freshwater from which ionic substances have been 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 can be concentrated and the hydrogen ions contained within the ionic substances can be reduced.

[0044] In addition to hydrogen ions, sodium ions (Na) are also ionic substances that can be concentrated in the ion-rich region Q. + ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ) and may further include at least one of these combinations. However, sodium ions (Na) + ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ Since cations such as ) have a much more negative reduction potential than hydrogen ions, hydrogen ions can be easily reduced in the hydrogen gas production unit 20 compared to other cations.

[0045] Thus, the brine desalination and hydrogen ion transport apparatus 1 according to the present invention can provide a platform for extracting fresh water from the ion depletion region P generated around the membrane in the direction of the oxidation electrode, by utilizing such ion concentration polarization phenomena, and simultaneously producing hydrogen at the reduction electrode.

[0046] Figure 4 is a schematic diagram showing a brine desalination and hydrogen ion transport apparatus according to one embodiment of the present invention.

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

[0048] The first microchannel 111 may include a first injection channel 1112 having an inlet at one end for injecting saltwater, a first discharge channel 1114 for discharging freshwater and a second discharge channel 1116 for discharging the remaining saltwater, branching off 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 may be positioned in contact with one side of the ion-selective permeable membrane 12, and the second microchannel 113 may be positioned in contact with the other side of the ion-selective permeable membrane 12.

[0050] The second microchannel 113 may include a third discharge channel 1133 through which brine (or concentrated substance) containing ionic substances 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 diverge, thereby forming an ion depletion region P, and an ion excess region Q may be formed in one region of the second microchannel section 113 opposite the ion depletion region P.

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

[0053] Figure 5 is a diagram illustrating electrohydrodynamic ion transport in a brine desalination and hydrogen ion transport apparatus according to one embodiment of the present invention.

[0054] The first microchannel 111 can be injected with brine [for example, seawater B] via the first injection channel 1112, and the desalted freshwater F can be discharged via the first discharge channel 1114. The remaining brine substance B' can be discharged via the second discharge channel 1116. The first microchannel 111 can be coupled to the anode section 13. The first discharge channel 1114 and the second discharge channel 1116 can be physically separated by a branch section 170, such as a channel wall.

[0055] The second microchannel 113 can be injected with brine [for example, seawater B] via the second injection channel 1131, and concentrated brine T can be discharged via the third discharge channel 1133 after additional ionic substances are transferred from the first microchannel 111.

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

[0057] In this case, the applied potential is preferably 100mV to 300V. The size of the ion depletion region P can vary depending on the potential difference. As an example, the voltage V applied to the anode section 13... anodic When the value decreases, the amount of cations transported from the first microchannel 111 to the second microchannel 113 via the ion-selective permeable membrane 12 decreases, and the generation of ion depletion regions weakens, which can reduce freshwater production efficiency.

[0058] Conversely, the voltage V applied to the anode section 13 anodic As V increases, cations move towards the ion-selective permeable membrane 12, increasing the amount of cations transported from the first microchannel 111 to the second microchannel 113. However, this can increase power consumption and reduce the efficiency of the water electrolysis device. Therefore, the voltage V applied to the anode section 13 should be adjusted. anodic The range is preferably 100mV to 300V.

[0059] Figure 6 is an illustrative diagram of a three-dimensional water electrolysis apparatus having the systems shown in Figures 1 and 2.

[0060] Referring to Figure 6, the housing 102 is provided with a first region 104 and a second region 106 separated by an ion exchange membrane 108. A brine supply flow 110 is supplied to the inside of the housing 102, the anode 105 is located in the first region 104, and the cathode 107 is located in the second region 106. The first region 104 can correspond to the freshwater generation unit 30, and the second region 106 can correspond to the hydrogen gas production unit 20.

[0061] In this case, the housing 102 and the pipes, tubes, etc. connected to the housing 102 may be macro channels with a diameter of mm, cm, or more. While devices based on micro channels can demonstrate high desalination and hydrogen gas production efficiency on a small scale, there may be limitations in scaling them up to an industrial scale. Therefore, it is preferable to form them with macro channels, which are advantageous for large-scale processing. However, the channel section 10 according to the present invention is not limited in size and may include both micro channels and macro channels.

