Magnetic carbon nanomaterial hydrogel, preparation method thereof and seawater desalination application

Abstract

The application discloses a magnetic carbon nanomaterial hydrogel, a preparation method thereof and seawater desalination application. The magnetic carbon nanomaterial hydrogel comprises a hydrogel, carbon nanomaterial and magnetic nanoparticles distributed in the hydrogel. The preparation method comprises the following steps: 1) mixing the hydrogel, the carbon nanomaterial and the magnetic nanoparticles to obtain a mixed solution; 2) freezing the mixed solution obtained in the step 1) to obtain a frozen product; 3) thawing the frozen product obtained in the step 2); 4) repeating the freezing in the step 2) and the thawing in the step 3) to obtain the magnetic carbon nanomaterial hydrogel. The magnetic carbon nanomaterial hydrogel prepared by the application can realize dynamic compression self-drainage through geometric deformation of an elastic magnetic evaporation body under the action of a magnetic field, and can improve the water evaporation rate of a photothermal interface water evaporation body.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a magnetic carbon nanomaterial hydrogel, its preparation method, and its application in seawater desalination. Background Technology

[0002] In recent years, with the continuous increase in the world's population, freshwater shortage has become one of the most serious global problems. Seawater is an abundant water resource, and its desalination and utilization will be an important means of obtaining freshwater. Traditional seawater desalination uses traditional and expensive fossil fuel energy, which may lead to increased air pollution and greenhouse gas emissions, has low energy conversion efficiency, and requires a large area. Therefore, the development of new seawater desalination technologies is urgently needed.

[0003] Chen et al. first proposed the concept of solar steam generation by heat localization in Nat. Commun. This work opens up a new avenue for seawater desalination. This photothermal interfacial water evaporation has the advantages of not consuming fossil fuels, low carbon emissions, and low pollution, and has potential application value. Under sunlight, some light is absorbed by the evaporator, while the rest is lost through reflection and transmission. The light absorbed by the photothermal evaporator is converted into heat, most of which is used to heat the water absorbed internally. The water undergoes a phase transformation at the interface into water vapor, which then escapes into the air. The remaining heat is transferred to the air through thermal radiation and convection, or to the lower water layer through thermal conduction.

[0004] Currently, the water evaporation rate of ordinary hydrogels can only reach about 4.0 kg / m³. -2 h -1 Therefore, it is essential to develop new and efficient seawater desalination technologies. Summary of the Invention

[0005] One of the objectives of this invention is to provide a magnetic carbon nanomaterial hydrogel, comprising a hydrogel, and carbon nanomaterials and magnetic nanoparticles distributed in the hydrogel.

[0006] Preferably, the mass ratio of the hydrogel, carbon nanomaterial and magnetic nanoparticles is 1:(0.5-1.5):(0.2-2).

[0007] Preferably, the hydrogel comprises sodium alginate and polyvinyl alcohol.

[0008] Preferably, the mass ratio of sodium alginate to polyvinyl alcohol is (0.2-2):1.

[0009] Preferably, the carbon nanomaterial includes at least one of graphene, carbon nanotubes, graphyne, fullerene, carbon black, carbon microtubes, activated carbon, and graphite.

[0010] Preferably, the magnetic nanoparticles include at least one of Fe3O4, Fe3N, hydroxyl iron powder, and alloy nanoparticles of Fe, Co, and Ni.

[0011] Another object of the present invention is to provide a method for preparing magnetic carbon nanomaterial hydrogels, comprising the following steps:

[0012] S10. Mix the hydrogel, carbon nanomaterials and magnetic nanoparticles to obtain a mixed solution;

[0013] S20. Freeze the mixed solution obtained in step S10 to obtain a frozen product;

[0014] S30. Thaw the frozen product obtained in step S20;

[0015] S40. Repeat the freezing process of step S20 and the thawing process of step S30 to obtain the magnetic carbon nanomaterial hydrogel.

[0016] Preferably, the freezing temperature range of step S20 is -20 to -50°C; the freezing rate is 1 to 10°C / min; and the freezing time is 5 to 12 hours.

[0017] Preferably, the thawing temperature range of step S30 is 20–40°C; the thawing rate is 1–10°C / min.

[0018] Preferably, step S40 is repeated 1 to 10 times.

