Hydrogel with directional conical porous structure and preparation method thereof

Abstract

The application discloses a hydrogel with a directional conical porous structure and a preparation method thereof, and belongs to the technical field of atmospheric water collection.The directional conical porous structure hydrogel with atmospheric water collection capacity is prepared by first preparing a uniform sodium alginate solution and an acid solution respectively, then pouring the sodium alginate solution into a mold, adding the acid solution, and finally obtaining the hydrogel with the directional conical porous structure through an acid-induced phase separation process.Compared with traditional hydrogels, the hydrogel obtained by the application not only has a rapid moisture absorption-desorption efficiency, but also has excellent cycle stability.In a plurality of moisture absorption-desorption cycles, the hydrogel can maintain a high moisture absorption amount, reduce moisture absorption salt loss, and prolong the service life of the material; and the preparation process of the application is simple, the cost is low, the environmental friendliness is high, and industrial production can be realized.

Description

Technical Field

[0001] This invention relates to the field of atmospheric water collection technology, specifically to a hydrogel with a directional conical porous structure and its preparation method. Background Technology

[0002] Water is an indispensable resource for humankind. With societal development, population growth, and intensifying climate change, the global water shortage problem is becoming increasingly severe. Adsorption-based atmospheric water harvesting technology utilizes hygroscopic materials to spontaneously adsorb water molecules from the air. Through methods such as light and heating, water is decomposed and absorbed, ultimately yielding usable liquid water. This technology boasts advantages such as wide applicability to humidity levels, good environmental and climatic adaptability, and low carbon footprint, making it one of the effective ways to alleviate the water crisis.

[0003] Hydrogels, as polymeric materials with a three-dimensional network structure, play a crucial role in adsorption-based atmospheric water collection technology due to their high hydrophilicity, easily adjustable physicochemical properties, good biocompatibility, and plasticity. Adding hygroscopic salts (such as lithium chloride and calcium chloride) to hydrogels can significantly improve their moisture absorption efficiency, enabling them to effectively absorb moisture under varying humidity conditions and thus expanding their application range. However, while traditional bulk hydrogels possess excellent water adsorption capacity, they suffer from slow hygroscopic-desorption rates in practical applications. Furthermore, after multiple hygroscopic-desorption cycles, the hygroscopic salts in the hydrogel gradually dissipate, leading to a significant decrease in its water adsorption capacity, thereby limiting its long-term application in atmospheric water collection.

[0004] Therefore, how to prepare hydrogel materials that combine rapid water vapor absorption-desorption rates with good cycling stability has become a key problem that urgently needs to be solved. To this end, it is necessary to further optimize the structural design and material composition of hydrogels to improve their absorption-desorption efficiency and enhance their stability in multiple cycles, thereby achieving more efficient and continuous water collection performance. Summary of the Invention

[0005] [Technical Issues]

[0006] While traditional bulk hydrogels possess excellent water adsorption capacity, they suffer from slow hygroscopic-desorption rates in practical applications. Furthermore, after multiple hygroscopic-desorption cycles, the hygroscopic salts in the hydrogel gradually dissipate, leading to a significant decrease in its water adsorption capacity and thus limiting its long-term application in atmospheric water collection.

[0007] [Technical Solution]

[0008] To address the aforementioned problems, this invention provides a hydrogel with a directional conical porous structure and its preparation method. This hydrogel possesses numerous micron-sized porous structures, significantly increasing its specific surface area and thus enhancing the number of adsorption sites for interaction with water molecules in the air, thereby significantly improving its hygroscopic-desorption rate. Furthermore, the directional conical pore structure of the hydrogel exhibits an asymmetric Laplace pressure gradient. This structural characteristic effectively mitigates the loss of hygroscopic salts from the hydrogel, significantly improving its stability during repeated hygroscopic-desorption cycles and ensuring the long-term reliability of the hydrogel in atmospheric water collection technology.

[0009] To achieve the above objectives, the following technical solution is provided:

[0010] The first objective of this invention is to provide a method for preparing a directional conical porous hydrogel with atmospheric water collection capability, comprising the following steps:

[0011] (1) Sodium alginate is mixed with water and stirred until it becomes a paste to obtain a sodium alginate solution;

[0012] (2) Mix the acidic substance with water and stir until homogeneous to obtain an acidic solution;

[0013] (3) Pour the sodium alginate solution obtained in step (1) into the mold, then add the acidic solution obtained in step (2), and after standing, a hydrogel with a directional cone-shaped porous structure is obtained.