[0062] Salt water contains sodium ions (Na + ) and chloride ions (Cl - This refers to various solutions containing ), and may include, for example, substances with a salt concentration of 0.1 to 35 g / L. Typically, this may include 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 made of a material containing Nafion.

[0064] Various suspended solids are present in the brine supplied to the first region 104, and these suspended solids must be removed during the desalination process. The suspended solids in the brine may include particulate matter, organic matter, inorganic matter, etc., and can be separated and removed into the suspended solid discharge stream 320 by ion concentration polarization when an electric current is applied.

[0065] Suspended solids in the saltwater are discharged through the suspended solids discharge flow 320, and salt ions move along the ion exchange membrane 108 to the second region 106, thereby forming a freshwater discharge flow 310. The salt ions are sodium ions (Na + ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ), potassium ions (K + ), lithium ion (Li + ) and at least one combination thereof may be included.

[0066] On the other hand, it is preferable to use an electrolyte in the second region 106 in order to impart a certain electrical conductivity to it, similar to the first region 104. 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 to the second region 106 via the ion exchange membrane 108, the amount of ions transported can be measured by ion chromatography or the like, and in this case, an electrolyte such as LiCl or KCl can act as a reference material.

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

[0068] The saline desalination and hydrogen ion transport method according to an embodiment of the present invention will be described below with reference to the apparatus shown in Figure 6.

[0069] First, the ion exchange membrane 108 is placed inside the housing 102, and the housing 102 is divided 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 the embodiments of the present invention, it is preferable to supply brine having a salinity in the range of 0.1 to 35 g / L. Generally, the average salinity of seawater is about 35 g / L, so according to the embodiments of the present invention, seawater can be used in the water electrolysis device without pretreatment or adjusting the concentration through a separate circulation system.

[0071] The concentration of the salt solution, i.e., the salt concentration, is determined by the hydrogen evolution reaction (H) that occurs at the cathode 107. + This can affect the reduction of electrolytes. Saltwater contains electrolytes such as NaCl, so the higher the salt concentration, the better the electric current can be transmitted. However, if the salt concentration is too high, the salt ions present in the saltwater may inhibit the mobility of hydrogen ions and 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 drops. This can reduce the rate at which hydrogen ions move to the electrodes and the rate of the electrochemical reaction necessary for the generation of hydrogen gas.

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

[0074] Subsequently, the anode section 105 and the cathode section 107 are connected to the first region 104 and the second region 106, respectively, and an electric current is applied between the anode section 105 and the cathode section 107 to transport hydrogen ions from the first region 104 to the second region 106.

[0075] The electric current, which is an electrical characteristic that affects freshwater production and hydrogen ion transport according to embodiments of the present invention, is one of the most important factors determining water electrolysis efficiency and performance.

[0076] Unlike two-dimensional water electrolysis devices, which rely on a planar design, three-dimensional water electrolysis devices involve fluid flow in a three-dimensional manner and have complex fluid 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 by electric field under a given voltage. The larger the current, the greater the charge moved per hour (i.e., the amount of ions transported through the ion exchange membrane).

[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 electrodes, the flow rate, and the flow velocity. In particular, the current is highly dependent on the area of ​​the ion exchange membrane and the concentration of the brine.

[0078] As the surface area of ​​an ion exchange membrane increases, the current density per unit area decreases even when the same current is applied, which can slow down the reaction rate. Therefore, the larger the surface area, the greater the current that must be applied to maintain an appropriate current density. Also, since more ions can pass through a larger surface area, even greater current must be applied to maintain sufficient ion movement.

[0079] On the other hand, as the concentration of salt water increases, the concentration of salt ions also increases, allowing for the application of a current that can process even more ions. The current density must be appropriately adjusted to find the optimal current value that allows the reaction to occur efficiently without putting stress on the ion exchange membrane or electrodes.

