Solar energy water evaporation and adsorption material, and preparation method and application thereof

Abstract

The application discloses a solar water evaporation and adsorption material, a preparation method and application thereof, and belongs to the technical field of wastewater treatment. A polydopamine modified zeolitic imidazolate framework material is stirred and reacted with a pre-oxidized nanocellulose solution and a polyvinyl alcohol solution to form a viscous liquid, the viscous liquid is transferred into a mold, and static bubble removal, freeze forming and freeze drying are sequentially performed, so that a solar water evaporation and adsorption material formed by pre-oxidized nanocellulose and polyvinyl alcohol and loaded with the polydopamine modified zeolitic imidazolate framework material is obtained. The solar water evaporation and adsorption material has the characteristics of high stability, and simultaneously has photo-thermal conversion function and rare earth ion adsorption activity. Solar radiation can be used to promote water evaporation, accelerate the mass transfer of rare earth ions in the aqueous solution and the combination of the adsorption active sites, so that the adsorption kinetics of the rare earth ions is accelerated, and the solar water evaporation and adsorption material can be used for rare earth wastewater treatment, especially low-concentration rare earth wastewater treatment.

Description

A solar water evaporation adsorbent material, its preparation method and application Technical Field

[0001] This invention relates to an adsorption material, particularly a solar-powered water evaporation adsorption material, as well as its preparation method and its application in purifying rare earth wastewater, belonging to the field of wastewater treatment technology. Background Technology

[0002] Rare earth elements, as one of the strategically critical metals, are hailed as "industrial vitamins" due to their excellent physicochemical properties and are widely used in fluorescent materials, permanent magnets, and alloys. To meet the ever-increasing demand for rare earths, global production has also been increasing year by year. However, the mining, processing, and end-of-life stages of rare earth production generate a large amount of rare earth waste, especially wastewater containing low concentrations of rare earth elements. It has been reported that for every ton of rare earth oxides produced from ion-adsorption rare earth ores through hydrometallurgical processes, 1,000 tons of rare earth wastewater are generated.

[0003] Therefore, the separation and recovery of rare earth resources from rare earth wastewater is of great significance. However, traditional methods for recovering rare earths from solutions, such as chemical precipitation, evaporation crystallization, and solvent extraction, suffer from drawbacks such as high energy consumption, low efficiency, and large amounts of organic wastewater. Adsorption methods offer advantages such as simple operation and large processing capacity, making them a potential means of treating low-concentration rare earth ion wastewater. Existing adsorption materials mainly include mineral-based, carbon-based, polymer-based, and metal-organic framework-based materials. Mineral-based and carbon-based materials are widely available but have low adsorption capacity, while polymer-based and metal-organic framework-based materials have high adsorption capacity but poor stability. Furthermore, the adsorption equilibrium time of existing adsorption materials is generally long; generally, the higher the adsorption capacity, the longer the equilibrium time required, making it difficult to achieve both high adsorption capacity and rapid adsorption equilibrium.

[0004] Solar water evaporators place the evaporator at the interface between water and air, using heat generated by solar radiation to accelerate water evaporation. Their structure mainly consists of a black photothermal conversion material and a water transport matrix material. Currently, they are primarily used in seawater desalination, oil (organic pollutant)-water separation, and medical sterilization; there are no reports of using solar water evaporators to adsorb and recover rare earth ions. This is mainly because the matrix material is primarily sponge-like, lacking active sites capable of adsorbing rare earth ions. Chinese patent (publication number: CN111675275B) reports an application of a solar water evaporation material made from wood to adsorb lead ions. This evaporation material utilizes the carbonization of wood, serving as both a photothermal conversion material and a water transport layer. Although it can adsorb some lead ions, the active sites within its channels are limited in variety, relying mainly on pores for adsorption. Furthermore, the mechanical properties of the wood are weakened after lignin removal with potassium hydroxide and potassium sulfite, and the material's mechanical stability is generally poor after carbonization, making it prone to problems such as shedding, breakage, and compression damage during use. Summary of the Invention

