Degradable microalgae-based asymmetric hydrogel interfacial photo-thermal evaporator and preparation method and application thereof

Abstract

This invention discloses a biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator, its preparation method, and its applications, belonging to the field of water treatment technology. The biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator includes a microalgae-PVA hydrogel and a photothermal material loaded on the microalgae-PVA hydrogel; wherein the microalgae include at least one of Chlorella, green algae, diatoms, and Haematococcus pluvialis; the photothermal material is a carbon-supported semiconductor material and its derivatives synthesized based on the adsorption of metal salts by microalgae. The photothermal evaporator possesses excellent pore structure, photothermal absorption capacity, and mechanical properties, while also exhibiting low enthalpy of vaporization and high thermal conductivity. These characteristics significantly improve the evaporation rate of solar evaporators. Furthermore, the photothermal evaporator prepared by this invention is mainly based on microalgae, possessing biodegradability, environmental friendliness, high salt tolerance, and excellent water purification capabilities. Therefore, this evaporator has broad application prospects in the fields of seawater desalination and wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and particularly relates to a biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator, its preparation method, and its application. Background Technology

[0002] Seawater desalination is considered a viable way to alleviate the global shortage of available water resources. Solar evaporation, a method of producing freshwater by evaporating seawater using solar energy, has attracted widespread attention due to its energy efficiency and low dependence on infrastructure. However, this method has significant drawbacks. Most of the heat obtained from sunlight is lost to the environment through diffusion before it is transferred to the water for evaporation, resulting in extremely low solar energy utilization.

[0003] Interfacial heating-based solar water evaporation works by using photothermal materials at the water-air interface to convert absorbed solar energy into heat, which is then retained at the water-air interface where evaporation occurs. Since almost all the heat is used to convert water molecules from liquid to gas, heat waste is greatly reduced, achieving extremely high solar energy utilization. Therefore, solar-driven interfacial water evaporation has broad application prospects in seawater desalination. Against this backdrop, the design of hydrogel-based interfacial photothermal evaporators offers a new approach to improving evaporation efficiency at the interface. These evaporators mainly consist of a hydrogel framework and a light absorber, but most of them use non-degradable raw materials, which not only exacerbates the environmental burden but also complicates the manufacturing process; furthermore, their photothermal absorption capacity needs improvement.

[0004] Therefore, it is of great significance to develop a biodegradable green photothermal evaporator for solar seawater desalination technology. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator, its preparation method, and its applications. This photothermal evaporator possesses excellent pore structure, photothermal absorption capacity, and mechanical properties, while also exhibiting low enthalpy of vaporization and high thermal conductivity. These characteristics significantly enhance the evaporation rate of solar evaporators. Furthermore, the biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator prepared by this invention is primarily based on microalgae, possessing biodegradability, environmental friendliness, high salt tolerance, and excellent water purification capabilities. Therefore, this evaporator has broad application prospects in seawater desalination and wastewater treatment.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One of the technical solutions of this invention:

[0008] A biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator includes a microalgae-PVA hydrogel and a photothermal material loaded on the microalgae-PVA hydrogel.

[0009] The microalgae include at least one of Chlorella, green algae, diatoms or Haematococcus pluvialis;

[0010] The photothermal material is a carbon-supported semiconductor material and its derivatives synthesized based on the adsorption of metal salts by microalgae.

[0011] Beneficial Effects: Microalgae possess functional groups such as -OH, -COOH, and -NH2. On one hand, this invention uses them as a raw material substrate, cross-linking them with PVA through hydrogen bonds to form a three-dimensional network structure. On the other hand, utilizing the strong adsorption capacity of microalgae, metal salts are adsorbed to synthesize semiconductor materials and their derivatives with photothermal properties. The synergistic preparation of these two methods yields a lightweight, porous, environmentally friendly, biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator. The unique pore structure of this evaporator not only guides rapid water transport within the hydrogel but also prevents salt accumulation on the surface, providing strong support for a continuous and stable solar steam generation process. Furthermore, this evaporator exhibits high salt resistance, good mechanical properties, and a lower enthalpy of vaporization, effectively improving the evaporation rate and extending the service life of solar evaporators. Therefore, the biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator prepared in this invention has broad application prospects in seawater desalination and wastewater purification.

