A portable seawater desalination device

Abstract

This paper provides a portable seawater desalination device, which uses a micro magnesium-air battery as a power supply and adds [Fe(CN6)] 4– / [Fe(CN6)] 3– The redox medium forms a high-concentration redox electrolyte, increasing current density and ion migration rate. The magnesium anode, in conjunction with the micro magnesium-air battery, optimizes the electrochemical environment, achieving efficient and high-water recovery seawater desalination. It can stably desalinate seawater into freshwater that meets drinking water standards (TDS ≤ 1000mg / L), making it suitable for outdoor adventures, emergency situations, and more.

Description

Technical Field

[0001] The present invention relates to the technical field of seawater desalination, and in particular to a portable seawater desalination device, which is intended to meet the urgent demand for convenient and efficient acquisition of fresh water in special scenarios such as outdoor exploration and emergency rescue. Background Art

[0002] In today's society, with people's increasing participation in outdoor activities and the real need for emergency rescue in various emergencies, freshwater supply has become a critical issue. Freshwater resources are extremely scarce in remote marine environments, island areas, and wilderness adventures. However, effectively converting seawater, a plentiful water resource, into freshwater would greatly alleviate water shortages in these areas.

[0003] At present, thermal desalination technologies such as multi-stage flash evaporation and multi-effect distillation, as well as membrane technologies such as reverse osmosis, have achieved remarkable results in the field of large-scale desalination projects. However, when these traditional technologies are applied to portable scenarios, they will expose many limitations. Specifically, thermal desalination technology requires huge equipment and a large amount of thermal energy, which makes the equipment not only bulky, but also energy-intensive, and the operating process is very complicated, making it difficult to meet the needs of portable use; and although reverse osmosis technology equipment is relatively compact, it needs to maintain a high pressure when treating high-salinity seawater, which will also increase the energy consumption of the equipment, and its operation and maintenance are highly dependent on professionals. These defects make it difficult for reverse osmosis technology equipment to function stably in special environments such as the field where there is a lack of professional support.

[0004] In recent years, some new desalination technologies have gradually emerged, such as solar distillation, freezing, and electrodialysis. Among them, electrodialysis technology has shown potential in the research and development of miniaturized and portable desalination equipment due to its advantages such as low energy consumption and modular and easy expansion of equipment. However, in practical applications, the dependence of traditional electrodialysis devices on external power sources makes them face problems such as unstable power supply and the need to carry additional power equipment in the field environment. Moreover, the high resistance of ion exchange membranes and the high osmotic pressure of seawater will seriously restrict the efficiency of ion migration during the electrodialysis process. In order to solve the power supply needs of electrodialysis equipment, some studies have considered using micro magnesium air batteries as the power source of electrodialysis equipment. However, although micro magnesium air batteries can achieve self-poweredness with seawater as the electrolyte, when the structure and volume of micro magnesium air batteries are simplified to meet the needs of portability, their power supply current is significantly reduced and can only provide 1 mA / cm 2 The current density below is still difficult to drive the desalination process (actual test electrodialysis desalination requires at least 10-20mA / cm 2At the same time, the electrodialysis unit in the portable electrodialysis equipment often uses a single-layer anion and cation exchange membrane, which makes it difficult to ensure the desalination effect in complex environments and cannot meet the actual fresh water demand.

[0005] Therefore, developing a technology that can achieve efficient and stable seawater desalination in portable devices has become a hot topic and difficulty in current research. Summary of the Invention

[0006] The purpose of the present invention is to provide a portable seawater desalination device. By deeply optimizing the combination of micro magnesium-air batteries and electrodialysis technology and cleverly introducing redox solutes, the current density and ion migration rate can be significantly improved while reducing the volume. Not only does it have excellent desalination performance and can achieve a seawater desalination process with high efficiency and high water recovery rate, it also has the advantages of being small in size, easy to carry, and able to adapt to various complex outdoor environments, providing users with reliable freshwater resource guarantees in scenarios where freshwater is scarce.