[0005] To address the technical shortcomings of existing rare earth adsorption materials, the first objective of this invention is to provide a solar water evaporation adsorption material (PDA-ZIF-8@CNF / PVA material). This material is composed of a dual network structure formed by pre-oxidized nanocellulose and polyvinyl alcohol, loaded with a polydopamine-modified zeolite imidazole ester framework. It exhibits high stability and simultaneously possesses photothermal conversion function and rare earth ion adsorption activity. It can utilize solar radiation to promote water evaporation, accelerate the mass transfer of rare earth ions in aqueous solution and their binding to adsorption active sites, thereby accelerating the adsorption kinetics of rare earth ions. This material can be used for rare earth wastewater treatment.

[0006] The second objective of this invention is to provide a method for preparing solar water evaporation adsorption materials that is simple, operates under mild conditions, and can be scaled up for production.

[0007] The third objective of this invention is to provide a solar water evaporation adsorption material for the purification of rare earth wastewater. The solar water evaporation adsorption material is used to construct a solar water evaporator, which promotes the evaporation of rare earth wastewater by means of solar radiation, accelerates the mass transfer of rare earth ions in the solution and their binding to adsorption sites, speeds up the adsorption kinetics, and can also obtain evaporated condensate.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing a solar water evaporation adsorption material. The method involves stirring and reacting a polydopamine-modified zeolite imidazole ester framework material with a pre-oxidized nanocellulose solution and a polyvinyl alcohol solution to form a viscous liquid. The viscous liquid is then transferred to a mold and subjected to static degassing, freeze-forming, and freeze-drying in sequence to obtain the final product.

[0009] This invention utilizes pre-oxidized nanocellulose and polyvinyl alcohol to construct a dual network structure, while simultaneously loading a polydopamine-modified zeolite imidazole ester framework material into the network structure via chemical bonding. The dual network structure constructed from pre-oxidized nanocellulose and polyvinyl alcohol possesses abundant porosity and contains numerous hydrophilic and adsorption-active groups such as hydroxyl and carboxyl groups, which facilitate water transport and rare earth ion adsorption. The polydopamine-modified zeolite imidazole ester framework material is immobilized by bonding the surface-modified polydopamine with oxygen-containing polar groups on the network structure surface through amino and phenolic hydroxyl groups, significantly improving its stability. Simultaneously, it allows for high dispersion of the zeolite imidazole ester framework material within the network structure, providing more adsorption active sites. Furthermore, polydopamine endows the zeolite imidazole ester framework material with photothermal conversion properties, enabling the utilization of solar radiation to promote water evaporation and enhance adsorption kinetics.

[0010] As a preferred embodiment, the mass concentration of the pre-oxidized nanocellulose solution is 1-2%. Pre-oxidized nanocellulose is nanocellulose pre-oxidized using Tempo, and its surface is rich in polar hydrophilic oxygen-containing groups such as carboxyl groups. Ordinary cellulose mainly contains alcohol hydroxyl groups and primary alcohol hydroxyl groups, while Tempo oxidation can oxidize the primary alcohol hydroxyl groups at the C6 position to carboxyl groups. Pre-oxidized nanofibers containing carboxyl groups play a crucial role in the formation of gel materials. On one hand, the carboxyl groups on the pre-oxidized nanocellulose (CNF) chain are combined with the hydroxyl groups on the polyvinyl alcohol (PVA) chain through hydrogen bonds, thereby constructing a dual network structure, i.e., CNF is one of the aerogel frameworks. On the other hand, the carboxyl groups on the CNF chain interact with the amino groups of the PDA modified on the outer layer of the zeolite imidazole ester framework to achieve stable loading of the zeolite imidazole ester framework, while uniformly loading the polydopamine-modified zeolite imidazole ester framework in the aerogel. Thirdly, carboxyl groups are also active groups for adsorbing rare earth ions. Carboxyl groups belong to Lewis bases and can combine with rare earth ions (Lewis acids), thereby achieving the adsorption of rare earth ions.

