A double-layer hydrogel membrane evaporator containing an activated water layer

Abstract

A double-layer hydrogel membrane evaporator containing an activated water layer, belonging to the field of polymer functional membranes, is constructed using optical cross-linking coupled in-situ polymerization technology. The lower hydrogel membrane contains a large number of hydrophilic functional groups, which weaken the hydrogen bonding between water molecules in the hydrogel membrane, increase the proportion of intermediate water, and reduce its evaporation enthalpy, thereby continuously providing activated water molecules for the generation of water vapor in the upper hydrogel membrane. The photothermal conversion material in the upper hydrogel layer provides energy for the efficient conversion of activated water into water vapor molecules, while the pore structure of the hydrogel membrane creates a rapid mass transfer channel for water molecules, achieving efficient water purification.

Description

Technical field:

[0001] The invention relates to the preparation of a double-layer photothermal water gel membrane evaporator for providing activated water and its application in seawater desalination and sewage treatment, and belongs to the field of polymer functional membranes. Background technology:

[0002] Safe and pure water is essential for maintaining human survival. However, climate change and water pollution have led to water shortages in many regions, threatening life and health, and becoming a global challenge. Seawater desalination and wastewater purification technologies have become feasible means to address this problem. However, traditional technologies such as multi-effect distillation and vapor compression require large equipment, which is expensive, energy-intensive, and causes environmental pollution, making them difficult to implement in many impoverished areas. Solar water evaporators utilize the advantages of solar energy, such as cleanliness, low environmental impact, and inexhaustible supply, to achieve water evaporation through photothermal conversion, thereby obtaining safe and pure water resources. This method has the advantages of high efficiency, simple equipment, and easy access, and is expected to provide high-quality water resources for water-scarce areas.

[0003] A membrane with rapid water mass transfer capability is one of the key factors determining the efficiency of solar evaporators. In recent years, methods such as regulating the hydrophilicity of the membrane, constructing water mass transfer channels, and increasing the specific surface area of ​​the membrane through microstructure have been used to improve the water production capacity of membrane evaporators. However, due to the high density of hydrogen bonds between water molecules, its evaporation enthalpy is high, resulting in a theoretical limit for water volatilization, which limits the efficiency of membrane evaporators in producing water using solar energy.

[0004] There are a large number of hydrophilic groups in the hydrogel, which have hydrogen bonds or electrostatic interactions with water molecules, weakening the hydrogen bonding between water molecules, which can significantly reduce the evaporation enthalpy of water and exceed the theoretical rate of solar water evaporation. In the hydrogel film, there are three types of water, namely bound water (water molecules with hydrogen bonds or electrostatic interactions with polymer segments), free water (with the same properties as water itself), and intermediate water (between bound water and free water, with weakened hydrogen bonding between water molecules). Among them, intermediate water plays a key role in reducing the evaporation enthalpy of water. Therefore, researchers have proposed changing the types of functional groups in the hydrogel film, increasing the content and proportion of intermediate water, and improving the water production efficiency of the hydrogel film evaporator (Zhou, X. et al., Sci. Adv. 2019, 5(6): eaaw5484.). Other researchers have improved the water production efficiency of pure water by regulating the pore size of the hydrogel membrane while increasing the proportion of intermediate water and the mass transfer rate of water molecules in the membrane (Guo, Y. et. al., Angew. Chem. Int. Ed. 2021, 61 (3): e202114074.). Although the above method can break through the theoretical rate of solar water evaporation, its preparation process is complicated, such as involving freeze drying, complex synthesis or microstructure preparation, which is difficult to scale up. In addition, the hydrogel membrane needs to be doped with a hydrophobic photothermal conversion material, which reduces the hydrophilicity of the hydrogel membrane, reduces the proportion of intermediate water, and limits the further improvement of the water evaporation rate.