[0007] To achieve the above goals, Figure 1 As shown, the present technical solution provides a portable seawater desalination device, comprising:

[0008] Micro magnesium air battery 10;

[0009] An electrodialysis unit 20 includes an ion exchange membrane assembly, an anode 21 and a cathode 22, wherein the anode 21 is a magnesium electrode and the cathode 22 is an inert electrode. The anode 21 is connected in series with the magnesium electrode of the micro magnesium air battery 10 and is placed in an anode chamber 23, and the cathode 22 is connected in series with the positive electrode of the micro magnesium air battery and is placed in a cathode chamber 24. The cathode chamber 24 and the anode chamber 23 are pre-stored with redox medium solutes; wherein the ion exchange membrane includes a single-layer anion exchange membrane 25 and a cation exchange membrane 26, and the anion exchange membrane and the cation exchange membrane are alternately arranged to form a fresh water chamber and a concentrated water chamber.

[0010] It should be noted that this solution uses a micro magnesium-air battery as a power source, utilizing seawater as a natural electrolyte. Leveraging the self-powered nature of the micro magnesium-air battery in seawater, it solves the power supply problem of the electrodialysis unit, effectively utilizing the micro magnesium-air battery + redox mediator + electrodialysis process to efficiently produce desalinated water. At the same time, the research team discovered that most of the electrical energy was consumed by water splitting at the anode and cathode surfaces of the electrodialysis unit, rather than being used for the directional migration of anions and cations within the desalination chamber. This resulted in the micro magnesium-air battery providing insufficient energy to support ion migration within the electrodialysis unit. Therefore, the research team innovatively incorporated a redox mediator into the anode and cathode chambers, using this redox mediator to replace the redox process of water splitting. This allowed most of the micro magnesium-air battery's electrical energy to be used for ion migration of anions and cations, significantly increasing the current density. Furthermore, the research team used a magnesium electrode as the anode of the electrodialysis unit. By connecting the electrodialysis unit anode and the magnesium electrode of the magnesium-air battery in series, the electron transfer efficiency of the magnesium-air battery was accelerated, thereby fundamentally improving the current density.

[0011] The electrodialysis unit of this solution is used to desalinate high-concentration saltwater such as seawater into fresh water that meets drinking water standards. The freshwater chamber in the electrodialysis unit is used to desalinate seawater and output the desalinated fresh water. The anion exchange membrane and cation exchange membrane in the electrodialysis unit are used to achieve selective permeation of anions and cations under a certain voltage. The redox medium solute in the anode chamber and cathode chamber of the electrodialysis unit is used to replace the energy-intensive water decomposition reaction through a reversible redox reaction under the action of seawater, thereby promoting more energy-saving and efficient ion migration.

[0012] In one embodiment of the present solution, the potential of the redox mediator solute is 0.46 V, while the redox standard potential of water is 1.23 V. This has the advantage that the redox mediator solute can be easily triggered to undergo a reversible redox reaction.

[0013] In one embodiment of this solution, the anode chamber 23 is pre-stored with [Fe(CN6)] 4– / [Fe(CN6)] 3– The redox medium solute is pre-stored in the cathode chamber 24 [Fe(CN6)] 4– / [Fe(CN6)] 3– The two ions dissolve in seawater to form a redox electrolyte, which transfers electrons through its own redox reaction, reducing the resistance of the electrodialysis process and thus increasing the current density and ion migration rate.

[0014] Furthermore, the redox medium solute forms a 0.1-0.7 M concentration of [Fe(CN6)] 4– / [Fe(CN6)] 3– Preferably, the redox medium solute forms a 0.5M concentration of [Fe(CN6)] 4– / [Fe(CN6)] 3– The research team conducted experiments and found that adding a redox mediator solute to the anode and cathode chambers increased the current density within the electrodialysis unit to 10–70 mA / cm², driving an increase in ion migration rate by approximately 30%–200%, compared to not adding a redox mediator solute.

[0015] In one embodiment of this solution, the micro magnesium-air battery 10 uses a magnesium electrode as the negative electrode 11 and an air electrode as the positive electrode 13. Using seawater as the electrolyte, it can maintain a stable operating voltage of 1.2 to 1.5 V. The electrodialysis unit can operate stably after the addition of seawater. The magnesium electrode is made of an optimized magnesium alloy, with precise control of the alloy composition, such as the addition of 1 to 10% aluminum, to enhance its electrochemical activity. The air electrode utilizes a porous carbon material with a high specific surface area and good air permeability to improve oxygen diffusion rate and reaction activity.