[0014] (4) Immerse the hydrogel with directional conical porous structure obtained in step (3) in a hygroscopic salt solution, and after standing, obtain a hydrogel with directional conical porous structure that has atmospheric water collection ability.

[0015] In one embodiment, the sodium alginate solution in step (1) is prepared by mixing sodium alginate and water to form a slurry; wherein the amount of sodium alginate in the sodium alginate solution is 1~5 wt%.

[0016] In one embodiment, the stirring conditions in step (1) are: temperature of 20~40 °C, stirring speed of 1000~5000 rpm, and time of 8~12 h.

[0017] In one embodiment, the acidic substance in step (2) is one or more of 2-acrylamide-2-methylpropanesulfonic acid, hydrochloric acid, and sulfuric acid; preferably 2-acrylamide-2-methylpropanesulfonic acid.

[0018] In one embodiment, the acidic solution in step (2) is obtained by mixing an acidic substance with water and stirring until homogeneous; wherein the amount of the acidic substance in the acidic solution is 1~55 wt%; preferably 10~30%; more preferably 15~25%.

[0019] In one embodiment, the stirring conditions in step (2) are: temperature of 20~40 °C, stirring speed of 500~1500 rpm, and time of 10~30 min.

[0020] In one embodiment, in step (3), the volume ratio of sodium alginate solution to acidic solution in the mold is 1:(1~3); preferably 1:2.

[0021] In one embodiment, the settling conditions in step (3) are: temperature of 20~40 °C and time of 6~36 h.

[0022] In one embodiment, the hygroscopic salt solution in step (4) is obtained by mixing hygroscopic salt and water and stirring evenly; wherein the amount of hygroscopic salt in the hygroscopic salt solution is 1~35 wt%; preferably 10%.

[0023] In one embodiment, the hygroscopic salt is one or more of lithium chloride (LiCl), calcium chloride (CaCl2), lithium bromide (LiBr), and magnesium chloride (MgCl2).

[0024] In one embodiment, the settling conditions in step (4) are: temperature of 20~40 °C and time of 12~24 h.

[0025] The second objective of this invention is to provide a directional conical porous hydrogel with atmospheric water collection capability, prepared by the preparation method described above.

[0026] In one embodiment, the porous hydrogel has multiple oriented conical porous channels with a pore size of 100~600 μm; preferably 100~300 μm.

[0027] A third objective of this invention is to provide the application of the directional conical porous hydrogel with atmospheric water collection capability described above in the field of atmospheric water collection.

[0028] A fourth objective of this invention is to provide a method for improving the hygroscopic-desorption cycle performance of hydrogels, comprising the following:

[0029] (1) Sodium alginate is mixed with water and stirred until it becomes a paste to obtain a sodium alginate solution;

[0030] (2) Mix the acidic substance with water and stir until homogeneous to obtain an acidic solution;

[0031] (3) Pour the sodium alginate solution obtained in step (1) into the mold, then add the acidic solution obtained in step (2), and after standing, a hydrogel with a directional cone-shaped porous structure is obtained.

[0032] (4) Immerse the hydrogel with directional conical porous structure obtained in step (3) in a hygroscopic salt solution, and after standing, obtain a hydrogel with directional conical porous structure that has atmospheric water collection ability.

[0033] Beneficial effects:

[0034] The directional conical porous hydrogel with atmospheric water collection capability provided by this invention is prepared by first preparing a homogeneous sodium alginate solution and an acidic solution, then pouring the sodium alginate solution into a mold and adding the acidic solution. After an acid-induced phase separation process, a hydrogel with a directional conical porous structure is finally obtained. Compared with traditional hydrogels, the hydrogel obtained by this invention not only has rapid moisture absorption-desorption efficiency but also excellent cycle stability. During multiple moisture absorption-desorption cycles, the hydrogel can maintain a high moisture absorption capacity, reduce moisture salt loss, and extend the material's service life.

