Thermosensitive polyelectrolyte double-network hydrogel material as well as preparation method and application thereof

Abstract

The invention belongs to the field of salt water desalination, and discloses a thermo-sensitive polyelectrolyte double-network hydrogel material as well as a preparation method and application thereof. The gel material comprises a first network and a second network, the first network is electrolyte hydrogel, the second network is temperature-sensitive hydrogel, and the first network and the second network are interwoven through a polymer chain to form a double-network structure. The thermal response temperature of the material can be flexibly regulated and controlled by adjusting the proportion of the monomers, so that the material can adapt to saline water with different concentrations. The preparation method comprises the following steps: preparing a gel precursor solution, removing oxygen, initiating polymerization forming through constant-temperature polymerization, soaking in a second network precursor solution, and finishing polymerization forming of the second network through photo-initiation or thermal initiation. The obtained gel shows excellent ion blocking efficiency and low energy consumption characteristics in brine desalination in a wide concentration range of 2wt.%-20wt.% by utilizing the repulsive interaction of polyelectrolyte on ions of the same charge, and has relatively high application potential.

Description

Technical Field

[0001] This invention relates to the field of brine desalination, and more particularly to a temperature-sensitive polyelectrolyte dual-network hydrogel material, its preparation method and application. This material exhibits superior desalination performance and low energy consumption compared to similar materials in the field of brine desalination. Background Technology

[0002] Global freshwater resources are becoming increasingly scarce. Against the backdrop of population growth and continuously expanding industrial and agricultural water demands, water shortages have become a key factor restricting sustainable social development. Traditional freshwater sources such as rivers, lakes, and groundwater are not only geographically unevenly distributed but also susceptible to climate change, seasonal droughts, and pollution, leading to increasingly saturated or even declining supply capacities. Seawater desalination technology, as a sustainable "open source" approach, can provide a stable, climate-independent freshwater supply and has become an important technological direction for alleviating water shortages in coastal and island regions and ensuring global water security. However, current mainstream seawater desalination technologies still face challenges such as high energy consumption, membrane fouling and scaling, system operational stability, and cost-effectiveness. There is an urgent need to develop new desalination materials and methods that are more efficient, energy-saving, and reliable.

[0003] In existing technologies, most research on hydrogels for brine desalination focuses on the photothermal evaporation-condensation pathway. For example, patent application CN202510769276A reports a chitosan-polyvinyl alcohol photothermal aerogel with high ion removal rate (99.9%) and high evaporation rate (3.8 kg·m³). - ²·h - ¹), the light absorption rate can reach 97% in humid environments. However, this type of technology relies on the phase change of water to achieve desalination, and the high latent heat of vaporization of water leads to high overall energy consumption, limiting its widespread application. Therefore, the preparation of a low-energy-consumption hydrogel applicable to a wider concentration range has broad application prospects. Summary of the Invention

[0004] In order to overcome the shortcomings and defects of the prior art, the primary objective of this invention is to provide a thermosensitive polyelectrolyte dual-network hydrogel material that combines the ion repulsion effect of polyelectrolytes with the volume shrinkage behavior of thermosensitive gels when heated, thereby enabling low-energy brine desalination.

[0005] Another object of the present invention is to provide a method for preparing a thermosensitive polyelectrolyte dual-network hydrogel material.

[0006] Another object of the present invention is to provide the application of the above-mentioned hydrogel material in the field of brine desalination.

[0007] The objective of this invention is achieved through the following technical solution: A thermosensitive polyelectrolyte dual-network hydrogel material includes a first network and a second network. The first network is an electrolyte hydrogel, and the second network is a thermosensitive hydrogel. The first network and the second network are interwoven with each other through polymer chains to form a dual-network structure.

[0008] Preferably, the thermosensitive polyelectrolyte dual-network hydrogel is synthesized by stepwise polymerization of the following monomers: By mass percentage, 0.5%–50% of monomer A, 0%–75% of monomer B, 1%–50% of monomer C and 0%–20% of monomer D, with the balance being water; Monomers A and D are polymerizable monomers containing acidic groups; monomer B is a neutral monomer; and monomer C is a temperature-sensitive monomer.

