Hydrogel material with high water-retaining property based on moisture absorption salt in-situ doping as well as preparation method and application of hydrogel material

Abstract

The invention belongs to the technical field of functional high polymer materials and water resources, and discloses a method for preparing a water-based hydrogel, which comprises the following steps: adding a solution containing acrylamides and a photoinitiator and a solution containing the photoinitiator and acrylic acid-2-hydroxyethyl ester into a saturated solution of hygroscopic salt to form a pre-gel solution; wherein the acrylamides are any one or more of acrylamide and N-isopropylacrylamide, and the acrylamide is one or more of acrylamide and N-isopropylacrylamide; and carrying out illumination polymerization on the pre-gel solution to form a gel base material, and drying to obtain the moisture absorption salt in-situ doped high-water-retention hydrogel material. According to the preparation method disclosed by the invention, a copolymerization reaction is initiated by ultraviolet light of acrylamide and acrylic acid-2-hydroxyethyl ester, moisture absorption salt is introduced in situ, and the double-network structure hydrogel with synergistic chemical cross-linking and physical cross-linking is constructed, so that the key problems of high energy consumption, salt leakage and limited humidity adaptability of traditional atmospheric water collection gel preparation are solved; and a solution is provided for obtaining low-cost and high-performance water resources in arid regions.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of moisture-absorbing materials, and particularly relates to a highly water-retentive hydrogel material based on in-situ doping of moisture-absorbing salts, a preparation method thereof, and applications thereof. Background Art

[0002] The freshwater resource crisis is threatening global sustainable development, and it is urgent to break through the traditional technical framework to develop a new water source supply system. As a potential alternative water source, atmospheric water vapor has a reserve of 1290 billion tons, which is six times the total amount of global river water, and has advantages such as wide spatial distribution and strong mobility. In theory, a water capture rate of about 5% can still be achieved in extremely arid regions. Existing fog collection and condensation technologies are limited in application due to their dependence on specific temperature and humidity conditions or the need for continuous energy supply. Adsorptive water collection technology, relying on the self-adsorption and desorption characteristics of materials, shows unique value in low energy consumption and all-weather operation. However, its industrial application is restricted by the need to synchronously optimize the adsorption capacity, humidity response range, water capture rate, and scalability of key material properties.

[0003] Hydrogels are materials with strong hydrophilicity and good three-dimensional porous structures, capable of continuously transporting water to the surface and quickly evaporating, showing great advantages in water absorption and transportation. They are promising environmental water collection materials, but still have problems such as complex preparation processes, high manufacturing costs, and salt leakage risks that limit environmental friendliness. For example, the patent CN118063839A uses a hydroxyethyl cellulose / carbon nanotube composite gel formed by freeze-drying for 48 hours, and the patent CN117582934A even requires two freeze-drying processes (8 - 12 hours each), greatly increasing the production cost. In addition, most existing materials load moisture-absorbing salts (such as LiCl, CaCl 2 ) through post-impregnation methods, and the salt ions are prone to leakage due to weak physical adsorption forces, not only reducing the moisture absorption efficiency but also polluting the environment. While considering synthesis time, cost-effectiveness, and sustainability, developing a new generation of atmospheric water collection materials with rapid preparation, controllable structure, wide-range humidity response, and long-term stability has become the key breakthrough direction in this field. Summary of the Invention

[0004] To overcome the problems of complex preparation processes and salt leakage in existing environmental water collection materials, the purpose of the present invention is to provide a highly water-retentive hydrogel material based on in-situ doping of moisture-absorbing salts, a preparation method thereof, and applications thereof. This hydrogel material has strong hydrophilicity, and the preparation method avoids the problem of salt leakage.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A preparation method of a highly water-retentive hydrogel material with in-situ doping of moisture-absorbing salts, comprising the following steps:

[0007] A solution containing acrylamide and a photoinitiator and a solution containing a photoinitiator and 2-hydroxyethyl acrylate are added to a saturated solution of a hygroscopic salt to form a pre-gel solution; wherein, the acrylamide is any one or more of acrylamide and N-isopropylacrylamide;

[0008] The pre-gel solution is subjected to photo-polymerization to form a gel substrate, and then dried to obtain a highly water-retaining hydrogel material with in-situ doping of hygroscopic salt.