[0005] In response to the above problems, this study designed and constructed a double-layer hydrogel membrane containing an active water (intermediate water) storage layer for efficient solar water evaporation to achieve seawater desalination and sewage purification. The lower hydrogel membrane was prepared using a fast and green optical cross-linking technology, and its strong hydrophilicity was used to produce a high proportion of intermediate water, providing active water molecules (low evaporation enthalpy) for the low-energy generation of upper water vapor. An upper hydrogel membrane with photothermal conversion and rapid water mass transfer functions was constructed on the surface of the lower hydrogel membrane through optical cross-linking coupled in-situ polymerization technology, providing energy and mass transfer paths for the generation of low evaporation enthalpy water vapor. The double-layer hydrogel membrane evaporator has mild preparation conditions, simple operation and flexibility, and has important scientific value and application prospects for solving the problem of water shortage. Summary of the invention:

[0006] The purpose of this invention is to fabricate a simple, efficient, and universally applicable double-layer hydrogel membrane evaporator to improve the efficiency of solar evaporation water production. By constructing a highly hydrophilic lower hydrogel membrane as the active water molecule generation and storage layer, and a highly efficient upper hydrogel membrane as the water vapor molecule generation and mass transfer layer, the double-layer hydrogel membrane is fabricated for efficient solar water purification. The double-layer hydrogel membrane evaporator prepared by this method demonstrates excellent efficiency in seawater desalination and wastewater treatment.

[0007] The preparation of a double-layer hydrogel film evaporator includes the following steps:

[0008] (1) Dissolve acrylamide (AM) and acrylic acid (AA) powder in deionized water and stir until fully dissolved to obtain a monomer solution for standby use; add crosslinker 1 and photoinitiator to the obtained solution and continue stirring until completely dissolved; take the stirred solution and place it in a mold, and initiate polymerization by UV to obtain a PAA-AM double network hydrogel film;

[0009] (2) dissolving chitosan (CS) or sodium alginate (Alginate) or polyvinyl alcohol (PVA) in a solvent and stirring until fully dissolved to obtain a polymer solution for standby use; adding crosslinker 2 to the obtained solution and continuing to stir until completely dissolved; taking the stirred solution and placing it in a mold to stand to obtain a CS or Alginate or PVA hydrogel film;

[0010] (3) dissolving the oxidative initiator in deionized water, stirring until fully dissolved, and setting aside for use; soaking the PAA-AM obtained in step (1) or the CS, Alginate, or PVA hydrogel film obtained in step (2) in the obtained oxidative initiator solution to obtain an immersed gel film; dissolving the pyrrole monomer (Py) in an organic solvent, stirring until uniformly dissolved to obtain a pyrrole monomer solution, weighing a crosslinker 3, adding it to the above pyrrole monomer solution, stirring uniformly until completely dissolved, and obtaining a crosslinking monomer mixed solution;

[0011] The cross-linking monomer mixed solution is added dropwise onto the soaked gel membrane until the soaked gel membrane turns completely black, thereby forming the corresponding upper hydrogel membrane;

[0012] (4) pressing the PAA-AM double network hydrogel film prepared in step (1) as a lower hydrogel film and the upper hydrogel film prepared in step (3) together to obtain a double-layer hydrogel film;

[0013] (5) Immersing the double-layer hydrogel membrane obtained in step (4) in an acidic solution such as hydrochloric acid reduces the pore size of the hydrogel, thereby reducing the intermediate water content and reducing the water evaporation rate; Immersing the double-layer hydrogel membrane obtained in step (4) in an alkaline solution such as sodium hydroxide increases the pore size of the hydrogel, thereby increasing the intermediate water content and increasing the water evaporation rate; the water evaporation rate is regulated by immersing in the above-mentioned acidic and alkaline solutions.

[0014] In step (1) of the present invention, the deionized water content in the monomer solution is 50-80% of the solution mass fraction, the crosslinker 1 and the initiator concentration are 0.1-1.0% and 0.1-0.2% of the sum of the mass fractions of AM and AA, respectively; ultraviolet light is used during photopolymerization, and the light power density is 100-535 mW cm -2, time is 30-500s; the mass ratio of AM to AA is (3-10):1, crosslinker 1 includes but is not limited to N,N'-methylenebisacrylamide (MBA), and photoinitiator includes but is not limited to 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959);

[0015] In step (2), the solvent in the polymer solution is 50-80% of the solution by mass; polymer solution 2 is calcium chloride or glutaraldehyde, with a mass fraction of 0.1-1.0% of the solution; the solvent is deionized water or acetic acid solution or hydrochloric acid solution; the mass fraction of acetic acid solution or hydrochloric acid solution is 1-5% of the solution;

[0016] In step (3), the oxidative initiator is ammonium persulfate (APS), the mass of which is 10-50% of the mass fraction of the solution;

[0017] The mass of the pyrrole monomer in step (3) is 10-30% of the mass fraction of the pyrrole monomer solution; the crosslinking agent 3 is phytic acid, the mass of which is 20-50% of the mass fraction of the pyrrole monomer solution;

[0018] Preferably, the minimum pH value of the acidic solution in step (5) is 1, and the maximum pH value of the alkaline solution is 11, that is, the double-layer hydrogel film obtained in step (4) can be immersed in different acidic and alkaline solutions with a pH of 1-11 to change the water evaporation rate.