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

[0081] [Formula 1] X = I / AC (Here, I: current (mA), A: area of ​​ion exchange membrane (cm²) 2 ), C: Salt concentration (mM))

[0082] If the coefficient (X) is lower than 0.05, the amount of Ca in the saltwater 2+ Mg 2+ Polyvalent cations such as these can form hydroxides or carbonates, which can deposit on the surface of ion exchange membranes and electrodes. For example, precipitates such as CaCO3 (calcium carbonate) and Mg(OH)2 (magnesium hydroxide) can induce membrane contamination and electrode corrosion, which can hinder the efficiency of hydrogen gas generation.

[0083] Conversely, if the coefficient (X) is higher than 5, power consumption increases, which can hinder the efficient operation of the water electrolysis device. For example, if the current becomes excessively high, the overall system resistance requires a higher potential, thus increasing power consumption.

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

[0085] Additionally, in this invention, it is important to actively control the supply flow rate of brine (NaCl) based on the concentration of the supplied brine and the concentration of the resulting freshwater. By appropriately controlling the supply flow rate of brine, the quality and yield of freshwater can be maintained at a certain level or higher. For example, the salinity of the freshwater is preferably 500 ppm or less as a standard for freshwater. Therefore, if the salinity of the freshwater obtained in this invention exceeds 500 ppm, it is preferable to control the concentration of the freshwater not only by changing the current value according to formula 1, but also by actively controlling the supply flow rate of brine.

[0086] The present invention will be described below with reference to manufacturing examples and embodiments. However, the scope of the present invention is not limited to such manufacturing examples and embodiments.

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

[0088] <Manufacturing Example 2> A water electrolysis apparatus as shown in Figure 6 was fabricated, and a Nafion 211 membrane was laid 1 cm 2 The device was installed to the size shown. Two platinum wire electrodes were positioned 8 mm apart on either side of this Nafion membrane. 20 mM NaCl was injected into the chamber containing the oxidation electrode at a rate of 0.2 mL / min using a syringe pump, and 20 mM LiCl was injected into the chamber containing the reduction electrode at a rate of 0.2 mL / min using a syringe pump. A DC power supply equipped with a voltmeter and ammeter was used to supply the DC current.

[0089] <Example 1> Figures 7 to 10 show the experimental results confirming whether hydrogen and freshwater were produced simultaneously by Production Example 1 of the present invention.

[0090] In Figures 7A and 7B, cations in the solution begin to move from the lower channel to the upper channel where the reducing electrode is located. We observed that the pH indicator near the ion-excess region (IEZ) around the Nafion membrane in the upper channel turned red. Through this, we were able to confirm that hydrogen ions had moved across the Nafion membrane.

[0091] In Figure 7A, the pH indicator turns blue in the lower channel where the oxidation electrode is connected. This is because, after hydrogen ions pass from the lower channel to the upper channel, the remaining hydroxide ions (OH) are released. -This is a change caused by ), which could also serve as evidence of hydrogen ion movement across the Nafion membrane.

[0092] In contrast, in Figure 7(b), no change in the pH indicator color was observed in the lower channel to which the oxidizing electrode was connected. This is judged to be because, instead of using the neutral salt potassium chloride (KCl), an acidic hydrochloric acid (HCl) solution was used, and therefore, despite the movement of hydrogen ions, the brine did not become base-positive.

[0093] Thus, we demonstrated that acidic brine for hydrogen production is generated in the ion-excess zone (IEZ) surrounding the cation exchange membrane, and that fresh water is produced in the ion-depleted zone (IDZ).

[0094] In Figure 8A, the acidification of the solution (red color change due to pH indicator) due to the movement of hydrogen ions toward the reducing electrode was observed. In Figure 8B, the basification of the solution in the channel on the oxidizing electrode side (blue color change due to pH indicator) was confirmed after the movement of hydrogen ions. In Figure 8C, the ion depletion region (black area where no fluorescence is observed) was confirmed.

