Solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel, preparation method and application

Abstract

The present invention provides a solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel, a preparation method and an application, belonging to the field of solar interface evaporation. The present invention combines the anti-polyelectrolyte effect of the amphoteric polyelectrolyte photothermal water gel and the porous capillary effect of the sponge to make a solar interface evaporator with a three-dimensional multi-faceted evaporation structure, which has the characteristics of high light absorption rate, good water absorption effect, excellent antibacterial properties, mechanical properties, salt resistance and evaporation performance. In particular, the application of the independently designed amphoteric ion hydrogel greatly improves the water transport capacity and salt resistance in higher concentration salt water compared to traditional hydrogel-based solar interface evaporators, and utilizes the hydration of salt-resistant ions to activate water molecules in the salt water, reduce the evaporation enthalpy, and have a great positive effect on improving the evaporation rate. The evaporator of the present invention is simple to prepare and has excellent multi-dimensional performance, providing a new approach and idea for application in seawater desalination and wastewater treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of solar interface evaporation, and relates to a solar interface evaporator based on an amphoteric polyelectrolyte photothermal water gel, and a preparation method and application thereof. Background Art

[0002] Water resources are a fundamental natural resource and a strategic economic resource for human survival. Faced with the intensifying imbalance between freshwater supply and demand, the development and utilization of seawater, which accounts for 97% of the world's water resources, has become a key solution. While current mainstream desalination technologies have achieved industrial application, their operation relies heavily on high-quality thermal energy or a stable electricity supply, resulting in high energy consumption and a significant carbon footprint. Compared to conventional fossil fuels, solar energy is one of the cleanest energy sources and is inexhaustible. Therefore, utilizing solar energy for desalination is an effective and sustainable path to freshwater production. The photothermal materials in traditional solar distillation devices are typically placed at the bottom of the water or dispersed in the form of nanofluids. Not only is a large amount of sunlight reflected at the water surface, but incident sunlight must also pass through a thick layer of water before being absorbed by the photothermal materials. Ultimately, this volumetric heating of the entire water column results in significant heat losses. The low evaporation rate (water production) per unit area requires a large footprint, making widespread use unfeasible.

[0003] The introduction of solar interfacial evaporation technology has improved the shortcomings of traditional solar distillation and has become a milestone in the development of solar evaporation technology. This is mainly attributed to the ability of photothermal materials to localize the heat converted from solar energy at the evaporation interface for water evaporation, greatly reducing heat loss and thereby increasing the evaporation rate. Hydrogels have performed well in many types of solar interfacial evaporators because they can change the hydrogen bonding state of water molecules and reduce the enthalpy of water evaporation by regulating the interaction between water-polymer network-hydrophilic functional groups. However, the strong hydration of salt ions and the problem of salt crystallization during long evaporation periods remain one of the bottlenecks in the treatment of saline liquids by solar interfacial evaporation technology. Salt ion hydration requires more energy for water evaporation, and salt crystallization seriously affects the evaporator's absorption of sunlight and water transport, and restricts the outward diffusion of water vapor, resulting in a decrease in evaporation rate and freshwater production. Drawing on the characteristics of biological ion channels that have both cation / anion selectivity and interaction selectivity, the charge on the polyelectrolyte hydrogel polymer chain is similar to the function of biological ion channels, and can effectively inhibit the binding of anion / cation salt ions through ion selectivity. However, due to the polyelectrolyte effect, most hydrogel polymer chains are in a folded conformation in salt water, which makes the water supply capacity and evaporation mismatched, and also leads to a decrease in evaporation rate. In addition, traditional hydrogel evaporators generally have poor mechanical properties, such as low mechanical strength (<120kPa), which is also one of the factors that limit the structural design and practical application of hydrogel-based evaporators. How to design a hydrogel-based evaporator with excellent multi-dimensional performance that does not affect or even improves evaporation performance when processing salt water remains a challenge. Summary of the Invention

