Hydrogel-based foam based on CNT / PDA / PVA, preparation method and application

Abstract

The invention discloses hydrogel-based foam based on CNT / PDA / PVA as well as a preparation method and application of the hydrogel-based foam. Belongs to the technical field of composite material preparation. A PVA solution, a hydrochloric acid solution and CNT / PDA are mixed, the PVA solution is subjected to phase transformation through mechanical stirring, a large number of bubbles are generated, PVA molecular chains are subjected to chemical crosslinking at low temperature, and a PVA hydrogel foam precursor II with a rich pore structure is formed. On the basis, the CNT / PDA / PVA hydrogel-based foam is soaked in a sodium chloride solution, chloride ions change the winding state and the crystalline state of PVA molecular chains, the pore structure is further changed, and the CNT / PDA / PVA hydrogel-based foam which is high in porosity, rich in pore structure, excellent in mechanical property, low in evaporation enthalpy change and excellent in salt resistance is successfully prepared. And technical support is provided for further development of seawater desalination.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material preparation, and more specifically, to a hydrogel-based foam based on CNT / PDA / PVA, a preparation method and an application thereof. Background Art

[0002] Due to the rising population growth rate and the expansion of industrial and agricultural activities, people's demand for fresh water resources is increasing day by day. However, the existing fresh water resources from rivers, groundwater, etc. are limited. Facing the increasing demand for fresh water, many cities are facing a water shortage crisis. Although the earth is rich in sea water resources, the high salt content in sea water makes it unsuitable for human use, as well as for industrial and agricultural use. In order to desalinate sea water to produce fresh water, over the years, a variety of desalination technologies have been developed based on technologies such as multi-effect evaporation, membrane separation, freezing, and electrodialysis. However, a serious drawback of these technologies is their high energy consumption, and their treatment cost is far higher than the selling price of fresh water. In recent years, with the global promotion of sustainable development, the renewable energy - solar energy has attracted more and more attention. Subsequently, the solar thermal desalination technology has also provided important technical support for sea water desalination. The solar thermal desalination technology is a method of preparing fresh water by using solar radiation to heat and collect steam located at the water / gas interface, which can effectively reduce energy consumption and treatment cost, and has become a research hotspot in the field of sea water desalination.

[0003] The photothermal materials for solar thermal desalination of sea water should have a wide solar absorption range, high photothermal conversion efficiency, low thermal conductivity, oriented pores and rich porosity for water molecule transport. So far, most evaporation materials have focused on optimizing heat localization and water management, minimizing heat loss and reducing the evaporation enthalpy change to improve the water evaporation performance. Among the reported evaporation materials, hydrogel-based evaporation materials have attracted much attention from researchers due to their advantages of adjustable pore structure, water transport volume and evaporation enthalpy change. In particular, the pore structure in the hydrogel not only affects the light absorption performance, water flux and water molecule transport path, but also affects the state of surrounding water molecules and the evaporation enthalpy change value. At present, the methods for regulating the pore structure of hydrogels include double crosslinking method, self-assembly template method, surfactant foaming and freeze-drying method. The above methods require additional multiple polymers, fixed-size templating agents and bubble stabilizers of high molecular polymers during the preparation process.

[0004] However, the hydrogels prepared by the above methods have low porosity, poor mechanical properties, limited stability and long transport paths. Moreover, during long-term operation in high-concentration salt water, the long transport path and the limited convection-diffusion effect of low porosity cause salt deposition on its surface, blocking the pore structure and reducing the light absorption performance, resulting in a decline in its water evaporation performance.