[0011] As a preferred embodiment, the mass concentration of the polyvinyl alcohol solution is 1-4%. The main chain of polyvinyl alcohol contains a large number of alcohol hydroxyl functional groups, which can form a dual-network structure aerogel matrix with CNF through hydrogen bonds, and is one of the aerogel skeletons. The dual-network structure aerogel constructed by the two is more stable than a single polyvinyl alcohol gel or CNF aerogel.

[0012] As a preferred embodiment, the mass ratio of the pre-oxidized nanocellulose solution to the polyvinyl alcohol solution is 1.5~2:1. When the CNF ratio is too low, the hydrogen bonding between CNF and PVA is weak, resulting in poor gel stability; when the CNF ratio is too high, most of the CNF will remain uncrosslinked with PVA, also leading to poor gel stability. A more reasonable approach is to have a CNF content slightly higher than PVA, ensuring that a framework can be formed between the two while also ensuring that some of the carboxyl groups capture rare earth ions.

[0013] As a preferred embodiment, the mass of the polydopamine-modified zeolite imidazole ester framework material accounts for 0.5-1% of the mass of the viscous liquid. The polydopamine-modified zeolite imidazole ester framework material is a key component of solar water evaporation materials (photothermal conversion materials), and also acts as a node (as shown in Figure 3). If too little PDA-ZIF8 is added, the photothermal conversion effect will be poor, making it difficult to enhance the adsorption process; if too much PDA-ZIF8 is added, it will occupy a large number of carboxyl groups on CNF, thereby reducing the adsorption sites of rare earth ions and hindering the capture of rare earths.

[0014] As a preferred embodiment, the mass ratio of polydopamine to zeolite imidazole ester framework material in the polydopamine-modified zeolite imidazole ester framework material is 2 to 1:1. If the amount of polydopamine modification on the surface of the zeolite imidazole ester framework material is too low, it is difficult to stably load the zeolite imidazole ester framework material in the dual network structure constructed from pre-oxidized nanocellulose and polyvinyl alcohol, and its photothermal conversion performance is also reduced. If the amount of polydopamine modification on the surface of the zeolite imidazole ester framework material is high, it will reduce the adsorption activity of the zeolite imidazole ester framework material.

[0015] As a preferred embodiment, the number-average molecular weight of the polyvinyl alcohol in the polyvinyl alcohol solution is 13,000 to 23,000. Higher molecular weight polyvinyl alcohol is more conducive to constructing gel materials.

[0016] As a preferred embodiment, the reaction conditions are: temperature of 30~50℃ and time of 2~4h.

[0017] The zeolite imidazole ester framework material involved in this invention is ZIF-8. The zeolite imidazole ester framework (ZIF-8) is obtained by existing preparation methods: zinc nitrate hexahydrate and dimethylimidazole solution are mixed at a certain mass ratio and placed in a water bath for stirring, aging, centrifugation to collect the white solid material, and vacuum drying. The mass ratio of zinc nitrate hexahydrate to dimethylimidazole is 1:8 to 1:10 to ensure that dimethylimidazole can coordinate with zinc ions to form a metal-organic framework material. The stirring temperature is 30-50℃, the stirring time is 30-60 min, and the aging time is 8-12 h to ensure crystal structure growth.

[0018] The preparation method of the polydopamine-modified zeolite imidazole ester framework material of the present invention is as follows: hydrophilic and stabilizing modification of the zeolite imidazole ester framework material (PDA-ZIF-8): ZIF-8 and an appropriate amount of dopamine are added to a Tris alkaline solution, and the mixture is stirred continuously until the solution turns black. The black solid material is collected by centrifugation and then vacuum dried. The pH value of the Tris alkaline solution is 8.0-8.8, and stirring for 8-12 hours is beneficial for dopamine polymerization on its surface. Furthermore, the mass ratio of dopamine to ZIF-8 is 2-1.