[0004] In light of this, the present invention aims to provide a solar interface evaporator based on an amphoteric polyelectrolyte photothermal hydrogel, addressing the problems of existing hydrogel-based evaporators, such as poor mechanical properties, water transport performance, and salt tolerance in saline solutions. The present invention utilizes the salt ion hydration effect of the amphoteric polyelectrolyte photothermal hydrogel to activate water molecules in saline, breaking the energy barrier required for evaporation and reducing energy consumption. The anti-polyelectrolyte effect causes the polymer chains to adopt a stretched conformation in saline, enhancing water transport performance. Simultaneously, the anionic and cation-containing groups on the polymer chains attract sodium and chloride ions in the saline, respectively, separating the positive and negative salt ions and effectively preventing salt crystallization. The layered porous structure of the sponge provides channels for water transport and salt ion diffusion back from the evaporation interface to the liquid reservoir, further enhancing water transport performance and salt tolerance. Furthermore, the soft sponge, serving as the basic framework of the evaporator, significantly enhances its mechanical strength. Furthermore, the antibacterial properties of the present evaporator effectively resist biofouling, thereby extending the evaporator's service life and reducing cleaning costs.

[0005] The first aspect of the present invention provides a solar interface evaporator based on an amphoteric polyelectrolyte photothermal water gel, comprising a porous sponge and an amphoteric polyelectrolyte photothermal water gel embedded in the pores of the porous sponge; the amphoteric polyelectrolyte photothermal water gel comprises a polymer network formed by a high molecular weight polymer and a photothermal conversion material dispersed in the polymer network; the high molecular weight polymer comprises polyvinyl alcohol, a cationic polymer, an anionic polymer and a crosslinking agent.

[0006] Preferably, the cross-linking degree of the amphoteric polyelectrolyte photothermal water gel is 1% to 2%; in the amphoteric polyelectrolyte photothermal water gel, the mass fractions of polyvinyl alcohol, cationic polymer, anionic polymer, and photothermal conversion material are 3 to 7 wt%, 0.5 to 1.5 wt%, 0.5 to 1.5 wt%, and 3 to 8 wt%, respectively.

[0007] Preferably, the cationic polymer includes one or a combination of two or more of chitosan, chitosan quaternary ammonium salt, polyallylamine hydrochloride, polyethyleneimine or polydimethyl ammonium chloride; the anionic polymer includes one or a combination of two or more of poly(p-styrene sulfonate), poly(p-styrene sulfonic acid), sodium hyaluronate or sodium dextran sulfate; the photothermal conversion material includes one or a combination of two or more of carbon nanotubes, graphene, carbonized biomass (such as carbonized wood chips), metal nanoparticles (such as gold and silver nanoparticles), titanium dioxide, polypyrrole or polydopamine; and the cross-linking agent is a mixture of hydrochloric acid solution and glutaraldehyde solution.

[0008] Preferably, the porous sponge includes polyvinyl alcohol sponge, melamine sponge, polyurethane sponge, cellulose sponge or polyester sponge; the porosity of the porous sponge is 80% to 99%, and the internal pore size distribution is 40 to 180 μm.

[0009] The second aspect of the present invention provides a method for preparing a solar interface evaporator based on an amphoteric polyelectrolyte photothermal water gel, comprising the following steps:

[0010] Step 1: adding polyvinyl alcohol powder and cationic polymer powder to an aqueous solution, heating and stirring to obtain a mixed solution A;

[0011] Step 2: adding anionic polymer powder and photothermal conversion material to the mixed solution A and stirring thoroughly to obtain a mixed solution B;

[0012] Step 3: adding a crosslinking agent to the mixed solution B at a crosslinking degree of 1% to 2%, and rapidly stirring to prepare a hydrogel precursor solution; in the hydrogel precursor solution, the mass fractions of polyvinyl alcohol, cationic polymer, anionic polymer, and photothermal conversion material are 3-7 wt%, 0.5-1.5 wt%, 0.5-1.5 wt%, and 3-8 wt%, respectively;

[0013] Step 4: completely immerse the porous sponge in the hydrogel precursor solution, and after the porous sponge is completely wetted, place it at room temperature to obtain a solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel.