[0019] Technical principle of the present invention:

[0020] The present invention constructs an evaporator with a double-layer hydrogel membrane through optical cross-linking coupled in-situ polymerization technology. By utilizing the large number of hydrophilic functional groups in the lower hydrogel membrane, the hydrogen bonding between water molecules in the hydrogel membrane is weakened, the proportion of intermediate water is increased, and its evaporation enthalpy is reduced, thereby continuously providing active water molecules for the generation of water vapor in the upper hydrogel membrane. The photothermal conversion material in the upper hydrogel provides energy for the efficient conversion of active water into water vapor molecules, while the pore structure of the hydrogel membrane constructs a rapid mass transfer channel for water molecules, thereby achieving efficient water purification. In addition, by regulating the hydrogen bonding between the polymer chain and water in the lower hydrogel membrane by pH, the proportion of intermediate water can be further optimized, thereby improving water production efficiency. Description of the drawings:

[0021] Figure 1 This is the electron microscopy image of PPy@PAA-AM hydrogel;

[0022] Figure 2 This is the electron microscopy image of PAA-AM hydrogel;

[0023] Figure 3 Comparison of water evaporation rates between double-layer hydrogel and single-layer hydrogel;

[0024] Figure 4This is the electron microscopy image of PAA-AM hydrogel after alkali treatment;

[0025] Figure 5 This is a comparison chart of ion concentrations in actual seawater and water collected by evaporation. Specific implementation method:

[0026] The present invention is described in detail below with reference to specific examples, but the present invention is not limited to the following examples.

[0027] Example 1

[0028] (1) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.2% of the total mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the total mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (optical power density: 535mW cm -2 ) polymerized for 300 s to obtain a PAA-AM double network hydrogel film;

[0029] (2) dissolving the initiator ammonium persulfate (APS) in deionized water and stirring with a magnetic stirrer until fully dissolved; immersing the PAA-AM hydrogel film obtained in step (1) in the obtained oxidative initiator solution; the mass of ammonium persulfate is 30% of the mass fraction of the solution;

[0030] (3) Dissolve the pyrrole monomer (Py) in isopropanol and stir with a magnetic stirrer until uniformly dissolved. Weigh the crosslinking agent phytic acid (PA) and add it to the above pyrrole monomer solution and stir until completely dissolved. Set aside; the amount of crosslinking agent phytic acid (PA) is 24% of the solution mass fraction;

[0031] (4) adding the solution stirred evenly in step (3) dropwise to the hydrogel film soaked in step (2) until the hydrogel film completely turns black, thereby obtaining an upper hydrogel film;

[0032] (5) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.3% of the sum of the mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the sum of the mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (light power density: 535mW cm -2 ) polymerized for 300 s to obtain the lower hydrogel film;

[0033] (6) Pressing the hydrogel film prepared in step (4) and the hydrogel film prepared in step (5) together to obtain a double-layer hydrogel film.

[0034] (7) soaking the hydrogel film obtained in step (6) in deionized water with a pH of 7;

[0035] The electron microscope image of the upper hydrogel membrane prepared above is as follows Figure 1 ; The electron microscope image of the lower hydrogel membrane prepared above is as follows Figure 2 The double-layer hydrogel film prepared above was used to test the evaporation performance of pure water under sunlight, and its performance was as follows: Figure 3 As shown, without the double-layer hydrogel film, the water evaporation rate is 0.54 kg m -2 h -1 ; When only the lower hydrogel film is present, the water evaporation rate is 1.34 kg m -2 h -1 When only the upper hydrogel film is present, the water evaporation rate is 1.72 kg m -2 h -1 ; In the case of double-layer hydrogel film, the water evaporation rate is 2.45 kg m -2 h -1 .