[0016] To ensure proper exchange of air between the electrodes and the outside air, while further reducing the battery's volume, the battery employs a sandwich structure consisting of a negative electrode, a separator, and a positive electrode, and is packaged in a plastic-encapsulated housing with ventilation holes. This design reduces the battery's size and internal resistance, improving energy conversion efficiency while ensuring proper exchange of air between the electrodes, ensuring a stable and efficient base voltage for the entire device.

[0017] Specifically, the micro magnesium-air battery 10 provided in this solution includes a negative electrode 11, an isolation material 12 and a positive electrode 13 arranged in sequence, and a plastic-sealed shell with air holes that wraps the negative electrode, the isolation material and the positive electrode.

[0018] In the embodiment of this solution, the isolation material 12 in the micro magnesium-air battery is non-woven fabric, the negative electrode 11 is a magnesium electrode made of a magnesium alloy material, and the positive electrode 13 is porous carbon.

[0019] In the embodiment of this solution, the volume of the micro magnesium-air battery 10 is 2*2*0.5 cm, and can be matched with an electrodialysis unit to form a small-sized portable seawater desalination device.

[0020] In the embodiment of the present scheme, the anode 21 of the electrodialysis unit 20 adopts the same magnesium alloy as the negative electrode of the micro magnesium-air battery. The advantage of this is that the electron transfer of the micro magnesium-air battery can be accelerated with the help of the anode of the electrodialysis unit. This is because the magnesium alloy is more active and will lose electrons more easily.

[0021] As a further preferred embodiment, the electrodialysis unit 20 of this embodiment uses a magnesium electrode as the anode 21 and a copper sheet as the cathode 22. Through the synergistic anode design of the electrodialysis unit and the micro magnesium air battery, when the micro magnesium air battery is working, the magnesium alloy as the anode in the electrodialysis unit not only participates in the reaction as the anode of the micro magnesium air battery, but also synergizes with the seawater in the electrodialysis unit: during the electrodialysis process, an oxidation reaction occurs on the surface of the magnesium electrode, and the released magnesium ions (Mg 2+ ) and chloride ions (Cl – ) combined with the electrolyte to promote the migration of chloride ions to the anode chamber, further optimizing the electrochemical environment during the electrodialysis process and improving the overall desalination efficiency.

[0022] In the embodiment of this solution, the ratio of the surface area of ​​the anode 21 of the electrodialysis unit 20 to the area of ​​the cation exchange membrane / anion exchange membrane is 1:1 to 1:4. Preferably, the ratio of the surface area of ​​the anode of the electrodialysis unit to the area of ​​the cation exchange membrane / anion exchange membrane is 1:2.

[0023] In the embodiment of this solution, the anion exchange membrane 25 and cation exchange membrane 26 in the electrodialysis unit are arranged in a simple single-layer structure. This has the advantage of further reducing the size of the electrodialysis unit. In some embodiments, the electrodialysis unit is 2*2*2 cm in size. The accompanying miniaturized magnesium-air battery allows the entire desalination device to be placed as a small unit in a filter device such as a water cup.

[0024] It should be noted that the electrodialysis unit in the traditional scheme often adopts a multi-layer ion exchange membrane to improve the desalination efficiency, but the disadvantage of this is that the volume of the electrodialysis unit is inevitably sacrificed. In order to make the volume of the electrodialysis unit as small as possible in this scheme, only a single layer of anion exchange membrane and cation exchange membrane is used in the electrodialysis unit, and then the current density is increased by selecting the redox medium solute and the anode, thereby compensating for the desalination efficiency of the single layer ion exchange membrane by increasing the current density.

[0025] In the embodiment of this scheme, both the anion exchange membrane 25 and the cation exchange membrane 26 adopt the low-resistance acid-base resistant ASTOM ion membrane, which has high ion selectivity, low resistance and good chemical stability, further improving the ion permeability and reducing the concentration polarization phenomenon.

[0026] In the embodiment of this solution, the membrane area of ​​the anion exchange membrane 25 and the cation exchange membrane 26 is 4 cm 2 The membrane spacing is 1-5 mm to simplify the electrodialysis unit volume. Preferably, the membrane spacing between the anion exchange membrane 25 and the cation exchange membrane 26 is 3 mm to balance the contradiction between the compactness of the equipment unit and the fresh water treatment capacity.