[0019] This invention also provides a solar water evaporation adsorbent material, obtained by the aforementioned preparation method. The solar water evaporation adsorbent material consists of a polydopamine-modified zeolite imidazole ester framework supported on a dual network structure formed by pre-oxidized nanocellulose and polyvinyl alcohol. The polydopamine on the surface of the zeolite imidazole ester framework utilizes chemical bonding between phenolic hydroxyl groups and amino groups and hydroxyl and carboxyl groups on the network structure surface, significantly improving the loading stability of the zeolite imidazole ester framework. Furthermore, polydopamine endows the adsorbent material with photothermal conversion capabilities. The abundant polar groups and the zeolite imidazole ester framework exhibit high rare earth ion adsorption activity, thus enabling the use of solar radiation to promote water evaporation, accelerate the mass transfer and binding of rare earth ions in aqueous solutions to adsorption active sites, and expedite the adsorption kinetics of rare earth ions. This allows for its application in rare earth wastewater treatment. In addition, the dual network structure formed by pre-oxidized nanocellulose and polyvinyl alcohol possesses abundant pores, and the pore surface is rich in hydrophilic groups, which is beneficial for water transport.

[0020] This invention also provides an application of a solar-powered water evaporation adsorbent material for the purification of rare earth wastewater. The solar-powered water evaporation adsorbent material is used to construct a solar water evaporator, which utilizes solar radiation to promote the evaporation of rare earth wastewater, accelerates the mass transfer of rare earth ions in the solution and their binding to adsorption sites, thus speeding up adsorption kinetics, and simultaneously yields evaporated condensate.

[0021] As a preferred embodiment, under sunlight, the solar-powered water evaporation adsorption material adsorbs rare earth metal ions from rare earth wastewater while simultaneously evaporating and condensing the water.

[0022] This invention provides a solar water evaporator, the simplified structural diagram and working principle of which are shown in Figure 4. The raw liquid chamber (1) contains a rare earth ion solution. The rare earth ion solution passes through the evaporation and condensation chamber (2) and the recovery chamber (3) in sequence through the water transport channel formed by the cotton gauze (2) by capillary action. In the evaporation and condensation chamber, the solar evaporation adsorption material (5) placed on the cotton gauze can heat the water adsorbed by the evaporation adsorption material under sunlight and adsorb the rare earth ions in the solution. The evaporated water is then condensed and recovered into the evaporation and condensation chamber.

[0023] The rare earth wastewater of the present invention can be low-concentration rare earth wastewater, such as rare earth wastewater with a concentration of less than 200 mg / L.

[0024] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0025] 1) The PDA-ZIF-8@CNF / PVA material designed in this invention serves as a solar water evaporator, combining the functions of rare earth ion adsorption and water purification.

[0026] 2) The dual network structure gel constructed by CNF and PVA through hydrogen bonding in the PDA-ZIF-8@CNF / PVA material of the present invention, like other gel materials, still has room for improvement in stability. However, the polyphenolic and amino groups on the surface of PDA-ZIF-8 can act as nodes to enhance the binding with CNF and PVA, thereby increasing the stability of the material and avoiding the use of traditional toxic crosslinking agents, as shown in Figure 3. At the same time, it also achieves high dispersion and stable loading of PDA-ZIF-8.

[0027] 3) The PDA-ZIF-8@CNF / PVA material of the present invention achieves stable loading of zeolite imidazole ester framework material, avoiding the disadvantage of fine-grained metal-organic frameworks being difficult to recover in solution, while utilizing its excellent photothermal conversion properties to accelerate its adsorption kinetics (the adsorption of rare earth ions is an endothermic process, and the increase in temperature is conducive to adsorption).