[0014] Preferably, the cationic polymer includes one or a combination of two or more of chitosan, polyallylamine hydrochloride, polyethyleneimine or polydimethyl ammonium chloride; the anionic polymer includes one or a combination of two or more of poly(p-styrene sulfonate), poly(p-styrene sulfonic acid), sodium hyaluronate or sodium dextran sulfate; the photothermal conversion material includes one or a combination of two or more of carbon nanotubes, graphene, carbonized biomass (such as carbonized wood chips), metal nanoparticles (such as gold and silver nanoparticles), titanium dioxide, polypyrrole or polydopamine.

[0015] Preferably, the cross-linking agent is a mixture of hydrochloric acid solution and glutaraldehyde solution; wherein the mass fraction of the hydrochloric acid solution is 2-4wt%, preferably 3wt%; the mass fraction of the glutaraldehyde solution is 50wt%; and the volume ratio of the hydrochloric acid solution to the glutaraldehyde solution is 6:1-3:1, preferably 5:1.

[0016] Preferably, the degree of cross-linking is calculated as follows:

[0017]

[0018] Here, GA represents glutaraldehyde, and PVA represents polyvinyl alcohol.

[0019] Preferably, in the hydrogel precursor solution, the mass fraction of polyvinyl alcohol is preferably 5 wt %; the mass fraction of cationic polymer is preferably 1 wt %; the mass fraction of anionic polymer is preferably 1 wt %; and the mass fraction of photothermal conversion material is preferably 5 wt %.

[0020] Preferably, the cross-linking degree of the hydrogel precursor solution is 1.5%.

[0021] Preferably, in step 1, the heating and stirring temperature is 80-95° C., preferably 90° C.; the stirring speed is 50-150 rpm, preferably 100 rpm; and the stirring time is 4-8 hours, preferably 6 hours;

[0022] In step 2, the stirring speed is 100 to 300 rpm, preferably 200 rpm; the stirring time is 0.5 to 1.5 hours, preferably 1 hour;

[0023] In step 3, the speed of rapid stirring is 400-600 rpm, preferably 500 rpm; the stirring time is 3-8 minutes, preferably 5 minutes;

[0024] In step 4, the immersion time is 20 to 40 minutes, preferably 30 minutes.

[0025] Preferably, the porous sponge includes polyvinyl alcohol (PVA) sponge, melamine sponge, polyurethane sponge, cellulose sponge or polyester sponge; the porosity of the porous sponge is 80% to 99%, and the internal pore size distribution is 40 to 180 μm.

[0026] The third aspect of the present invention provides an application of a solar interface evaporator based on an amphoteric polyelectrolyte photothermal water gel in the preparation of solar seawater desalination materials.

[0027] The beneficial effects of the present invention are as follows: the solar interface evaporator based on the amphoteric polyelectrolyte photothermal gel provided by the present invention utilizes the anti-polyelectrolyte effect and anti-salt ion hydration effect of the amphoteric ion hydrogel to improve the water transport capacity and salt resistance of the evaporator in salt water, and utilizes the polyvinyl alcohol sponge with a layered porous structure to improve the water transport capacity and mechanical strength (>560kPa), thereby enhancing the evaporation performance of the evaporator in salt water. The evaporation rate can reach 3.35kg / (m3) in a 10wt% NaCl solution for 9 hours continuously. 2 ·h), and there is no obvious salt deposition and structural change on the evaporator surface. The evaporation rate in 15wt% NaCl solution can reach 2.94kg / (m 2 ·h), the evaporation rate in 20wt% NaCl solution can reach 2.87kg / (m 2 h), and the evaporator has an antibacterial rate of up to 100% against Escherichia coli. The above evaporator provides a new approach and idea for the development of next-generation solar interfacial evaporation systems for seawater desalination and wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The electron microscope image and X-ray spectrometer element analysis image of the solar interface evaporator prepared in Example 1 of the present invention under dry conditions.

[0029] Figure 2 It is the FTIR infrared absorption peak of polyvinyl alcohol (PVA), chitosan (CS), poly(p-styrene sulfonate) (PSS) and amphoteric polyelectrolyte photothermal gel in Example 1 of the present invention.

[0030] Figure 3 This is a UV-visible-near-infrared absorption spectrum of the solar interface evaporator (PCP evaporator) prepared in Example 1 of the present invention under dry conditions.