[0027] In some embodiments, the portable seawater desalination device includes a fresh water collection module, wherein the fresh water collection module is connected to the fresh water chamber of the electrodialysis unit to collect desalinated fresh water.

[0028] In some embodiments, the portable seawater desalination device includes a water quality monitoring module for monitoring the total dissolved solids content of the desalinated fresh water and issuing an alarm signal when the total dissolved solids content exceeds a threshold value (eg, 1000 mg / L).

[0029] In some embodiments, the portable desalination device's magnesium-air battery, electrodialysis unit, and functional modules are connected via standardized plug-in interfaces. The functional modules include one or any combination of a freshwater collection module, a control module, and / or a water quality monitoring module. This allows for a modular design of the entire portable desalination device, facilitating subsequent disassembly, assembly, and maintenance.

[0030] The usage of the portable seawater desalination device is as follows:

[0031] When seawater enters the fresh water chamber, cathode chamber, and anode chamber of the electrodialysis unit through the water inlet pipe, the magnesium-air battery starts working under the action of seawater. The magnesium electrode of the magnesium-air battery undergoes oxidation to release electrons, thereby generating a stable voltage of about 1.3V.

[0032] At the same time, the redox medium solute in the cathode chamber and the anode chamber of the electrodialysis unit rapidly undergoes redox reaction under the voltage provided by the magnesium air battery: Fe 2+ Oxidized to Fe 3+ , electrons are released in the anode chamber, and the electrons flow to the air electrode through the external circuit. On the surface of the air electrode, oxygen obtains electrons and undergoes a reduction reaction. At the same time, Fe 3+ In the cathode chamber, electrons are obtained and reduced to Fe 2+ This rapid redox reaction generates a large current density (10 – 70 mA / cm ² ), the current drives the sodium ions (Na 2+ ), chloride ion (Cl –) and other salt separation ions migrate to the concentrated water chamber through the cation exchange membrane and the anion exchange membrane respectively. And the magnesium electrode serves as the anode. During the electrodialysis process, the magnesium atoms on the anode surface lose electrons to form magnesium ions (Mg 2+ ) enters the solution, and the magnesium ions combine with the chloride ions in the seawater to form magnesium chloride (MgCl2), which promotes the migration of chloride ions to the anode chamber. At the same time, the electrons lost by the magnesium atoms enter the micro magnesium air battery, improving the current efficiency. This synergistic effect further optimizes the electrodialysis process and improves the efficiency of seawater desalination.

[0033] After a period of electrodialysis, the seawater in the freshwater chamber is gradually desalinated, and the desalinated water is collected through the outlet pipe. Testing shows that the total dissolved solids (TDS) content of the freshwater is ≤1000mg / L, meeting drinking water standards. The salt in the electrode chamber gradually concentrates and is eventually replaced with the new electrode chamber.

[0034] Compared with the existing technology, this technical solution has the following characteristics and beneficial effects:

[0035] The portable seawater desalination device provided in this solution uses a micro-air battery as a power source, and adds a redox medium solute to the cathode and anode chambers of the electrodialysis unit, so that the redox medium solute replaces the redox of water decomposition to produce a reversible redox reaction, thereby fully providing the electrical energy of the magnesium-air battery to drive the ions in the seawater. The anode of the electrodialysis unit uses the same magnesium alloy material as the magnesium electrode of the micro-magnesium-air battery. Through synergistic effects, the efficiency of ion migration is further promoted, thereby achieving a high-efficiency seawater desalination effect in a small-volume portable seawater desalination device. It can stably desalinate seawater (3.5 wt% NaCl) into fresh water that meets drinking water standards (TDS ≤ 1000 mg / L), making it suitable for outdoor adventures, emergency situations, and other scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the structure of the portable seawater desalination device provided by this solution.

[0037] Figure 2 It is a comparison of the current density of redox couple solute at different concentrations.

[0038] Figure 3 This is a graph showing the change in brine conductivity with electrodialysis time.