[0095] In other words, simultaneously with the movement of hydrogen ions, an ion depletion zone (IDZ) was observed in the lower channel on the oxidizing electrode side, where the fluorescence signal disappeared near the Nafion membrane (Figure 8(c)), and freshwater can be extracted from this region.

[0096] To summarize the results, as shown in Figure 9, the generation of freshwater and the generation of gas can be simultaneously confirmed using the ion concentration polarization phenomenon within the microchannel.

[0097] In Figure 9, when a reduction potential of +200V 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 side along with the fluid flowing in from the left side. Simultaneously with the generation of such gas, an ion depletion region was observed near the cation exchange membrane (nafion), demonstrating that it is possible to realize a system for the simultaneous production of fresh water and hydrogen using electrohydrodynamic ion concentration polarization phenomena.

[0098] To determine the composition of the bubbles generated at the aforementioned reducing electrode (cathode), argon (Ar), a carrier gas, was injected into the apparatus shown in Figure 7, and the emitted gas was collected and analyzed by gas chromatography.

[0099] Figure 10 shows the results of analysis using this type of gas chromatography. Figure 10A is a graph comparing the hydrogen (H2) peak with the peaks of other gases (reference gases), and Figure 10B is a magnified graph of the hydrogen peak.

[0100] In Figure 10A, it can be seen that hydrogen gas was generated at the reducing electrode, as indicated by region X, which is the peak region for hydrogen. This demonstrates that it is possible to realize a system that produces hydrogen using nanoelectrohydrodynamic ion concentration polarization phenomena through the generation of such hydrogen gas. For reference, region Y can be seen not as a peak of a specific substance, but as a baseline that appears when a large amount of argon or air is injected.

[0101] <Example 2> Figure 11 is a graph showing the production results of fresh water and hydrogen gas depending on the magnitude of the current in the water electrolysis apparatus according to the manufacturing example 2.

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

[0103] Furthermore, while freshwater was generated by ion concentration polarization at all currents, it can be seen that at 4mA, the concentration of the freshwater exceeds the salinity of 500ppm (approximately 8.56mM), which is undesirable. In comparison, when the current values ​​are 10mA and 20mA, the concentration of the freshwater (C desalted It can be seen that the concentration of ) decreased and the quality of the freshwater improved. However, since the concentrations of freshwater at 10mA and 20mA were almost identical, it can be seen that applying a current of 20mA, which is more favorable to the hydrogen gas generation reaction, is the most preferable.

[0104] Through this, the concentration of saltwater (NaCl) and the concentration of freshwater (C) can be determined. desalted Based on this, it is clear that it is important to actively control the magnitude of the applied current.

[0105] <Example 2> Figure 12 is a graph showing the competitive transport of hydrogen ions and salt ions across the ion exchange membrane in the water electrolysis apparatus according to the manufacturing example 2.

[0106] In Figure 12, the amount of ion transported was compared with respect to the magnitude of the current when 4mA, 10mA, and 20mA were applied under constant current conditions. The amount of movement of sodium ions (ΔNa), which make up the largest proportion of salt ions present in saltwater, was calculated. + ) and the amount of hydrogen ion transfer (ΔH + When the total amount of ions moving, including (ΔNa), is denoted as ΔQ, the ion concentration polarization phenomenon was observed differently depending on the magnitude of the current. When the current was supplied for 1 hour, the amount of sodium ions moving (ΔNa) was the total amount of ions moving through the ion exchange membrane. + The value of / ΔQ) was measured and shown in a graph.

[0107] As shown in Figure 12, with a current of 4mA, Na + Ion movement H + It can be seen that it is superior to (ΔNa + >ΔH +This means that the movement of other cations in saltwater is smoother compared to that of hydrogen ions. Also, OH is generated after hydrogen gas is produced at the reducing electrode. - The fewer hydrogen ions that can neutralize ions are transported through the ion exchange membrane, the less Ca can be present around the reducing electrode. 2+ Mg 2+ This means that polyvalent cations like these are more likely to form hydroxides or carbonates and deposit on the surface of ion exchange membranes or electrodes.