[0005] Therefore, developing a hydrogel-based photothermal conversion material with high porosity, excellent mechanical properties, water evaporation performance and salt tolerance is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0006] In view of this, the present invention provides a CNT / PDA / PVA-based hydrogel foam, a preparation method and an application thereof. By using a special ion effect, a CNT / PDA / PVA hydrogel foam with high porosity and excellent mechanical properties is prepared. The solar evaporator assembled with this material has excellent enthalpy change value, water evaporation performance and salt tolerance.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A preparation method of a CNT / PDA / PVA-based hydrogel foam, comprising the following steps:

[0009] (1) Disperse CNT and dopamine hydrochloride in a buffer solvent, add CuSO4·5H2O and H2O2, and stir at room temperature for 4-5 h, then centrifuge, wash with water and dry to obtain a CNT / PDA light absorber;

[0010] (2) Dissolve PVA and glutaraldehyde in distilled water and reflux in an oil bath to obtain a PVA solution;

[0011] (3) Mix the PVA solution, HCl solution and CNT / PDA complex, and stir to obtain a precursor I of the CNT / PDA / PVA hydrogel foam;

[0012] (4) Place the precursor I obtained in step (3) in a water bath for a chemical cross-linking reaction to obtain a precursor II of the CNT / PDA / PVA hydrogel foam;

[0013] (5) Immerse the precursor II obtained in step (4) in a sodium chloride solution for 70-75 h, and then dry and wash to obtain the CNT / PDA / PVA hydrogel foam.

[0014] The beneficial effects of the above operations are as follows: In step (1), CNT, dopamine hydrochloride, CuSO4·5H2O and H2O2 act as a substrate, a carrier, an oxidant and an inducer respectively, and a polymerization reaction occurs to promote PDA to be loaded or coated on the surface of CNT; in step (3), the PVA solution, HCl solution and CNT / PDA complex act as a cross-linking solvent, an initiator and a light absorber respectively; in step (4), the precursor I is placed in a water bath to promote the chemical cross-linking reaction of PVA molecular chains; in step (5), the immersion in the sodium chloride solution can make the PVA molecular chains arrange orderly.

[0015] Preferably, the mass ratio of CNT, dopamine hydrochloride and CuSO4·5H2O in step (1) is 195 - 205 mg: 95 - 105 mg: 60 - 65 mg. The buffer solvent is trimethylolpropane with a pH of 8.5 - 8.8, and the concentration of H2O2 is 30 wt%. The volume ratio of the buffer solvent to H2O2 is 50 - 55 mL: 0.09 - 0.1 mL. Based on 195 - 205 mg of CNT, 95 - 105 mg of dopamine hydrochloride and 60 - 65 mg of CuSO4·5H2O, the amount of the buffer solvent added is 50 - 55 mL. The drying temperature is 70 - 80 °C and the time is 12 - 24 h.

[0016] Preferably, the addition ratio of PVA and glutaraldehyde in step (2) is: 14.5 - 16.5 g: 1.80 - 2.0 mL. The temperature of the oil bath is 80 - 90 °C and the reflux time is 2 - 3 h. The PVA content in the PVA solution is 9.7 - 11 wt%.

[0017] Preferably, the volume ratio of the PVA solution to the HCl solution in step (3) is 20:1. The ratio of the CNT / PDA composite to the PVA solution is 15 - 20 mg: 0.75 - 1.25 mL. The concentration of the HCl solution is 3 wt%. The stirring speed is 2000 - 2500 r / min and the stirring time is 3 - 4 min.

[0018] Preferably, the temperature of the water bath in step (4) is 60 - 65 °C and the time is 30 - 35 min.

[0019] Preferably, the concentration of the sodium chloride solution in step (5) is 4.5 - 5.5 mol / L. It is dried at room temperature and washed with distilled water.

[0020] Another object of the present invention is to provide: a CNT / PDA / PVA-based hydrogel foam prepared by the above method.

[0021] Another object of the present invention is to provide: the application of the above CNT / PDA / PVA-based hydrogel foam in solar seawater desalination.