[0039] In the figure: 10 - micro magnesium-air battery, 11 - negative electrode, 12 - isolation material, 13 - positive electrode, 20 - electrodialysis unit, 21 - anode, 22 - cathode, 23 - anode chamber, 24 - cathode chamber, 25 - anion exchange membrane, 26 - cation exchange membrane. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0041] Example 1:

[0042] The micro magnesium-air battery used in this embodiment has a magnesium electrode as the negative electrode made of magnesium-aluminum alloy AZ31 (Mg-Al-Zn, mass ratio 96:3:1) with a surface area of ​​1*5 cm 2 , with a thickness of 1 mm, and the air battery as the positive electrode uses activated carbon cloth material with a surface area of ​​1*5 cm 2 , with a thickness of 1 mm, ensuring it has a high specific surface area and good air permeability. Non-woven fabric is used as a separator between the positive and negative electrodes, which facilitates the diffusion and distribution of the electrolyte to form a complete electrode system. Finally, the outer layer is sealed with a plastic with air holes to assemble the magnesium electrode and the air electrode into a micro magnesium-air battery, and seawater (3.5%) is used as the electrolyte to form a stable power supply.

[0043] The anion exchange membrane and cation exchange membrane used in the electrodialysis unit of this embodiment are ASTOM ion exchange membranes with high ion selectivity, which are arranged alternately in single layers. The membrane area is 4 cm 2 The membrane spacing is precisely controlled to 3 mm. 32.92 mg of potassium ferricyanide (K3[Fe(CN6)]) and 42.24 mg of potassium ferrocyanide (K4[Fe(CN6)]) redox media solid powders are pre-added to the anode and cathode chambers, respectively. Purity testing ensures accurate concentrations and extremely low impurity levels. The magnesium electrode of the electrodialysis unit and the magnesium electrode of the micro magnesium-air battery are connected in parallel via low-resistance wires to ensure good electrical connection and minimal resistance loss. Through calculation and design, the ratio of the magnesium electrode surface area to the ion exchange membrane area is 1:2.

[0044] Before the experiment, a concentrated brine with a NaCl concentration of 3.5% was prepared. After the concentrated brine was injected into the fresh water chamber and the cathode chamber of the electrodialysis unit through the injection port, the average conductivity of the concentrated brine was 52 mS / cm, the stable output voltage of the magnesium-air battery was 1.37 V, and the initial average current density was 68 mA / cm 2 After 140 minutes of experiment, the average conductivity of the fresh water in the fresh water chamber was 1.32 mS / cm, that is, the total dissolved solids (TDS) content of the fresh water at this time was 888 mg / L, which met the drinking water standard.

[0045] Example 2:

[0046] The micro magnesium-air battery used in this embodiment has a magnesium electrode as the negative electrode made of magnesium-aluminum alloy AZ31 (Mg-Al-Zn, mass ratio 96:3:1) with a surface area of ​​1*5 cm 2 , thickness is 1mm; the air battery uses activated carbon cloth material with a surface area of ​​1*5 cm 2 , with a thickness of 1 mm, ensuring it has a high specific surface area and good air permeability; non-woven fabric is used as a separator in the middle, which facilitates the diffusion and distribution of the electrolyte to form a complete electrode system; finally, the outer layer is sealed with a plastic with air holes to assemble the magnesium electrode and the air electrode into a micro magnesium-air battery, and seawater (3.5%) is used as the electrolyte to form a stable power supply.

[0047] The anion exchange membrane and cation exchange membrane used in the electrodialysis unit of this embodiment are ASTOM ion exchange membranes with high ion selectivity, which are arranged alternately in single layers. The membrane area is 4 cm 2 The membrane spacing is precisely controlled to 5 mm. 32.92 mg of potassium ferricyanide (K3[Fe(CN6)]) and 42.24 mg of potassium ferrocyanide (K4[Fe(CN6)]) solid powders of redox mediators were pre-added to the anode and cathode chambers, respectively. Purity testing ensured accurate concentrations and minimal impurity levels. The magnesium electrode of the electrodialysis unit and the magnesium electrode of the micro magnesium-air battery were connected in parallel via a low-resistance wire to ensure good electrical connection and minimal resistance losses. Through calculation and design, the ratio of the surface area of ​​the magnesium electrode to the area of ​​the ion exchange membrane reached 1:3.