[0009] Preferably, the quality ratio of the first network to the second network is 1:1 to 5.

[0010] Preferably, the electrolyte hydrogel is prepared by polymerization reaction of monomer A, or monomer A and monomer B, crosslinking agent and initiator; The monomer A is selected from at least one of sodium acrylate, sodium methacrylate, sodium 2-acrylamido-2-methylpropanesulfonate, sodium vinyl sulfonate, sodium allyl sulfonate, and sodium propylene phosphonate; the monomer B is selected from at least one of acrylamide, N-hydroxymethylacrylamide, and N-vinylpyrrolidone; the molar ratio of monomer A to monomer B is 1:1 to 3.

[0011] Preferably, the thermosensitive hydrogel is prepared by polymerization reaction of monomer C, or monomer C and monomer D, crosslinking agent and initiator; the monomer C is selected from at least one of N-isopropylacrylamide, N-vinylcaprolactam, N-acryloylpyrrolidine, N,N-diethylacrylamide; the molar ratio of monomer C to monomer D is 2~20:1.

[0012] A method for preparing a thermosensitive polyelectrolyte dual-network hydrogel material includes the following steps: S1. Mix monomer A, or monomer A and monomer B, crosslinking agent and initiator with water to form a homogeneous solution, and deoxygenate the homogeneous solution to obtain a polyelectrolyte gel precursor solution. S2. The polyelectrolyte gel precursor solution is subjected to a polymerization reaction under constant temperature conditions to form a polyelectrolyte gel. S3. Mix monomer C, or monomer C with monomer D, crosslinking agent, initiator and water to obtain thermosensitive gel precursor solution; S4. The polyelectrolyte gel is immersed in the thermosensitive gel precursor solution, and a thermosensitive network is formed by polymerization reaction to obtain a thermosensitive polyelectrolyte dual-network hydrogel material.

[0013] Preferably, based on the polyelectrolyte gel precursor solution, it comprises, by mass percentage, 15% to 50% monomer A, 0% to 20% monomer B, 50% to 90% water, with the balance being crosslinking agent and initiator.

[0014] Preferably, based on the thermosensitive gel precursor solution, it comprises, by mass percentage, 0.5% to 10% monomer C, 0% to 10% monomer D, 80% to 95% water, with the balance being crosslinking agent and initiator.

[0015] Preferably, the amount of crosslinking agent added in S1 and S3 is 1% to 0.1% of the total molar amount of monomer A and monomer B, or monomer C and monomer D; the amount of initiator added is 0.5% to 0.01% of the total molar amount of monomer A and monomer B, or monomer C and monomer D.

[0016] Preferably, the crosslinking agent is selected from polyethylene glycol diacrylate and N,N'-methylenebisacrylamide; the initiator is selected from ammonium persulfate, hydrogen peroxide, azobisisobutyrazoline hydrochloride, V-50 initiator, α-ketoglutarate, or 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone.

[0017] Preferably, the deoxygenation in S1 is to introduce nitrogen gas into the homogeneous solution for 10-30 min; the constant temperature in S2 is 20-80℃ for 1-24 h; the mixing in S1 and S3 includes stirring until all solid components are dissolved; the impregnation time in S4 is 12-36 h; and the polymerization in S4 is photoinitiated polymerization for 10-60 min.

[0018] Application of the aforementioned thermosensitive polyelectrolyte dual-network hydrogel material in the field of brine desalination.

[0019] The innovation of this invention lies in combining the ion repulsion effect of polyelectrolytes with the volume shrinkage behavior of thermosensitive gels upon heating, thereby achieving a brine desalination process without heating the water to the phase transition temperature. This mechanism not only significantly reduces energy consumption but also avoids crystallization and contamination problems caused by salt leaching, making it suitable for brine treatment with a wider concentration range and demonstrating good engineering applicability and economic prospects.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The material prepared by the present invention can be used for the desalination of brine with a wide concentration range of 2wt.% to 20wt.%.