[0035] The hydrogel prepared by this invention possesses a large number of micron-sized porous structures, significantly increasing the adsorption sites for interaction with water molecules in the air, thereby enhancing its hygroscopic-desorption rate and effectively accelerating the adsorption and release of moisture. Simultaneously, the hydrogel obtained by this invention has a directional conical pore structure, and its asymmetric Laplace pressure difference can effectively trap the hygroscopic salt solution within the hydrogel, preventing its loss during repeated hygroscopic-desorption cycles. This structural characteristic significantly improves the cyclic stability of the hydrogel, enabling it to maintain a high hygroscopic capacity during prolonged use.

[0036] In addition, the preparation process of this invention is simple, low-cost, and highly environmentally friendly, and can be industrialized. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the cross-sectional structure of the porous hydrogel prepared in Example 1 of the present invention;

[0038] Figure 2 Microscopic images of the cross-sectional structure of the porous hydrogel prepared in Example 1 of this invention;

[0039] Figure 3 This is a schematic diagram comparing the moisture absorption cycle curves of the water-collecting hydrogels prepared in Example 1 and Comparative Example 3 of the present invention. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.

[0041] Example 1

[0042] A method for preparing a water-collecting porous hydrogel includes the following steps:

[0043] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0044] (2) Add 15 g of 2-acrylamide-2-methylpropanesulfonic acid powder to 85 g of water, and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform acidic solution with a mass fraction of 15%.

[0045] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of acidic solution and let it stand at room temperature for 10 h to obtain a hydrogel with a directional cone-shaped porous structure.

[0046] (4) Add 10 g LiCl to 90 g water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform hygroscopic salt solution with a mass fraction of 10%; immerse the hydrogel obtained in step (3) in the hygroscopic salt solution and let it stand for 12 h to obtain a porous hydrogel for atmospheric water collection.

[0047] Example 2

[0048] A method for preparing a water-collecting porous hydrogel includes the following steps:

[0049] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0050] (2) Add 5 g of 2-acrylamide-2-methylpropanesulfonic acid powder to 95 g of water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform acidic solution with a mass fraction of 5%.

[0051] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of acidic solution and let it stand at room temperature for 10 h to obtain hydrogel.

[0052] (4) Add 10 g LiCl to 90 g water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform hygroscopic salt solution with a mass fraction of 10%; immerse the hydrogel obtained in step (3) in the hygroscopic salt solution and let it stand for 12 h to obtain a porous hydrogel for atmospheric water collection.

[0053] Example 3

[0054] A method for preparing a water-collecting porous hydrogel includes the following steps:

[0055] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0056] (2) Add 25 g of 2-acrylamide-2-methylpropanesulfonic acid powder to 75 g of water, and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform acidic solution with a mass fraction of 25%.

[0057] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of acidic solution and let it stand at room temperature for 10 h to obtain a hydrogel with a directional cone-shaped porous structure.

[0058] (4) Add 10 g LiCl to 90 g water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform hygroscopic salt solution with a mass fraction of 10%; immerse the hydrogel obtained in step (3) in the hygroscopic salt solution and let it stand for 12 h to obtain a porous hydrogel for atmospheric water collection.

[0059] Example 4

[0060] A method for preparing a water-collecting porous hydrogel includes the following steps:

[0061] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0062] (2) Add 15 g of hydrochloric acid (purity 36.0~38.0%) to 85 g of water and stir at 25 °C and 1000 rpm for 10 min to obtain a uniform hydrochloric acid solution with a mass fraction of 15%.

[0063] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of hydrochloric acid solution and let it stand at room temperature for 24 h to obtain hydrogel.

[0064] (4) Add 10 g LiCl to 90 g water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform hygroscopic salt solution with a mass fraction of 10%; immerse the hydrogel obtained in step (3) in the hygroscopic salt solution and let it stand for 12 h to obtain a porous hydrogel for atmospheric water collection.

[0065] Example 5

[0066] A method for preparing a water-collecting porous hydrogel includes the following steps:

[0067] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0068] (2) Add 15 g of sulfuric acid (purity 95.0~98.0%) to 85 g of water and stir at 25 °C and 1000 rpm for 10 min to obtain a uniform sulfuric acid solution with a mass fraction of 15%;

[0069] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of sulfuric acid solution and let it stand at room temperature for 36 h to obtain hydrogel.