[0022] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0023] In the present invention, a PVA solution is mixed with a hydrochloric acid solution and CNT / PDA. Through the short-time mechanical stirring in step (2) and the chemical crosslinking in step (3), a large number of bubbles are generated in the phase-transformed PVA solution. At low temperature, the PVA molecular chains undergo chemical crosslinking to form a PVA hydrogel foam precursor II with a rich pore structure. On this basis, by soaking in a sodium chloride solution, chloride ions change the entanglement state and crystalline state of the PVA molecular chains, further altering the pore structure, and a CNT / PDA / PVA hydrogel-based foam with an interpenetrating network structure, rich pore structure (macropores and micropores), excellent mechanical properties, and low evaporation enthalpy change is prepared. When the prepared CNT / PDA / PVA hydrogel-based foam is placed in a water evaporation system assembled with a one-dimensional water channel and a pearl-patterned paper towel, it not only absorbs ambient energy to promote water evaporation but also exhibits excellent salt tolerance in high-salinity solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0025] Figure 1 It is: a preparation flow chart of the CNT / PDA / PVA hydrogel-based foam prepared in Example 1.

[0026] Figure 2 It is: a scanning electron microscope image of the CNT / PDA / PVA hydrogel-based foam prepared in Example 1, where a represents the scanning electron microscope image at 500 μm, and b represents the scanning electron microscope image at 50 μm.

[0027] Figure 3 It is: a mechanical property diagram of the CNT / PDA / PVA hydrogel-based foam prepared in Example 1.

[0028] Figure 4 It is: a stress-strain diagram of the CNT / PDA / PVA hydrogel-based foam prepared in Example 1.

[0029] Figure 5 It is: a super-lightweight diagram of the CNT / PDA / PVA hydrogel-based foam prepared in Example 1.

[0030] Figure 6 It is: a scanning electron microscope image of the CNT / PDA / PVA hydrogel-based foams prepared in Examples 2 and 3.

[0031] Figure 7It is: the change of intermediate water in the CNT / PDA / PVA hydrogel-based foams prepared in Example 1 and Comparative Examples 1-6.

[0032] Figure 8 It is: the change of the evaporation enthalpy change value of the CNT / PDA / PVA hydrogel-based foams prepared in Example 1 and Comparative Examples 1-6.

[0033] Figure 9 It is: the comparison of the evaporation performance between the CNT / PDA / PVA hydrogel foam prepared in Example 1 and water.

[0034] Figure 10 It is: the salt tolerance of the CNT / PDA / PVA hydrogel foam prepared in Example 1 in high-concentration saline. Specific Embodiments

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Example 1

[0037] A preparation method of a CNT / PDA / PVA-based hydrogel-based foam includes the following steps:

[0038] (1) Disperse 200 mg of CNT, 100 mg of dopamine hydrochloride, and 60 mg of CuSO4·5H2O in 50 mL of a buffer solvent (pH = 8.5 - 8.8, trimethylolpropane), add 0.1 mL of H2O2, stir for 4 - 5 h, centrifuge, wash with water, and dry (70 - 80 °C) to obtain a CNT / PDA light absorber.

[0039] (2) Dissolve 15 g of PVA-203 (molecular weight of 15000) and 1.865 mL of glutaraldehyde (50 wt%) in 150 mL of distilled water. The solution is refluxed in an oil bath at 90 °C for 2 h to obtain a 10 wt% PVA solution, and it is cooled to room temperature for standby;

[0040] (3) Take 20 mL of the 10 wt% PVA solution, 1 mL of the 3 wt% HCl solution, and 300 mg of CNT / PDA and place them in a plastic beaker. Stir at a mechanical stirring speed of 2500 r / min for 3 min to obtain a precursor I of the CNT / PDA / PVA hydrogel-based foam;

[0041] (4) The precursor I in step (3) was crosslinked at a water bath temperature of 60 °C for 30 min to obtain the CNT / PDA / PVA hydrogel foam precursor II;

[0042] (5) The precursor II in step (4) was placed in a 5 mol / L sodium chloride solution for 72 h, taken out, dried at room temperature, and washed to obtain the CNT / PDA / PVA hydrogel-based foam.

