Amidoximated MOF enteromorpha cellulose / sodium alginate aerogel as well as preparation method and application thereof

Abstract

The invention discloses amidoximation MOF enteromorpha cellulose / sodium alginate aerogel and a preparation method and application thereof, and belongs to the technical field of adsorbents, and the preparation method comprises the following steps: mixing enteromorpha cellulose and sodium alginate in water, dropwise adding the mixture into a metal ion solution for crosslinking, performing solvent exchange on the obtained gel, and drying to obtain the amidoximation MOF enteromorpha cellulose / sodium alginate aerogel. The preparation method comprises the following steps: taking enteromorpha cellulose and sodium alginate as raw materials, putting the enteromorpha cellulose and the sodium alginate into a ligand solution for in-situ growth to obtain a cyanation MOF composite porous material, and finally performing amidoximation treatment to obtain the amidoximation MOF enteromorpha cellulose / sodium alginate aerogel. The aerogel provided by the invention has excellent adsorption capacity and selectivity on hexavalent uranium, the used raw materials are environment-friendly, non-toxic and harmless, a high-performance adsorption material can be prepared by utilizing a simple method, and industrial popularization and application are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of adsorbents, and in particular relates to an amidoximated MOF enteromorpha cellulose / sodium alginate aerogel and a preparation method and application thereof. Background Art

[0004] In recent years, metal organic frameworks (MOFs) have been widely used in many fields due to their unique structure and properties. This material is composed of metal ion nodes or metal clusters connected with organic ligands. It has a very high specific surface area, an ordered and adjustable porous structure, is easy to be functionalized, and contains molecules that can tightly bind uranyl ions (UO2 2+ ) chelating ligand. Based on this, researchers have invested a lot of energy in developing MOFs adsorbents for uranium adsorption and have achieved certain results. However, in practical applications, the recovery and reuse of MOF crystal particles is still a major problem that needs to be solved urgently.

[0005] Since the 1970s, eutrophication of water bodies has become one of the most prominent environmental problems in coastal areas around the world, and the green tide phenomenon caused by it has had a serious negative impact on the ecological environment of water bodies. In my country's coastal areas, especially in the Yellow Sea region, the outbreak of Enteromorpha is a common ecological disaster. Therefore, exploring the potential high-value-added product development channels of Enteromorpha biomass and realizing the "waste to treasure" of Enteromorpha are of great significance for controlling environmental pollution. Enteromorpha is rich in carbohydrates, proteins, crude fiber and various minerals, and also contains a certain amount of fat and vitamins. Among them, the cellulose and Enteromorpha polysaccharides of Enteromorpha have high extraction and utilization value. As a three-dimensional cross-linked polymer material, aerogel is receiving more and more attention due to its excellent cycle stability and broad application prospects in solving problems in many fields such as ecology, biology and industry.

[0006] Therefore, in view of the problems of low adsorption efficiency, poor selectivity and difficulty in recovery of hexavalent uranium by existing adsorbents in water, how to provide a uranium enrichment composite material with high adsorption capacity, stable structure and repeated utilization is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0007] In order to solve the above technical problems, the present invention proposes an amidoximated MOF enteromorpha cellulose / sodium alginate aerogel and a preparation method and application thereof.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing amidoximated MOF enteromorpha cellulose / sodium alginate aerogel comprises the following steps:

[0010] After mixing Enteromorpha cellulose and sodium alginate in water, it was added dropwise to a metal ion solution for crosslinking. After solvent exchange of the obtained gel, it was placed in a ligand solution for in-situ growth to obtain a cyanated MOF composite porous material. Finally, amidoximation treatment was carried out to obtain the amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel.

[0011] Beneficial effects: In the present invention, by adding the Enteromorpha cellulose / sodium alginate mixture dropwise to the metal ion solution, controllable ion crosslinking is achieved to form a uniform and stable three-dimensional network structure. After solvent exchange, a MOF ligand solution is introduced into the gel system, and the uniformly distributed metal ions inside the gel are used as nucleation sites to realize the in-situ growth of MOF. This method avoids the aggregation of MOF particles and enables them to be tightly combined with the cellulose / sodium alginate matrix.

