Aerogel material for photo-thermal evaporation and radiation ion removal and preparation method and application thereof

Abstract

The invention discloses an aerogel material for photo-thermal evaporation and radiation ion removal and a preparation method and application thereof, and belongs to the technical field of photo-thermal evaporation and seawater desalination. The method comprises the following steps: sequentially carrying out hydrothermal reaction modification on expanded vermiculite in a saturated NaCl solution and a LiCl solution, and then carrying out ultrasonic stripping and freeze drying to obtain Li-VMT nanosheets; the Li-VMT nanosheets, bacterial cellulose and ultrapure water are mixed and then subjected to directional freezing casting and freeze drying, and the vertical vermiculite-based aerogel is obtained; hydroxylated multi-walled carbon nanotubes are sprayed on the surface of the vertical vermiculite-based aerogel, and the aerogel with photo-thermal evaporation cooperating with radiation ion removal is obtained. The material has excellent light absorption, rapid water transmission, efficient heat management and excellent Cs < + > removal performance. Multi-process collaboration is achieved through vermiculite modification optimization, the limitation that traditional seawater desalination is high in energy consumption and single in function is broken through, and the method has remarkable advantages in the field of radioactive pollution treatment and wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the fields of water treatment technology and photothermal evaporation materials. Specifically, it relates to an aerogel material that combines photothermal evaporation with radiation-induced ion removal, its preparation method, and its applications. Background Technology

[0002] With the development of nuclear energy, the problem of nuclear-contaminated water discharge has become increasingly serious, especially the discharge of radioactive cesium (Cs). + The pollution problem of radioactive cesium. Radioactive cesium has a long half-life (e.g., 137 Cesium (Cs) has a half-life of approximately 30 years and its chemical properties are similar to those of potassium (K), an essential element for life. It easily enters the biosphere through the food chain, water bodies, and atmospheric circulation, posing a serious threat to human health. Therefore, developing efficient technologies for removing radioactive cesium from seawater is of great significance.

[0003] Currently, the main methods for treating cesium-containing wastewater include adsorption, reverse osmosis, evaporation and concentration, and chemical precipitation. Among these, adsorption has attracted widespread attention due to its advantages such as simple operation, low cost, and good treatment effect. However, existing adsorbents, such as minerals, polymers, and activated carbon, have limited adsorption capacity and are insufficient to meet the removal requirements of low concentrations of radioactive cesium in seawater. Furthermore, the low concentration of cesium ions in seawater makes the complete removal of radioactive cesium from seawater a significant challenge.

[0004] In recent years, photothermal evaporation technology has attracted widespread attention due to its ability to utilize solar energy for seawater desalination. However, most existing photothermal evaporation materials focus only on water evaporation efficiency, neglecting the removal of radioactive nuclides from seawater. Therefore, developing a material that combines photothermal evaporation and radioactive cesium removal functions is of significant practical importance. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention aims to provide an aerogel material that combines photothermal evaporation with radiation-induced ion removal. Another technical problem is a method for preparing this aerogel material. A further aspect of this invention is a method for preparing the aerogel material and its application in the efficient photothermal evaporation and radiation-induced ion removal of radioactive cesium ions from seawater. This aerogel, through interlayer regulation and surface modification, exhibits excellent photothermal evaporation performance and radioactive cesium adsorption performance, enabling simultaneous seawater desalination and radioactive cesium removal.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] The application discloses a preparation method of an aerogel with photothermal evaporation and ion removal by radiation, and the method comprises the following steps: modifying expanded vermiculite in a saturated NaCl solution and a LiCl solution through a hydrothermal reaction, and then performing ultrasonic peeling and freeze-drying to obtain Li-VMT nanosheets; mixing the Li-VMT nanosheets, bacterial cellulose and ultrapure water, and then performing directional freeze casting and freeze-drying to obtain a vertical vermiculite-based aerogel; and spraying hydroxylated multi-walled carbon nanotubes on the surface of the vertical vermiculite-based aerogel to obtain the aerogel with photothermal evaporation and ion removal by radiation.