[0019] The present invention also provides a magnetic carbon nanomaterial hydrogel prepared by the aforementioned preparation method.

[0020] The present invention also provides the application of the magnetic carbon nanomaterial hydrogel in seawater desalination.

[0021] Another object of the present invention is to provide a seawater desalination method comprising the following steps:

[0022] S11. Contact the magnetic carbon nanomaterial hydrogel with seawater; the magnetic carbon nanomaterial hydrogel includes a hydrogel, and carbon nanomaterials and magnetic nanoparticles distributed in the hydrogel;

[0023] S21. Evaporate the magnetic carbon nanomaterial hydrogel that is in contact with seawater obtained in step S11, and simultaneously apply a magnetic field to the magnetic carbon nanomaterial hydrogel that is in contact with seawater obtained in step S11, so that the magnetic carbon nanomaterial hydrogel that is in contact with seawater obtained in step S11 undergoes compression deformation.

[0024] Preferably, the evaporation in step S21 includes light irradiation.

[0025] Preferably, the magnetic field in step S21 is a static magnetic field or a dynamic magnetic field.

[0026] Preferably, the magnetic field strength in step S21 is in the range of 0–1000 mT. For example, it can be 100 mT, 100 mT, 200 mT, 300 mT, 400 mT, 500 mT, 600 mT, 700 mT, 800 mT, or 900 mT. More preferably, it is 300–700 mT.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The magnetic carbon nanomaterial hydrogel provided by this invention includes a hydrogel, and carbon nanomaterials and magnetic nanoparticles distributed within the hydrogel. Compared to current photothermal evaporation systems where water evaporates in a static state during photothermal evaporation, with water passively escaping from the pores under photothermal energy, resulting in a low evaporation rate, the magnetic carbon nanomaterial hydrogel of this invention is compressed and shaped internally under the influence of a magnetic field, which accelerates water expulsion and thus improves evaporation efficiency.

[0029] 2. The magnetic carbon nanomaterial hydrogel prepared by the preparation method provided by the present invention exhibits improved mechanical properties after freezing and thawing.

[0030] 3. The seawater desalination method provided by this invention involves applying a static magnetic field to a magnetic carbon nanomaterial hydrogel under sunlight, specifically 1 sun (1W / m²). -2 When a magnetic field is applied, the evaporation rate of the magnetic carbon nanomaterial hydrogel reaches as high as 8.0 kg / m³. -2 h -1 . Attached Figure Description

[0031] Figure 1 The graph shows the evaporation rate of pure water and the magnetic carbon nanomaterial hydrogel prepared in Example 1 (with and without magnetic field) under one day of sunlight.

[0032] Figure 2 The absorbance test results of the magnetic carbon nanomaterial hydrogel prepared in Example 1 in the range of 250-2500 nm.

[0033] Figure 3 Example 1: Temperature change over time of magnetic carbon nanomaterial hydrogel and pure water under 1 Sun light irradiation.

[0034] Figure 4Example 1: The mass change of the magnetic carbon nanomaterial hydrogel prepared in salt water of different concentrations under 1 Sun light irradiation over time.

[0035] Figure 5 Example 1: Magnetic carbon nanomaterial hydrogels prepared for use with different Na ions + Mg 2+ K + Ca 2+ A comparison chart of ion concentrations before and after solution evaporation. Detailed Implementation

[0036] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0037] A method for preparing a magnetic carbon nanotube hydrogel includes the following steps:

[0038] (1) Add a dispersant to deionized water, then add carbon nanomaterials and stir to obtain a carbon nanomaterial slurry;

[0039] (2) Molds with different geometric configurations were prepared by 3D printing;

[0040] (3) Prepare an aqueous solution of magnetic nanoparticles;

[0041] (4) Prepare a polyvinyl alcohol aqueous solution;

[0042] (5) Prepare an aqueous solution of sodium alginate;

[0043] (6) The carbon nanomaterial slurry, magnetic nanoparticle aqueous solution, sodium alginate aqueous solution and polyvinyl alcohol aqueous solution prepared above are mixed and poured into the mold prepared in step (2). After freezing and thawing, magnetic carbon nanomaterial hydrogel is obtained.