[0009] Furthermore, the hygroscopic salt is any one or more of calcium chloride, lithium chloride and magnesium chloride.

[0010] Furthermore, the photoinitiator is diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide.

[0011] Furthermore, in the solution containing monomer A and the photoinitiator, the mass ratio of the photoinitiator to monomer A is 0.1-0.2:100.

[0012] Furthermore, in the solution containing the photoinitiator and monomer B, the mass ratio of the photoinitiator to monomer B is 0.1-0.2:100.

[0013] Furthermore, the volume ratio of the solution containing monomer A and the photoinitiator to the solution containing the photoinitiator and monomer B is 1-4:1.

[0014] Furthermore, the volume ratio of the solution containing the photoinitiator and monomer B to the saturated solution of the hygroscopic salt is 0.01-0.1:0.5.

[0015] Furthermore, the photo-polymerization is carried out under the full-spectrum irradiation of a 300W xenon lamp, the irradiation distance of the sample is 5-15 cm, and the irradiation time is 3-10 min.

[0016] A highly water-retaining hydrogel material with in-situ doping of hygroscopic salt.

[0017] An application of a highly water-retaining hydrogel material with in-situ doping of root hygroscopic salt for air water intake at different humidities in arid regions.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention proposes an innovative method for preparing an atmospheric water collection hydrogel: through the ultraviolet light-initiated copolymerization reaction of acrylamide (AAm) and 2-hydroxyethyl acrylate (HEA), a hygroscopic salt (such as LiCl) is in-situ introduced to construct a double-crosslinked network structure hydrogel. This technology breaks through the dependence on traditional freeze-drying and has the following core advantages: (1) High-efficiency and low-energy consumption preparation: Ultraviolet light polymerization can complete gel curing within a few minutes, without freeze pretreatment and vacuum dehydration, reducing energy consumption and enabling large-scale production; (2) Precise structure regulation: By adjusting the mass ratio of AAm and HEA and the mass ratio of photoinitiator to monomer, a double-network hydrogel system is constructed using ultraviolet light-initiated in-situ polymerization technology. The first network is a covalent crosslinked network formed by AAm and HEA, endowing the material with structural stability; the second network is a physical crosslinked network formed by the coordination of the hydroxyl groups on the HEA molecular chain with the amide groups of AAm through dynamic hydrogen bonds and the coordination of the carboxylic acid groups of HEA with the cations in the hygroscopic salt solution (such as Li + ). The double-network structure synergistically formed by chemical crosslinking (covalent bonds) and physical crosslinking (hydrogen bonds / ionic bonds) endows the material with excellent mechanical strength and water retention capacity, avoiding the leakage of salt ions; (3) Wide humidity adaptability: The hygroscopic salt is uniformly dispersed in the gel network in-situ, reducing the water vapor adsorption barrier through the dissociation of salt ions, enabling the material to maintain a high adsorption capacity in the range of 30%-90% RH. This technology provides a new path for the development of low-cost and high-performance atmospheric water collection materials, and has important practical significance for alleviating the water resource crisis in arid regions. Description of the Drawings

[0020] Figure 1 SEM images of PAAm, P(AcH) and PHEA samples; among them, (a) is PAAm, (b) is P(AcH), and (c) is PHEA;

[0021] Figure 2 XRD patterns of PAAm-L, P(AcH)-L and PHEA-L samples;

[0022] Figure 3 FTIR spectra of PAAm-L, P(AcH)-L and PHEA-L samples;

[0023] Figure 4 For the hygroscopic material PH 0.75 -L, PH 1 -L, PH 1.5 -L, PH 2 -L, P(A 0.5 H 0.5 )-L, P(A 1 H 0.5 )-L, P(A 1.5 H 0.5 )-L, P(A2 H 0.5 )-L, P(A 8 )-L's saturated moisture absorption capacity and the distribution ratio of water inside or outside the gel;

[0024] Figure 5 Are the morphological diagrams of PHEA-L, P(AcH)-L and PAAm-L samples after moisture absorption; among them, (a) is PHEA-L, (b) is P(AcH)-L, and (c) is PAAm-L;