[0036] Example 2

[0037] (1) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.2% of the total mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the total mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (optical power density: 535mW cm -2 ) polymerized for 300 s to obtain a PAA-AM double network hydrogel film;

[0038] (2) dissolving the initiator ammonium persulfate (APS) in deionized water and stirring with a magnetic stirrer until fully dissolved; immersing the PAA-AM hydrogel film obtained in step (1) in the obtained oxidative initiator solution; the mass of ammonium persulfate is 30% of the mass fraction of the solution;

[0039] (3) Dissolve the pyrrole monomer (Py) in isopropanol and stir with a magnetic stirrer until uniformly dissolved. Weigh the crosslinking agent phytic acid (PA) and add it to the above pyrrole monomer solution and stir until completely dissolved. Set aside; the amount of crosslinking agent phytic acid (PA) is 24% of the solution mass fraction;

[0040] (4) adding the solution stirred evenly in step (3) dropwise to the hydrogel film soaked in step (2) until the hydrogel film completely turns black, thereby obtaining an upper hydrogel film;

[0041] (5) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.3% of the sum of the mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the sum of the mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (light power density: 535mW cm -2 ) polymerized for 300 s to obtain the lower hydrogel film;

[0042] (6) Pressing the hydrogel film prepared in step (4) and the hydrogel film prepared in step (5) together to obtain a double-layer hydrogel film.

[0043] (7) soaking the hydrogel film obtained in step (6) in a hydrochloric acid solution with a pH of 5;

[0044] The double-layer hydrogel film prepared above was used to test the evaporation performance of pure water under sunlight, and its performance was as follows:

[0045] The water evaporation rate was reduced to 2.33 kg m -2 h -1 ;

[0046] Example 3

[0047] (1) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.2% of the total mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the total mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (optical power density: 535mW cm -2) polymerized for 300 s to obtain a PAA-AM double network hydrogel film;

[0048] (2) dissolving the initiator ammonium persulfate (APS) in deionized water and stirring with a magnetic stirrer until fully dissolved; immersing the PAA-AM hydrogel film obtained in step (1) in the obtained oxidative initiator solution; the mass of ammonium persulfate is 30% of the mass fraction of the solution;

[0049] (3) Dissolve the pyrrole monomer (Py) in isopropanol and stir with a magnetic stirrer until uniformly dissolved. Weigh the crosslinking agent phytic acid (PA) and add it to the above pyrrole monomer solution and stir until completely dissolved. Set aside; the amount of crosslinking agent phytic acid (PA) is 24% of the solution mass fraction;

[0050] (4) adding the solution stirred evenly in step (3) dropwise to the hydrogel film soaked in step (2) until the hydrogel film completely turns black, thereby obtaining an upper hydrogel film;

[0051] (5) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.3% of the sum of the mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the sum of the mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (light power density: 535mW cm -2 ) polymerized for 300 s to obtain the lower hydrogel film;

[0052] (6) Pressing the hydrogel film prepared in step (4) and the hydrogel film prepared in step (5) together to obtain a double-layer hydrogel film.

[0053] (7) soaking the hydrogel film obtained in step (6) in a sodium hydroxide solution with a pH of 9;

[0054] The electron microscopy image of the PAA-AM double network hydrogel film prepared above is as follows Figure 4 .

[0055] The prepared double-layer hydrogel film was used to test the evaporation performance of pure water under sunlight. The performance was as follows: the water evaporation rate increased to 2.79 kg m -2 h-1 ;like Figure 5 As shown, it has a good removal effect on common ions in seawater.

[0056] Example 4

[0057] (1) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.2% of the total mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the total mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (optical power density: 535mW cm -2 ) polymerized for 300 s to obtain a PAA-AM double network hydrogel film;

[0058] (2) dissolving the initiator ammonium persulfate (APS) in deionized water and stirring with a magnetic stirrer until fully dissolved; immersing the PAA-AM hydrogel film obtained in step (1) in the obtained oxidative initiator solution; the mass of ammonium persulfate is 30% of the mass fraction of the solution;

[0059] (3) Dissolve the pyrrole monomer (Py) in isopropanol and stir with a magnetic stirrer until uniformly dissolved. Weigh the crosslinking agent phytic acid (PA) and add it to the above pyrrole monomer solution and stir until completely dissolved. Set aside; the amount of crosslinking agent phytic acid (PA) is 24% of the solution mass fraction;

[0060] (4) adding the solution stirred evenly in step (3) dropwise to the hydrogel film soaked in step (2) until the hydrogel film completely turns black, thereby obtaining an upper hydrogel film;

[0061] (5) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.2% of the sum of the mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the sum of the mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (light power density: 535mW cm -2 ) polymerized for 300 s to obtain the lower hydrogel film;

[0062] (6) Pressing the hydrogel film prepared in step (4) and the hydrogel film prepared in step (5) together to obtain a double-layer hydrogel film.