[0044] The dispersant in step (1) can be anionic surfactant, including anionic surfactants (such as sodium dodecylbenzenesulfonate, SDBS), cationic surfactants (such as hexadecyltrimethylammonium bromide, C16TMAB), zwitterionic surfactants (surfactants composed of cationic and anionic parts, wherein the cationic part can be an ammonium salt or a quaternary ammonium salt, and the anionic part can be a carboxylate, sulfate, or carbonate), and nonionic surfactants (such as Triton X-305).

[0045] The carbon nanomaterial in step (1) can be at least one of graphene, carbon nanotubes, graphyne, fullerene, carbon black, carbon microtubes, activated carbon, and graphite.

[0046] The dispersant addition ratio in step (1) can be 0.1% to 1.0%, and the carbon nanomaterial concentration can be 1% to 10%.

[0047] The stirring speed in step (1) can be 10-2000 r / min. -1 The stirring time can be 1 to 6 hours.

[0048] In step (3), the magnetic nanoparticles can be at least one of Fe3O4, Fe3N, hydroxyl iron powder, and alloy nanoparticles of Fe, Co, and Ni, and the particle size of the magnetic nanoparticles can be 10 to 500 nm.

[0049] In step (3), the concentration of magnetic nanoparticles can be 1–10 g / mL. -1 .

[0050] In step (4), the concentration of polyvinyl alcohol can be 1–10 g / mL. -1 .

[0051] In step (5), the concentration of polyvinyl alcohol can be 5–20 g / mL. -1 .

[0052] In step (6), the freezing time can be 5 to 12 hours, and the thawing time can be 15 to 12 hours.

[0053] This invention uses a mixture of sodium alginate, polyvinyl alcohol, carbon nanomaterials, and magnetic nanoparticles to prepare a magnetic carbon nanomaterial hydrogel. This hydrogel has good biocompatibility, hydrophilicity, high light absorption, and good mechanical properties. The addition of carbon nanomaterials can effectively improve the photothermal evaporation rate.

[0054] The magnetic nanoparticles and the components of the hydrogel (polyvinyl alcohol and sodium alginate) are uniformly mixed together. After several freeze-thaw cycles, they will combine with these materials and remain fixed. Carbon nanomaterials, as photothermal materials, can also improve the mechanical properties of magnetic carbon nanomaterial hydrogels to a certain extent when preferably composited as one-dimensional tubular materials within them.

[0055] When a magnetic field (e.g., a static magnetic field, a magnet) is applied beneath a magnetic carbon nanomaterial hydrogel, the magnitude of the magnetic force exerted on the hydrogel can be adjusted by changing the magnet and the number of magnets. This application and adjustment of the magnetic field can, on the one hand, dynamically and over a wide range alter the structure of the internal pores of the hydrogel. This compression change in the pore structure accelerates the outward expulsion of water, and also alters the state and enthalpy of vaporization of the water, thereby regulating the evaporation rate. On the other hand, it can control the state and speed of water expulsion (during the day, the water in the pores forms a thin layer on the surface of the hydrogel, ensuring sufficient water supply for evaporation while preventing excessive water overflow and heat loss, thus synergistically increasing the evaporation rate with light; at night, the magnetic field accelerates the outward expulsion of water, causing it to overflow and flow onto the salt particles precipitated on the surface during the day, increasing the rate of salt particle remelting and achieving rapid salt self-cleaning).

[0056] This invention employs a repeated freezing and thawing process; the more times it is repeated, the better the mechanical properties of the hydrogel become. However, too many repetitions will increase cost and time; therefore, the preferred number of freezing and thawing cycles is 3 to 10.

[0057] Example 1

[0058] A magnetic carbon nanomaterial hydrogel was prepared by the following method:

[0059] (1) Add SDBS dispersant to deionized water at a ratio of 0.2%; then add single-walled carbon nanotube powder and heat at 500 rpm. -1 A carbon nanomaterial slurry was prepared under stirring conditions, and the concentration of the prepared carbon nanomaterial slurry was 5%.

[0060] (2) A square mold with a side length of 2.5cm was prepared by 3D printing.

[0061] (3) Preparation of magnetic nanoparticle aqueous solution: Add 20g of Fe3O4 with a particle size of 50nm to 10mL of deionized water, and stir at 500r / min. -1 The mixture was stirred at a constant speed for 3 hours to prepare an aqueous solution of magnetic particles with a concentration of 2 g / mL. -1 .