[0031] Figure 4 This is a process diagram of a water droplet with a diameter of 3 mm hitting the upper surface of the solar interface evaporator prepared in Example 1 of the present invention from a height of 5 cm.

[0032] Figure 5 The evaporator (3×3×7 cm) prepared in Example 1 of the present invention was operated at 1 kW / m 2 Evaporation mass change diagram and evaporation rate diagram in brine with different salinity under light irradiance; (a) is the evaporation mass change diagram, and (b) is the evaporation rate diagram.

[0033] Figure 6 Schematic diagram of the evaporator (3×3×7 cm) prepared in Example 1 of the present invention returning to its original shape after being mechanically compressed.

[0034] Figure 7 The graphs show the changes of Example 1 and Comparative Example 1 after continuous evaporation in a 20 wt% NaCl solution for 9 hours, respectively; (a) is a graph showing the surface changes during evaporation of Example 1, and (b) is a graph showing the surface changes during evaporation of Comparative Example 1.

[0035] Figure 8 These are comparison diagrams of the evaporator prepared in Example 1 of the present invention before and after seawater desalination in an outdoor evaporation experiment, where (a) shows the change in ion concentration of seawater and collected fresh water before and after seawater desalination, and (b) shows the change in clarity of turbid seawater and collected fresh water before and after seawater desalination. DETAILED DESCRIPTION

[0036] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0037] All reagents used in this invention were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0038] Example 1

[0039] 5 g of PVA powder and 1 g of CS powder were weighed and added to 92.5 g of acetic acid aqueous solution (2 wt %), and the beaker was stirred at 100 rpm in a 90 ° C water bath for 6 h; after cooling to room temperature, 1 g of PSS powder and 0.5 g of carbon nanotubes (CNTs) were added, and stirred at 200 pm for 1 h. A mixed solution of 3 wt % HCl solution and 50 wt % GA solution was used as a cross-linking agent and 810 μL of the cross-linking agent was added dropwise according to a volume ratio of 5:1. The cross-linking degree was controlled to be 1.5%. After rapid stirring at 500 rpm for 5 min, a hydrogel precursor solution was prepared. Then, a PVA sponge (3×3×9 cm, effective evaporation height of 7 cm) was completely immersed in the beaker for 30 min. After being taken out, it was placed at room temperature for 8 h to prepare a solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel.

[0040] Example 2

[0041] 3 g PVA powder and 1.5 g CS powder were weighed and added to 93.5 g acetic acid aqueous solution (2 wt %). The beaker was stirred at 100 rpm in a 90 ° C water bath for 6 h. After cooling to room temperature, 1.5 g PSS powder and 0.5 g carbon nanotubes (CNTs) were added. After stirring at 200 pm for 1 h, a mixed solution of 3 wt % HCl solution and 50 wt % GA solution was used as a cross-linking agent and 486 μL of the cross-linking agent was added dropwise according to a volume ratio of 5:1. The cross-linking degree was controlled to be 1.5%. After rapid stirring at 500 rpm for 5 min, a hydrogel precursor solution was prepared. Then, a PVA sponge (3 × 3 × 9 cm, effective evaporation height of 7 cm) was completely immersed in the beaker for 30 min. After being taken out, it was placed at room temperature for 8 h to prepare a solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel.

[0042] Example 3

[0043] 7g PVA powder and 1.5g CS powder were weighed and added to 89.5g acetic acid aqueous solution (2wt%). The beaker was stirred at 100rpm in a 90℃ water bath for 6h. After cooling to room temperature, 1.5g PSS powder and 0.5g carbonized jujube sawdust were added. After stirring at 200pm for 1h, a mixed solution of 3wt% HCl solution and 50wt% GA solution was used as a cross-linking agent and 1122μL of cross-linking agent was added dropwise according to a volume ratio of 5:1. The cross-linking degree was controlled to be 1.5%. After rapid stirring at 500rpm for 5min, a hydrogel precursor solution was prepared. Then, a melamine sponge (3×3×9cm, effective evaporation height of 7cm) was completely immersed in the beaker for 30min. After being taken out, it was placed at room temperature for 8h to prepare a solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel.