[0021] The desalination mechanism of this invention lies in the mutual repulsion between groups and ions carrying the same charge, thus achieving a desalination effect unaffected by the salt concentration. A 20% desalination rate can be achieved in a single application to a 3.5 wt.% sodium chloride solution. In contrast, existing literature, such as the study by Wael Ali et al. in *Applied Materials & Interfaces* (Vol. 7, 2015) entitled "Design of Thermally Responsive Polymeric Hydrogels for Brackish Water Desalination: Effect of Architecture on Swelling, Deswelling, and Salt Rejection," achieves a maximum desalination rate of 23% in a 2 g / L KCl solution, which is less suitable for a lower salt concentration than this invention.

[0022] (2) The present invention can further regulate the transition temperature of the hydrophilic monomer content in the temperature-sensitive network to adapt to a wider operating temperature range.

[0023] (3) The present invention provides a method for desalination of brine, which does not require heating the water to the phase change temperature, significantly reducing energy consumption, and effectively avoiding salt crystallization and pollution problems.

[0024] (4) The gel of the present invention can achieve a water recovery rate of 2-15% in a single cycle, and the material can be recycled and reused, which has good application prospects in the field of seawater desalination. Attached Figure Description

[0025] Figure 1 The images shown are a series of physical images of the preparation process in Example 1. Image a is a physical image of the gel prepared in step S2 of Example 1; image b is a physical image of the gel formed in step S4 of Example 1.

[0026] Figure 2 These are the Fourier transform infrared spectra of Examples 1 and 2.

[0027] Figure 3 This is a graph showing the swelling rate of Examples 1 and 2 in pure water (a) and 3.5 wt.% brine (b).

[0028] Figure 4 These are the test data from the desalination experiments in 3.5 wt.% saline solution of Examples 1, 2, and 3.

[0029] Figure 5 This is the desalination cycle experiment data in Example 3 in 3.5 wt.% brine. Detailed Implementation

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0031] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0032] NIPAM: N-isopropylacrylamide; SA: sodium acrylate; SAMPS: sodium 2-acrylamide-2-methylpropanesulfonate; NaMA: sodium methacrylate; AIBI: azobisisobutyrazoline hydrochloride.

[0033] Example 1 A method for preparing a thermosensitive polyelectrolyte dual-network hydrogel material includes the following steps: (1) Dissolve the acidic monomer SA (13.5 g), crosslinking agent N,N'-methylenebisacrylamide (180 mg), and initiator AIBI (137 mg) in deionized water (25 ml) and stir until all solids are dissolved to obtain a preliminary gel precursor solution, which includes 34.77% acidic monomer SA, 0.4637% crosslinking agent, 0.3529% initiator AIBI, and 64.40% deionized water. Then, purge nitrogen gas into the gel precursor solution for a period of time (10 min) to remove dissolved oxygen to obtain an oxygen-free preliminary gel precursor solution; (2) Transfer 3g of the precursor liquid into the mold and place it in a constant temperature water bath. Polymerize at 44℃ for 10 hours to obtain polyelectrolyte gel.

[0034] (3) Dissolve the thermosensitive monomer NIPAM (0.7770g), the acidic monomer SA (0.0777g), the crosslinking agent N,N'-methylenebisacrylamide (2.8mg), and the photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (15.6 mg) in deionized water (12ml) and stir until all solids are dissolved to obtain 12.8731g of thermosensitive gel precursor solution, which includes 6.04% thermosensitive monomer NIPAM, 0.60% acidic monomer SA, 0.02% crosslinking agent, 0.12% photoinitiator and 93.22% deionized water.