[0063] (7) soaking the hydrogel film obtained in step (6) in deionized water with a pH of 7;

[0064] The double-layer hydrogel film prepared above was used to test the evaporation performance of pure water under sunlight. The performance was as follows: the water evaporation rate was 2.36 kg m -2 h -1 ;

[0065] Example 5

[0066] (1) Dissolve chitosan (CS) in an acetic acid solution having an acetic acid mass fraction of 2% and stir until fully dissolved to obtain a chitosan solution for standby use; the mass of the acetic acid solution is 80% of the mass of the total solution; add a crosslinking agent, glutaraldehyde, to the obtained solution and continue stirring until completely dissolved; the mass of glutaraldehyde is 0.2% of the mass of the solution; take the stirred solution and place it in a mold to stand to obtain a CS hydrogel film;

[0067] (2) dissolving the initiator ammonium persulfate (APS) in deionized water and stirring with a magnetic stirrer until fully dissolved, wherein the mass of ammonium persulfate is 30% of the mass fraction of the solution; immersing the CS hydrogel film obtained in step (1) in the obtained oxidative initiator solution;

[0068] (3) Dissolve the pyrrole monomer (Py) in isopropanol and stir with a magnetic stirrer until uniformly dissolved. Weigh the crosslinking agent phytic acid (PA) and add it to the above pyrrole monomer solution and stir until completely dissolved. Set aside; the amount of crosslinking agent phytic acid (PA) is 24% of the solution mass fraction;

[0069] (4) adding the solution stirred evenly in step (3) dropwise onto the CS hydrogel film soaked in step (2) until the hydrogel film completely turns black, thereby obtaining an upper hydrogel film;

[0070] (5) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.3% of the sum of the mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the sum of the mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (light power density: 535mW cm -2 ) polymerized for 300 s to obtain the lower hydrogel film;

[0071] (6) Pressing the hydrogel film prepared in step (4) and the hydrogel film prepared in step (5) together to obtain a double-layer hydrogel film.

[0072] (7) soaking the hydrogel film obtained in step (6) in deionized water with a pH of 7;

[0073] The double-layer hydrogel film prepared above was used to test the evaporation performance of pure water under sunlight. The performance was as follows: when only the upper hydrogel film was present, the water evaporation rate was 2.08 kg / m -2 h -1 ; In the case of double-layer hydrogel film, the water evaporation rate is 2.33 kgm -2 h -1 .

[0074] Example 6

[0075] (1) Sodium alginate is dissolved in deionized water and stirred until fully dissolved to obtain a sodium alginate solution for use; the mass of the deionized water solution is 80% of the mass of the total solution; glutaraldehyde, a crosslinking agent, is added to the above-obtained solution and stirred until completely dissolved; the mass of calcium chloride is 0.2% of the mass of the solution; the above-mentioned stirred solution is placed in a mold and allowed to stand to obtain an alginate hydrogel film;

[0076] (2) dissolving the initiator ammonium persulfate (APS) in deionized water and stirring with a magnetic stirrer until fully dissolved, wherein the mass of the ammonium persulfate is 30% of the mass fraction of the solution; immersing the Alginate hydrogel film obtained in step (1) in the obtained oxidative initiator solution;

[0077] (3) Dissolve the pyrrole monomer (Py) in isopropanol and stir with a magnetic stirrer until uniformly dissolved. Weigh the crosslinking agent phytic acid (PA) and add it to the above pyrrole monomer solution and stir until completely dissolved. Set aside; the amount of crosslinking agent phytic acid (PA) is 24% of the solution mass fraction;

[0078] (4) adding the solution stirred evenly in step (3) dropwise onto the Alginate hydrogel film soaked in step (2) until the hydrogel film completely turns black, thereby obtaining an upper hydrogel film;

[0079] (5) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.3% of the sum of the mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the sum of the mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (light power density: 535mW cm -2 ) polymerized for 300 s to obtain the lower hydrogel film;

[0080] (6) Pressing the hydrogel film prepared in step (4) and the hydrogel film prepared in step (5) together to obtain a double-layer hydrogel film.

[0081] (7) soaking the hydrogel film obtained in step (6) in deionized water with a pH of 7;

[0082] The double-layer hydrogel film prepared above was used to test the evaporation performance of pure water under sunlight. The performance was as follows: when only the upper hydrogel film was present, the water evaporation rate was 1.98 kg / m -2 h -1 ; In the case of double-layer hydrogel film, the water evaporation rate is 2.24 kgm -2 h -1 .