[0025] Figure 6 Is the moisture absorption capacity diagram of PAAm-L, P(AcH)-L and PHEA-L moisture absorption materials at 30% RH;

[0026] Figure 7 Is the moisture absorption capacity diagram of PAAm-L, P(AcH)-L and PHEA-L moisture absorption materials at 90% RH;

[0027] Figure 8 _Is the moisture absorption capacity diagram of PAAm-C, P(AcH)-C and PHEA-C moisture absorption materials at 90% RH;

[0028] Figure 9 Is the moisture absorption capacity diagram of P(AcH)-C sample at 30%, 60%, 70% and 90% RH. Detailed implementation manners

[0029] For the convenience of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0030] The present invention provides a preparation method of a highly water-retaining hydrogel material with in-situ doping of hygroscopic salts, which has high efficiency, low energy consumption, and wide humidity adaptability, can alleviate the global shortage of fresh water resources, and at the same time provides a new feasible way to solve the global energy crisis, and solves the problems of complex preparation process and high energy consumption existing in the prior art.

[0031] A preparation method of a highly water-retaining hydrogel material with in-situ doping of hygroscopic salts according to the present invention includes the following steps:

[0032] 1) Dissolve monomer A in water, add a photoinitiator and mix ultrasonically to form solution A;

[0033] 2) Mix the photoinitiator and monomer B and ultrasonically form solution B;

[0034] 3) Dissolve the hygroscopic salt in water and stir to form a saturated salt solution C;

[0035] 4) Respectively take solution A and solution B, add them to the saturated salt solution C, and mix evenly to form a pre-gel solution;

[0036] 5) Place the pre-gel solution under a xenon lamp for photo-polymerization to form a gel substrate;

[0037] 6) Dry the polymerized gel to obtain an atmospheric water harvesting hydrogel material.

[0038] The monomer A is any one or more of acrylamide and N-isopropylacrylamide; the monomer B is 2-hydroxyethyl acrylate; the solution C is selected from any one or more of aqueous solutions of calcium chloride, lithium chloride and magnesium chloride; the photoinitiator is diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide.

[0039] In step 1), the mass ratio of monomer A to water is 0.5-2:1, preferably 0.5:1, 1:1, 1.5:1 or 2:1, and most preferably 1:1. The mass ratio of the photoinitiator to monomer A is 0.1-0.2:100, preferably 0.1:100, 0.15:100 or 0.2:100, and most preferably 0.15:100.

[0040] Preferably, in step 1), the ultrasonic time is 3-10 min.

[0041] In step 2), the mass ratio of the photoinitiator to monomer B is 0.1-0.2:100, preferably 0.1:100, 0.15:100 or 0.2:100, and most preferably 0.15:100.

[0042] Preferably, in step 2), the ultrasonic time is 2-5 min.

[0043] In step 4), the volume ratio of solution A to solution B is 1-4:1, preferably 1:1, 2:1 or 4:1, and most preferably 2:1. The volume ratio of solution B to the saturated salt solution C is 0.01-0.1:0.5, preferably 0.01:0.5, 0.03:0.5, 0.06:0.5 or 0.1:0.5, and most preferably 0.06:0.5.

[0044] In step 4), solutions A, B and the saturated salt solution C are all stored in a light-proof environment to prevent the solutions from gelation. The mixing method of solutions A, B and the saturated salt solution C is ultrasonic or shaking to mix evenly, and the mixing time is 5-10 min.

[0045] In step 5), the wavelength range of the xenon lamp is 300 - 800 nm, and most preferably, it is the full-spectrum irradiation of a 300W xenon lamp. The distance between the xenon lamp and the pre-gel solution is 5 - 15 cm, most preferably 10 cm, and the irradiation time is 3 - 10 min. The irradiation time is adjusted according to the thickness and size of the sample.

[0046] Preferably, in step 6), the drying process of the gel substrate is either ordinary oven drying or vacuum drying. The temperature for ordinary oven drying is 70 - 90 °C, and the drying time is 5 - 12 h. The temperature for vacuum drying oven drying is 70 - 90 °C, and the drying time is 12 - 24 h.

[0047] The highly water-retentive hydrogel material prepared by the in-situ doping of hygroscopic salts of the present invention can be used for air water intake applications at different humidities in arid regions.