[0012] Optionally, the metal salt includes at least one of copper salt, molybdenum salt, titanium salt, or manganese salt.

[0013] The second technical solution of the present invention:

[0014] A method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator includes the following steps:

[0015] Microalgae were added to a PVA aqueous solution and heated and stirred to obtain a precursor solution. A pore-forming agent was then added to the precursor solution, followed by freeze-thaw cycles, thawing, and solvent soaking to prepare a microalgae-PVA hydrogel.

[0016] The photothermal material was deposited on the surface of the microalgae-PVA hydrogel by vacuum filtration to prepare the biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator.

[0017] Optionally, the mass ratio of the microalgae to PVA in the PVA aqueous solution is (6-9):(1-4); preferably 9:1, 8:2, 7:3 and 6:4.

[0018] Furthermore, the mass fraction of the PVA aqueous solution is 1-15 wt%.

[0019] Optionally, the temperature during the heating and stirring process is 50-110℃.

[0020] Optionally, the mass ratio of the pore-forming agent to the solute in the precursor solution is (2.5-20):1; preferably 2.5:1, 5:1, 10:1, 15:1, and 20:1. The solute in the precursor solution is the sum of microalgae and PVA.

[0021] Furthermore, the pore-forming agent is at least one of edible white sugar, sugar cubes, sodium chloride, or sodium carbonate.

[0022] Optionally, the freeze-thaw temperature is -20°C, the freeze-thaw time is 1-5 hours, and the thawing time is 1-5 hours.

[0023] Optionally, the preparation process of the photothermal material is as follows:

[0024] The photothermal material is prepared by calcining or hydrothermal synthesis of microalgae that have adsorbed metal salts.

[0025] Furthermore, the mass ratio of microalgae to metal salt in the microalgae adsorbed with metal salt is 1-3:1-6.

[0026] Furthermore, the calcination conditions are: 1-5℃ min -1 The heating rate is set to 500-800℃, and the temperature is maintained at this level for 1-3 hours.

[0027] Furthermore, the hydrothermal synthesis conditions are: hydrothermal reaction at 100-300℃ for 5-24 hours.

[0028] The third technical solution of this invention:

[0029] The above-mentioned biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator is used in seawater desalination and wastewater purification.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] (1) Green and biodegradable: From the perspective of raw materials, microalgae have many advantages such as abundant sources, low cost, and biodegradability, making them an ideal green evaporator material; from the perspective of function, microalgae have abundant functional groups. The biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator disclosed in this invention consists of a microalgae-based hydrogel and a photothermal material based on microalgae synthesis loaded on the hydrogel. The hydrogel prepared by this method has the advantages of high porosity and light weight, and the entire preparation process is simple to operate and highly reproducible; in addition, the raw materials are mainly microalgae, which is green and environmentally friendly.

[0032] (2) High-efficiency evaporation: The microalgae-based asymmetric hydrogel interface photothermal evaporator prepared in this invention exhibits excellent photothermal conversion efficiency. Under sunlight irradiation, its temperature can reach a maximum of 41.6℃. Furthermore, the evaporator prepared in this invention not only possesses a low enthalpy of vaporization and high thermal conductivity, significantly improving the solar evaporation rate, but also demonstrates excellent salt tolerance and water purification capabilities. These characteristics enable the evaporator to operate stably for extended periods, achieving both efficient seawater desalination and effective wastewater treatment. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0034] Figure 1 This is a process flow diagram of the biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator prepared according to an embodiment of the present invention;

[0035] Figure 2 The microalgae-based asymmetric hydrogel interfacial photothermal evaporator (Chlorella@MoS2 / C hydrogel) prepared in Example 1 was tested at 1kW m -2 Infrared thermal images at 0 min, 6 min, 12 min, 18 min, 24 min, and 30 min under illumination intensity;

[0036] Figure 3 The porous Chlorella hydrogel prepared in step (1) of Example 1, the Chlorella@MoS2 / C hydrogel prepared in steps (1) to (3) of Example 1, the PVA hydrogel prepared in Comparative Example 1, the pure Chlorella hydrogel prepared in Comparative Example 2, and deionized water were subjected to a reaction at 1 kWm -2 A comparison of evaporation rates after 0.5 hours of irradiation under different light intensities;

[0037] Figure 4 The enthalpy of evaporation of the porous Chlorella hydrogel prepared in step (1) of Example 1, the Chlorella@MoS2 / C hydrogel prepared in steps (1) to (3) of Example 1, the PVA hydrogel prepared in Comparative Example 1, the pure Chlorella hydrogel prepared in Comparative Example 2, and deionized water are compared.