[0043] The above preparation process is as Figure 1 shown. Mechanically stir the PVA solution, CNT / PDA sample, and HCl solution to obtain a black viscous foam. After crosslinking in a water bath and soaking in a sodium chloride solution, a black CNT / PDA / PVA hydrogel-based foam is obtained.

[0044] The CNT / PDA / PVA hydrogel-based foam prepared in Example 1 was subjected to electron microscopy scanning, mechanical property testing, stress-strain testing, and ultra-light testing. The experimental results are respectively as Figures 2 - 5 shown:

[0045] Result analysis: The CNT / PDA / PVA hydrogel-based foam prepared in Example 1 was scanned under an electron microscope at different magnifications to obtain a scanning electron microscope image (SEM image). As shown in Figure 2 a, the CNT / PDA / PVA hydrogel-based foam is interconnected pores, forming a three-dimensional foam-like structure; as shown in Figure 2 b, there are pores with different pore sizes in the space between different layers, which is beneficial to multiple internal refraction of light and diffusion of water molecules.

[0046] As Figure 3 shown, the height comparison of the sample before and after loading a 500 g weight. After removing the weight, the sample quickly returned to its initial state, and the sample structure did not collapse, indicating that the sample has excellent mechanical properties

[0047] As Figure 4 shown, in 10 stress-strain tests, the CNT / PDA / PVA hydrogel-based foam can still return to its original state, further indicating the excellent mechanical properties of the CNT / PDA / PVA hydrogel-based foam.

[0048] As Figure 5 shown, the CNT / PDA / PVA hydrogel-based foam can stand stably on the branches and leaves, indicating that the prepared CNT / PDA / PVA hydrogel-based foam has ultra-light weight.

[0049] Example 2

[0050] A preparation method of a CNT / PDA / PVA-based hydrogel-based foam, comprising the following steps:

[0051] (1) Disperse 200 mg of CNT, 100 mg of dopamine hydrochloride, and 60 mg of CuSO4·5H2O in 50 mL of buffer solvent (pH = 8.5 - 8.8, trimethylolpropane), add 0.1 mL of H2O2, stir for 4 - 5 h, centrifuge, wash with water, and dry at 70 - 80 °C to obtain the CNT / PDA light absorber.

[0052] (2) Dissolve 14.5 g of PVA - 203 (molecular weight 15000) and 1.8 mL of glutaraldehyde (50 wt%) in 150 mL of distilled water. The solution is refluxed in an oil bath at 80 °C for 3 h and cooled to room temperature for standby.

[0053] (3) Take 20 mL of PVA solution, 1 mL of 3 wt% HCl solution, and 300 mg of CNT / PDA and place them in a plastic beaker. Stir at a mechanical stirring speed of 2000 r / min for 4 min to obtain precursor I of the CNT / PDA / PVA hydrogel - based foam.

[0054] (4) Cross - link precursor I from step (2) in a water bath at 65 °C for 35 min to obtain precursor II of the CNT / PDA / PVA hydrogel foam.

[0055] (5) Place precursor II from step (3) in a 4.5 mol / L sodium chloride solution for 72 h, take it out, dry at room temperature, and wash to obtain the CNT / PDA / PVA hydrogel - based foam.

[0056] Example 3

[0057] A preparation method of a CNT / PDA / PVA - based hydrogel - based foam, comprising the following steps:

[0058] (1) Disperse 205 mg of CNT, 105 mg of dopamine hydrochloride, and 65 mg of CuSO4·5H2O in 50 mL of buffer solvent (pH = 8.5 - 8.8, trimethylolpropane), add 0.1 mL of H2O2, stir for 4 - 5 h, centrifuge, wash with water, and dry at 70 - 80 °C to obtain the CNT / PDA light absorber.

[0059] (2) Dissolve 16.5 g of PVA - 203 and 2.0 mL of glutaraldehyde (50 wt%) in 150 mL of distilled water. The solution is refluxed in an oil bath at 85 °C for 2 h to obtain a PVA solution, and cooled to room temperature for standby.

