High-salt-resistance double-layer self-floating hydrogel evaporator and preparation method and application thereof

Abstract

The invention discloses a high-salt-resistance double-layer self-floating hydrogel evaporator and a preparation method and application thereof.The preparation method comprises the steps that firstly, sodium alginate is dissolved in water, then pyrrole is fully stirred in the sodium alginate solution, and a uniformly-mixed solution is obtained; dipping the melamine foam in the mixed solution, soaking the melamine foam in a CaCl2 solution for crosslinking, and finally soaking the primarily crosslinked melamine foam in a FeCl3 solution to oxidize the surface of the melamine foam; the preparation process is simple, the hydrogel evaporator has extremely high hydrophilicity, the three-dimensional network structure provides a favorable channel for water transmission, a certain amount of calcium alginate grids are damaged during oxidation to form capillary action with melamine foam of a carrier, the escape efficiency of water molecules is improved, and the service life of the hydrogel evaporator is prolonged. The polypyrrole nanospheres with the three-dimensional structure can perform multiple times of refraction and reflection on light to enhance light absorption, and the evaporation efficiency of aerogel intermediate water is accelerated.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials and relates to a solar-driven interfacial water evaporation material, in particular to a highly salt-resistant double-layer self-floating hydrogel evaporator and a preparation method and application thereof. Background Art

[0002] As global water scarcity worsens, developing efficient, low-cost water treatment technologies has become a key priority for addressing the crisis. While traditional water treatment methods such as reverse osmosis, distillation, and electrodialysis are highly efficient, they often consume significant amounts of energy, require complex equipment, and incur high maintenance costs, limiting their application in remote and resource-scarce areas. Therefore, developing low-energy, environmentally friendly water treatment technologies is crucial.

[0003] Solar-driven interfacial water evaporation technology is considered an efficient and sustainable water restoration strategy and a promising method for obtaining freshwater. It is particularly promising for providing clean water in disaster-stricken and remote areas because it requires only sunlight, is low-cost, and is simple to operate. The core of this technology lies in the design of an interfacial solar evaporator, which consists of three major components: a photothermal conversion layer for broad-spectrum light absorption, a water transport layer for efficient water transfer, and a thermally insulating support layer. The performance of these components, particularly the light absorption and conversion efficiency of the photothermal layer, the water channel's transport capacity, and thermal management capabilities, are key factors in determining evaporator performance.

[0004] Hydrogels are ideal candidate materials for optimizing solar evaporation technology due to their unique three-dimensional network structure and high water holding capacity. Hydrogel materials not only have excellent light-to-heat conversion capabilities, but can also quickly conduct water through their porous networks to achieve efficient water evaporation. However, pure hydrogel materials usually have poor mechanical properties, especially after absorbing water and swelling, they are more prone to structural deformation or rupture. They are difficult to resist external forces such as water flow impact and wind during long-term use. In addition, the materials are expensive, and scalability and large-scale production still face challenges. When treating salty water (such as seawater desalination) or sewage, salt crystallization and pollutant accumulation are common problems. Even though people have made a lot of efforts to inhibit salt crystallization, salt crystallization will still block the pore structure of the hydrogel, affecting water transfer and evaporation efficiency, and may also reduce the service life of the evaporator. At the same time, the attachment of pollutants will also interfere with the evaporation process. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a highly salt-resistant double-layer self-floating hydrogel evaporator and its preparation method and application, which has high mechanical strength, excellent photothermal conversion efficiency and thermal management capabilities, efficient water evaporation rate and high salt resistance, and is environmentally friendly, simple in preparation process and low in cost.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a high-salt-resistant double-layer self-floating hydrogel evaporator comprises the following steps:

[0008] Step 1: Add sodium alginate to water and stir with a constant temperature magnetic stirrer until completely dissolved to obtain a solution A with a concentration of 0.001 to 0.1 g / mL;

[0009] Step 2: After natural cooling, pyrrole monomer is added to solution A, and stirred with a magnetic stirrer to form a uniformly dispersed slurry B, wherein the content of pyrrole monomer is 0.05-0.3 g / mL;

[0010] Step 3: Dip the melamine foam into slurry B and soak it in a CaCl2 solution with a concentration of 0.001-0.5 g / mL for 0.5-3 hours to perform the first crosslinking step;

[0011] Step 4: Soak the melamine foam treated in step 3 in a 1 mol / L FeCl3 solution for 1 to 10 hours to obtain a highly salt-resistant double-layer self-floating hydrogel evaporator.