[0038] Figure 5 The Chlorella@MoS2 / C hydrogel prepared in Example 1 was subjected to a 1kWm -2 Graph showing the surface dissolution process of 0.5g salt under light intensity;

[0039] Figure 6The image shows the UV-Vis absorption spectra of Chlorella@MoS2 / C hydrogel prepared in Example 1 before and after purification of industrial wastewater containing methylene blue (MB). The inset shows optical photographs before and after MB purification.

[0040] Figure 7 This is a photograph of the Chlorella@MoS2 / C hydrogel prepared in Example 1.

[0041] Figure 8 The figure shows the effect of different mass ratios of microalgae (Ch) to PVA in aqueous PVA solution on the mechanical properties of the final biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator.

[0042] Figure 9 The figure shows the effect of different mass ratios of pore-forming agent and solute in the precursor solution on the compressive mechanical properties of the final biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator.

[0043] Figure 10 A comparison of the evaporation rates of the final biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator with different amounts of photothermal material (MoS2 / C). Detailed Implementation

[0044] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0045] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0046] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0047] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0048] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0049] This invention provides a biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator material, comprising microalgae-PVA hydrogel and photothermal material loaded on the microalgae-PVA hydrogel.

[0050] In some alternative embodiments, the microalgae-PVA hydrogel is a three-dimensional network hydrogel structure formed by cross-linking microalgae rich in functional groups such as -COOH and -NH2 with the -OH group of PVA through hydrogen bonding and other interactions.

[0051] In some alternative embodiments, the microalgae include at least one of Chlorella, green algae, diatoms, and Haematococcus pluvialis.

[0052] In some alternative embodiments, the photothermal material is based on the special microstructure of microalgae, which utilizes the strong adsorption capacity of its functional groups such as hydroxyl groups to metals, adsorbing metal salts such as copper salts, molybdenum salts, titanium salts or manganese salts, to synthesize carbon-supported semiconductor materials (MoS2, Ti2O3, CuO, TiN or MnO2) and their derivatives with photothermal properties.

[0053] This invention discloses a method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator, comprising the following steps:

[0054] Step 1: Dissolve PVA in deionized water, heat and stir to prepare PVA aqueous solution, then add microalgae to the above solution, stir and sonicate to obtain precursor solution;

[0055] Step 2: Add a certain amount of pore-forming agent to the precursor solution, mix well, pour into a mold and freeze-thaw, use solvent to soak and wash to remove the pore-forming agent in the gel, and obtain a lightweight porous microalgae-PVA hydrogel.

[0056] Step 3: Dissolve the photothermal material powder synthesized from microalgae in deionized water, disperse it by ultrasonication, and then deposit the photothermal material powder on the surface of the microalgae-PVA hydrogel matrix by vacuum filtration to obtain an asymmetric hydrogel photothermal conversion material.

[0057] In some optional embodiments, the PVA aqueous solution prepared in step 1 has a mass fraction of 1-15 wt%; the heating and stirring temperature is 50-110°C; and the mass ratio of microalgae to PVA in the PVA aqueous solution is 9:1, 8:2, 7:3, and 6:4.

[0058] In some optional embodiments, the pore-forming agent in step 2 includes at least one of edible white sugar, sugar cubes, sodium chloride, or sodium carbonate; the mass ratio of the pore-forming agent to the solute in the precursor solution is 2.5:1, 5:1, 10:1, 15:1, and 20:1; the freezing temperature during the freeze-thaw process is -20°C, the freezing time is 1-5 hours, the thawing time is 1-5 hours, and the solvent soaking and washing time is 12-24 hours.