[0108] When the current is 10mA, the electric field becomes strong, and an ion separation phenomenon occurs, H + Ion movement is Na + It can be seen that it is superior to (ΔH + >ΔNa + The total amount of ions to move (ΔQ) can increase as the current increases. Of the ions passing through the ion exchange membrane, hydrogen ions have a very small size and high mobility, so they can move even faster with the same current. As the current increases, hydrogen ions move even faster, and sodium ions also move, but at a slower rate than hydrogen ions. As a result, the amount of hydrogen ion movement (ΔH + ) increases as the current increases, but the amount of sodium ion movement (ΔNa) + Because the increase in the current is small or negligible as the current increases, the difference in the amount of hydrogen ions and sodium ions that can move can become even more pronounced as the current increases.

[0109] When the current is 20mA, the amount of hydrogen ion movement (ΔH) is greater than when the current is 10mA. + ) increases, and the amount of sodium ion movement (ΔNa + The coefficient of the graph decreases, but the absolute value of the slope of the graph also decreases.

[0110] When the current exceeds 20mA, the overall system's resistance requires a higher potential, which can increase power consumption.

[0111] Therefore, in order to improve the amount of hydrogen ions transferred across the ion exchange membrane, prevent contamination of the ion exchange membrane and 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 Equation 1 is 0.5 to 1 mA / cm 2 This corresponds to ·mM).

[0112] <Example 4> Figure 13 is a graph comparing the amount of hydrogen gas produced (ΔH2) and the change in pH when the charge amount (Q) is controlled to be the same in the water electrolysis apparatus according to the manufacturing example 2 described 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 hours, and a current of 40 mA for 0.25 hours. When using a Pt electrode, the Faraday efficiency is close to 100%, and it was assumed that most of the charge amount (Q) flowing through the electrode is used for hydrogen production. The purpose of controlling the charge amount at this time was to keep the amount of hydrogen gas produced the same and to reduce the amount of H on the reduction electrode side due to hydrogen production. + This is to control the consumption so that the amount of each component used is the same.

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

[0115] The hydrogen gas production amount (ΔH2) shown on the y-axis in Figure 13 is the value quantitatively measured by gas chromatography of the gas collected after the application of electric current. As a result, the hydrogen gas production amount tended to increase slightly as the electric current increased, but remained almost constant.

[0116] Before the application of current, the initial pH of the solution on the chamber side where the reducing electrode was located was 5.58, but after the production of hydrogen gas, H +Due to the depletion of the ion exchange membrane, the pH rose to above 11 in all experimental cases. However, it can be confirmed that the pH gradually decreases as the applied current increases, even with almost the same amount of hydrogen gas production. This is because as the applied current increases, the amount of hydrogen ions transported through the ion exchange membrane increases, and the OH produced by hydrogen gas production at the reducing electrode decreases. - This means that the concentration of [the substance] has decreased.

[0117] Also, the OH in the solution on the y axis - The concentration of ([OH - When comparing ]), OH at 4mA - The concentration is OH under the condition of 40mA - The concentration is about three times higher than that of OH. - The higher the concentration, the greater the amount of cation precipitate that can be formed.

[0118] Furthermore, given that hydrogen gas production remains roughly the same as the current increases, it can be inferred that currents exceeding 40mA are undesirable because they result in excessive power consumption compared to hydrogen gas production.

[0119] In summary, the results shown in Figure 13 indicate that by increasing the applied current in the water electrolysis apparatus of the present invention, the transport of hydrogen ions across the ion exchange membrane is improved, thereby increasing the supply of protons for hydrogen gas production. Furthermore, by reducing the increase in pH after hydrogen gas production on the reducing electrode side, electrode contamination due to the precipitation of other cations in the brine is prevented, thereby improving the durability and stability of the water electrolysis apparatus. 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 apparatus can be improved.