[0028] 4) The PDA-ZIF-8@CNF / PVA material of the present invention has abundant hydrophilic pores that allow aqueous solutions to enter and exit freely. At the same time, the nanocellulose and polydopamine have abundant carboxyl, hydroxyl and amino functional groups that belong to Lewis bases and can coordinate with rare earth cations (Lewis acids) to achieve selective adsorption.

[0029] 5) The preparation method of the PDA-ZIF-8@CNF / PVA material of the present invention is simple and the conditions are mild, which is conducive to large-scale production.

[0030] In summary, the PDA-ZIF-8@CNF / PVA material of this invention has the following significant advantages: the phenolic hydroxyl and amino functional groups on the surface of the polydopamine (PDA)-modified zeolite imidazole ester framework (ZIF-8) can interact with nanocellulose (carboxyl groups) and polyvinyl alcohol (hydroxyl groups), becoming nodes in the dual-network structure aerogel and enhancing its stability; PDA-ZIF-8 possesses photothermal conversion capabilities, providing energy for the adsorption (endothermic process) of rare earth ions and accelerating adsorption kinetics. Simultaneously, the abundant oxygen and nitrogen-containing (Lewis bases) in the aerogel provide numerous binding sites for the adsorption of rare earth ions (Lewis acids), ensuring a high adsorption capacity; and it achieves loading of the zeolite imidazole ester framework material, avoiding the difficulty in recycling metal-organic framework materials (nano / micron-scale materials). Under sunlight, the solar water evaporation material using this material can achieve over 90% removal of rare earth ions while simultaneously producing evaporative condensate. Therefore, the solar water evaporation material based on the zeolite imidazole ester framework of this invention possesses the dual functions of key metal recovery and water purification. Attached Figure Description

[0031] Figure 1 shows a physical image of the PDA-ZIF-8@CNF / PVA material.

[0032] Figure 2 shows a physical image of CNF / PVA material (CNF to PVA ratio is 2:1).

[0033] Figure 3 is a schematic diagram of the network structure of PDA-ZIF-8@CNF / PVA material.

[0034] Figure 4 is a schematic diagram of the working principle of PDA-ZIF-8@CNF / PVA material as a solar water evaporation device.

[0035] Figure 5 shows a physical image of CNF / PVA material (CNF to PVA ratio is 1:5). Detailed Implementation

[0036] To make the objectives, technical solutions, and beneficial effects of the present invention clearer, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] The following embodiments are merely exemplary and are not intended to limit the scope of protection of the claims of this invention. Unless otherwise specified, all chemical reagents used in these embodiments are commercially available products.

[0038] Example 1

[0039] 1) Preparation of ZIF-8: 4 mL of 25 g / L zinc nitrate hexahydrate solution was added to 20 mL of 40 g / L dimethylimidazole solution, and the mixture was placed in a 35°C water bath and stirred for 40 min. After aging for 10 h, the ZIF-8 material was separated by centrifugation and then vacuum dried.

[0040] 2) Preparation of PDA-ZIF-8: 500 mg of ZIF-8 was placed in a Tris alkaline solution (500 mL) with pH=8.5, and 800 mg of dopamine was added. The mixture was stirred for 10 h until the solution turned completely black. The PDA-ZIF-8 material was obtained by centrifugation and then vacuum dried.

[0041] 3) PDA-ZIF-8@CNF / PVA: 20g of a cellulose nanoparticle solution (2% by mass) pretreated with Tempo oxidation was mixed with 10g of a polyvinyl alcohol solution (average molecular weight approximately 20,000) (2% by mass) and 300mg of PDA-ZIF-8 was added. The mixture was stirred in a 40℃ water bath for 3 hours to obtain a black viscous liquid. This liquid was poured into a mold and allowed to stand for 12 hours to remove air bubbles. It was then frozen at -20℃ for 8 hours, and finally freeze-dried to obtain the PDA-ZIF-8@CNF / PVA aerogel material. As shown in Figure 1, this aerogel has abundant pores on its surface, is black in appearance, and can be placed on the surface of a blade, demonstrating its low density and suitability for evaporation at the water-air interface.