[0059] In some optional embodiments, the photothermal material in step 3 is prepared by microalgae adsorbing metal salts and then calcining or hydrothermal synthesis; wherein the mass ratio of microalgae to metal salts is 1-3:1-6. Further, the calcination conditions are: 1-5℃ min... -1 The heating rate is set to 500-800℃, and the temperature is maintained at this level for 1-3 hours.

[0060] In some optional embodiments, the amount of photothermal material added in step 3 is 0g, 0.005g, 0.01g, 0.03g, and 0.05g, which are dissolved in 500mL of deionized water and then filtered onto the microalgae-PVA hydrogel.

[0061] Furthermore, this invention also discloses the application of the above-mentioned biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator material in seawater desalination and wastewater purification.

[0062] The technical solution of the present invention will be further illustrated by the following embodiments.

[0063] Example 1

[0064] like Figure 1 As shown, a method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator includes the following steps:

[0065] (1) PVA was dissolved in deionized water and heated and stirred at 95°C to prepare a 10wt% PVA aqueous solution. Chlorella proteoglycans was added to the PVA aqueous solution (the mass ratio of Chlorella proteoglycans to PVA was 7:3), mechanically stirred for 30 min, and sonicated for 60 min to obtain a precursor solution. Edible sugar granules were added to the precursor solution (the mass ratio of edible sugar granules to the solute in the precursor solution was 5:1), mechanically stirred, poured into a mold, and frozen at -20°C for 3 h. After thawing for 1 h, the gel was washed with deionized water for 24 h until it floated on the surface, yielding a lightweight porous microalgae-PVA hydrogel (porous Chlorella hydrogel).

[0066] (2) Place Chlorella vulgaris with adsorbed phosphomolybdic acid in a tube furnace and incubate at 5°C for 5 min under an H2 / Ar atmosphere. -1 The temperature was increased to 600℃ and calcined for 3 hours to obtain MoS2 / C powder (photothermal semiconductor material).

[0067] The preparation process of Chlorella adsorbed with phosphomolybdic acid is as follows:

[0068] Add 0.2g of Chlorella proteoglycans and 0.5g of phosphomolybdic acid to 20mL of deionized water and stir continuously for 24h (280rpm). -1 A uniform green solution was formed; then it was centrifuged (2000 rpm) to form a solution. -1 Centrifuge 3 times (5 min each time). 1 ), thus obtaining Chlorella vulgaris adsorbed with phosphomolybdic acid.

[0069] (3) Disperse 0.01g MoS2 / C powder in 500mL of deionized water, sonicate to make it evenly dispersed, and finally filter to deposit MoS2 / C on the surface of the microalgae-based hydrogel matrix to obtain a microalgae-based asymmetric hydrogel interface photothermal evaporator (Chlorella@MoS2 / C hydrogel).

[0070] Comparative Example 1

[0071] The preparation process of PVA hydrogel is as follows:

[0072] PVA was dissolved in deionized water and heated and stirred at 95°C to prepare a 10wt% PVA aqueous solution, which was then poured into a mold and frozen for 3 hours before thawing.

[0073] Comparative Example 2

[0074] The preparation process of pure Chlorella hydrogel is as follows:

[0075] PVA was dissolved in deionized water and heated and stirred at 95°C to prepare a 10wt% PVA aqueous solution. Chlorella proteoglycans was added to the PVA aqueous solution (the mass ratio of Chlorella proteoglycans to PVA in the PVA aqueous solution was 7:3), mechanically stirred for 30 min, and sonicated for 60 min to obtain a precursor solution. The precursor solution was poured into a mold, frozen for 3 h, and then thawed.

[0076] Figure 2 The microalgae-based asymmetric hydrogel interfacial photothermal evaporator (Chlorella@MoS2 / C hydrogel) prepared in Example 1 was tested at 1kW m -2 Infrared thermal images at 0 min, 6 min, 12 min, 18 min, 24 min, and 30 min under illumination; from Figure 2As can be seen from the above, the Chlorella@MoS2 / C hydrogel (i.e., the microalgae-based asymmetric hydrogel interfacial photothermal evaporator) prepared in Example 1 of this invention exhibits a performance of 1kWm -2 The temperature change under light intensity can be as rapid as 22.3℃ within 0.5 hours, with the highest temperature reaching 41.6℃, indicating that the evaporator has excellent photothermal conversion performance.