[0048] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0049] Example 1

[0050] This example provides a preparation method of a highly water-retentive hydrogel material with in-situ doping of hygroscopic salts, and the steps are as follows:

[0051] Dissolve 1 g of acrylamide in 1 mL of water and disperse it evenly by ultrasonic treatment. Add 1.5 mg of photoinitiator and ultrasonic for 3 min, and mix evenly to obtain solution A. Then, take 1 mL of 2-hydroxyethyl acrylate and add 1.5 mg of photoinitiator and mix evenly by ultrasonic treatment to obtain solution B. Take 60 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 1 mL of saturated LiCl solution to the pre-gel solution, mix it evenly by a rotary shaker for 5 min, place it under a xenon lamp for light polymerization for 2 min, and the irradiation distance is 10 cm. After the sample is completely polymerized, transfer it to an oven at 80 °C and dry it for 12 h to obtain a highly water-retentive hydrogel material with in-situ doping of hygroscopic salts, that is, P(A 0.5 H 0.5 )-L gel substrate.

[0052] Example 2

[0053] This example provides a preparation method of a highly water-retentive hydrogel material with in-situ doping of hygroscopic salts, and the steps are as follows:

[0054] Dissolve 1 g of acrylamide in 1 mL of water and disperse it evenly by ultrasonic treatment. Add 1.5 mg of photoinitiator and ultrasonicate for 10 min to obtain a homogeneous solution A. Then, take 1 mL of 2-hydroxyethyl acrylate, add 1.5 mg of photoinitiator, and ultrasonically mix to obtain solution B. Take 120 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 1 mL of saturated LiCl solution to the pre-gel solution and mix it evenly by a rotary shaker for 10 min. Place it under a xenon lamp for photo-polymerization for 2 min at a distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, namely P(A 1 H 0.5 )-L gel substrate, named P(AcH)-L.

[0055] Example 3

[0056] This example provides a method for preparing a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0057] Dissolve 1 g of acrylamide in 1 mL of water and disperse it evenly by ultrasonic treatment. Add 1.5 mg of photoinitiator and ultrasonicate for 5 min to obtain a homogeneous solution A. Then, take 1 mL of 2-hydroxyethyl acrylate, add 1.5 mg of photoinitiator, and ultrasonically mix to obtain solution B. Take 180 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 1 mL of saturated LiCl solution to the pre-gel solution and mix it evenly by a rotary shaker for 7 min. Place it under a xenon lamp for photo-polymerization for 2 min at a distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, namely P(A 1.5 H 0.5 )-L gel substrate.

[0058] Example 4

[0059] This example provides a method for preparing a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0060] Dissolve 1 g of acrylamide in 1 mL of water and disperse it evenly by ultrasonic treatment. Add 1.5 mg of photoinitiator and ultrasonicate for 7 min to obtain a homogeneous solution A. Then, take 1 mL of 2-hydroxyethyl acrylate, add 1.5 mg of photoinitiator, and ultrasonically mix to obtain solution B. Take 240 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 1 mL of saturated LiCl solution to the pre-gel solution and mix it evenly by a rotary shaker for 8 min. Place it under a xenon lamp for photo-polymerization for 2 min at a distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, namely P(A 2 H 0.5 )-L gel substrate.

[0061] Comparative Example 1

[0062] This comparative example provides a method for preparing a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0063] Add 1 mL of 2-hydroxyethyl acrylate to 1.5 mg of photoinitiator and ultrasonically mix to obtain solution B. Take 45 μL of solution B to obtain a pre-gel solution. Then, add 1 mL of saturated LiCl solution to the pre-gel solution and mix it evenly by a rotary shaker. Place it under a xenon lamp for photo-polymerization for 2 min at a distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a hydrogel material, namely PH 0.75 -L gel substrate.

[0064] Comparative Example 2

[0065] This comparative example provides a method for preparing a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0066] Add 1 mL of 2-hydroxyethyl acrylate to 1.5 mg of photoinitiator and ultrasonically mix to obtain solution B. Take 60 μL of solution B to obtain a pre-gel solution. Then, add 1 mL of saturated LiCl solution to the pre-gel solution and mix it evenly by a rotary shaker. Place it under a xenon lamp for photo-polymerization for 2 min. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a hydrogel material, namely PH 1 -L gel substrate, named PHEA-L.