[0012] Preferably, the Enteromorpha cellulose is extracted from natural Enteromorpha, and the specific preparation method includes the following steps:

[0013] Natural Enteromorpha and inorganic salts are mixed and reacted in a solvent. After the reaction, the obtained product is washed to neutrality, dried and crushed to obtain the Enteromorpha cellulose.

[0014] Preferably, the inorganic salt is sodium chlorite; and / or,

[0015] The solvent is a mixed solvent of glacial acetic acid and water, and the volume ratio of glacial acetic acid to water is (0.25 - 1):1.

[0016] More preferably, the addition ratio of natural Enteromorpha, sodium chlorite and water is 10 g:(3 - 12) g:160 mL.

[0017] Preferably, the temperature of the mixed reaction is 70 °C and the time is 0.5 - 2 h.

[0018] Beneficial effects: The present invention uses natural Enteromorpha as a raw material, which is rich in sources and renewable, meeting the concept of green chemistry. Sodium chlorite added in the reaction can effectively remove impurities such as lignin and hemicellulose in Enteromorpha, thus retaining the cellulose main body, and the reaction temperature is relatively low, effectively avoiding the destruction of the fiber structure at high temperature.

[0019] More preferably, the mass ratio of Enteromorpha cellulose to sodium alginate is 1:(1 - 3);

[0020] More preferably, the temperature of mixing in water is 90 °C.

[0021] Beneficial effects: The introduction of sodium alginate in the present invention can improve the formability, flexibility and biocompatibility of the composite material, while Enteromorpha cellulose provides mechanical strength and thermal stability, and the performance balance is achieved when the ratio of the two is 1:1 to 3. At 90 °C, sodium alginate is more easily dissolved and fully interacts with the molecular chains of Enteromorpha cellulose to form a uniform composite system, avoiding the agglomeration phenomenon at low temperatures.

[0022] Preferably, the metal ions in the metal ion solution include Zr 4+ , Fe 3+ , Cu 2+ and Zn 2+ One or more of them, and the concentration is 0.15 - 3 mol / L.

[0023] Beneficial effects: Multivalent metal ions form strong coordination bonds or ionic cross - linked networks with the carboxyl groups of sodium alginate, which can significantly improve the mechanical strength (such as tensile strength, hardness) and water resistance of the composite material, and serve as the crystallization sites of MOF to further in - situ construct MOF on the aerogel matrix.

[0024] More preferably, the cross - linking temperature is room temperature and the time is 24 h.

[0025] More preferably, the exchange solvent used for solvent exchange is methanol, and the solvent exchange time is 8 h.

[0026] Beneficial effects: Cross - linking at room temperature in the present invention can prevent the degradation of the molecular chains of Enteromorpha cellulose or sodium alginate caused by high temperature and maintain the natural porous structure of the material. The gentle reaction time of 24 h ensures that metal ions fully penetrate and uniformly combine with carboxyl groups to form a stable three - dimensional network structure. Methanol is selected for solvent exchange because its polarity is close to that of water but it is more volatile, which can quickly displace the free water molecules in the hydrogel and reduce the collapse of the pore structure caused by drying shrinkage.

[0027] Preferably, the concentration of the ligand in the ligand solution is 0.4 mol / L.

[0028] Preferably, the ligand is 2 - methylimidazole and 1H - imidazole - 4 - carbonitrile, and the molar ratio of 2 - methylimidazole to 1H - imidazole - 4 - carbonitrile is 1:(0 - 3).

[0029] Beneficial effects: At a concentration of 0.4 mol / L, it can ensure that the ligand fully combines with metal ions to form a stable metal - organic framework structure, avoiding insufficient cross - linking at low concentrations or ligand waste at high concentrations. The use of dual - ligand synergistic coordination avoids the blockage of pore channels by excessive functional groups while introducing cyano groups.