[0077] Figure 3 The porous Chlorella hydrogel prepared in step (1) of Example 1, the Chlorella@MoS2 / C hydrogel prepared in steps (1)-(3) of Example 1, the PVA hydrogel prepared in Comparative Example 1, the pure Chlorella hydrogel prepared in Comparative Example 2, and deionized water were subjected to a reaction at 1 kWm -2 A comparison of evaporation rates after 0.5 hours of irradiation at different light intensities; from Figure 3 As can be seen, under the same light conditions, the evaporation rates of different materials differed significantly, with Chlorella@MoS2 / C hydrogel showing the best performance, achieving an evaporation rate as high as approximately 3.4 kg·m³. -2 ·h -1 This invention demonstrates that by introducing a porous structure (such as porous Chlorella hydrogel), the evaporation rate is significantly improved. This is likely because the porous structure increases the effective surface area for water transport and evaporation. Furthermore, Example 1 of this invention further enhanced the evaporation rate by incorporating MoS2 / C into Chlorella hydrogel (Chlorella@MoS2 / C hydrogel), indicating that MoS2 / C possesses excellent photothermal conversion capabilities and can more effectively utilize light energy to promote water evaporation.

[0078] Figure 4 The graph shows a comparison of the enthalpy of evaporation of the porous Chlorella hydrogel prepared in step (1) of Example 1, the Chlorella@MoS2 / C hydrogel prepared in step (3) of Example 1, the PVA hydrogel prepared in Comparative Example 1, the pure Chlorella hydrogel prepared in Comparative Example 2, and deionized water. As can be seen from the graph, the Chlorella@MoS2 / C hydrogel prepared in this invention has a low enthalpy of evaporation, approximately 1400 J g. -1 Around 100 J / g, while the enthalpy of evaporation of pure water under the same conditions is 2460 J / g. -1 This demonstrates that the Chlorella@MoS2 / C hydrogel prepared in this invention significantly reduces the energy required for water evaporation (enthalpy of vaporization) through efficient photothermal conversion, unique asymmetric structural design, and regulation of interfacial water behavior, thereby improving the overall efficiency of solar-driven evaporation. This provides a solid experimental basis and broad application prospects for its application in the field of efficient, energy-saving, and sustainable water resource treatment and utilization technology.

[0079] Figure 5The Chlorella@MoS2 / C hydrogel prepared in Example 1 was subjected to a 1kWm -2 The image shows the surface dissolution process of 0.5 g of salt under light intensity, demonstrating the desalination performance of the Chlorella@MoS2 / C hydrogel prepared in this invention, at 0.007 m. 2 0.5g of solid sodium chloride particles were deposited on the surface. After about 30 minutes, the sodium chloride particles on the surface completely disappeared, indicating that the evaporator has a high salt resistance.

[0080] Figure 6 The image shows the UV-Vis absorption spectra of the Chlorella@MoS2 / C hydrogel prepared in Example 1 before and after purification of methylene blue (MB) from industrial wastewater. The inset shows optical photographs of MB before and after purification. This demonstrates the purification capability of the prepared Chlorella@MoS2 / C hydrogel for industrial wastewater. The UV-Vis absorption spectrum of MB shows that the characteristic peaks of MB disappear after purification, indicating that this evaporator has broad application prospects in the field of wastewater treatment.

[0081] Figure 7 This is a photograph of the lightweight Chlorella@MoS2 / C hydrogel prepared in Example 1.

[0082] Based on Example 1, the following series of experiments were conducted by controlling a single variable to prepare microalgae-based asymmetric hydrogel interface photothermal evaporators:

[0083] I. Compared to Example 1, only the mass ratio of microalgae (Ch) to PVA in the PVA aqueous solution was changed: 9:1, 8:2, and 6:4;

[0084] II. Compared to Example 1, only the mass ratio of the pore-forming agent to the solute in the precursor solution was changed: 2.5:1, 10:1, 15:1 and 20:1;

[0085] III. Compared to Example 1, only the amount of photothermal material (MoS2 / C) added was changed: 0g, 0.005g, 0.03g, 0.05g.