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

[0121] Although the present invention has been described with reference to the embodiments shown in the drawings, these are merely illustrative, and a person with ordinary skill in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true scope of technical protection of the present invention must be determined by the technical idea of ​​the appended claims. This disclosure includes the following aspects: <1> A desalination and hydrogen ion transport apparatus for brine using the ion concentration polarization (ICP) phenomenon, A channel section includes a channel into which salt water is injected, an ion-selective membrane connected to the channel, and a cathode section and an anode section to which a voltage can be applied at both ends of the channel. A freshwater generation unit is provided in which freshwater is obtained from which ionic substances have been removed from the saltwater by an ion concentration polarization phenomenon in a first region adjacent to the anode portion of the ion-selective permeable membrane. In the second region adjacent to the cathode portion of the ion-selective permeable membrane, the ionic substance is concentrated, and hydrogen ions (H) contained within the ionic substance are concentrated. + A brine desalination and hydrogen ion transport apparatus, including a hydrogen gas production section where ) is reduced. <2> The first region includes an ion depletion zone, and the second region includes an ion enrichment zone. <1> A desalination and hydrogen ion transport apparatus for brine described above. <3> The aforementioned channel is A first microchannel coupled to one side of the anode portion, The cathode portion includes a second microchannel coupled to one side and connected to the ground voltage, <1> A desalination and hydrogen ion transport apparatus for brine described above. <4> The aforementioned ionic substance is Hydrogen ions (H + ) including, Sodium ions (Na + ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ), and further including at least one of these combinations, <1> A desalination and hydrogen ion transport apparatus for brine described above. <5> The aforementioned ion-selective permeable membrane is a Nafion membrane. <1> A desalination and hydrogen ion transport apparatus for brine described above. <6> The potential applied to the first microchannel is 100mV to 300V. <3> A desalination and hydrogen ion transport apparatus for brine described above. <7> The first microchannel is, A first injection channel having an inlet at one end for injecting the aforementioned saltwater, The system includes a first discharge channel through which freshwater is discharged and a second discharge channel through which the remaining saltwater is discharged, branching off from the other end of the first injection channel. <3> A desalination and hydrogen ion transport apparatus for brine described above. <8> The second microchannel is The system includes a third discharge channel through which concentrated brine containing ionic substances transmitted from the first microchannel is discharged. <7> A desalination and hydrogen ion transport apparatus for brine described above. <9> A method for desalination of saltwater and transport of hydrogen ions using the ion concentration polarization (ICP) phenomenon, (a) A step of preparing an apparatus comprising: a channel section including a channel into which saltwater is injected, an ion-selective permeable membrane connected to the channel, and a cathode section and an anode section to which a voltage can be applied to both ends of the channel; a freshwater generation section in which freshwater is obtained from which ionic substances have been removed from the saltwater by an ion concentration polarization phenomenon in a first region adjacent to the anode section of the ion-selective permeable membrane; and a hydrogen gas production section in which the ionic substances are concentrated in a second region adjacent to the cathode section of the ion-selective permeable membrane and hydrogen ions contained in the ionic substances are reduced; (b) The step of supplying salt water to the first region, (c) Between the anode portion located in the first region and the cathode portion located in the second region, the coefficient (X) calculated based on the following formula 1 is 0.05 to 5 mA / (cm 2 The steps include applying a current of (mM) to transport hydrogen ions in the first region to the second region, (d) A method for desalination of brine and transporting hydrogen ions, comprising the steps of obtaining fresh water from which impurities have been removed in the first region and simultaneously collecting hydrogen gas in the second region.

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Claims

1. A saline desalination and hydrogen ion transport apparatus using the ion concentration polarization (ICP) phenomenon, A channel section includes a channel into which saltwater is injected, an ion-selective membrane connected to the channel, and a cathode section and an anode section to which a voltage can be applied at both ends of the channel. A freshwater generation unit is provided in which freshwater is obtained from the brine by an ion concentration polarization phenomenon in a first region adjacent to the anode portion of the ion-selective permeable membrane, In the second region adjacent to the cathode portion of the ion-selective permeable membrane, the ionic substance is concentrated, and hydrogen ions (H) contained within the ionic substance are concentrated. ＋ It includes a hydrogen gas production section where ) is reduced, The first region includes an ion depletion zone, and the second region includes an ion enrichment zone. The channel includes a first microchannel coupled to one side of the anode portion and a second microchannel coupled to one side of the cathode portion and connected to the ground voltage. The ion-selective permeable membrane is a cation-permeable membrane in a saline desalination and hydrogen ion transport apparatus.