[0044] Example 4

[0045] 5g PVA powder and 1g CS powder were weighed and added to 93g acetic acid aqueous solution (2wt%). The beaker was stirred at 100rpm in a 90℃ water bath for 6h. After cooling to room temperature, 0.5g PSS powder and 0.5g graphene were added. After stirring at 200pm for 1h, a mixed solution of 3wt% HCl solution and 50wt% GA solution was used as a cross-linker and 536μL of cross-linker was added dropwise according to a volume ratio of 5:1. The cross-linking degree was controlled to be 1%. After rapid stirring at 500rpm for 5min, a hydrogel precursor solution was prepared. Then, a polyurethane sponge (3×3×9cm, effective evaporation height of 7cm) was completely immersed in the beaker for 30min. After being taken out, it was placed at room temperature for 8h to prepare a solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel.

[0046] Example 5

[0047] 5 g of PVA powder and 1 g of polyallylamine hydrochloride powder were weighed and added to 92.5 g of deionized water. The beaker was stirred at 100 rpm in a 90 ° C water bath for 6 h. After cooling to room temperature, 1 g of sodium dextran sulfate powder and 0.5 g of carbon nanotubes (CNTs) were added. After stirring at 200 pm for 1 h, a mixed solution of 3 wt% HCl solution and 50 wt% GA solution was used as a cross-linking agent and 810 μL of cross-linking agent was added dropwise according to a volume ratio of 5:1. The cross-linking degree was controlled to be 1.5%. After rapid stirring at 500 rpm for 5 min, a hydrogel precursor solution was prepared. Then, a melamine sponge (3×3×9 cm, effective evaporation height of 7 cm) was completely immersed in the beaker for 30 min. After being taken out, it was placed at room temperature for 8 h to prepare a solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel.

[0048] Example 6

[0049] 5g PVA powder and 1g polyethyleneimine powder were weighed and added to 92.5g deionized water. The beaker was stirred at 100rpm in a 90℃ water bath for 6h. After cooling to room temperature, 1g polystyrene sulfonic acid powder and 0.5g carbon nanotubes (CNTs) were added. After stirring at 200pm for 1h, a mixed solution of 3wt% HCl solution and 50wt% GA solution was used as a cross-linker and 1084μL of cross-linker was added dropwise according to a volume ratio of 5:1. The cross-linking degree was controlled to be 2%. After rapid stirring at 500rpm for 5min, a hydrogel precursor solution was prepared. A polyurethane sponge (3×3×9cm, effective evaporation height of 7cm) was completely immersed in the beaker for 30min. After being taken out, it was placed at room temperature for 8h to prepare a solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel.

[0050] Comparative Example 1

[0051] The difference between Comparative Example 1 and Example 1 is that the high molecular polymer in the hydrogel precursor solution of Comparative Example 1 is only PVA, and the specific preparation steps are as follows: 5g of PVA powder is weighed and added to 94.5g of deionized water, and the beaker is stirred at 100rpm in a water bath at 90°C for 6h. After cooling to room temperature, 0.5g of CNTs is added and stirred at 200pm for 1h. A mixed solution of 3wt% HCl solution and 50wt% GA solution is used as a cross-linking agent and 810μL of cross-linking agent is added dropwise according to a volume ratio of 5:1. The cross-linking degree is controlled to be 1.5%, and the hydrogel precursor solution is prepared after rapid stirring at 500rpm for 5min. A PVA sponge (3×3×9cm, effective evaporation height of 7cm) is completely immersed in the beaker for 30min. After taking it out, it is placed at room temperature for 8h to prepare a solar interface evaporator based on PVA hydrogel.