[0008] In some embodiments, the preparation method of the aerogel with photothermal evaporation and ion removal by radiation comprises the following steps.

[0009] S1: dispersing expanded vermiculite in a saturated NaCl solution, performing a hydrothermal reaction at 140-160 DEG C for 20-32 hours, and then performing centrifugal washing to obtain Na + intercalated vermiculite;

[0010] S2: dispersing the Na + intercalated vermiculite in a 1.9-2.1M LiCl solution, performing a hydrothermal reaction at 140-160 DEG C for 20-32 hours, and then performing centrifugal washing to obtain Li + intercalated vermiculite;

[0011] S3: performing ultrasonic peeling and freeze-drying on the Li + intercalated vermiculite obtained in step S2 to obtain Li-VMT nanosheets;

[0012] S4: mixing the Li-VMT nanosheets, bacterial cellulose and ultrapure water obtained in step S3 to form a uniform mixed solution;

[0013] S5: transferring the mixed solution obtained in step S4 into a mold, performing directional freeze casting and then freeze-drying to obtain a vertical vermiculite-based aerogel;

[0014] S6: spraying hydroxylated multi-walled carbon nanotubes on the surface of the vertical vermiculite-based aerogel obtained in step S5 to obtain the aerogel with photothermal evaporation and ion removal by radiation.

[0015] In some embodiments, the preparation method of the saturated NaCl solution is as follows: adding excess NaCl powder into 200 mL ultrapure water, stirring at room temperature until the NaCl powder cannot be dissolved any more, and then obtaining the saturated NaCl solution.

[0016] In some embodiments, the Li + intercalated vermiculite is subjected to ultrasonic peeling in the following specific manner: the Li + intercalated vermiculite is subjected to ultrasonic peeling for 3 hours, and then centrifuged at 1000 rpm for 15 minutes.

[0017] In some embodiments, the Li-VMT nanosheets, bacterial cellulose and ultrapure water are mixed in a ratio of 0.08-0.12:1.2-1.4:2 by weight.

[0018] In some embodiments, the concentration of the hydroxylated multi-walled carbon nanotubes is 0.008-0.012 mg / mL.

[0019] The aerogel material prepared by any of the methods described above for photothermal evaporation synergized with radiation ion removal.

[0020] The aerogel material described above for photothermal evaporation synergized with radiation ion removal is used in seawater desalination treatment and / or removal of radioactive cesium ions in seawater.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] The present application first performs interlayer regulation and surface modification on the original expanded vermiculite, selects the best Cs + adsorption material (Li-VMT), and then mixes the Li-VMT with cellulose to successfully manufacture a "dual-function" evaporator that can be used for photothermal evaporation synergized with seawater cesium removal. The evaporator absorbs Cs + in seawater while performing photothermal evaporation, thereby achieving the purpose of removing radioactive Cs + in seawater. The evaporator has excellent light absorption, fast water transport, efficient heat management and excellent Cs + removal performance.

[0023] The main advantages of the aerogel material VS-Gel evaporator prepared by the method of the present application include: 1) efficient photothermal evaporation: the VS-Gel evaporator has excellent light absorption capacity and photothermal conversion efficiency, and can achieve efficient seawater desalination under solar irradiation; 2) efficient radioactive cesium removal: the Li-VMT nanosheets in the VS-Gel evaporator have excellent cesium ion adsorption performance, and can effectively remove radioactive cesium in seawater; 3) salt accumulation resistance: the VS-Gel evaporator has a vertical pore structure, which can effectively prevent salt from depositing on the surface of the evaporator, ensuring long-term stable evaporation performance; 4) multifunctionality: the VS-Gel evaporator has both photothermal evaporation and radioactive cesium removal functions, and can simultaneously solve the problems of seawater desalination and radionuclide removal.