[0042] 4) Rare Earth Adsorption Experiment: Assemble the solar water evaporator as shown in Figure 4. 1 is the raw solution chamber containing rare earth ion solution; 2 is the evaporation and condensation chamber; 3 is the recovery chamber; 4 is a cotton gauze that acts as a water transport channel (water can be transported from chamber 1 to chamber 3 via capillary action) and also supports the solar evaporation material; 5 is a PDA-ZIF-8@CNF / PVA aerogel placed on the cotton gauze surface, which can add water and evaporate under sunlight, adsorbing rare earth ions from the solution; 6 and 7 are electronic balances. During the experiment, a 100 mg / L rare earth Gd ion solution was poured into the raw solution chamber (1), the other parts were assembled, and the chamber was placed outdoors under sunlight. The removal rate of rare earth ions was calculated by measuring the difference in rare earth mass between the recovery chamber (3) and the raw solution chamber (1). The measured rare earth removal rate after 30 minutes was 92.5%, indicating good rare earth removal performance. Furthermore, the observation of refluxed evaporated water in the condensation chamber indicates good photothermal efficiency of the material.

[0043] Comparative Example 1

[0044] CNF / PVA aerogel material was prepared in the same manner as in Example 1, except that PDA-ZIF-8 was not added in Comparative Example 1. Specifically, 20g of a 2% (w / w) nanocellulose solution pretreated with Tempo oxidation was mixed with 10g of a 2% (w / w) polyvinyl alcohol solution (average molecular weight approximately 20,000) and stirred in a 40°C water bath for 3 hours to obtain a viscous liquid. This liquid was poured into a mold and allowed to stand for 12 hours to remove air bubbles. It was then frozen at -20°C for 8 hours and finally freeze-dried to obtain the CNF / PVA aerogel material. The material is shown in Figure 2; its surface is a white, porous material with a relatively low density, allowing it to be placed above blades.

[0045] Rare earth adsorption experiment: The experiment was conducted outdoors under sunlight, similar to Example 1. The removal rate of rare earth ions was calculated by measuring the difference in rare earth mass between the No. 3 recovery chamber and the No. 1 raw solution chamber. After 30 minutes, the rare earth removal rate was calculated to be 7.2%, indicating poor removal efficiency. Furthermore, a small amount of water mist was observed on the surface of the No. 2 condensation chamber, indicating low photothermal efficiency.

[0046] Experimental results show that PDA-ZIF-8 plays a key role in the water evaporation process. Although the carboxyl functional groups in cellulose can serve as adsorption sites for rare earth ions, once the aerogel is saturated with the solution, it is difficult for it to combine with other rare earth ions, resulting in low removal rate and poor evaporation effect.

[0047] Comparative Example 2

[0048] PDA-ZIF-8@CNF / PVA aerogel material was prepared in the same manner as in Example 1, except that the evaporator in Comparative Example 2 of the rare earth adsorption experiment was placed in a closed, dark indoor environment. The removal rate of rare earth ions was calculated by measuring the difference in rare earth mass between the No. 3 recovery chamber and the No. 1 stock solution chamber. After 30 minutes, the rare earth removal rate was calculated to be 11.4%, indicating poor removal efficiency, and no water mist formation was observed on the surface of the No. 2 condensation chamber. After 2 hours, the rare earth removal rate was approximately 13.8%, with no water mist formation observed on the surface of the No. 2 condensation chamber, and the liquid level in the recovery chamber remained essentially unchanged.

[0049] Experimental results show that under light conditions, the adsorption kinetics of PDA-ZIF-8@CNF / PVA can be accelerated. When light is lacking, the mass transfer rate decreases after the solution in PDA-ZIF-8@CNF / PVA becomes saturated, making it difficult to adsorb other ions, resulting in poor removal efficiency.

[0050] Example 2

[0051] The same ZIF-8 and PDA-ZIF-8 preparation methods were used as in Example 1, except for the amount of CNF and PVA added in step 3).