[0067] Comparative Example 3

[0068] This comparative example provides a method for preparing a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0069] 1 mL of 2-hydroxyethyl acrylate was added with 1.5 mg of photoinitiator and ultrasonically mixed evenly to obtain Solution B. 90 μL of Solution B was taken to obtain a pre-gel solution. Then, 1 mL of saturated LiCl solution was added to the pre-gel solution and mixed evenly by a rotary shaker. It was placed under a xenon lamp for photo-polymerization for 2 min. After the sample was completely polymerized, it was transferred to an oven and dried at 80 °C for 12 h to obtain a hydrogel material, namely PH 1.5 -L gel substrate.

[0070] Comparative Example 4

[0071] This comparative example provides a preparation method of a highly water-retaining hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0072] 1 mL of 2-hydroxyethyl acrylate was added with 1.5 mg of photoinitiator and ultrasonically mixed evenly to obtain Solution B. 120 μL of Solution B was taken to obtain a pre-gel solution. Then, 1 mL of saturated LiCl solution was added to the pre-gel solution and mixed evenly by a rotary shaker. It was placed under a xenon lamp for photo-polymerization for 2 min. After the sample was completely polymerized, it was transferred to an oven and dried at 80 °C for 12 h to obtain a hydrogel material, namely PH 2 -L gel substrate.

[0073] Comparative Example 5

[0074] This comparative example provides a preparation method of a highly water-retaining hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0075] 1 g of acrylamide was dissolved in 1 mL of water and ultrasonically dispersed evenly, then 1.5 mg of photoinitiator was added and ultrasonically mixed evenly to obtain Solution A. 480 μL of Solution A was taken to obtain a pre-gel solution. Then, 1 mL of saturated LiCl solution was added to the pre-gel solution and mixed evenly by a rotary shaker. It was placed under a xenon lamp for photo-polymerization for 2 min. After the sample was completely polymerized, it was transferred to an oven and dried at 80 °C for 12 h to obtain a hydrogel material, namely PA 8 -L, named PAAm-L gel substrate.

[0076] Example 5

[0077] This example provides a preparation method of a highly water-retaining P(AAm-HEA)-CaCl 2 hydrogel material, and the steps are as follows:

[0078] Dissolve 1 g of acrylamide in 1 mL of water and disperse it evenly by ultrasonic treatment. Add 1.5 mg of photoinitiator and ultrasonicate for 3 min to obtain a homogeneous solution A. Then, take 1 mL of 2-hydroxyethyl acrylate, add 1.5 mg of photoinitiator, and ultrasonically mix to obtain solution B. Take 120 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 1 mL of saturated CaCl 2 solution, mix it evenly using a rotary shaker for 5 min, place it under a xenon lamp for photo-polymerization for 2 min at a distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, namely the P(AcH)-C gel substrate.

[0079] Comparative Example 6

[0080] This comparative example provides a method for preparing a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0081] Dissolve 1 g of acrylamide in 1 mL of water and disperse it evenly by ultrasonic treatment. Add 1.5 mg of photoinitiator and ultrasonically mix to obtain solution A. Take 480 μL of solution A to obtain a pre-gel solution. Then, add 1 mL of saturated CaCl 2 solution, mix it evenly using a rotary shaker, place it under a xenon lamp for photo-polymerization for 2 min at a distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a hydrogel material, namely the PAAm-C gel substrate.

[0082] Comparative Example 7

[0083] This comparative example provides a method for preparing a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0084] Add 1 mL of 2-hydroxyethyl acrylate to 1.5 mg of photoinitiator and ultrasonically mix to obtain solution B. Take 120 μL of solution B to obtain a pre-gel solution. Then, add 1 mL of saturated CaCl 2 solution, mix it evenly using a rotary shaker, place it under a xenon lamp for photo-polymerization for 2 min at a distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a hydrogel material, namely the PHEA-C gel substrate.