[0062] (4) Preparation of polyvinyl alcohol aqueous solution: Add 50g of polyvinyl alcohol to 10mL of deionized water, and incubate at 90℃ with a flow rate of 500 rpm. -1 The mixture was stirred at a constant speed for 3 hours to prepare a solution with a concentration of 5 g / mL. -1 A polyvinyl alcohol solution.

[0063] (5) Preparation of sodium alginate aqueous solution: Add 50g of sodium alginate to 10mL of deionized water, and incubate at 70℃ with a flow rate of 500 rpm. -1 The mixture was stirred at a constant speed for 3 hours to prepare a solution with a concentration of 5 g / mL. -1 Sodium alginate solution.

[0064] (6) The carbon nanomaterial slurry, magnetic nanoparticle aqueous solution, sodium alginate aqueous solution, and polyvinyl alcohol aqueous solution prepared above are mixed and poured into the mold prepared in step (2). The mass ratio of magnetic nanoparticles, magnetic nanoparticles, sodium alginate, and polyvinyl alcohol is 1:1:1:0.2. During mixing, the mixture is stirred for 2 hours at a stirring speed of 500 rpm. -1 .

[0065] (7) A magnetic carbon nanomaterial hydrogel was prepared by freezing and thawing.

[0066] The freezing temperature range is -20℃, the freezing rate is 10℃ / min, and the freezing time is 12h.

[0067] The thawing temperature range is 20℃, the thawing rate is 10℃ / min, and the thawing time is 5h.

[0068] The cycle repeats 6 times.

[0069] A static magnetic field (magnetic field distance 5cm, magnitude 500mT, moving vertically downwards) was applied to the prepared magnetic carbon nanomaterial hydrogel, and its seawater desalination performance under light irradiation and internal extrusion deformation force was tested.

[0070] Figure 1 The magnetic carbon nanomaterial hydrogel provided in this embodiment shows the water evaporation rate over time under 1 Sun illumination, with and without a magnetic field, and the water evaporation rate of pure water over time in a magnetic field-free environment. Figure 1 It was observed that the water evaporation rate of the magnetic carbon nanomaterial hydrogel with a magnetic field was twice that of the magnetic carbon nanomaterial hydrogel without a magnetic field. This indicates that the magnetic field causes deformation of the magnetic carbon nanomaterial hydrogel, accelerating the outward expulsion of internal water and significantly increasing its photothermal evaporation rate. Furthermore, compared to pure water without the addition of magnetic carbon nanomaterial hydrogel, both the presence and absence of a magnetic field effectively improved the water evaporation efficiency.

[0071] Figure 2 The absorbance test results of the magnetic carbon nanomaterial hydrogel provided in this embodiment are shown in the range of 250–2500 nm. Figure 2It can be observed that the magnetic carbon nanomaterial hydrogel provided in this embodiment has an absorbance of 98% in the range of 250 to 2500 nm, exhibiting broad and high light absorption performance.

[0072] Figure 3 The graph shows the temperature change over time of the magnetic carbon nanomaterial hydrogel and pure water under 1 Sun illumination provided in this embodiment. Figure 3 It can be observed that, under 1 sun, the magnetic carbon nanomaterial hydrogel provided in this embodiment can reach temperature equilibrium after 15 minutes, with an equilibrium temperature of 36.8℃, which is higher than the temperature of pure water (27.5℃) at 15 minutes, indicating its good photothermal conversion performance.

[0073] Figure 4 The magnetic carbon nanomaterial hydrogel provided in this embodiment was added to saline solutions of different concentrations (0.8%, 3.5%, and 10%). + A graph showing the change in the mass of salt over time. (Through...) Figure 4 It can be observed that the obtained curves are linear and have similar slopes under different concentrations of salt water, indicating that the evaporator has good desalination performance after adding the magnetic carbon nanomaterial hydrogel provided in this embodiment.