[0024] The experimental results of the present application show that: 1) under standard solar irradiation, the aerogel for photothermal evaporation synergized with radioactive ion removal has a photothermal conversion efficiency as high as 92.9% and a water transport rate of 3.33 kg m -2 h -1; 2) Under standard solar irradiation, the VS-Gel aerogel removes cesium ions in simulated nuclear contaminated seawater by photothermal evaporation and synergistic radiation ion removal, and the adsorption capacity of cesium ions in 5 hours can reach 160mg·g -1 ; the adsorption capacity in darker conditions (58mg·g -1 ) is increased by 275%.

[0025] In summary, the aerogel material has outstanding photothermal evaporation rate and efficiency and excellent cesium ion adsorption performance in nuclear contaminated seawater, and the preparation process is simple, and has wide application prospect in the fields of seawater desalination, wastewater treatment and the like. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a preparation flowchart of the vermiculite-based aerogel for photothermal evaporation and synergistic radiation ion removal according to the present application.

[0027] Figure 2 It is a light absorption rate test, heat insulation performance test and principle diagram of the VS-Gel according to the present application; (a) multiple reflection effect, (b) diffuse reflectance spectrum, (c) heat insulation performance; (d) VS-Gel surface infrared imaging photo under one sun irradiation; (e) VS-Gel surface temperature rise and fall after one sun irradiation and shutdown;

[0028] Figure 3 It is a surface contact angle and water transport capacity test result diagram of the VS-Gel according to the present application; wherein (a-b) is the contact angle of the VS-Gel; (c-e) is the water transport capacity of the VS-Gel;

[0029] Figure 4 It is a test and principle diagram that the evaporation enthalpy of the VS-Gel evaporator is lower than the evaporation enthalpy of pure water; (a) is the DSC curve of the VS-Gel aerogel; (b) is the water form in the evaporation process of the VS-Gel aerogel;

[0030] Figure 5 It is a test comparison diagram of the BC-Gel and the VS-Gel in the evaporation process of the cesium-containing simulated seawater under one sun irradiation according to the present application; wherein (a) is the water mass change curve, (b) is the evaporation efficiency;

[0031] Figure 6 It is a radioactive cesium adsorption performance test result diagram of the VS-Gel evaporator according to the present application, wherein (a) is a comparison diagram of the Cs + adsorption capacity of the BC-Gel and the VS-Gel; (b) is the photothermal evaporation of the VS-Gel synergistically adsorbing cesium ions under irradiation; (c) is a comparison of the cesium adsorption of the VS-Gel in the simulated seawater under irradiation and the cesium adsorption without irradiation; (d) is a three-dimensional infrared image display result diagram of the VS-Gel in the cesium-containing seawater;

[0032] Figure 7 Schematic diagram of the synergistic effect of cesium ion adsorption and seawater desalination. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described below in combination with specific examples. If no detailed description is given in the following examples, the technical means used are all conventional means well known to those skilled in the art. Or according to the reagent kit and product instruction. The materials, reagents, etc. used in the following examples, if no special description, can be obtained from commercial channels. Bacterial nanocellulose (BC) (65%, Guilin Qihong Technology Co., Ltd.), hydroxylated multi-walled carbon nanotubes (MWCNTs) (95%, Aladdin Reagent Co., Ltd.), vermiculite (VMT) (95%, Macklin Reagent Co., Ltd.), sodium chloride (NaCl) (AR, Aladdin Reagent Co., Ltd.), lithium chloride (LiCl) (AR, Aladdin Reagent Co., Ltd.).

[0034] Comparative Example 1: Preparation of BC-Gel

[0035] A method for preparing a BC-Gel, comprising the following steps:

[0036] (1) Ultrasonic exfoliation of expanded vermiculite to obtain a nanosheet dispersion.

[0037] (2) Mix 100 mg of the nanosheet dispersion with 1 mL of bacterial cellulose (BC) to form a uniform mixed solution.

[0038] (3) Transfer the mixed solution to a mold for directional freeze casting, and after freeze-drying, obtain a vertical vermiculite-based aerogel (BC-Gel).

[0039] Example 1: Preparation of a vertical vermiculite-based aerogel (VS-Gel)

[0040] A method for preparing a vermiculite-based aerogel for photothermal evaporation and synergistic radiation ion removal, comprising the following steps:

[0041] (1) Disperse 1 g of expanded vermiculite in 60 mL of saturated NaCl solution, and perform hydrothermal reaction at 150°C for 24 hours, and after centrifugal washing, obtain Na-VMT.