[0085] Example 6

[0086] This example provides a method for preparing a highly water-retentive P(AAm-HEA)-MgCl 2 hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0087] Dissolve 1 g of acrylamide in 1 mL of water and disperse it evenly by ultrasonic treatment. Add 1.5 mg of photoinitiator and ultrasonicate for 8 min, and mix evenly to obtain solution A. Then, take 1 mL of 2-hydroxyethyl acrylate, add 1.5 mg of photoinitiator, and ultrasonically mix evenly to obtain solution B. Take 120 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 1 mL of saturated MgCl 2 solution, mix it evenly by a rotary shaker for 5 min, place it under a xenon lamp for photo-polymerization for 2 min, with the irradiation distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, namely the P(AcH)-M gel substrate.

[0088] Example 7

[0089] This example provides a method for preparing a highly water-retentive P(NIPAA-HEA)-LiCl 2 hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0090] Dissolve 1 g of N-isopropylacrylamide in 1 mL of water and disperse it evenly by ultrasonic treatment. Add 1.5 mg of photoinitiator and ultrasonicate for 3 min, and mix evenly to obtain solution A. Then, take 1 mL of 2-hydroxyethyl acrylate, add 1.5 mg of photoinitiator, and ultrasonically mix evenly to obtain solution B. Take 120 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 0.5 mL of saturated LiCl solution to the pre-gel solution, mix it evenly by a rotary shaker for 5 min, place it under a xenon lamp for photo-polymerization for 2 min, with the irradiation distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, namely the P(NcH)-L gel substrate.

[0091] Example 8

[0092] This example provides a method for preparing a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt, and the steps are as follows:

[0093] Dissolve 0.5 g of acrylamide in 1 mL of water and disperse it evenly by ultrasonic treatment. Add 1.5 mg of photoinitiator and ultrasonicate for 3 min, and mix evenly to obtain solution A. Then, take 1 mL of 2-hydroxyethyl acrylate, add 2 mg of photoinitiator, and ultrasonically mix evenly to obtain solution B. Take 60 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 0.3 mL of saturated LiCl solution to the pre-gel solution, mix it evenly by a rotary shaker for 5 min, place it under a xenon lamp for photo-polymerization for 2 min, with the irradiation distance of 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a highly water-retentive hydrogel material with in-situ doping of hygroscopic salt.

[0094] Example 9

[0095] This example provides a method for preparing a highly water-retaining hydrogel material with in-situ doping of hygroscopic salts, and the steps are as follows:

[0096] Dissolve 1 g of acrylamide and 0.5 g of N-isopropylacrylamide in 1 mL of water, ultrasonically disperse evenly, add 2 mg of photoinitiator and ultrasonically mix for 3 min to obtain solution A. Then, take 1 mL of 2-hydroxyethyl acrylate, add 1 mg of photoinitiator and ultrasonically mix evenly to obtain solution B. Take 180 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 3 mL of saturated magnesium chloride solution to the pre-gel solution, mix evenly by a rotary shaker for 5 min, place it under a xenon lamp for photo-polymerization for 2 min, and the irradiation distance is 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a highly water-retaining hydrogel material with in-situ doping of hygroscopic salts.

[0097] Example 10

[0098] This example provides a method for preparing a highly water-retaining hydrogel material with in-situ doping of hygroscopic salts, and the steps are as follows:

[0099] Dissolve 2 g of acrylamide in 1 mL of water, ultrasonically disperse evenly, add 1.5 mg of photoinitiator and ultrasonically mix for 3 min to obtain solution A. Then, take 1 mL of 2-hydroxyethyl acrylate, add 1.5 mg of photoinitiator and ultrasonically mix evenly to obtain solution B. Take 240 μL of solution A and 60 μL of solution B and mix them to obtain a pre-gel solution. Then, add 1.5 mL of saturated calcium chloride solution to the pre-gel solution, mix evenly by a rotary shaker for 5 min, place it under a xenon lamp for photo-polymerization for 2 min, and the irradiation distance is 10 cm. After the sample is completely polymerized, transfer it to an oven and dry it at 80 °C for 12 h to obtain a highly water-retaining hydrogel material with in-situ doping of hygroscopic salts.

[0100] As Figure 1 shown in (a), (b) and (c), the scanning electron microscope (SEM) images of PAAm, P(AcH) and PHEA samples are shown in sequence, and the samples all exhibit a loose porous structure and pore channels.