[0052] Comparative Example 2

[0053] The difference between Comparative Example 2 and Example 1 is that the crosslinking degree of the hydrogel precursor solution in Comparative Example 2 is 3%. The specific preparation steps are as follows: 5g of PVA powder and 1g of CS powder are weighed and added to 92.5g of acetic acid aqueous solution (2wt%), and the beaker is stirred at 100 rpm in a water bath at 90°C for 6h; after cooling to room temperature, 1g of PSS powder and 0.5g carbon nanotubes (CNTs) were stirred at a speed of 200pm for 1h, and then a mixed solution of 3wt% HCl solution and 50wt% GA solution was used as a cross-linker and a total of 1642μL of cross-linker was added according to a volume ratio of 5:1. The cross-linking degree was controlled to 3%. After rapid stirring at a speed of 500rpm for 5min, a hydrogel precursor solution was prepared. Then, a PVA sponge (3×3×9cm, effective evaporation height of 7cm) was completely immersed in a beaker for 30min, taken out and placed at room temperature for 8h. Due to the excessive degree of cross-linking, the viscosity of the hydrogel precursor was too high, resulting in the failure to fill the internal gaps of the porous sponge with photothermal water gel, that is, the solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel was not successfully prepared.

[0054] The evaporator prepared in Example 1 (solar interface evaporator) and the evaporator prepared in Comparative Example 1 (PVA evaporator) were characterized and tested, and the results are as follows:

[0055] (1) Characterization of dry solar interfacial evaporators. Polyvinyl alcohol sponges filled with amphoteric polyelectrolyte photothermal gel (prepared as solar interfacial evaporators, see Figure 1) Due to the addition of CNTs, the overall appearance is black, which lays the foundation for high light absorption and efficient photothermal conversion. The existence of the multilayer structure will cause multiple refractions and scattering of light, thereby increasing the light path and further enhancing light utilization. In addition to the hydrogel tightly adhering to the PVA sponge skeleton, the pores in the middle of the skeleton are also evenly filled with a large amount of amphoteric polyelectrolyte photothermal hydrogel, which increases the roughness while still retaining the porous structure. This high surface activity makes it easier for water molecules to adsorb on the surface of the material, thereby increasing the hydrophilicity, which also provides a strong guarantee for efficient solar interface evaporation and seawater desalination. In addition, the X-ray energy spectrometer also proved the successful preparation of the amphoteric polyelectrolyte photothermal hydrogel and the uniform distribution of each component. In the position where the amphoteric polyelectrolyte photothermal hydrogel is filled in the middle of the polyvinyl alcohol sponge skeleton, C and O are the basic elements of all components. The presence of the N element represents CS, and the presence of the S element represents PSS. Figure 2 The Fourier transform infrared (FTIR) spectra of amphoteric polyelectrolyte photothermal gel (PCP), PVA, CS, and PSS without CNTs are shown. All samples were detected at 3000–3700 cm -1 In the infrared spectrum of pure PVA, there are broad and strong absorption peaks at 1087cm -1 and 2931cm -1 The peaks at 1640 cm-1 correspond to the stretching vibration of CO and the symmetrical -CH2 vibration. The C=O characteristic absorption peak of CS appears at 1640 cm-1. -1 At 1260cm -1 and 1607cm -1 The absorption peaks at 1039cm correspond to the stretching vibrations of CH and NH, respectively. With the gradual addition of PVA and CS, the stretching vibration peaks of -OH and -NH2 in the amphoteric polyelectrolyte photothermal gel shift slightly to the low wavenumber direction, which is due to the formation of intramolecular and intermolecular hydrogen bonds. In addition, the peaks at 1039cm -1 and 1182cm -1 The absorption peaks at - The S=O symmetrical stretching vibration and asymmetrical stretching vibration of the group. The C=C characteristic absorption peak of PSS appears at 1450~1600cm -1 In the range of 810-833 cm -1 The C=N bond formed after CS is cross-linked with glutaraldehyde (GA) is at 1630-1690 cm -1 The stretching vibration peaks are shown in the range of 1050-1200 cm-1. PVA and GA form COCO polyether structure through aldehyde condensation reaction, and its coupling vibration peak appears in the range of 1050-1200 cm-1. -1The infrared spectrum of the amphoteric polyelectrolyte hydrogel showed the main characteristic peaks of PVA, CS and PSS, indicating that the hydrogel was successfully prepared.