[0070] (4) Add 10 g LiCl to 90 g water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform hygroscopic salt solution with a mass fraction of 10%; immerse the hydrogel obtained in step (3) in the hygroscopic salt solution and let it stand for 12 h to obtain a porous hydrogel for atmospheric water collection.

[0071] Comparative Example 1

[0072] A method for preparing a water-collecting porous hydrogel includes the following steps:

[0073] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0074] (2) Add 15 g of anhydrous acetic acid to 85 g of water and stir at 25 °C and 1000 rpm for 10 min to obtain a uniform acetic acid solution with a mass fraction of 15%.

[0075] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of acetic acid solution and let it stand at room temperature for 10 h to obtain the product and observe its state.

[0076] Comparative Example 2

[0077] A method for preparing a water-collecting porous hydrogel includes the following steps:

[0078] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0079] (2) Add 1 g of 2-acrylamide-2-methylpropanesulfonic acid powder to 99 g of water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform acidic solution with a mass fraction of 1%.

[0080] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of acidic solution and let it stand at room temperature for 10 h to obtain the product and observe its state.

[0081] Comparative Example 3

[0082] The preparation of sodium alginate hydrogel for atmospheric water collection according to patent CN114214847A includes the following steps:

[0083] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0084] (2) Add 10 g CaCl2 to 90 g water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform hygroscopic salt solution with a mass fraction of 10%.

[0085] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of hygroscopic salt solution and let it stand at room temperature for 10 h to obtain sodium alginate hydrogel with atmospheric water collection ability.

[0086] Comparative Example 4

[0087] A method for preparing a water-collecting porous hydrogel includes the following steps:

[0088] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0089] (2) Add 15 g of acrylamide powder to 85 g of water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform acrylamide solution with a mass fraction of 15%.

[0090] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of acrylamide solution and let it stand at room temperature for 10 h to obtain the product and observe its state.

[0091] Comparative Example 5

[0092] A method for preparing a water-collecting porous hydrogel includes the following steps:

[0093] (1) Add 4 g of sodium alginate powder to 96 g of water, stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved, and let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%.

[0094] (2) Add 15 g of sodium p-styrene sulfonate powder to 85 g of water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform sodium p-styrene sulfonate solution with a mass fraction of 15%.

[0095] (3) Add 10 mL of sodium alginate solution to the mold and spread it out. Then add 20 mL of sodium p-styrene sulfonate solution and let it stand at room temperature for 10 h to obtain the product and observe its state.

[0096] Results Analysis

[0097] 1. The morphology and pore size of the samples prepared in the examples and comparative examples were described and measured. The results are shown in Table 1:

[0098] Table 1. Morphology and pore size of different samples

[0099]

[0100] 2. The hygroscopic properties of the water-collecting hydrogels prepared in the examples and comparative examples were measured.

[0101] The samples prepared in the examples and comparative examples were dried and then placed at 25 °C and 90% RH for 2 h for atmospheric water collection tests. The moisture absorption rate of each sample was calculated, and the results are shown in Table 2.

[0102] Table 2. Hygroscopic properties of different samples

[0103]

[0104] 3. The photothermal desorption properties of the water-collecting hydrogels prepared in the examples and comparative examples were measured.

[0105] The samples prepared in the examples and comparative examples were placed at 25 °C and 90% RH for 24 h to absorb moisture, and then placed at 1 kW m at 25 °C and 30% RH. -2 After irradiation under a xenon lamp for 6 hours, the desorption rate of each sample was calculated, and the results are shown in Table 3.

[0106] Table 3 Photothermal desorption properties of different samples

[0107]

[0108] 4. The cyclic stability of the water-collecting hydrogels prepared in the examples and comparative examples was determined.

[0109] The samples prepared in the examples and comparative examples were placed at 25 °C and 90% RH for 24 h to reach moisture equilibrium. Then, the samples were dried at 120 °C for 12 h, constituting one moisture absorption-desorption cycle. A total of 10 moisture absorption-desorption cycles were then performed, and the moisture absorption of each sample was calculated. The results are as follows: Figure 3 As shown.

[0110] Analysis of the above results, comparing Examples 1 to 3 and Comparative Example 2, shows that the concentration of the acidic solution has a significant impact on the gelation process of sodium alginate solution and the pore structure of the formed hydrogel. By controlling the concentration of the acidic solution, hydrogels of different morphologies can be prepared, thus enabling customized production according to actual application needs. Compared to Example 2, the hydrogels prepared in Examples 1 and 3 have a uniform conical porous structure, exhibiting a faster hygroscopic-desorption rate. Furthermore, when the concentration of the acidic solution is too low, the sodium alginate solution cannot form a hydrogel.