[0101] As Figure 2 shown, the X-ray diffraction (XRD) patterns of PAAm-L, P(AcH)-L and PHEA-L samples are shown. The characteristic peaks corresponding to LiCl and LiCl·H 2 2O crystals confirm the successful loading of lithium chloride in the samples.

[0102] As Figure 3As shown, the Fourier transform infrared spectroscopy (FTIR) diagrams of PAAm-L, P(AcH)-L, and PHEA-L samples are presented. The obvious characteristic peak of C-N stretching vibration in the FTIR spectrum of the P(AcH)-L sample confirms that AAm has been successfully introduced into the polymer network and a double network structure has been formed.

[0103] The following is the moisture absorption performance test of a highly water-retaining hydrogel material doped with hygroscopic salts in-situ:

[0104] Example 12

[0105] Place the dried composite hygroscopic materials PH 0.75 -L, PH 1 -L, PH 1.5 -L, PH 2 -L, P(A 0.5 H 0.5 )-L, P(A 1 H 0.5 )-L, P(A 1.5 H 0.5 )-L, P(A 2 H 0.5 )-L, P(A 8 )-L in a thermostatic and humidistatic chamber, adjust the temperature to 25 °C and the relative humidity (RH) to 90%, and measure their mass changes every 1 h for 12 consecutive hours.

[0106] As Figure 4 shown, in order to verify the advantages of the double cross-linked network, Comparative Examples 1-5 are the material compositions of adding LiCl hygroscopic salts when the gel substrate only contains different contents of monomer HEA and only contains monomer AAm. By Figure 4 proving their moisture absorption effects and water leakage problems, and making a comparison with the examples to prove the high-efficiency water retention advantages of the double network cross-linking. Among them, when the gel system only contains the HEA monomer (PH 0.75 -L), its maximum moisture absorption reaches 4.55 g g -1 . However, due to the weak binding force of the single physical cross-linked network (hydrogen bond), about 57.8% of the adsorbed water (2.63 g g -1 ) exists in the free state outside the gel, and there is a risk of salt ion leakage. This phenomenon stems from the low cross-linking density of the single HEA network and the easy dissociation characteristics of dynamic hydrogen bonds, resulting in the inability of the hygroscopic salt to be effectively anchored on the polymer chain. By introducing acrylamide (AAm) to construct a double cross-linked network (P(HEA-AAm)-L), the synergistic effect of chemical cross-linking (AAm covalent bond) and physical cross-linking (HEA hydrogen bond) significantly improves the structural stability of the hydrogel, and its water retention is significantly improved. However, excessive AAm will cause pore collapse due to over-cross-linking, resulting in a decrease in moisture absorption.

[0107] AsFigure 5 As shown in (a), (b) and (c), the morphological comparison of PHEA-L, P(AcH)-L and PAAm-L samples after moisture absorption shows that obvious liquid water seeps out on the surface and around the PHEA-L sample, while P(AcH)-L shows significant volume expansion and no free water is precipitated, confirming that its double-crosslinked network effectively inhibits water escape and significantly improves the water retention rate by enhancing the rigidity of polymer chains and efficiently anchoring the moisture-absorbing salt LiCl.

[0108] Example 13

[0109] Place the dried PAAm-L, P(AcH)-L and PHEA-L composite moisture-absorbing materials in a thermostatic and humidistatic chamber, adjust the temperature to 25 °C, and the relative humidity (RH) to 30% and 90%. Test their mass changes every 1 h and continuously test for 12 h.

[0110] As Figure 6 shown, the moisture absorption amounts of PAAm-L, P(AcH)-L and PHEA-L composite moisture-absorbing materials at 30% RH are 0.79 g / g -1 , 1.49 g / g -1 and 1.49 g / g -1 ; as Figure 7 shown, the moisture absorption amounts of PAAm-L, P(AcH)-L and PHEA-L composite moisture-absorbing materials at 90% RH are 3.08 g / g -1 , 4.07 g / g -1 and 4.49 g / g -1 .

[0111] Example 14

[0112] Place the dried PAAm-C, P(AcH)-C and PHEA-C composite moisture-absorbing materials in a thermostatic and humidistatic chamber, adjust the temperature to 25 °C, and the relative humidity (RH) to 90%. Test their mass changes every 1 h and continuously test for 12 h.