[0056] (2) Figure 3 The absorbance test results of the solar interface evaporator (PCP evaporator) in the wavelength range of 280 to 2500nm under completely dry conditions are displayed. Under the action of MWCNTs and the layered porous structure, the light absorption rate of the solar interface evaporator is calculated to be 95.9% based on the test results. It is worth noting that the light absorption rate of the evaporator will be higher in the actual evaporation process, that is, in the wet state.

[0057] (3) Figure 4 The high-speed camera captured the impact of a 3mm diameter water droplet falling freely from a height of 5cm onto the upper surface of the solar interface evaporator. The experiment showed that the droplet was completely absorbed about 711ms after hitting the surface of the solar interface evaporator. This phenomenon confirms that the material has excellent water absorption properties, thus effectively ensuring the continuous water supply during the evaporation process. 2 Under light irradiance, Figure 5 (a) shows the mass change of the feed liquid during evaporation in different salinity feed liquids using a solar interface evaporator with an effective evaporation height of 7 cm. It is obvious that the mass of the 10 wt% feed liquid decreases the fastest, that is, the evaporation rate is the largest. Figure 5 (b) shows the change of evaporation rate of the liquid during evaporation in liquids with different salinities using a solar interface evaporator with an effective evaporation height of 7 cm. The evaporation rate of the 10 wt% liquid is as high as 3.35 kg / (m 2 ·h), the evaporation rate in 15wt% NaCl solution is as high as 2.94kg / (m 2 ·h), the evaporation rate in 20wt% NaCl solution can reach 2.87kg / (m 2 ·h); It is worth noting that due to the anti-salt ion hydration of the amphoteric polyelectrolyte photothermal gel, the evaporation rate of the evaporator in salt water is slightly higher than that in pure water.

[0058] (4) Typical solar interface evaporator compression test process Figure 6 As shown, the 7 cm high solar interface evaporator has robust compression performance and withstands 80% compression strain without any structural damage. After the pressure is removed, the solar interface evaporator can recover its original shape, showing super strong mechanical stability.

[0059] (5)1kW / m 2Under light irradiance, the solar interface evaporator (PCP evaporator) prepared in Example 1 and the PVA evaporator prepared in Comparative Example 1 were compared to see whether salt precipitation occurred on the evaporator surface during evaporation in a 20wt% liquid for 9h, in order to evaluate the durable salt resistance of the evaporator. Figure 7 (a) shows the surface changes of the solar interface evaporator. During the 9-hour evaporation process, not only is there no salt crystallization on the upper surface, but the evaporation rate also does not decrease significantly. Since the evaporation rate on the upper surface is faster than that on the side, there is naturally no salt crystallization on the side of the solar interface evaporator. Figure 7 As can be seen in (b), a small amount of salt crystals began to appear on the edges of the PVA evaporator after 1 hour. After 2 hours, large areas of salt crystals began to appear on each evaporation surface. After 9 hours, the surface of the PVA evaporator had become hard due to salt accumulation.

[0060] (6) By Figure 8 As shown in (a), the solar interface evaporator based on the amphoteric polyelectrolyte photothermal water gel prepared in Example 1 was used to desalinate turbid seawater from the Bohai Bay in the winter outdoor environment in Dalian. The ion concentration in the collected fresh water was reduced to below the drinking water standard specified by the World Health Organization, and the fresh water became significantly clear and transparent. Figure 8 (b).

[0061] In summary, the solar interface evaporator based on the amphoteric polyelectrolyte photothermal water gel prepared by the present invention can improve the performance of the solar interface evaporator in treating saline liquid.

[0062] Although the above embodiments describe the technical solutions of the present invention in detail, they are only some preferred embodiments of the present invention and not all implementation methods. Other embodiments obtained through non-creative work based on this embodiment without departing from the design spirit and principles of the present invention, as well as any modifications, equivalent replacements, or improvements thereto, are within the scope of protection of the claims of the present invention.