[0035] (4) The polyelectrolyte gel prepared in step 2 is soaked in the thermosensitive gel precursor solution for 24 hours. The thermosensitive gel precursor solution is completely swollen and absorbed by the polyelectrolyte gel. The polyelectrolyte gel that has swollen and absorbed the thermosensitive gel precursor solution is placed under a UV lamp for photo-initiated polymerization for 20 minutes to obtain a thermosensitive polyelectrolyte double network hydrogel material, including 6.5% of acidic monomer SA, 4.9% of thermosensitive monomer NIPAM, 0.49% of acidic monomer SA, and the remainder is water.

[0036] Example 2 A method for preparing a thermosensitive polyelectrolyte dual-network hydrogel material includes the following steps: (1) Dissolve 21.00 g of SAMPS containing acidic groups, 190 mg of N,N'-methylenebisacrylamide crosslinking agent, and 147 mg of AIBI in deionized water (25 ml) and stir until all solids are dissolved to obtain a preliminary gel precursor solution, which includes 45.32% SAMPS containing acidic groups, 0.4100% of crosslinking agent, 0.3172% of AIBI initiator, and 53.95% of deionized water. Then, purge nitrogen gas into the gel precursor solution for a period of time (10 min) to remove dissolved oxygen to obtain an oxygen-free preliminary gel precursor solution; (2) Transfer 3g of the precursor liquid into the mold and place it in a constant temperature water bath. Polymerize at 44℃ for 10 hours to obtain polyelectrolyte gel.

[0037] (3) Dissolve the thermosensitive monomer NIPAM (0.7770g), the acidic monomer SA (0.0777g), the crosslinking agent N,N'-methylenebisacrylamide (2.8mg), and the photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (15.6 mg) in deionized water (12ml) and stir until all solids are dissolved to obtain the thermosensitive gel precursor solution.

[0038] (4) The polyelectrolyte gel prepared in step 2 is soaked in the thermosensitive gel precursor solution for 24 hours. The thermosensitive gel precursor solution is completely swollen and absorbed by the polyelectrolyte gel. The polyelectrolyte gel that has swollen and absorbed the thermosensitive gel precursor solution is placed under a UV lamp for photo-initiated polymerization for 20 minutes to obtain a thermosensitive polyelectrolyte double network hydrogel material, including 8.6% of acidic monomer SAMPS, 4.9% thermosensitive monomer NIPAM, 0.49% acidic monomer SA, and the remainder is water.

[0039] Example 3 A method for preparing a thermosensitive polyelectrolyte dual-network hydrogel material includes the following steps: (1) Dissolve the acidic monomer NaMA (12.9684 g), crosslinking agent N,N'-methylenebisacrylamide (180 mg), and initiator AIBI (137 mg) in deionized water (25 ml) and stir until all solids are dissolved to obtain a preliminary gel precursor solution, which includes 33.87% acidic monomer NaMA, 0.4702% crosslinking agent, 0.3578% initiator AIBI, and 65.30% deionized water. Then, purge nitrogen gas into the gel precursor solution for a period of time (10 min) to remove dissolved oxygen to obtain an oxygen-free preliminary gel precursor solution; (2) Transfer 3g of the precursor liquid into the mold and place it in a constant temperature water bath. Polymerize at 44℃ for 10 hours to obtain polyelectrolyte gel.

[0040] (3) Dissolve the thermosensitive monomer NIPAM (0.7770g), the acidic monomer SA (0.0777g), the crosslinking agent N,N'-methylenebisacrylamide (2.8mg), and the photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (15.6 mg) in deionized water (12ml) and stir until all solids are dissolved to obtain the thermosensitive gel precursor solution.

[0041] (4) The polyelectrolyte gel prepared in step 2 is soaked in a thermosensitive gel precursor solution for 24 hours. The thermosensitive gel precursor solution is completely swollen and absorbed by the polyelectrolyte gel. The polyelectrolyte gel that has swollen and absorbed the thermosensitive gel precursor solution is placed under a UV lamp for photo-initiated polymerization for 20 minutes to obtain a thermosensitive polyelectrolyte double network hydrogel material, including 6.5% of acidic monomer NaMA, 4.9% of thermosensitive monomer NIPAM, 0.49% of acidic monomer SA, and the remainder is water.