[0113] As Figure 8 shown, by comparing the P(AcH)-C material prepared in Example 6, the PAAm-C gel substrate containing only the monomer AAm in Comparative Example 6, and the PHEA-C gel substrate containing only the monomer HEA in Comparative Example 7, the corresponding moisture absorption amounts of PAAm-C, P(AcH)-C and PHEA-C when reaching saturation are 1.93 g / g -1 , 2.38 g / g -1 , 2.45 g / g -1 . It is proved that the moisture-absorbing salt loaded with CaCl 2 still has high moisture absorption performance at 90% humidity.

[0114] Example 15

[0115] Put the dried P(AcH)-C composite hygroscopic material in a thermostatic and humidity-controlled chamber, adjust the temperature to 25 °C, and the relative humidity (RH) to 30%, 60%, 70% and 90%. Test its mass change every 1 h and continuously test for 12 h.

[0116] As Figure 9 shown, the corresponding moisture absorption amounts when P(AcH)-C reaches saturation are 0.64 g g -1 、1.02 g g -1 、1.53 g g -1 、2.38 g g -1 . It is proved that the loaded CaCl 2 hygroscopic salt still has hygroscopic properties at relatively low humidity.

[0117] The preparation method of the present invention is more environmentally friendly and green on the basis of the existing preparation technology, and the process is simple and easy to operate. This method generates useful energy by absorbing moisture in the atmosphere and sunlight, solves the problem of atmospheric water intake and at the same time photocatalytic overall water splitting for hydrogen production, and opens up a new way for the development of photocatalytic hydrogen production in areas with sufficient light but water shortage.

[0118] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high water-retaining hydrogel material in situ doped with hygroscopic salt, characterized in that: The following steps are involved: Adding a solution containing acrylamide and a photoinitiator and a solution containing a photoinitiator and 2-hydroxyethyl acrylate to a saturated solution of a hygroscopic salt to form a pre-gel solution; wherein the acrylamide is any one or more of acrylamide and N-isopropylacrylamide; The pre-gel solution is photopolymerized to form a gel matrix, and then dried to obtain a high water-retaining hydrogel material in situ doped with hygroscopic salt.

2. The method for preparing a high water-retaining hydrogel material in situ doped with hygroscopic salt according to claim 1, characterized in that: The hygroscopic salt is any one or more of calcium chloride, lithium chloride and magnesium chloride.

3. The method for preparing a high water-retaining hydrogel material in situ doped with hygroscopic salt according to claim 1, characterized in that: The photoinitiator is diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide.

4. The method for preparing a high water-retaining hydrogel material in situ doped with hygroscopic salt according to claim 1, characterized in that: In the solution containing monomer A and photoinitiator, the mass ratio of photoinitiator to monomer A is 0.1-0.2:

100.

5. The method for preparing a high water-retaining hydrogel material in situ doped with hygroscopic salt according to claim 1, characterized in that: In the solution containing the photoinitiator and the monomer B, the mass ratio of the photoinitiator to the monomer B is 0.1-0.2:

100.

6. The method for preparing a high water-retaining hydrogel material in situ doped with hygroscopic salt according to claim 1, characterized in that: The volume ratio of the solution containing monomer A and photoinitiator to the solution containing photoinitiator and monomer B is 1-4:

1.

7. The method for preparing a high water-retaining hydrogel material in situ doped with hygroscopic salt according to claim 1, characterized in that: The volume ratio of the solution containing the photoinitiator and the monomer B to the saturated solution of the hygroscopic salt is 0.01-0.1:0.

5.

8. The method for preparing a high water-retaining hydrogel material in situ doped with hygroscopic salt according to claim 1, characterized in that: The photopolymerization was carried out under full spectrum irradiation of a 300W xenon lamp, the irradiation distance to the sample was 5-15cm, and the irradiation time was 3-10min.

9. A high water-retaining hydrogel material in situ doped with hygroscopic salt prepared by the method according to any one of claims 1 to 8.

10. Use of a high water-retaining hydrogel material in situ doped with hygroscopic salt prepared by the method according to any one of claims 1 to 8 for air water extraction at different humidity levels in arid areas.

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