Claims

1. A solar interface evaporator based on amphoteric polyelectrolyte photothermal gel, characterized in that: The invention relates to a porous sponge and an amphoteric polyelectrolyte photothermal water gel embedded in the pores of the porous sponge; the amphoteric polyelectrolyte photothermal water gel comprises a polymer network formed by a high molecular weight polymer and a photothermal conversion material dispersed in the polymer network; the high molecular weight polymer comprises polyvinyl alcohol, a cationic polymer, an anionic polymer and a crosslinking agent; the crosslinking degree of the amphoteric polyelectrolyte photothermal water gel is 1% to 2%, and the mass fractions of polyvinyl alcohol, cationic polymer, anionic polymer and photothermal conversion material in the amphoteric polyelectrolyte photothermal water gel are 3 to 7 wt%, 0.5 to 1.5 wt%, 0.5 to 1.5 wt% and 3 to 8 wt%, respectively; The cationic polymer includes one or a combination of two or more of chitosan, chitosan quaternary ammonium salt, polyallylamine hydrochloride, polyethyleneimine or polydiallyldimethylammonium chloride; the anionic polymer includes one or a combination of two or more of poly(p-styrene sulfonate), poly(p-styrene sulfonic acid), sodium hyaluronate or sodium dextran sulfate; the photothermal conversion material includes one or a combination of two or more of carbon nanotubes, graphene, carbonized biomass, metal nanoparticles, titanium dioxide, polypyrrole or polydopamine; and the cross-linking agent is a mixture of a hydrochloric acid solution and a glutaraldehyde solution.

2. A solar interface evaporator based on amphoteric polyelectrolyte photothermal gel according to claim 1, characterized in that: The porous sponge includes polyvinyl alcohol sponge, melamine sponge, polyurethane sponge, cellulose sponge or polyester sponge; the porosity of the porous sponge is 80% to 99%, and the internal pore size distribution is 40 to 180 μm.

3. The method for preparing a solar interface evaporator based on an amphoteric polyelectrolyte photothermal gel according to claim 1 or 2, characterized in that: include: Step 1: adding polyvinyl alcohol powder and cationic polymer powder to an aqueous solution, heating and stirring to obtain a mixed solution A; Step 2: adding anionic polymer powder and photothermal conversion material to the mixed solution A and stirring thoroughly to obtain a mixed solution B; Step 3: Add a crosslinking agent to the mixed solution B at a crosslinking degree of 1% to 2%, and rapidly stir to prepare a hydrogel precursor solution; in the hydrogel precursor solution, the mass fractions of polyvinyl alcohol, cationic polymer, anionic polymer, and photothermal conversion material are 3 to 7 wt%, 0.5 to 1.5 wt%, 0.5 to 1.5 wt%, and 3 to 8 wt%, respectively; Step 4: completely immerse the porous sponge in the hydrogel precursor solution, and after the porous sponge is completely wetted, place it at room temperature to obtain a solar interface evaporator based on amphoteric polyelectrolyte photothermal water gel.

4. The preparation method according to claim 3, characterized in that The cross-linking agent is a mixture of hydrochloric acid solution and glutaraldehyde solution; wherein the mass fraction of the hydrochloric acid solution is 2-4 wt %; the mass fraction of the glutaraldehyde solution is 50 wt %; and the volume ratio of the hydrochloric acid solution to the glutaraldehyde solution is 6:1-3:

1.

5. The preparation method according to claim 4, characterized in that The mass fraction of the hydrochloric acid solution is 3 wt %, and the volume ratio of the hydrochloric acid solution to the glutaraldehyde solution is 5:

1.

6. The preparation method according to claim 5, characterized in that The degree of cross-linking is calculated according to the following formula: Here, GA represents glutaraldehyde, and PVA represents polyvinyl alcohol.

7. The preparation method according to claim 3, characterized in that In step 1, the heating and stirring temperature is 80-95°C, the stirring speed is 50-150 rpm, and the stirring time is 4-8 hours; in step 2, the stirring speed is 100-300 rpm, and the stirring time is 0.5-1.5 hours; in step 3, the rapid stirring speed is 400-600 rpm, and the stirring time is 3-8 minutes; in step 4, the immersion time is 20-40 minutes.

8. Use of a solar interface evaporator based on an amphoteric polyelectrolyte photothermal water gel prepared by the preparation method according to any one of claims 3 to 7 in the preparation of solar seawater desalination materials.

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