[0074] Figure 5 To allow the magnetic carbon nanomaterial hydrogel provided in this embodiment to be added to substrates containing different Na ions, + Mg 2 + K + Ca 2+ Comparison of ion concentrations before and after solution evaporation. Figure 5 It can be observed that the ion concentration in the distilled water collected after evaporation is lower than that obtained by traditional membrane methods and thermal distillation methods, by nearly four orders of magnitude. This demonstrates that the addition of the magnetic carbon nanomaterial hydrogel provided in this embodiment results in the evaporator having excellent seawater desalination performance.

[0075] Example 2

[0076] A magnetic carbon nanotube hydrogel was prepared by the following method:

[0077] (1) Add SDBS dispersant to deionized water at a ratio of 0.2%; then add single-walled carbon nanotube powder and heat at 500 rpm. -1 A carbon nanomaterial slurry was prepared under stirring conditions; the concentration of the prepared carbon nanomaterial slurry was 5%.

[0078] (2) A square mold with a side length of 2.5cm was prepared by 3D printing.

[0079] (3) Preparation of magnetic nanoparticle aqueous solution: Add 50g of Fe3O4 with a particle size of 50nm to 10mL of deionized water, and spray at 1500r / min. -1 The mixture was stirred at a constant speed for 3 hours to prepare an aqueous solution of magnetic nanoparticles with a concentration of 2 g / mL. -1 .

[0080] (4) Preparation of polyvinyl alcohol aqueous solution: Add 100g of polyvinyl alcohol to 10mL of deionized water, and incubate at 90℃ with a flow rate of 500 rpm. -1 The mixture was stirred at a constant speed for 3 hours to prepare a solution with a concentration of 5 g / mL. -1 A polyvinyl alcohol solution.

[0081] (5) Preparation of sodium alginate aqueous solution: Add 50g of sodium alginate to 10mL of deionized water, and incubate at 70℃ with a flow rate of 500 rpm. -1 The mixture was stirred at a constant speed for 3 hours to prepare a solution with a concentration of 5 g / mL. -1 Sodium alginate solution.

[0082] (6) The carbon nanomaterial slurry, magnetic nanoparticle aqueous solution, sodium alginate aqueous solution, and polyvinyl alcohol aqueous solution prepared above are mixed and poured into the mold prepared in step (2). The mass ratio of magnetic nanoparticles, magnetic nanoparticles, sodium alginate, and polyvinyl alcohol is 1:1:1:1. During mixing, the mixture is stirred for 2 hours at a stirring speed of 1000 rpm. -1 .

[0083] (7) A magnetic carbon nanomaterial hydrogel was prepared by freezing and thawing.

[0084] The freezing temperature range is -20℃, the freezing rate is 10℃ / min, and the freezing time is 12h.

[0085] The thawing temperature range is 30℃, the thawing rate is 10℃ / min, and the thawing time is 12h.

[0086] The cycle repeats 6 times.

[0087] A static magnetic field was applied to the prepared magnetic carbon nanotube hydrogel, and the distance of the magnetic field was adjusted to 1 cm and the magnitude to 500 mT. The desalination performance of the above magnetic nanotube hydrogel under light irradiation and internal extrusion deformation force was tested. Similar to Example 1, the evaporator has excellent seawater desalination performance.

[0088] Comparative Example 1

[0089] (1) A square mold with a side length of 2.5cm was prepared by 3D printing.

[0090] (2) Preparation of magnetic nanoparticle aqueous solution: Add 20g of Fe3O4 with a particle size of 50nm to 10mL of deionized water, and stir at 500r / min. -1 The mixture was stirred at a constant speed for 3 hours to prepare an aqueous solution of magnetic nanoparticles with a concentration of 2 g / mL. -1 .

[0091] 3) Preparation of polyvinyl alcohol aqueous solution: Add 50g of polyvinyl alcohol to 10mL of deionized water, and incubate at 90℃ with a flow rate of 500 rpm. -1 The mixture was stirred at a constant speed for 3 hours to prepare a solution with a concentration of 5 g / mL. -1 A polyvinyl alcohol solution.

[0092] 4) Preparation of sodium alginate aqueous solution: Add 50g of sodium alginate to 10mL of deionized water, and incubate at 70℃ with a flow rate of 500 rpm. -1 The mixture was stirred at a constant speed for 3 hours to prepare a solution with a concentration of 5 g / mL. -1 Sodium alginate solution.