[0048] Before the experiment, a concentrated brine with a NaCl concentration of 3.5% was prepared. After the concentrated brine was injected into the fresh water chamber and the cathode chamber through the injection port, the average conductivity of the concentrated brine was 52 mS / cm, the stable output voltage of the magnesium-air battery was 1.37 V, and the initial average current density was 51 mA / cm 2 After 4 hours of experiment, the average conductivity of fresh water in the fresh water chamber was 2.12mS / cm, that is, the total dissolved solids (TDS) content of the fresh water at this time was 1426 mg / L.

[0049] Example 3:

[0050] The micro magnesium-air battery used in this embodiment has a magnesium electrode as the negative electrode made of magnesium-aluminum alloy AZ31 (Mg-Al-Zn, mass ratio 96:3:1) with a surface area of ​​1*5 cm 2 , thickness is 1mm; the air battery uses activated carbon cloth material with a surface area of ​​1*5 cm 2, with a thickness of 1 mm, ensuring it has a high specific surface area and good air permeability; non-woven fabric is used as a separator in the middle, which facilitates the diffusion and distribution of the electrolyte to form a complete electrode system; finally, the outer layer is sealed with a plastic with air holes to assemble the magnesium electrode and the air electrode into a micro magnesium-air battery, and seawater (3.5%) is used as the electrolyte to form a stable power supply.

[0051] The anion exchange membrane and cation exchange membrane used in the electrodialysis unit of this embodiment are ASTOM ion exchange membranes with high ion selectivity, which are arranged alternately in single layers. The membrane area is 4 cm 2 The membrane spacing is precisely controlled to 3 mm. 19.75 mg of potassium ferricyanide (K3[Fe(CN6)]) and 25.34 mg of potassium ferrocyanide (K4[Fe(CN6)]) solid powders were pre-added to the anode and cathode chambers, respectively. Purity testing ensured accurate concentrations and minimal impurity levels. The magnesium electrode in the electrodialysis unit was replaced with a copper electrode, connected in parallel to the magnesium electrode of the micro magnesium-air battery via a low-resistance wire, ensuring good electrical connection and minimal resistance losses. Through calculation and design, the surface area ratio of the copper electrode to the ion exchange membrane was achieved at 1:2.

[0052] Before the experiment, a concentrated brine with a NaCl concentration of 3.5% was prepared. After the concentrated brine was injected into the fresh water chamber and the cathode chamber through the injection port, the average conductivity of the concentrated brine was 52 mS / cm, the stable output voltage of the magnesium-air battery was 1.37 V, and the initial average current density was 10 mA / cm 2 After 8 hours of experiment, the final conductivity of the fresh water in the fresh water chamber was 4.34 mS / cm, that is, the total dissolved solids (TDS) content of the fresh water at this time was 2921 mg / L.

[0053] The experimental test results above demonstrate that the magnesium-air battery-driven electrodialysis desalination device of the present invention can produce desalinated water based on a magnesium-air battery + redox medium + electrodialysis combined process, achieving efficient and energy-saving seawater desalination. Furthermore, increasing the concentration of the redox medium within a certain range and adjusting the membrane spacing can further enhance the performance and efficiency of the desalination device. This miniaturized, modular device design is industrially feasible and suitable for a variety of scenarios, such as outdoor exploration on islands and emergency rescue, to meet the demand for freshwater acquisition.

[0054] Example 4:

[0055] The micro magnesium-air battery used in this embodiment has a magnesium electrode as the negative electrode made of magnesium-aluminum alloy AZ31 (Mg-Al-Zn, mass ratio 96:3:1) with a surface area of ​​1*5 cm 2, with a thickness of 1 mm, and the air battery as the positive electrode uses activated carbon cloth material with a surface area of ​​1*5 cm 2 , with a thickness of 1 mm, ensuring it has a high specific surface area and good air permeability. Non-woven fabric is used as a separator between the positive and negative electrodes, which facilitates the diffusion and distribution of the electrolyte to form a complete electrode system. Finally, the outer layer is sealed with a plastic with air holes to assemble the magnesium electrode and the air electrode into a micro magnesium-air battery, and seawater (3.5%) is used as the electrolyte to form a stable power supply.