[0086] Figure 8 The figure shows the effect of different mass ratios of microalgae (Ch) and PVA in the PVA aqueous solution on the mechanical properties of the final biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator. As can be seen from the figure, the mechanical properties are optimal when the ratio of microalgae to PVA is 7:3.

[0087] Figure 9The figure shows the effect of different mass ratios of pore-forming agent (edible white sugar) and solute in the precursor solution on the compressive mechanical properties of the final biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator. As can be seen from the figure, the mechanical properties are optimal when the ratio of pore-forming agent to solute in the precursor solution is 5:1, reaching the maximum compressive strain of 80%.

[0088] Figure 10 The figure shows a comparison of the evaporation rates of the biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator prepared with different amounts of photothermal material (MoS2 / C). It can be seen from the figure that when the amount of photothermal material added is 0.01 g, the evaporation rate reaches a threshold of 3.4 kg m³. -2 h -1 .

[0089] Example 2

[0090] A method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator includes the following steps:

[0091] (1) PVA was dissolved in deionized water and heated and stirred at 95°C to prepare a 10wt% PVA aqueous solution. Chlorella proteoglycans was added to the PVA aqueous solution (the mass ratio of Chlorella proteoglycans to PVA in the PVA aqueous solution was 7:3), mechanically stirred for 30 min, and sonicated for 60 min to obtain a precursor solution. Edible sugar granules were added to the precursor solution (the mass ratio of edible sugar granules to the solute in the precursor solution was 10:1), mechanically stirred, poured into a mold, and frozen at -20°C for 3 h. After thawing for 1 h, the gel was washed several times with deionized water until it floated on the surface, yielding a lightweight, porous microalgae-based hydrogel.

[0092] (2) The protein-nucleated Chlorella adsorbed with copper nitrate was hydrothermally reacted at 150°C for 20 h, and then calcined at 500°C for 2 h under a nitrogen atmosphere to obtain copper oxide / carbon powder.

[0093] The preparation process of Chlorella proteoglycans with adsorbed copper nitrate is as follows:

[0094] Add 0.2g of Chlorella peptidans and 0.5g of copper nitrate to 20mL of deionized water and stir continuously for 24h (280rmin). -1 A homogeneous green solution was formed; then centrifuged (2000 r min) to form a uniform green solution. -1 Centrifuge 3 times (5 min each time). -1 ), thus obtaining Chlorella containing copper nitrate.

[0095] (3) Disperse 0.01g of copper oxide / carbon powder in 400mL of deionized water and sonicate it to make it evenly dispersed; finally, filter it to deposit copper oxide / carbon on the surface of microalgae-based hydrogel matrix to obtain microalgae-based composite hydrogel interface photothermal evaporator.

[0096] Example 3

[0097] A method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator includes the following steps:

[0098] (1) PVA was dissolved in deionized water and heated and stirred at 95°C to prepare a 10wt% PVA aqueous solution. Haematococcus pluvialis was added to the PVA aqueous solution (the mass ratio of PVA in the PVA aqueous solution to Chlorella proteoglycans was 6:4), mechanically stirred for 30 min, and sonicated for 60 min to obtain a precursor solution. Sodium carbonate was added to the precursor solution (the mass ratio of sodium carbonate to the precursor solution solute was 2.5:1), mechanically stirred, poured into a mold, and frozen at -20°C for 3 h. After thawing for 1 h, the gel was washed several times with deionized water until it floated on the surface, yielding a lightweight and porous microalgae-based hydrogel.

[0099] (2) Same as step (2) in Example 1.

[0100] (3) Place the 0.05g MoS2 / C powder material prepared in step (2) of Example 1 into 500mL of deionized water, sonicate it to disperse evenly, and finally filter it to deposit MoS2 / C on the surface of the microalgae-based hydrogel matrix to obtain a microalgae-based composite hydrogel interface photothermal evaporator.