[0012] The present invention also has the following technical features:

[0013] Preferably, in the step 1, the insulation temperature of the constant temperature magnetic stirrer is 10-60° C., and the stirring time is 1-20 h.

[0014] Preferably, the stirring time of the magnetic stirrer in step 2 is 1 to 20 hours.

[0015] The present invention also protects a highly salt-resistant double-layer self-floating hydrogel evaporator prepared by the above-mentioned method and its application in seawater desalination, sewage treatment and oil-water separation.

[0016] Compared with the prior art, the present invention has the following technical effects:

[0017] The present invention adopts an "immersion-crosslinking-oxidation" method, firstly dissolving sodium alginate in water, then adding pyrrole to the sodium alginate solution and stirring thoroughly to obtain a uniform slurry, then dipping melamine foam in the slurry and soaking it in a CaCl2 solution for crosslinking, and finally soaking the preliminarily crosslinked melamine foam in a FeCl3 solution for oxidizing its surface to form a gel layer, which has extremely high hydrophilicity and a three-dimensional network structure that provides a favorable channel for water transmission. During oxidation, a certain amount of calcium alginate grids are destroyed to form a capillary effect with the melamine foam carrier, and the capillary structure can timely discharge salt accumulated on the interface and timely transmit water, thereby improving the escape efficiency of water molecules and facilitating the discharge of interface salts, so that it can be The evaporator maintains excellent salt resistance and water evaporation performance during the continuous separation of seawater. The three-dimensional polypyrrole nanospheres can refract and reflect light multiple times to enhance light absorption, accelerating the evaporation efficiency of water in the aerogel, achieving efficient photothermal evaporation and avoiding energy consumption. A porous, hydrophilic integral evaporator can be prepared on melamine foam of any size on a large scale at low cost, exhibiting high mechanical strength, excellent photothermal conversion efficiency and thermal management capabilities, and efficient water evaporation rate. The melamine foam, as the supporting layer of the evaporator, effectively compensates for the shortcomings of poor mechanical properties. In an actual high-concentration brine resistance experiment, a saturated sodium chloride solution was evaporated for eight hours, and no obvious white crystals appeared on the surface, indicating its high salt resistance.

[0018] The preparation method of the present invention is low-cost, environmentally friendly, has a simple preparation process, can be prepared on a large scale, and is easy to industrialize. It has broad application prospects in the fields of seawater desalination, sewage treatment, and oil-water separation.

[0019] The hydrogel evaporator has a simple preparation process, high light-to-heat conversion efficiency, high mechanical stability, and can be prepared on a large scale. It has extremely high benefits in seawater desalination and sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the temperature of the hydrogel prepared in Example 1 of the present invention under one solar intensity for 1 hour;

[0021] Figure 2 is the amount of water evaporation of the hydrogel prepared in Example 1 of the present invention under different solution environments under 1 sun;

[0022] Figure 3 This is a physical picture of the compression and bending resistance of the large-area hydrogel prepared in Example 4 of the present invention;

[0023] Figure 4 The self-floating performance of the hydrogel prepared in Example 5 of the present invention;

[0024] Figure 5This is the desalination performance of the aerogel prepared in Example 6 of the present invention. DETAILED DESCRIPTION

[0025] The specific contents of the present invention are further explained in detail below with reference to the embodiments.

[0026] Example 1

[0027] This embodiment provides a method for preparing a highly salt-resistant double-layer self-floating hydrogel evaporator, comprising the following steps:

[0028] Step 1: Add sodium alginate to water and stir with a constant temperature magnetic stirrer until completely dissolved at 10°C for 3 hours to obtain a solution A with a concentration of 0.01 g / mL;

[0029] Step 2: After natural cooling, pyrrole monomer was added to solution A and stirred with a magnetic stirrer to form a uniformly dispersed slurry B for 3 h, wherein the content of pyrrole monomer was 0.06 g / mL;

[0030] Step 3: Take a 2cm*2cm melamine foam, dip it in slurry B, and soak it in a CaCl2 solution with a concentration of 0.005g / mL for 0.5h to perform the first step of crosslinking;

[0031] Step 4: Immerse the melamine foam treated in step 3 in a 1 mol / L FeCl3 solution for oxidation for 1 hour to obtain a highly salt-resistant double-layer self-floating hydrogel evaporator.