[0052] 3) PDA-ZIF-8@CNF / PVA: Take 20g of a cellulose nanoparticle solution (mass fraction of 2%) that has been pretreated with Tempo oxidation and mix it with 12g of a polyvinyl alcohol (average molecular weight of about 20,000) solution (mass fraction of 2%) and add 300mg of PDA-ZIF-8.

[0053] The same test was conducted under outdoor sunlight conditions, and the removal rate of rare earth ions was calculated by measuring the difference in rare earth mass between the No. 3 recovery chamber and the No. 1 raw solution chamber. The results showed that after 30 minutes, the rare earth removal rate was 90.2%, indicating a good rare earth removal effect. Furthermore, the observation of refluxed evaporated water in the condensation chamber indicated good photothermal efficiency of the material.

[0054] Comparative Example 3

[0055] Similar to Comparative Example 1, this comparative example mainly investigated the effect of the ratio of Tempo-oxidized pretreated nanocellulose solution to polyvinyl alcohol solution on the stability of aerogel. In the experiment, 2g of Tempo-oxidized pretreated nanocellulose solution (mass fraction 2%) and 10g of polyvinyl alcohol solution (average molecular weight approximately 20,000) (mass fraction 2%) were mixed and stirred in a 40℃ water bath for 3 hours to obtain a viscous liquid. This liquid was poured into a mold and allowed to stand for 12 hours to remove air bubbles. Then, it was frozen in a -20℃ freezer for 8 hours and finally freeze-dried to obtain CNF / PVA aerogel material. The material is shown in Figure 5. The surface of the material is a white porous material. After freeze-drying, it fractured and the surface was incomplete. This is because the addition of less Tempo-oxidized pretreated nanocellulose resulted in a limited number of carboxyl groups in its structure and hydroxyl groups in the polyvinyl alcohol structure bonded by hydrogen bonds, leading to poor stability and a brittle texture.

Claims

1. A method for preparing a solar water evaporation adsorbent material, characterized in that: A viscous liquid is formed by stirring a polydopamine-modified zeolite imidazole ester framework material with a pre-oxidized nanocellulose solution and a polyvinyl alcohol solution. The viscous liquid is then transferred to a mold and subjected to static degassing, freeze-forming, and freeze-drying in sequence to obtain the final product. The mass concentration of the pre-oxidized nanocellulose solution is 1-2%, the mass concentration of the polyvinyl alcohol solution is 1-4%, and the mass ratio of the pre-oxidized nanocellulose solution to the polyvinyl alcohol solution is 1.5-2:

1.

2. The method for preparing a solar water evaporation adsorption material according to claim 1, characterized in that: The mass of the polydopamine-modified zeolite imidazole ester framework material accounts for 0.5 to 1% of the mass of the viscous liquid.

3. The method for preparing a solar water evaporation adsorption material according to claim 1, characterized in that: The mass ratio of polydopamine to zeolite imidazole ester framework material in the polydopamine-modified zeolite imidazole ester framework material is 2~1:

1.

4. The method for preparing a solar water evaporation adsorption material according to claim 1, characterized in that: The number-average molecular weight of polyvinyl alcohol in the polyvinyl alcohol solution is 13,000 to 23,000.

5. A method for preparing a solar water evaporation adsorption material according to claim 1 or 3, characterized in that: The reaction conditions are: temperature 30~50℃, time 2~4h.

6. A solar water evaporation adsorption material, characterized in that: It is obtained by the preparation method according to any one of claims 1 to 5.

7. The application of the solar water evaporation adsorption material according to claim 6, characterized in that: Used for the purification and treatment of rare earth wastewater.

8. The application of the solar water evaporation adsorption material according to claim 7, characterized in that: Under sunlight, the solar water evaporation adsorption material adsorbs rare earth metal ions in rare earth wastewater while simultaneously evaporating and condensing the water.

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