[0042] Example 4 A method for preparing a thermosensitive polyelectrolyte dual-network hydrogel material includes the following steps: (1) Dissolve the acidic monomer SA (5.6424 g), crosslinking agent N,N'-methylenebisacrylamide (46 mg), and initiator AIBI (34 mg) in deionized water (25 ml) and stir until all solids are dissolved to obtain a preliminary gel precursor solution, which includes 18.37% acidic monomer SA, 0.1497% crosslinking agent, 0.1107% initiator AIBI, and 81.37% deionized water. Then, purge nitrogen gas into the gel precursor solution for a period of time (10 min) to remove dissolved oxygen to obtain an oxygen-free preliminary gel precursor solution; (2) Transfer 3g of the precursor liquid into the mold and place it in a constant temperature water bath. Polymerize at 44℃ for 10 hours to obtain polyelectrolyte gel.

[0043] (3) Dissolve the thermosensitive monomer NIPAM (0.7770g), the acidic monomer SA (0.0777g), the crosslinking agent N,N'-methylenebisacrylamide (2.8mg), and the photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (15.6 mg) in deionized water (12ml) and stir until all solids are dissolved to obtain the thermosensitive gel precursor solution.

[0044] (4) The polyelectrolyte gel prepared in step 2 is soaked in a thermosensitive gel precursor solution for 24 hours. The thermosensitive gel precursor solution is completely swollen and absorbed by the polyelectrolyte gel. The polyelectrolyte gel that has swollen and absorbed the thermosensitive gel precursor solution is placed under a UV lamp for photo-initiated polymerization for 20 minutes to obtain a thermosensitive polyelectrolyte double network hydrogel material, including 3.5% of acidic monomer SA, 4.9% of thermosensitive monomer NIPAM, 0.49% of acidic monomer SA, and the remainder is water.

[0045] Example 5 A method for preparing a thermosensitive polyelectrolyte dual-network hydrogel material includes the following steps: (1) Dissolve the acidic monomer SA (8.4671 g), acrylamide (6.3953 g), crosslinking agent N,N'-methylenebisacrylamide (139 mg), and initiator AIBI (129 mg) in deionized water (25 ml) and stir until all solids are dissolved to obtain a preliminary gel precursor solution, which includes 21.10% acidic monomer SA, 15.94% neutral monomer, 0.3464% crosslinking agent, 0.3215% initiator AIBI, and 62.29% deionized water. Then, purge nitrogen gas into the gel precursor solution for a period of time (10 min) to remove dissolved oxygen to obtain an oxygen-free preliminary gel precursor solution; (2) Transfer 3g of the precursor liquid into the mold and place it in a constant temperature water bath. Polymerize at 44℃ for 10 hours to obtain polyelectrolyte gel.

[0046] (3) Dissolve the thermosensitive monomer NIPAM (0.7770g), the acidic monomer SA (0.0777g), the crosslinking agent N,N'-methylenebisacrylamide (2.8mg), and the photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (15.6 mg) in deionized water (12ml) and stir until all solids are dissolved to obtain the thermosensitive gel precursor solution.

[0047] (4) Soak the polyelectrolyte gel prepared in step 2 in a thermosensitive gel precursor solution for 24 hours. Place the polyelectrolyte gel that has swollen and absorbed the thermosensitive gel precursor solution under a UV lamp for photo-initiated polymerization for 20 minutes to obtain a thermosensitive polyelectrolyte double network hydrogel material, including 4.0% of acidic monomer SA, 3.0% of neutral monomer acrylamide, 4.9% of thermosensitive monomer NIPAM, 0.49% of acidic monomer SA, and the remainder is water.