[0032] Figure 1 is the temperature of the hydrogel prepared in Example 1 of the present invention under a certain sunlight intensity for 1 hour; the pictures from left to right are 0 min, 5 min, 10 min, 30 min, and 60 min, as shown in FIG. Figure 1 As shown in the figure, under 1 sun, the temperature of the hydrogel evaporator at the water interface rises rapidly until the temperature reaches 44.3℃ and then stabilizes.

[0033] Figure 2 is the amount of water evaporated from the hydrogel prepared in Example 1 of the present invention under different solution environments under 1 sun; Figure 2 As shown in Figure 2, the average water evaporation under different solution environments under 1 sun is 3.42 kg / m 2 .

[0034] Example 2

[0035] This embodiment provides a method for preparing a highly salt-resistant double-layer self-floating hydrogel evaporator, comprising the following steps:

[0036] Step 1: Add sodium alginate to water and stir with a constant temperature magnetic stirrer until completely dissolved at 20°C for 6 hours to obtain a solution A with a concentration of 0.02 g / mL;

[0037] Step 2: After natural cooling, pyrrole monomer was added to solution A and stirred with a magnetic stirrer to form a uniformly dispersed slurry B for 6 h, wherein the content of pyrrole monomer was 0.1 g / mL;

[0038] Step 3: Take a 2cm*2cm melamine foam, dip it in slurry B, and soak it in a 0.1g / mL CaCl2 solution for 2h to perform the first step of crosslinking;

[0039] Step 4: Immerse the melamine foam treated in step 3 in a 1 mol / L FeCl3 solution for oxidation for 4 h to obtain a highly salt-resistant double-layer self-floating hydrogel evaporator.

[0040] Example 3

[0041] This embodiment provides a method for preparing a highly salt-resistant double-layer self-floating hydrogel evaporator, comprising the following steps:

[0042] Step 1: Add sodium alginate to water and stir with a constant temperature magnetic stirrer until completely dissolved at 30°C for 15 hours to obtain a solution A with a concentration of 0.03 g / mL;

[0043] Step 2: After natural cooling, pyrrole monomer was added to solution A and stirred with a magnetic stirrer to form a uniformly dispersed slurry B for 15 h, wherein the content of pyrrole monomer was 0.07 g / mL;

[0044] Step 3: Take a 2cm*2cm melamine foam, dip it in slurry B, and soak it in a 0.3g / mL CaCl2 solution for 0.5-3h to perform the first crosslinking step;

[0045] Step 4: Immerse the melamine foam treated in step 3 in a 1 mol / L FeCl3 solution for oxidation for 6 h to obtain a highly salt-resistant double-layer self-floating hydrogel evaporator.

[0046] Example 4

[0047] This embodiment provides a method for preparing a highly salt-resistant double-layer self-floating hydrogel evaporator, comprising the following steps:

[0048] Step 1: Add sodium alginate to water and stir with a constant temperature magnetic stirrer until it is completely dissolved at 40°C for 20 hours to obtain a solution A with a concentration of 0.04 g / mL;

[0049] Step 2: After natural cooling, pyrrole monomer was added to solution A and stirred with a magnetic stirrer to form a uniformly dispersed slurry B for 20 h, wherein the content of pyrrole monomer was 0.15 g / mL;

[0050] Step 3: Take a 30cm*30cm melamine foam, dip it in slurry B, and soak it in a 0.4g / mL CaCl2 solution for 3 hours to perform the first step of crosslinking;

[0051] Step 4: Soak the melamine foam treated in step 3 in a 1 mol / L FeCl3 solution for oxidation for 8 hours to obtain a highly salt-resistant double-layer self-floating hydrogel evaporator. Figure 3 As shown, the prepared large-area hydrogel product has good compression and bending resistance.

[0052] Example 5

[0053] This embodiment provides a method for preparing a highly salt-resistant double-layer self-floating hydrogel evaporator, comprising the following steps:

[0054] Step 1: Add sodium alginate to water and stir with a constant temperature magnetic stirrer until it is completely dissolved at 60°C for 20 hours to obtain a solution A with a concentration of 0.05 g / mL;

[0055] Step 2: After natural cooling, pyrrole monomer was added to solution A and stirred with a magnetic stirrer to form a uniformly dispersed slurry B for 20 h, wherein the content of pyrrole monomer was 0.12 g / mL;

[0056] Step 3: Take a 2cm*2cm melamine foam, dip it in slurry B, and soak it in a 0.5g / mL CaCl2 solution for 3 hours to perform the first step of crosslinking;

[0057] Step 4: Immerse the melamine foam treated in step 3 in a 1 mol / L FeCl3 solution for oxidation for 10 h to obtain a highly salt-resistant double-layer self-floating hydrogel evaporator. Figure 4 The hydrogel prepared in this example has self-floating properties and can automatically float to the surface after being sunk to the bottom of water.