[0101] Example 4

[0102] A method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator includes the following steps:

[0103] (1) PVA was dissolved in deionized water and heated and stirred at 95°C to prepare a 10wt% PVA aqueous solution. Haematococcus pluvialis was added to the PVA aqueous solution (the mass ratio of PVA in the PVA aqueous solution to Chlorella proteoglycans was 8:2), mechanically stirred for 30 min, and sonicated for 60 min to obtain a precursor solution. Sodium chloride was added to the precursor solution (the mass ratio of sodium chloride to the precursor solution solute was 15:1), mechanically stirred, poured into a mold, and frozen at -20°C for 3 h. After thawing for 1 h, the gel was washed several times with deionized water until it floated on the surface, yielding a lightweight and porous microalgae-based hydrogel.

[0104] (2) Same as step (2) in Example 1.

[0105] (3) Place the 0.01g MoS2 / C powder material prepared in step (2) of Example 1 into 500mL of deionized water, sonicate it to disperse it evenly, and finally filter it to deposit MoS2 / C on the surface of the microalgae-based hydrogel matrix to obtain a microalgae-based composite hydrogel interface photothermal evaporator.

[0106] Example 5

[0107] A method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator includes the following steps:

[0108] (1) PVA was dissolved in deionized water and heated and stirred at 95°C to prepare a 10wt% PVA aqueous solution. Haematococcus pluvialis was added to the PVA aqueous solution (the mass ratio of PVA in the PVA aqueous solution to Chlorella proteoglycans was 9:1), mechanically stirred for 30 min, and sonicated for 60 min to obtain a precursor solution. Sugar cubes were added to the precursor solution (the mass ratio of sugar cubes to the solute in the precursor solution was 20:1), mechanically stirred, poured into a mold, and frozen at -20°C for 3 h. After thawing for 1 h, the gel was washed several times with deionized water until it floated on the surface, yielding a lightweight and porous microalgae-based hydrogel.

[0109] (2) Same as step (2) in Example 1.

[0110] (3) Place the 0.03g MoS2 / C powder material prepared in step (2) of Example 1 into 500mL of deionized water, sonicate it to disperse evenly, and finally filter it to deposit MoS2 / C on the surface of the microalgae-based hydrogel matrix to obtain a microalgae-based composite hydrogel interface photothermal evaporator.

[0111] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator, characterized in that, The biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator includes a microalgae-PVA hydrogel and a photothermal material loaded on the microalgae-PVA hydrogel. The microalgae are selected from at least one of Chlorella and Haematococcus pluvialis; The photothermal material is a carbon-supported semiconductor material and its derivatives synthesized based on the adsorption of metal salts by microalgae. The preparation method of the biodegradable microalgae-based asymmetric hydrogel interface photothermal evaporator includes the following steps: Microalgae were added to a PVA aqueous solution and heated and stirred to obtain a precursor solution. A pore-forming agent was then added to the precursor solution, followed by freeze-thaw cycles, thawing, and solvent soaking to prepare a microalgae-PVA hydrogel. The photothermal material was deposited on the surface of the microalgae-PVA hydrogel by vacuum filtration to prepare the biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator. The photothermal material is prepared by calcining or hydrothermally synthesizing microalgae that have adsorbed metal salts.

2. The method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator according to claim 1, characterized in that, The metal salt is selected from at least one of copper salt, molybdenum salt, titanium salt, or manganese salt.

3. The method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator according to claim 1, characterized in that, The mass ratio of microalgae to PVA in the PVA aqueous solution is (6-9):(1-4).

4. The method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator according to claim 1, characterized in that, The mass ratio of the pore-forming agent to the solute in the precursor solution is (2.5-20):

1.

5. The method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator according to claim 4, characterized in that, The pore-forming agent is selected from at least one of white sugar, sodium chloride, or sodium carbonate.

6. The method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator according to claim 1, characterized in that, The mass ratio of microalgae to metal salt in the microalgae that adsorb metal salt is 1~3:1~6.

7. The method for preparing a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator according to claim 1, characterized in that, The calcination conditions are: 1-5℃ min. -1 The heating rate is set to 500-800℃, and the temperature is maintained for 1-3 hours. Alternatively, the hydrothermal synthesis conditions are: hydrothermal reaction at 100-300℃ for 5-24 h.

8. The application of a biodegradable microalgae-based asymmetric hydrogel interfacial photothermal evaporator prepared by the preparation method according to any one of claims 1-7 in seawater desalination and wastewater purification.

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