[0083] Example 7

[0084] (1) Dissolving polyvinyl alcohol (PVA) in a 2% hydrochloric acid solution and stirring until fully dissolved to obtain a polyvinyl alcohol solution for use; the mass of the hydrochloric acid solution is 80% of the total mass of the solution; adding a crosslinking agent, glutaraldehyde, to the obtained solution and continuing to stir until completely dissolved; the mass of the glutaraldehyde is 0.2% of the mass of the solution; taking the stirred solution and placing it in a mold to stand, to obtain a PVA hydrogel film;

[0085] (2) dissolving the initiator ammonium persulfate (APS) in deionized water and stirring it with a magnetic stirrer until it is fully dissolved, and the mass of ammonium persulfate is 30% of the mass fraction of the solution; (2) dissolving the initiator ammonium persulfate (APS) obtained in step (1) in deionized water and stirring it with a magnetic stirrer until it is fully dissolved, and the mass of ammonium persulfate is 30% of the mass fraction of the solution; immersing the Alginate hydrogel film obtained in step (1) in the obtained oxidative initiator solution;

[0086] (3) Dissolve the pyrrole monomer (Py) in isopropanol and stir with a magnetic stirrer until uniformly dissolved. Weigh the crosslinking agent phytic acid (PA) and add it to the above pyrrole monomer solution and stir until completely dissolved. Set aside; the amount of crosslinking agent phytic acid (PA) is 24% of the solution mass fraction;

[0087] (4) adding the solution stirred evenly in step (3) dropwise onto the Alginate hydrogel film soaked in step (2) until the hydrogel film completely turns black, thereby obtaining an upper hydrogel film;

[0088] (5) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.3% of the sum of the mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the sum of the mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (light power density: 535mW cm -2 ) polymerized for 300 s to obtain the lower hydrogel film;

[0089] (6) Pressing the hydrogel film prepared in step (4) and the hydrogel film prepared in step (5) together to obtain a double-layer hydrogel film.

[0090] (7) soaking the hydrogel film obtained in step (6) in deionized water with a pH of 7;

[0091] The hydrogel film is immersed in the obtained oxidative initiator solution;

[0092] (3) Dissolve the pyrrole monomer (Py) in isopropanol and stir with a magnetic stirrer until uniformly dissolved. Weigh the crosslinking agent phytic acid (PA) and add it to the above pyrrole monomer solution and stir until completely dissolved. Set aside; the amount of crosslinking agent phytic acid (PA) is 24% of the solution mass fraction;

[0093] (4) adding the solution stirred evenly in step (3) dropwise onto the PVA hydrogel film soaked in step (2) until the hydrogel film completely turns black, thereby obtaining an upper hydrogel film;

[0094] (5) Dissolve acrylamide monomer (AM) and acrylic acid (AA) monomer powder in deionized water at a ratio of 3:1, stir until fully dissolved by a magnetic stirrer, and set aside; the deionized water content is 70% of the solution mass fraction; weigh the crosslinker N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), add them to the solution stirred evenly in step (1), and continue stirring until completely dissolved (room temperature, ≤25°C); the amount of crosslinker N,N'-methylenebisacrylamide (MBA) is 0.3% of the sum of the mass of AM and AA, and the amount of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is 0.15% of the sum of the mass of AM and AA; pipette the above-mentioned stirred solution into a mold (different molds can be selected according to needs), and irradiate at a wavelength of 365nm (light power density: 535mW cm -2 ) polymerized for 300 s to obtain the lower hydrogel film;

[0095] (6) Pressing the hydrogel film prepared in step (4) and the hydrogel film prepared in step (5) together to obtain a double-layer hydrogel film.

[0096] (7) soaking the hydrogel film obtained in step (6) in deionized water with a pH of 7;

[0097] The double-layer hydrogel film prepared above was used to test the evaporation performance of pure water under sunlight. The performance was as follows: when only the upper hydrogel film was present, the water evaporation rate was 2.04 kg / m -2 h -1 ; In the case of double-layer hydrogel film, the water evaporation rate is 2.54 kgm -2 h -1 .