[0042] (2) Disperse the Na-VMT in 60 mL of 2M LiCl solution, and perform hydrothermal reaction at 150°C for 24 hours, and after centrifugal washing, obtain Li-VMT.

[0043] (3) The Li-VMT prepared in step (2) was ultrasonicated for 3 hours and centrifuged at 1000 rpm for 15 minutes to remove the precipitate, and finally a nanosheet dispersion of lithium-modified vermiculite (Li-VMT) was obtained. The Li-VMT nanosheets were obtained by freeze-drying.

[0044] (4) The Li-VMT nanosheets obtained in step (3) were mixed with bacterial cellulose (BC) and ultrapure water to form a uniform mixed solution, and the Li-VMT nanosheets, bacterial cellulose (BC), and ultrapure water were mixed in a weight ratio of 0.08-0.12:1.2-1.4:2.

[0045] (5) The mixed solution was transferred to a mold for directional freeze casting, and after freeze-drying, a vertical vermiculite-based aerogel (VS-Gel) was obtained.

[0046] (6) The surface of the VS-Gel was sprayed with an ethanol dispersion of hydroxylated multi-walled carbon nanotubes (MWCNTs, concentration 0.01 mg / mL) using an airbrush to obtain a VS-Gel evaporator with photothermal evaporation performance (VS-Gel-Evaporator). Figure 1 ).

[0047] UV-Vis-NIR absorption spectrum analysis showed that the light absorption rate of the VS-Gel evaporator under wet conditions was as high as ~95% (b), benefiting from its unique 3D porous structure and the high light absorption performance of carbon materials, the VS-Gel evaporator exhibited excellent light absorption capacity. The porous structure of the VS-Gel evaporator can increase the scattering and reflection of light on the material surface, and the multiple scattering of light in the three-dimensional porous structure increases the contact times of light and light-absorbing materials and the "trapping" effect of light-absorbing materials on light, thereby increasing the light absorption rate (a). Figure 2 Figure 2

[0048] The photothermal conversion capacity is another key factor for efficient photothermal evaporation, and an infrared thermal imager was used to record the change in the surface temperature of the material under simulated sunlight (1 kW m -2 ). As shown in Figure 2 d and Figure 2 e, the surface temperature of the VS-Gel in a dry state rapidly increased after irradiation. The temperature of the VS-Gel rapidly rose to 72.4°C within 20 s; within 300 s, the surface temperature of the material increased with the increase in irradiation time, and the VS-Gel had good light-to-heat conversion capacity. In addition, due to the low thermal conductivity of vermiculite, the thermal insulation performance of the VS-Gel was better than that of the BC-Gel, as shown in Figure 2 c, which played an important role in reducing heat loss in photothermal evaporation.

[0049] The contact angle and water transport capacity of the aerogel surface (water transport capacity) were measured. The results showed that the VS-Gel had a contact angle of 0° and a water transport capacity of 0.5 kg m Figure 3 ​​) of VS-Gel evaporator, the droplet was quickly absorbed within 100 ms of contact with the VS-Gel evaporator evaporation surface, the water contact angle was 0°, which proved the superhydrophilic property of VS-Gel evaporator Figure 3 a-b) The dry paper was placed above the VS-Gel, and after 2 s, it could be observed that the upper layer of paper was wetted due to the absorption of water. It can be concluded that the VS-Gel evaporator has strong capillary force, which can quickly transport water to the evaporation surface Figure 3 c-e) Moreover, the temperature gradient along the VS-Gel evaporator induces Marangoni convection, which improves the flow rate of water in the VS-Gel evaporator microstructure, achieving a faster evaporation rate.