[0056] The anion exchange membrane and cation exchange membrane used in the electrodialysis unit of this embodiment are ASTOM ion exchange membranes with high ion selectivity, which are arranged alternately in single layers. The membrane area is 4 cm 2 The membrane spacing was precisely controlled to 3 mm. Redox mediator solid powders (6.58, 13.17, 19.75, 26.336, 32.92, 39.50, and 46.09 mg of potassium ferricyanide (K3[Fe(CN6)]) and 8.45, 16.90, 25.35, 33.80, 42.24, 50.70, and 59.15 mg of potassium ferrocyanide (K4[Fe(CN6)])) were pre-added to the anode and cathode chambers, respectively. Purity testing ensured accurate concentrations and minimal impurity levels. The magnesium electrode of the electrodialysis unit and the magnesium electrode of the micro magnesium-air battery were connected in parallel via low-resistance wires to ensure good electrical connection and minimal resistance loss. Through calculation and design, the surface area ratio of the magnesium electrode to the ion exchange membrane was 1:2.

[0057] Before the experiment, a concentrated brine solution with a NaCl concentration of 3.5% was prepared. This brine was injected into the freshwater chamber and the anode and cathode chambers of the electrodialysis unit through the inlet. The concentrations of the redox medium solution were 0.1M, 0.2M, 0.3M, 0.4M, 0.5M, 0.6M, and 0.7M, respectively. At this point, the anode and cathode of the electrodialysis unit were connected to an electrochemical workstation. In constant voltage mode at 1.37V, the current density values ​​of the electrodialysis unit circuit were recorded at different concentrations, and the test results were plotted as a concentration-current curve.

[0058] The current density comparison of redox couple solute at different concentrations is shown in the figure below. Figure 2 As shown, the redox mediator solute ([Fe(CN6)] 4– / [Fe(CN6)] 3–) The change of current density in the electrodialysis unit at different concentrations (0.1M, 0.2M, 0.3M, 0.4M, 0.5M, 0.6M, 0.7M). By comparing the current density curves at different concentrations, it can be seen intuitively that the current density reaches the maximum value at a concentration of 0.7M, thereby verifying that the redox pair has the most significant promoting effect on ion migration at this concentration. However, considering the reagent cost and current efficiency, the 0.5M concentration is preferred.

[0059] Embodiment 5:

[0060] The micro magnesium-air battery used in this embodiment has a magnesium electrode as the negative electrode made of magnesium-aluminum alloy AZ31 (Mg-Al-Zn, mass ratio 96:3:1) with a surface area of ​​1*5 cm 2 , with a thickness of 1 mm, and the air battery as the positive electrode uses activated carbon cloth material with a surface area of ​​1*5 cm 2 , with a thickness of 1 mm, ensuring it has a high specific surface area and good air permeability. Non-woven fabric is used as a separator between the positive and negative electrodes, which facilitates the diffusion and distribution of the electrolyte to form a complete electrode system. Finally, the outer layer is sealed with a plastic with air holes to assemble the magnesium electrode and the air electrode into a micro magnesium-air battery, and seawater (3.5%) is used as the electrolyte to form a stable power supply.

[0061] The anion exchange membrane and cation exchange membrane used in the electrodialysis unit of this embodiment are ASTOM ion exchange membranes with high ion selectivity, which are arranged alternately in single layers. The membrane area is 4 cm 2 The membrane spacing is precisely controlled to 3 mm. 32.92 mg of potassium ferricyanide (K3[Fe(CN6)]) and 42.24 mg of potassium ferrocyanide (K4[Fe(CN6)]) redox media solid powders are pre-added to the anode and cathode chambers, respectively. Purity testing ensures accurate concentrations and extremely low impurity levels. The magnesium electrode of the electrodialysis unit and the magnesium electrode of the micro magnesium-air battery are connected in parallel via low-resistance wires to ensure good electrical connection and minimal resistance loss. Through calculation and design, the ratio of the magnesium electrode surface area to the ion exchange membrane area is 1:2.