[0048] Example 6 A method for preparing a thermosensitive polyelectrolyte dual-network hydrogel material includes the following steps: (1) Dissolve the acidic monomer SA (13.5 g), crosslinking agent N,N'-methylenebisacrylamide (180 mg), and initiator AIBI (137 mg) in deionized water (25 ml) and stir until all solids are dissolved to obtain a preliminary gel precursor solution. Then, purge nitrogen gas into the gel precursor solution for a period of time (10 min) to remove dissolved oxygen to obtain an oxygen-free preliminary gel precursor solution; (2) Transfer 3g of the precursor liquid into the mold and place it in a constant temperature water bath. Polymerize at 44℃ for 10 hours to obtain polyelectrolyte gel.

[0049] (3) Dissolve the thermosensitive monomer NIPAM (0.7770g), the acidic monomer SA (0.7770g), the crosslinking agent N,N'-methylenebisacrylamide (2.8mg), and the photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (15.6 mg) in deionized water (12ml) and stir until all solids are dissolved to obtain 13.5724g of thermosensitive gel precursor solution, which includes 5.72% thermosensitive monomer NIPAM, 5.72% acidic monomer SA, 0.02% crosslinking agent and 88.54% deionized water.

[0050] (4) The polyelectrolyte gel prepared in step 2 is soaked in a thermosensitive gel precursor solution for 24 hours. The thermosensitive gel precursor solution is completely swollen and absorbed by the polyelectrolyte gel. The polyelectrolyte gel that has swollen and absorbed the thermosensitive gel precursor solution is placed under a UV lamp for photo-initiated polymerization for 20 minutes to obtain a thermosensitive polyelectrolyte double network hydrogel material, including 6.3% of acidic monomer SA, 4.7% of thermosensitive monomer NIPAM, 4.7% of acidic monomer SA, and the remainder is water.

[0051] Comparative Example 1 (1) Dissolve the acidic monomer SA (5.6424 g), crosslinking agent N,N'-methylenebisacrylamide (46 mg), and initiator AIBI (34 mg) in deionized water (25 ml) and stir until all solids are dissolved to obtain a preliminary gel precursor solution, which includes 18.37% acidic monomer SA, 0.1497% crosslinking agent, 0.1107% initiator AIBI, and 81.37% deionized water. Then, purge nitrogen gas into the gel precursor solution for a period of time (10 min) to remove dissolved oxygen to obtain an oxygen-free preliminary gel precursor solution; (2) Transfer 3g of the precursor liquid into the mold and place it in a constant temperature water bath. Polymerize at 44℃ for 10 hours to obtain polyelectrolyte gel.

[0052] Comparative Example 2 (1) Dissolve the thermosensitive monomer NIPAM (0.7770g), the acidic monomer SA (0.0777g), the crosslinking agent N,N'-methylenebisacrylamide (2.8mg), and the photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (15.6 mg) in deionized water (12ml) and stir until all solids are dissolved to obtain the thermosensitive gel precursor solution.

[0053] (2) Transfer 3g of the thermosensitive gel precursor liquid into the mold and place it under a UV lamp for photo-initiated polymerization for 20 minutes to obtain the thermosensitive hydrogel material.

[0054] Comparative Example 3 (1) Dissolve the acidic monomer SA (13.5 g), the thermosensitive monomer NIPAM (10 g), the crosslinking agent N,N'-methylenebisacrylamide (358 mg), and the initiator AIBI (133 mg) in deionized water (75 ml) and stir until all solids are dissolved to obtain a preliminary gel precursor solution. Then, purge nitrogen gas into the gel precursor solution for a period of time (10 min) to remove dissolved oxygen to obtain an oxygen-free preliminary gel precursor solution; (2) The precursor liquid was transferred into the mold and placed in a constant temperature water bath. The mixture was polymerized at 44°C for 10 hours to obtain a thermosensitive polyelectrolyte gel.

[0055] Material characterization Figure 1 The images shown are a series of physical images of the preparation process in Example 1. a is a physical image of the gel prepared in step S2 of Example 1; b is a physical image of the gel formed in step S4 of Example 1.