[0060] (3) Take 20 mL of 11 wt% PVA solution, 1 mL of 3 wt% HCl solution, and 400 mg of CNT / PDA and place them in a plastic beaker. Stir mechanically at a speed of 2000 r / min for 3 min to obtain precursor I of the CNT / PDA / PVA hydrogel-based foam;

[0061] (4) Place precursor I from step (2) in a water bath at 63 °C and crosslink for 30 min to obtain precursor II of the CNT / PDA / PVA hydrogel foam;

[0062] (5) Place precursor II from step (3) in a 5.5 mol / L sodium chloride solution for 72 h, take it out, dry at room temperature, and wash to obtain the CNT / PDA / PVA hydrogel-based foam.

[0063] The CNT / PDA / PVA hydrogel-based foams prepared in Examples 2 and 3 were subjected to electron microscopy scanning, and the experimental results are as Figure 6 shown:

[0064] Result analysis: The CNT / PDA / PVA hydrogel-based foams prepared in Examples 2 and 3 were placed under an electron microscope for scanning to obtain scanning electron microscope images (SEM images). As Figure 6 shown in a, the CNT / PDA / PVA hydrogel-based foam prepared in Example 2 is a three-dimensional foam-like structure with pores of different pore sizes connected to each other; as Figure 6 shown in b, the CNT / PDA / PVA hydrogel-based foam prepared in Example 3 is also a three-dimensional foam-like structure with pores of different pore sizes connected to each other, and it is beneficial for multiple internal refraction of light and diffusion of water molecules.

[0065] Comparative Example 1

[0066] The difference from Example 1 is that the concentration of sodium chloride is 2 mol / L and the soaking time is 72 h. The rest of the content is the same as in Example 1 to obtain the CNT / PDA / PVA hydrogel-based foam.

[0067] Comparative Example 2

[0068] The difference from Example 1 is that the concentration of sodium chloride is 3 mol / L and the soaking time is 72 h. The rest of the content is the same as in Example 1 to obtain the CNT / PDA / PVA hydrogel-based foam.

[0069] Comparative Example 3

[0070] The difference from Example 1 is that the concentration of sodium chloride is 4 mol / L and the soaking time is 72 h. The rest of the content is the same as in Example 1 to obtain the CNT / PDA / PVA hydrogel-based foam.

[0071] Comparative Example 4

[0072] The difference from Example 1 is that the concentration of sodium chloride is 5 mol / L and the soaking time is 24 h. The rest is the same as in Example 1, and a CNT / PDA / PVA hydrogel-based foam is obtained.

[0073] Comparative Example 5

[0074] The difference from Example 1 is that the concentration of sodium chloride is 5 mol / L and the soaking time is 48 h. The rest is the same as in Example 1, and a CNT / PDA / PVA hydrogel-based foam is obtained.

[0075] Comparative Example 6

[0076] The difference from Example 1 is that the concentration of sodium chloride is 5 mol / L and the soaking time is 96 h. The rest is the same as in Example 1, and a CNT / PDA / PVA hydrogel-based foam is obtained.

[0077] Intermediate water content test

[0078] After cutting the CNT / PDA / PVA hydrogel-based foam samples prepared in Example 1 and Comparative Examples 1-6, Raman tests were carried out. The water states in all samples are divided into three types: intermediate water (the bound water forms weak hydrogen bonds with surrounding water molecules, less than the free water where the adjacent water molecules interact with four water molecules), bound water (the water molecules form strong hydrogen bonds with hydrophilic polar functional groups on the polymer chain), and free water (the water molecules form four hydrogen bonds with surrounding water molecules). The Raman curves were Gaussian-fitted to analyze the ratio of intermediate water to bound water.