[0050] In the VS-Gel evaporator, due to the strong hydrogen bond interaction between water molecules and the -OH functional groups on the bacterial cellulose and exfoliated vermiculite nanosheets Figure 4 b), the hydrogen bond interaction between these water molecules and the surrounding water molecules is weak, resulting in a large amount of intermediate water. The energy required for intermediate water to break hydrogen bonds and escape from the liquid surface is less than that of bulk water, therefore, the evaporation enthalpy of VS-Gel evaporator is lower than that of pure water. As shown in Figure 4 a, the equivalent evaporation enthalpy of VS-Gel was measured by DSC to be about 1292 J g -1 , which is much lower than the evaporation enthalpy of water (2334 J g -1 ).

[0051] Example 2: Test of the photothermal evaporation performance of VS-Gel evaporator

[0052] (1) The VS-Gel evaporator was placed in 120 mL of simulated seawater and subjected to photothermal evaporation test under 1 kW·m -2 of solar irradiation.

[0053] (2) The evaporation rate of VS-Gel evaporator was 3.33 kg·m -2 ·h -1 , and the evaporation efficiency was 92.9%.

[0054] (3) The surface temperature of VS-Gel evaporator rapidly rose to 72.4℃ within 20 seconds, indicating its excellent photothermal conversion ability.

[0055] Under standard solar irradiation, the evaporation rate of VS-Gel was 3.33 kg m -2 h -1 , which was about 8.1 times that of pure water (0.41 kg m -2 h -1 ) ( Figure 5 a). In addition, by calculation, the evaporation rate of VS-Gel evaporator under 1 kW m-2 )The photo-thermal conversion efficiency of pure water and VS-Gel evaporator under irradiation intensity was 35.6% and 92.9% respectively Figure 5 b)The above results show that VS-Gel has a faster temperature response characteristic and can efficiently drive the generation of water vapor.

[0056] Example 3: Test of cesium adsorption performance of VS-Gel evaporator

[0057] (1) The VS-Gel evaporator was placed in cesium-containing simulated seawater, and the cesium adsorption test was carried out under 1 kW·m -2 of solar light irradiation.

[0058] (2) The cesium ion adsorption capacity of VS-Gel evaporator in 5 hours in simulated nuclear contaminated seawater can reach 160 mg·g -1 , which is 275% higher than the adsorption capacity (58 mg·g -1 ) under dark conditions.

[0059] (3) After 5 hours of continuous evaporation, no salt crystal deposition occurred on the surface of the VS-Gel evaporator, indicating that it has excellent anti-salt performance.

[0060] Under 1 sun simulated sunlight irradiation, the cesium adsorption capacity of VS-Gel was tested Figure 6 ). First, the Cs + adsorption capacity of VS-Gel and BC-Gel under the same conditions was tested Figure 6 a), the Cs + adsorption capacity of BC-Gel was 36 mg g -1 , and the Cs + adsorption capacity of VS-Gel was 160 mg g -1 , indicating that VS-Gel prepared from Li-VMT has excellent removal performance for Cs + in seawater, and the adsorption performance of VS-Gel is mainly due to the high adsorption of Li-VMT for Cs + .

[0061] Under 1 kW m -2 of simulated solar light irradiation, photo-thermal evaporation and cesium ion adsorption were carried out in 1 g L -1 of simulated nuclear contaminated seawater Figure 6 b and c), after 5h of evaporation and adsorption, the saturated cesium adsorption capacity reached 160 mg g -1 . Under dark conditions, 5h of nuclear contaminated seawater adsorption, the cesium adsorption capacity was 58 mg g -1 . Therefore, the cesium adsorption of VS-Gel in simulated seawater under light is 275% higher than that of the control group without irradiation.

[0062] In addition, Figure 6 The temperature-distance diagram of the suspended VS-Gel aerogel adsorbent in seawater added with cesium shows that the heat is concentrated on the suspended aerogel interface, and has no obvious effect on the water temperature, which excludes the effect of light irradiation on the water temperature. The three-dimensional infrared image of VS-Gel in cesium-containing seawater shows that under the irradiation of one sun, the surface temperature of VS-Gel can reach 42℃ from 25℃, and the increase of the evaporator surface temperature and the seawater flow driven by evaporation will accelerate the ion migration, thereby enhancing the adsorption of VS-Gel to Cs + The synergistic effect of cesium ion adsorption and seawater desalination is shown in Figure 7 High-efficiency water evaporation will accelerate the transmission speed of seawater in the evaporator, so that the cesium ion is more easily to reach the adsorption sites on VS-Gel. The high-efficiency water evaporation caused by solar light-heat conversion not only improves the adsorption efficiency of VS-Gel, but also widens the application range of VS-Gel in practical application, so that the VS-Gel evaporator is more multifunctional and practical.