[0056] Figure 2 The images show the Fourier transform infrared spectra of Examples 1 and 2. In the spectra, Example 2 can be observed to be located at 1040 cm⁻¹. -1 and 1220cm-1 Characteristic peaks attributable to antisymmetric and symmetric stretching vibrations of sulfonic acid groups were observed at 1550 cm⁻¹. Furthermore, since both Examples 1 and 2 contain the crosslinking agents MBA and NIPAM, peaks at 1550 cm⁻¹ were observed. -1 Bending vibrations of the NH group in the amide bond were observed at 1650 cm⁻¹. -1 Stretching vibration at C=O. Furthermore, it can also occur at 3400 cm. -1 A broad absorption peak attributable to the stretching vibration of the OH group in the carboxylic acid group was observed.

[0057] Performance testing (1) Swelling rate test The swelling rate was determined by immersing the gel in pure water and a 3.5 wt.% NaCl solution and measuring the change in gel mass over time at fixed time intervals. The water absorption rate (WAR%) of the gel at a given moment can be calculated using the following method:

[0058] W s W represents the mass of the swollen gel after removing excess surface moisture at a given moment. d W represents the mass of the dry gel after drying at 85°C to a constant weight. t The weight of the gel at a given moment.

[0059] Figure 3 (a) and Figure 3 (b) The swelling rate curves of Examples 1 and 2 in pure water and 3.5 wt.% NaCl solution are shown respectively. It should be noted that the horizontal axis in the figure is a logarithmic scale. The results show that the swelling rate of Example 1 is lower than that of Example 2 in both pure water and NaCl solution, and both Examples 1 and 2 reach swelling equilibrium at around 200 min.

[0060] (2) Desalination performance test The desalination experiment involved heating the gel at 50°C for 30 minutes and collecting the water released. The water recovery rate was calculated by subtracting the mass of water released after heating from the gel and the mass of the gel before heating, using the following formula:

[0061] Among them W s W represents the mass of the swollen gel after removing excess surface moisture at a given moment. d W represents the mass of the dry gel after drying at 85°C to a constant weight. R This represents the amount of gel water released during the dehydration experiment.

[0062] The desalination rate of the gel was determined using a Shanghai Leici DDS-2 conductivity meter. In the experiment, NaCl solutions with concentration gradients of 10–50 g / L were first prepared. The conductivity corresponding to each concentration was measured, and a standard curve was plotted. The desalination rate of the gel was then calculated using the following formula:

[0063] Where C R C0 and C0 represent the concentrations of NaCl released from the gel during the water recovery experiment and the initial simulated seawater, respectively.

[0064] Figure 4 This document presents desalination test data in 3.5 wt.% NaCl solution for Examples 1, 2, 3, 4, 5, 6, Comparative Examples 1, 2, and 3. The results show that Example 3 has a relatively high desalination rate of 20.59%, but from a practical perspective, Example 2 is the optimal choice, with a desalination rate of 12.23% and a water recovery rate of 13.93%. The performance differences among the three examples are mainly attributed to the different types of acidic monomers selected. Different monomer structures and group types affect the desalination and water recovery efficiency of the gel material. It is worth noting that the desalination and water recovery rates of Comparative Examples 1 and 3 are both 0. The reasons are as follows: Comparative Example 1 does not contain a temperature-sensitive network, making heat-driven water release impossible. Comparative Example 3 has an excessively high content of the hydrophilic monomer SA, whose transition temperature is much higher than 50°C, resulting in a test result of 0. Comparative Example 2 has a low desalination rate due to its very low content of the hydrophilic monomer SA.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A thermosensitive polyelectrolyte dual-network hydrogel material, characterized in that, It includes a first network and a second network. The first network is an electrolyte hydrogel, and the second network is a temperature-sensitive hydrogel. The first network and the second network are interwoven with each other through polymer chains to form a dual-network structure.