[0079] Result analysis: As Figure 7 shown, the water molecule states of all samples prepared in Comparative Examples 1-6 and Example 1 are divided into bound water, free water, and combined water. Compared with free water and combined water, intermediate water is prone to breakage and change from liquid water to water vapor. The higher the content of intermediate water, the easier the water molecules are to become water vapor. The ratio of the fitted curve areas of intermediate water to bound water in the CNT / PDA / PVA hydrogel-based foam of the sample in Example 1 is as high as 2.52, which is greater than that of other comparative samples, indicating that under the conditions of a sodium chloride concentration of 5 mol / L and a soaking time of 72 h in Example 1, it is easier to form intermediate water inside the structure of the CNT / PDA / PVA hydrogel-based foam, prone to hydrogen bond breakage, and reducing the energy required for evaporation.

[0080] Evaporation enthalpy change test

[0081] Pour a certain amount of distilled water into an open beaker with a volume of 100 mL. The liquid level is in contact with the environment, and record its mass as m0. Then, place the hydrogel-based foam with the same diameter as the beaker into the above-mentioned open beaker. The upper surface layer of the hydrogel-based foam is in contact with the environment. Place the hydrogel-based foam in the beaker containing distilled water, and transfer the beaker to a vacuum dryer containing saturated potassium carbonate. Wrap it with tin foil and place it in a constant temperature (25 °C) environment for 12 h. Calculate the mass difference of the distilled water and the hydrogel-based foam before and after, and calculate △H according to the following formula vap m 0＝ △H equ m g Calculate the equivalent evaporation enthalpy, and repeat the experiment three times and take the average value.

[0082] Where H equ is the equivalent evaporation enthalpy of the hydrogel-based foam, m g is the measured mass change of the hydrogel-based foam, H vap is the evaporation enthalpy of water at 25 °C (2455 J / g), and m0 is the mass change of distilled water.

[0083] In the test of evaporation enthalpy change, sodium chloride solution affects the enthalpy change value. The lower the evaporation enthalpy change value, the lower the energy required for evaporation, and the easier it is for water molecules to escape. As Figure 8 shown, when the sodium chloride concentration = 5 mol / L and the soaking time = 72 h, the equivalent enthalpy change value (1404 J / g) of the CNT / PDA / PVA hydrogel-based foam prepared in Example 1 is much lower than that of water (2455 J / g), indicating that sodium chloride can effectively adjust the evaporation enthalpy change value and reduce the energy required for evaporation.

[0084] Test of water evaporation performance

[0085] The entire solar evaporation system test system includes a solar light simulator, an analytical balance (0.0001 g), a heat-insulating foam sleeve, a computer, and a solar simulator calibrator. The model of the solar light simulator is 94023A, with a 450 W xenon lamp as the light source. An AM1.5G filter is built-in to obtain a beam spectrum similar to solar radiation, and the irradiation fluctuation is <±2%. Before the test, use a solar simulator calibrator of Sol 3A (calibrate the solar cell (91150V, single crystal silicon and fused quartz window), instrument, quartz) to measure and collect the numerical value of the simulated solar radiation intensity, and adjust the solar light simulator to reach a light intensity of 1000 W m -2 . Secondly, after the light intensity reaches stability, connect the calibrated analytical balance (range 200 g) to the computer, and test the evaporation system assembled with a 100 mL beaker, a photothermal material, and a heat-insulating foam, and collect and record the mass data in real time every minute.

[0086] In the water evaporation test, the evaporator assembled with the CNT / PDA / PVA hydrogel-based foam, 1D channels, and textile fabric prepared in Example 1 absorbed ambient energy from the side and promoted water evaporation. As Figure 9 shown, the water evaporation performance of the CNT / PDA / PVA hydrogel-based foam was as high as 3.0 kg m -2 h -1 , more than seven times that of water, indicating that not only could the pore structure under this condition rapidly transport water, but also that water molecules inside the hydrogel were prone to form intermediate water under this condition, promoting the rapid evaporation of water molecules.