[0058] Example 6

[0059] This embodiment provides a method for preparing a highly salt-resistant double-layer self-floating hydrogel evaporator, comprising the following steps:

[0060] Step 1: Add sodium alginate to water and stir with a constant temperature magnetic stirrer until it is completely dissolved at 60°C for 20 hours to obtain a solution A with a concentration of 0.1 g / mL;

[0061] Step 2: After natural cooling, pyrrole monomer was added to solution A and stirred with a magnetic stirrer to form a uniformly dispersed slurry B for 20 h, wherein the content of pyrrole monomer was 0.3 g / mL;

[0062] Step 3: Take a 2cm*2cm melamine foam, dip it in slurry B, and soak it in a 0.5g / mL CaCl2 solution for 1 hour to perform the first step of crosslinking;

[0063] Step 4: Immerse the melamine foam treated in step 3 in a 1 mol / L FeCl3 solution for oxidation for 10 h to obtain a highly salt-resistant double-layer self-floating hydrogel evaporator. Figure 5 is the desalination performance of the aerogel prepared in this embodiment, such as Figure 5 As shown, sodium chloride particles were placed on the surface of the hydrogel, and the salt particles disappeared quickly during the photothermal evaporation process, indicating that it has good anti- / desalination properties.

[0064] Example 7

[0065] This embodiment provides a method for preparing a highly salt-resistant double-layer self-floating hydrogel evaporator, comprising the following steps:

[0066] Step 1: Add sodium alginate to water and stir with a constant temperature magnetic stirrer until completely dissolved at 60°C for 1 hour to obtain a solution A with a concentration of 0.001 g / mL;

[0067] Step 2: After natural cooling, pyrrole monomer was added to solution A and stirred with a magnetic stirrer to form a uniformly dispersed slurry B for 1 h, wherein the content of pyrrole monomer was 0.05 g / mL;

[0068] Step 3: Take a 2cm*2cm melamine foam, dip it in slurry B, and soak it in a CaCl2 solution with a concentration of 0.001g / mL for 3h to perform the first step of crosslinking;

[0069] Step 4: Immerse the melamine foam treated in step 3 in a 1 mol / L FeCl3 solution for oxidation for 10 h to obtain a highly salt-resistant double-layer self-floating hydrogel evaporator.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a high salt-resistant double-layer self-floating hydrogel evaporator, characterized in that: The following steps are involved: Step 1: Add sodium alginate to water and stir with a constant temperature magnetic stirrer until completely dissolved to obtain a solution A with a concentration of 0.001 to 0.1 g / mL; Step 2: After natural cooling, pyrrole monomer is added to solution A, and stirred with a magnetic stirrer to form a uniformly dispersed slurry B, wherein the content of pyrrole monomer is 0.05-0.3 g / mL; Step 3: Dip the melamine foam into slurry B and soak it in a CaCl2 solution with a concentration of 0.001-0.5 g / mL for 0.5-3 hours to perform the first crosslinking step; Step 4: Soak the melamine foam treated in step 3 in a 1 mol / L FeCl3 solution for 1 to 10 hours to obtain a highly salt-resistant double-layer self-floating hydrogel evaporator.

2. The method for preparing a high salt resistance double-layer self-floating hydrogel evaporator according to claim 1, characterized in that: In the step 1, the insulation temperature of the constant temperature magnetic stirrer is 10 to 60° C., and the stirring time is 1 to 20 hours.

3. The method for preparing a high salt resistance double-layer self-floating hydrogel evaporator according to claim 1, characterized in that: The stirring time of the magnetic stirrer in the step 2 is 1 to 20 hours.

4. A highly salt-resistant double-layer self-floating hydrogel evaporator prepared by the method according to any one of claims 1 to 3.

5. Use of the highly salt-resistant double-layer self-floating hydrogel evaporator according to claim 4 in seawater desalination, sewage treatment, and oil-water separation.

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