2. The thermosensitive polyelectrolyte dual-network hydrogel material according to claim 1, characterized in that, The thermosensitive polyelectrolyte dual-network hydrogel is synthesized by stepwise polymerization of the following monomers: By mass percentage, 0.5%–50% of monomer A, 0%–75% of monomer B, 1%–50% of monomer C and 0%–20% of monomer D, with the balance being water; Monomers A and D are polymerizable monomers containing acidic groups; monomer B is a neutral monomer; and monomer C is a temperature-sensitive monomer.

3. The thermosensitive polyelectrolyte dual-network hydrogel material according to claim 1, characterized in that, The quality ratio of the first network to the second network is 1:1 to 5.

4. The thermosensitive polyelectrolyte dual-network hydrogel material according to claim 1, characterized in that, The electrolyte hydrogel is prepared by polymerization reaction of monomer A, or monomer A and monomer B, crosslinking agent and initiator; The monomer A is selected from at least one of sodium acrylate, sodium methacrylate, sodium 2-acrylamido-2-methylpropanesulfonate, sodium vinyl sulfonate, sodium allyl sulfonate, and sodium propylene phosphonate; the monomer B is selected from at least one of acrylamide, N-hydroxymethylacrylamide, and N-vinylpyrrolidone; the molar ratio of monomer A to monomer B is 1:1 to 3.

5. The thermosensitive polyelectrolyte dual-network hydrogel material according to claim 1, characterized in that, The thermosensitive hydrogel is prepared by polymerization reaction of monomer C, or monomer C and monomer D, crosslinking agent and initiator; monomer C is selected from at least one of N-isopropylacrylamide, N-vinylcaprolactam, N-acryloylpyrrolidine, N,N-diethylacrylamide; the molar ratio of monomer C to monomer D is 2~20:

1.

6. A method for preparing the thermosensitive polyelectrolyte dual-network hydrogel material according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Mix monomer A, or monomer A and monomer B, crosslinking agent and initiator with water to form a homogeneous solution, and deoxygenate the homogeneous solution to obtain a polyelectrolyte gel precursor solution. S2. The polyelectrolyte gel precursor solution is subjected to a polymerization reaction under constant temperature conditions to form a polyelectrolyte gel. S3. Mix monomer C, or monomer C with monomer D, crosslinking agent, initiator and water to obtain thermosensitive gel precursor solution; S4. The polyelectrolyte gel is immersed in the thermosensitive gel precursor solution, and a thermosensitive network is formed by polymerization reaction to obtain a thermosensitive polyelectrolyte dual-network hydrogel material.

7. The method for preparing the thermosensitive polyelectrolyte dual-network hydrogel material according to claim 6, characterized in that, The amount of crosslinking agent added in S1 and S3 is 1% to 0.1% of the total molar amount of monomer A and monomer B, or monomer C and monomer D; the amount of initiator added is 0.5% to 0.01% of the total molar amount of monomer A and monomer B, or monomer C and monomer D.

8. The method for preparing the thermosensitive polyelectrolyte dual-network hydrogel material according to claim 6, characterized in that, The crosslinking agent is selected from polyethylene glycol diacrylate and N,N'-methylenebisacrylamide; the initiator is selected from ammonium persulfate, hydrogen peroxide, azobisisobutyrazoline hydrochloride, V-50 initiator, α-ketoglutarate or 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone.

9. The method for preparing the thermosensitive polyelectrolyte dual-network hydrogel material according to claim 6, characterized in that, S1 The deoxygenation is carried out by introducing nitrogen gas into the homogeneous solution for 10-30 min; S2 The constant temperature is 20-80℃ for 1-24 h; S1 and S3 The mixing includes stirring until all solid components are dissolved; S4 The impregnation time is 12-36 h; S4 The polymerization is photoinitiated polymerization for 10-60 min.

10. The application of the thermosensitive polyelectrolyte dual-network hydrogel material according to any one of claims 1 to 5 in the field of brine desalination.

Images