2. The aforementioned ionic substance is Hydrogen ions (H ＋ ) including, Sodium ions (Na ＋ ), calcium ions (Ca ２＋ ), magnesium ions (Mg ２＋ The saline desalination and hydrogen ion transport apparatus according to claim 1, further comprising at least one of the combinations thereof.

3. The saline desalination and hydrogen ion transport apparatus according to claim 1, wherein the ion-selective permeable membrane is a Nafion membrane.

4. The saline desalination and hydrogen ion transport apparatus according to claim 1, wherein the potential applied to the first microchannel is 100 mV to 300 V.

5. The first microchannel is A first injection channel having an inlet at one end for injecting the aforementioned saltwater, The brine desalination and hydrogen ion transport apparatus according to claim 1, comprising a first discharge channel for discharging fresh water and a second discharge channel for discharging the remaining brine, branching off from the other end of the first injection channel.

6. The second microchannel is The brine desalination and hydrogen ion transport apparatus according to claim 5, further comprising a third discharge channel through which concentrated brine containing an ionic substance transmitted from the first microchannel is discharged.

7. A method for desalination of saline water and transport of hydrogen ions using the ion concentration polarization (ICP) phenomenon, (a) A step of preparing an apparatus comprising: a channel section including a channel into which saltwater is injected, an ion-selective membrane connected to the channel, and a cathode section and an anode section to which a voltage can be applied to both ends of the channel; a freshwater generation section in which freshwater is obtained from which ionic substances have been removed from the saltwater by an ion concentration polarization phenomenon in a first region adjacent to the anode section of the ion-selective membrane; and a hydrogen gas production section in which the ionic substances are concentrated in a second region adjacent to the cathode section of the ion-selective membrane and hydrogen ions contained in the ionic substances are reduced; (b) The step of supplying salt water to the first region, (c) Between the anode portion located in the first region and the cathode portion located in the second region, the coefficient (X) calculated based on the following formula 1 is 0.05 to 5 mA / cm ２ The steps include: applying a current of - mM to transport hydrogen ions in the first region to the second region; (d) The step of obtaining fresh water from which impurities have been removed in the first region, and at the same time collecting hydrogen gas in the second region, The first region includes an ion depletion zone, and the second region includes an ion enrichment zone. The channel includes a first microchannel coupled to one side of the anode portion and a second microchannel coupled to one side of the cathode portion and connected to the ground voltage. The ion-selective permeable membrane is a cation-permeable membrane, and the method is for desalination of saline water and transport of hydrogen ions. [Math 1] (Here, I: current (mA), A: area of ​​ion-selective permeable membrane (cm²) ２ ), C: Salt concentration (mM))

8. Step (c) above is, The coefficient (X) is 0.2 to 2 mA / cm ２ The method for desalination of brine and transporting hydrogen ions according to claim 7, characterized by the step of applying a current of (mM).

9. Step (c) above 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 brine and hydrogen ion transport according to claim 7.

10. The method for desalination of brine and transporting hydrogen ions according to claim 7, characterized in that the pH of the second region decreases as the current increases.

11. Step (c) above is, The concentration of the saltwater and the concentration of the freshwater obtained in step (d) (C ｄｅｓａｌｔｅｄ The method for desalination of brine and transporting hydrogen ions according to claim 7, wherein the magnitude of the applied current is actively controlled based on ).

12. Step (b) above is: The concentration of the saltwater and the concentration of the freshwater obtained in step (d) (C ｄｅｓａｌｔｅｄ The method for desalination of brine and transporting hydrogen ions according to claim 7, wherein the supply flow rate of brine is actively controlled based on ).

13. The method for desalination of brine and transporting hydrogen ions according to claim 7, wherein the ion-selective permeable membrane is a Nafion membrane.

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