[0087] Salt tolerance test

[0088] In the above solar evaporation test system, the evaporator assembled with the CNT / PDA / PVA hydrogel-based foam, 1D water channels, and textile fabric prepared in Example 1 was continuously operated in a 10 wt% NaCl solution for 100 h. Every 24 h, 10 mL of the 10 wt% NaCl solution was replenished with a 10 mL syringe. The results are as Figure 10 shown

[0089] Result analysis: As Figure 10 shown, during the continuous operation of the evaporator assembled with the CNT / PDA / PVA hydrogel-based foam, 1D water channels, and textile fabric prepared in Example 1 in a 10 wt% NaCl solution, water evaporation remained stable and salt was deposited around.

[0090] The present invention is not limited to the above embodiments. Based on the technical solutions disclosed in the present invention, those skilled in the art can make equivalent transformations or modifications according to the disclosed technical content, and all such transformations or modifications should be covered within the protection scope of the present invention.

[0091] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other.

[0092] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a hydrogel-based foam based on CNT / PDA / PVA, characterized in that it comprises the following steps: (1) Disperse CNT and dopamine hydrochloride in a buffer solvent, add CuSO4·5H2O and H2O2, and stir at room temperature for 4-5 h, then centrifuge, wash with water, and dry to obtain a CNT / PDA light absorber; (2) Dissolve PVA and glutaraldehyde in distilled water and reflux in an oil bath to obtain a PVA solution; (3) Mix the PVA solution, HCl solution and CNT / PDA composite, and stir to obtain a precursor I of the CNT / PDA / PVA hydrogel-based foam; (4) Place the precursor I obtained in step (3) in a water bath for a chemical cross-linking reaction to obtain a precursor II of the CNT / PDA / PVA hydrogel-based foam; (5) Immerse the precursor II obtained in step (4) in a sodium chloride solution for 70-75 h, and then dry and wash to obtain the CNT / PDA / PVA hydrogel-based foam.

2. The preparation method of the CNT / PDA / PVA-based hydrogel foam according to claim 1, wherein In step (1), the mass ratio of CNT, dopamine hydrochloride and CuSO4·5H2O is 195-205 mg: 95-105 mg: 60-65 mg, the buffer solvent is trimethylolpropane with a pH of 8.5-8.8, and the concentration of H2O2 is 30 wt%; the volume ratio of the buffer solvent to H2O2 is 50-55 mL: 0.09-0.1 mL; based on 195-205 mg of CNT, 95-105 mg of dopamine hydrochloride and 60-65 mg of CuSO4·5H2O, the amount of the buffer solvent added is 50-55 mL; the drying temperature is 70-80 °C and the time is 12-24 h.

3. The preparation method of the CNT / PDA / PVA-based hydrogel foam according to claim 1, characterized in that, In step (2), the addition ratio of PVA and glutaraldehyde is: 14.5-16.5 g: 1.80-2.0 mL, the temperature of the oil bath is 80-90 °C, and the reflux time is 2-3 h; the PVA content in the PVA solution is 9.7-11 wt%.

4. The preparation method of the CNT / PDA / PVA-based hydrogel foam according to claim 1, characterized in that, In step (3), the volume ratio of the PVA solution to the HCl solution is 20:1; the ratio of the CNT / PDA composite to the PVA solution is 15-20 mg: 0.75-1.25 mL; the concentration of the HCl solution is 3 wt%; the stirring speed is 2000-2500 r / min and the stirring time is 3-4 min.

5. The preparation method of the CNT / PDA / PVA-based hydrogel foam according to claim 1, characterized in that, In step (4), the temperature of the water bath is 60-65 °C and the time is 30-35 min.

6. The preparation method of the CNT / PDA / PVA-based hydrogel foam according to claim 1, characterized in that In step (5), the concentration of the sodium chloride solution is 4.5-5.5 mol / l; dry at room temperature and wash with distilled water.

7. A hydrogel-based foam based on CNT / PDA / PVA prepared by the method according to any one of claims 1-6.

8. Use of the hydrogel-based foam based on CNT / PDA / PVA according to claim 7 in solar seawater desalination.

Images