Claims

1. A method for preparing a double-layer hydrogel membrane evaporator containing an activated water layer, characterized in that: The following steps are involved: (1) Dissolve acrylamide (AM) and acrylic acid (AA) powder in deionized water and stir until fully dissolved to obtain a monomer solution for standby use; add crosslinker 1 and photoinitiator to the monomer solution and continue stirring until completely dissolved; take the stirred solution and place it in a mold, and initiate polymerization by UV to obtain a PAA-AM double network hydrogel film; (2) Dissolve chitosan or sodium alginate (Alginate) or polyvinyl alcohol (PVA) in a solvent and stir until fully dissolved to obtain a polymer solution for standby use; add crosslinker 2 to the polymer solution and continue stirring until completely dissolved; take the stirred solution and place it in a mold to stand to obtain a chitosan or Alginate or PVA hydrogel film; (3) dissolving the oxidative initiator in deionized water, stirring until fully dissolved, and setting aside for use; soaking the PAA-AM obtained in step (1) or the chitosan, Alginate, or PVA hydrogel film obtained in step (2) in the obtained oxidative initiator solution to obtain an immersed gel film; dissolving the pyrrole monomer in an organic solvent, stirring until uniformly dissolved to obtain a pyrrole monomer solution, weighing the crosslinker 3, adding it to the above pyrrole monomer solution, stirring uniformly until completely dissolved, and obtaining a crosslinking monomer mixed solution; The cross-linking monomer mixed solution is added dropwise onto the soaked gel film until the soaked gel film turns completely black, which serves as the corresponding upper hydrogel film; (4) The PAA-AM double network hydrogel film prepared in step (1) is used as a lower hydrogel film and is pressed together with the upper hydrogel film prepared in step (3) to obtain a double-layer hydrogel film, wherein the lower hydrogel film with high hydrophilicity serves as an active water molecule generation and storage layer, and the upper hydrogel film with high photothermal conversion efficiency serves as a water vapor molecule generation and mass transfer layer; (5) The water evaporation rate was regulated by immersing the double-layer hydrogel membrane in an acidic solution. When the double-layer hydrogel membrane was immersed in an acidic solution, the pore size of the hydrogel decreased, which reduced the water content in the middle and reduced the water evaporation rate. When the double-layer hydrogel membrane was immersed in an alkaline solution, the pore size of the hydrogel increased, which increased the water content in the middle and increased the water evaporation rate.

2. The method according to claim 1, characterized in that Step (1) The deionized water content in the monomer solution is 50-80% of the solution mass fraction, the crosslinker 1 and initiator concentrations are 0.1-1.0% and 0.1-0.2% of the sum of the mass fractions of AM and AA, respectively; ultraviolet light is used for ultraviolet initiation polymerization, and the light power density is 100-535 mW cm -2 , time is 30-500s; the mass ratio of AM and AA is (3-10):1, the crosslinker 1 includes N,N'-methylenebisacrylamide, and the photoinitiator includes 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

3. The method according to claim 1, characterized in that In step (2), the solvent in the polymer solution is 50-80% of the solution by mass; the crosslinking agent 2 is calcium chloride or glutaraldehyde, with a mass fraction of 0.1-1.0% of the solution; the solvent is deionized water or acetic acid solution or hydrochloric acid solution; the mass fraction of the acetic acid solution or hydrochloric acid solution is 1-5% of the solution.

4. The method according to claim 1, characterized in that In step (3), the oxidizing initiator is ammonium persulfate, the mass of which is 10-50% of the mass fraction of the solution.

5. The method according to claim 1, characterized in that In step (3), the mass of the pyrrole monomer is 10-30% of the mass fraction of the pyrrole monomer solution; and the cross-linking agent 3 is phytic acid, the mass of which is 20-50% of the mass fraction of the pyrrole monomer solution.

6. The method according to claim 1, characterized in that The minimum pH value of the acidic solution in step (5) is 1, and the maximum pH value of the alkaline solution is 11, that is, the double-layer hydrogel film obtained in step (4) can be immersed in different acidic and alkaline solutions with a pH of 1-11 to change the water evaporation rate.

7. The method according to claim 1, characterized in that In step (5), the acidic solution is hydrochloric acid, and the alkaline solution is sodium hydroxide solution.

8. A double-layer hydrogel film evaporator containing an activated water layer prepared according to the method according to any one of claims 1 to 7.

9. Application of a double-layer hydrogel membrane evaporator containing an activated water layer prepared by the method according to any one of claims 1 to 7, characterized in that: Used for seawater desalination and sewage treatment.

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