[0063] In summary, the present application provides a preparation method of a vertical vermiculite-based aerogel (VS-Gel) and its application in photothermal evaporation removal of radioactive cesium in seawater. The aerogel has excellent photothermal evaporation performance and radioactive cesium adsorption performance through interlayer regulation and surface modification, and can simultaneously realize seawater desalination and removal of radioactive cesium. The present application has the advantages of high efficiency, environmental protection, multifunctionality, etc., and is suitable for the fields of seawater desalination and nuclear contaminated water treatment.

[0064] The above description is only illustrative and not limiting, and those skilled in the art understand that many modifications, changes or equivalents can be made without departing from the spirit and scope defined by the appended claims, but all will fall within the protection scope of the present application.

Claims

1. A method of preparing an aerogel for photothermal evaporation synergized with removal of ions by radiation, characterized in that, The application relates to a light-thermal evaporation and radiation ion removal aerogel material. The application relates to a light-thermal evaporation and radiation ion removal aerogel material.

2. The method of claim 1, wherein the method further comprises, S4: mixing the Li-VMT nanosheet, bacterial cellulose and ultrapure water in step S3 to form a uniform mixed solution; S1: Disperse the expanded vermiculite in saturated NaCl solution, and conduct hydrothermal reaction at 140-160°C for 20-32 hours. After centrifugal washing, Na + intercalated vermiculite; S2: The Na + The intercalated vermiculite is dispersed in 1.9-2.1 M LiCl solution, and a hydrothermal reaction is carried out at 140-160 °C for 20-32 hours. After centrifugal washing, Li + The intercalated vermiculite; S3: Li-VMT nanosheets were prepared by ultrasonic exfoliation of the Li-VMT prepared in step S2. + The intercalated vermiculite was subjected to ultrasonic exfoliation and freeze-drying to obtain Li-VMT nanosheets. S5: transferring the mixed solution in step S4 into a mold, directional freezing casting and then freeze-drying to obtain a vertical vermiculite-based aerogel; S6: spraying hydroxylated multi-walled carbon nanotubes on the surface of the vertical vermiculite-based aerogel prepared in step S5 to obtain the light-thermal evaporation and radiation ion removal aerogel. The preparation method of the saturated NaCl solution is as follows: adding excessive NaCl powder into 200 mL ultrapure water, stirring at room temperature until the NaCl powder cannot be dissolved any more, and obtaining the saturated NaCl solution.

3. The method of claim 2, wherein the method further comprises, The Li-VMT nanosheet, bacterial cellulose and ultrapure water are mixed in a proportion of 0.08-0.12:1.2-1.4:2 by weight.

4. The method for preparing the aerogel by photothermal evaporation and synergistic radiation ion removal according to claim 2, characterized in that, The Li + The specific method for ultrasonic exfoliation of intercalated vermiculite is as follows: Li + Intercalated vermiculite is ultrasonicated for 3 hours and centrifuged at 1000 rpm for 15 minutes.

5. The method for preparing the aerogel by photothermal evaporation and synergistic radiation ion removal according to claim 2, characterized in that, The concentration of the hydroxylated multi-walled carbon nanotubes is 0.008-0.012 mg / mL.

6. The method for preparing the aerogel by photothermal evaporation and synergistic radiation ion removal according to claim 2, characterized in that, 7. The light-thermal evaporation and radiation ion removal aerogel material prepared by the method in any one of claims 1-6.

8. The application of the light-thermal evaporation and radiation ion removal aerogel material in seawater desalination treatment and / or removal of radioactive cesium ions in seawater. ​

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