[0093] 5) The magnetic nanoparticle aqueous solution, sodium alginate aqueous solution, and polyvinyl alcohol aqueous solution prepared above are mixed and poured into the mold prepared in step (2). The mass ratio of magnetic nanoparticles, sodium alginate, and polyvinyl alcohol is 1:1:0.2. During mixing, the mixture is stirred for 2 hours at a stirring speed of 500 rpm. -1 .

[0094] 6) Magnetic hydrogels were prepared by freezing and thawing.

[0095] The freezing temperature range is -20℃, the freezing rate is 10℃ / min, and the freezing time is 12h.

[0096] The thawing temperature range is 20℃, the thawing rate is 10℃ / min, and the thawing time is 5h.

[0097] The cycle repeats 6 times.

[0098] A static magnetic field was applied to the magnetic hydrogels containing carbon nanotubes (Example 1) and those without carbon nanotubes in Comparative Example 1, and their water evaporation rates were tested at 1 sun. The water evaporation rate of the magnetic hydrogel with carbon nanotubes was higher than that of the magnetic hydrogel without carbon nanotubes. This is because carbon nanotubes have photothermal effects, which can accelerate water evaporation.

[0099] The above embodiments are merely optimized implementations of the present invention, used to illustrate the principles and effects of the present invention, and are not intended to limit the present invention. It should be noted that any modifications made to the above embodiments by those skilled in the art without departing from the spirit and scope of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. Seawater desalination methods, including the following steps: S11. Contact the magnetic carbon nanomaterial hydrogel with seawater; the magnetic carbon nanomaterial hydrogel includes a hydrogel, and carbon nanomaterials and magnetic nanoparticles distributed in the hydrogel; S21. Evaporate the magnetic carbon nanomaterial hydrogel that is in contact with seawater obtained in step S11, and simultaneously apply a magnetic field to the magnetic carbon nanomaterial hydrogel that is in contact with seawater obtained in step S11, so that the magnetic carbon nanomaterial hydrogel that is in contact with seawater obtained in step S11 undergoes compression deformation.

2. The seawater desalination method as described in claim 1, characterized in that, The magnetic field in step S21 is either a static magnetic field or a dynamic magnetic field.

3. The seawater desalination method as described in claim 1, characterized in that, The magnetic field strength in step S21 is in the range of 0~1000 mT.

4. The seawater desalination method as described in claim 1, characterized in that: In step S11, the mass ratio of the hydrogel, carbon nanomaterial and magnetic nanoparticles is 1:(0.5~1.5):(0.2~2).

5. The seawater desalination method as described in claim 1, characterized in that: In step S11, the hydrogel comprises sodium alginate and polyvinyl alcohol.

6. The seawater desalination method as described in claim 5, characterized in that: The mass ratio of sodium alginate to polyvinyl alcohol is (0.2~2):

1.

7. The seawater desalination method as described in claim 1, characterized in that: In step S11, the carbon nanomaterial includes at least one of graphene, carbon nanotubes, graphyne, fullerene, carbon black, carbon microtubes, activated carbon, and graphite.

8. The seawater desalination method as described in claim 1, characterized in that: The magnetic nanoparticles include at least one of Fe3O4, Fe3N, hydroxyl iron powder, and alloy nanoparticles of Fe, Co, and Ni.

9. The seawater desalination method as described in claim 1, characterized in that: In step S11, the preparation method of the magnetic carbon nanomaterial hydrogel includes the following steps: S10. Mix the hydrogel, carbon nanomaterials and magnetic nanoparticles to obtain a mixed solution; S20. Freeze the mixed solution obtained in step S10 to obtain a frozen product; S30. Thaw the frozen product obtained in step S20; S40. Repeat the freezing process of step S20 and the thawing process of step S30 to obtain the magnetic carbon nanomaterial hydrogel.

10. The seawater desalination method as described in claim 9, characterized in that, The freezing temperature range of step S20 is -20 to -50°C; the freezing rate is 1 to 10°C / min; and the freezing time is 5 to 12 hours.

11. The seawater desalination method as described in claim 9, characterized in that, The thawing temperature range of step S30 is 20~40℃; the thawing rate is 1~10℃ / min.

12. The seawater desalination method as described in claim 9, characterized in that, The number of times step S40 is repeated is 1 to 10.

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