[0062] Before the experiment, a concentrated brine with a NaCl concentration of 3.5% was prepared. After the concentrated brine was injected into the fresh water chamber and the cathode chamber of the electrodialysis unit through the injection port, the stable output voltage of the magnesium-air battery was 1.37 V, and the initial average current density was 68 mA / cm 2At this time, the average conductivity of the concentrated brine measured by the conductivity meter was 52 mS / cm. Subsequently, the conductivity value of the brine was recorded every 20 minutes. After 140 minutes of experiment, the average conductivity of the fresh water in the fresh water chamber was 1.32 mS / cm, that is, the total dissolved solids (TDS) content of the fresh water at this time was 888 mg / L, which met the drinking water standard, and a time-conductivity change graph was drawn.

[0063] The change of brine conductivity with electrodialysis time is shown in the figure Figure 3 As shown in the figure, the brine conductivity, i.e., the change trend of the brine conductivity, i.e., the brine concentration, during the electrodialysis treatment process using the portable seawater desalination device of the present invention, is shown with time as the horizontal axis and the brine conductivity as the vertical axis. As can be seen from the figure, as the electrodialysis time increases, the brine concentration shows a clear downward trend. In the initial stage, the brine concentration drops rapidly. This is because after the device is started, the redox medium quickly takes effect, generating a large current density, driving the rapid migration of ions, so that the salt in the seawater quickly passes through the ion exchange membrane into the concentrated water chamber. As time goes by, the rate of decrease in the brine concentration gradually slows down, but it still continues to decrease. After a certain period of treatment, the brine concentration can be reduced to close to or below the freshwater standard of 1000 mg / L, which fully verifies the seawater desalination effect of the device and intuitively shows that the device can effectively remove salt from seawater and realize the conversion of seawater into fresh water.

[0064] Those skilled in the art should understand that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The above embodiments merely illustrate several embodiments of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A portable seawater desalination device, characterized in that: include: micro magnesium air batteries; An electrodialysis unit includes an ion exchange membrane assembly, an anode and a cathode, wherein the anode is a magnesium electrode and the cathode is an inert electrode. The anode is connected in series with the magnesium electrode of the micro magnesium air battery and is placed in the anode chamber, and the cathode is connected in series with the positive electrode of the micro magnesium air battery and is placed in the cathode chamber. Redox medium solutes are pre-stored in the cathode chamber and the anode chamber. The ion exchange membrane includes a single-layer anion exchange membrane and a cation exchange membrane, and the anion exchange membrane and the cation exchange membrane are alternately arranged to form a fresh water chamber and a concentrated water chamber.

2. The portable seawater desalination device according to claim 1, characterized in that: Anode indoor pre-storage [Fe(CN6)] 4– / [Fe(CN6)] 3– The redox medium solute, the cathode chamber pre-stored [Fe(CN6)] 4– / [Fe(CN6)] 3– redox mediator solute.

3. The portable seawater desalination device according to claim 2, characterized in that: The redox mediator solute forms a 0.1~0.7 M concentration of [Fe(CN6)] 4– / [Fe(CN6)] 3– redox electrolyte.

4. The portable seawater desalination device according to claim 1, characterized in that: The micro magnesium air battery adopts a sandwich structure design of negative electrode-isolation material-positive electrode, and the micro magnesium air battery is packaged in a plastic shell with air holes.

5. The portable seawater desalination device according to claim 4, characterized in that: The isolation material in the micro magnesium air battery is non-woven fabric, the negative electrode is a magnesium electrode made of magnesium alloy material, and the positive electrode is porous carbon.

6. The portable seawater desalination device according to claim 1, characterized in that: The membrane area of ​​the anion exchange membrane and the cation exchange membrane is 4 cm 2 , the membrane spacing is 1~5 mm.

7. The portable seawater desalination device according to claim 1, characterized in that: The ratio of the surface area of ​​the anode of the electrodialysis unit to the area of ​​the cation exchange membrane / anion exchange membrane is 1:1 to 1:

4.

8. The portable seawater desalination device according to claim 1, characterized in that: The portable seawater desalination device includes a water quality monitoring module for monitoring the total dissolved solids content of the desalinated fresh water and issuing an alarm signal when the total dissolved solids content exceeds a threshold value.

9. The portable seawater desalination device according to claim 1, characterized in that: It includes a functional module, and the micro magnesium-air battery, the electrodialysis unit and the functional module are connected through a standardized plug-in interface, wherein the functional module includes one or any combination of a fresh water collection module and / or a water quality monitoring module.

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