[0111] Comparing Examples 1, 4, and 5 with Comparative Example 1, it is evident that the type of acidic solution significantly influences the gelation process of sodium alginate solution and the pore structure of the formed hydrogel. Compared to acetic acid, 2-acrylamido-2-methylpropanesulfonic acid, hydrochloric acid, and sulfuric acid can induce hydrogel formation in sodium alginate solution. Furthermore, compared to hydrochloric acid and sulfuric acid, using 2-acrylamido-2-methylpropanesulfonic acid as the acidic component results in a shorter gelation time for the sodium alginate solution, and the formed hydrogel exhibits a moderately conical porous structure.

[0112] Comparing Example 1, Comparative Example 4 and Comparative Example 5, it can be seen that acrylamide and sodium p-styrene sulfonate cannot induce sodium alginate solution to form a hydrogel, while 2-acrylamide-2-methylpropanesulfonic acid can induce sodium alginate solution to form a hydrogel through the hydrogen ions generated by the ionization of its aqueous solution.

[0113] Comparing Example 1 and Comparative Example 3, it can be seen that the hydrogel with the directional conical pore structure has excellent performance in preventing salt solution leakage. After 10 moisture absorption-desorption cycle tests, its moisture absorption amount did not change significantly.

[0114] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a directional conical porous hydrogel with atmospheric water collection capability, characterized in that, The method includes the following steps: (1) Sodium alginate is mixed with water and stirred until it becomes a paste to obtain a sodium alginate solution; wherein the amount of sodium alginate in the sodium alginate solution is 1~5 wt%; (2) The acidic substance is mixed with water and stirred until homogeneous to obtain an acidic solution; the acidic substance is 2-acrylamide-2-methylpropanesulfonic acid; the amount of the acidic substance in the acidic solution is 10~30 wt%; (3) Pour the sodium alginate solution obtained in step (1) into the mold, then add the acidic solution obtained in step (2), and after standing, a hydrogel with a directional cone-shaped porous structure is obtained; the volume ratio of sodium alginate solution to acidic solution in the mold is 1: (1~3). (4) Immerse the hydrogel with directional conical porous structure obtained in step (3) in a hygroscopic salt solution, and after standing, obtain a hydrogel with directional conical porous structure that has atmospheric water collection ability.

2. The method according to claim 1, characterized in that, The amount of acidic substance used in step (2) in the acidic solution is 15~25 wt%.

3. The method according to claim 1, characterized in that, The hygroscopic salt solution in step (4) is obtained by mixing hygroscopic salt and water and stirring evenly; wherein the amount of hygroscopic salt in the hygroscopic salt solution is 1~35 wt%.

4. The method according to claim 3, characterized in that, The hygroscopic salt is one or more of lithium chloride, calcium chloride, lithium bromide, and magnesium chloride.

5. A directional conical porous hydrogel with atmospheric water collection capability prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the directional conical porous hydrogel with atmospheric water collection capability as described in claim 5 in the field of atmospheric water collection.

7. A method for improving the hygroscopic-desorption cycle performance of hydrogels, characterized in that, The method includes the following steps: (1) Sodium alginate is mixed with water and stirred until it becomes a paste to obtain a sodium alginate solution; wherein the amount of sodium alginate in the sodium alginate solution is 1~5 wt%; (2) The acidic substance is mixed with water and stirred until homogeneous to obtain an acidic solution; the acidic substance is 2-acrylamide-2-methylpropanesulfonic acid; the amount of the acidic substance in the acidic solution is 10~30 wt%; (3) Pour the sodium alginate solution obtained in step (1) into the mold, then add the acidic solution obtained in step (2), and after standing, a hydrogel with a directional cone-shaped porous structure is obtained; the volume ratio of sodium alginate solution to acidic solution in the mold is 1: (1~3). (4) Immerse the hydrogel with directional conical porous structure obtained in step (3) in a hygroscopic salt solution, and after standing, obtain a hydrogel with directional conical porous structure that has atmospheric water collection ability.

Images