[0030] Preferably, the amidoximation treatment specifically includes the following steps:

[0031] Mix the cyanated MOF composite porous material, hydroxylamine hydrochloride and potassium carbonate evenly in an ethanol solution, and react at 60 - 90 °C for 6 - 12 h under a nitrogen atmosphere.

[0032] Advantageous effects: The present invention selects a solution of ethanol and water as the solvent, which is environmentally friendly, easy to recycle, and does not damage the MOF pore structure, being superior to strongly polar solvents (such as DMF). Potassium carbonate provides a weakly alkaline environment, promoting the release of active NH2OH from hydroxylamine hydrochloride, while avoiding the corrosion of the material structure by strong alkalis (such as NaOH). The reaction process in the present invention is carried out under an inert atmosphere, which can avoid the oxidation of the amidoxime group to nitro or nitroso compounds, ensuring the purity and activity of the functional group.

[0033] The mass ratio of the cyanated MOF composite porous material, hydroxylamine hydrochloride and sodium carbonate is (0.2 - 1):1:(1 - 0.5).

[0034] The ethanol solution is obtained by mixing water and absolute ethanol in a volume ratio of 1:(5 - 10).

[0035] Advantageous effects: The appropriate ratio of the cyanated MOF composite porous material, hydroxylamine hydrochloride and sodium carbonate avoids the waste of reagents while ensuring a relatively high amidoxime conversion rate.

[0036] The amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel prepared by the preparation method as described above. An application of the amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel in adsorbing uranium elements.

[0037] Preferably, the uranium element is hexavalent uranium.

[0038] Preferably, the application includes the following steps:

[0039] Add the amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel into the water body containing uranium elements to adsorb hexavalent uranium, wherein the adsorption time is 5 - 180 min, the addition amount of the amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel is 40 mg / L, the pH of the water body containing uranium elements is 3 - 8, and the concentration of the uranium element is 25 - 175 mg / L.

[0040] Advantageous effects: By optimizing the adsorption conditions (pH 3 - 8, uranium concentration 25 - 175 mg / L, adsorbent dosage 40 mg / L, time 5 - 180 min), the optimal adsorption conditions of the aerogel are explored, and the excellent structural characteristics of the aerogel under complex environmental conditions are indirectly verified.

[0041] Compared with the prior art, the present invention has the following advantages and technical effects:

[0042] The present invention provides an amidoximated MOF enteromorpha cellulose / sodium alginate aerogel, its preparation method and application. Moreover, the enteromorpha cellulose obtained by treating natural enteromorpha in the present invention has abundant oxygen-containing groups, which increases the number of adsorption sites in the adsorbent. The enteromorpha cellulose / sodium alginate aerogel prepared by cross-linking with metal ions has a relatively high specific surface area and abundant pore structure, which improves the mass transfer rate and greatly enhances the utilization rate of adsorption sites. At the same time, in the present invention, an MOF composite porous aerogel is formed by in-situ growth, which effectively weakens the aggregation of the MOF material, improves the recyclability of the material, and also greatly enhances the adsorption performance for uranium. And the adsorbent prepared in the present invention has abundant amidoxime groups and has a strong complexing effect on uranyl ions, which can effectively increase the adsorption effect of the adsorbent on uranyl ions, and has an adsorption selectivity for hexavalent uranium, and can preferentially adsorb uranium even in the coexistence of other ions. Moreover, the raw materials used in the present invention are environmentally friendly, non-toxic and harmless, and high-performance adsorbents can be prepared by simple methods, which is conducive to industrial promotion and application. Description of the Drawings

[0043] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0044] Figure 1 SEM diagrams of the aerogels prepared in Example 1, Example 2, Example 3 and Comparative Example 1, wherein, a is Comparative Example 1, b is Example 2, c is Example 3, and d is Example 1;

[0045] Figure 2 X-ray diffraction diagrams of the aerogels prepared in Example 1 and Example 3;

[0046] Figure 3 Infrared spectrum diagram of the aerogel prepared in Example 1;

[0047] Figure 4 Adsorption performance diagrams of the adsorbents prepared in Example 1, Example 4, Example 5, Example 6, Example 7 and Example 8 for hexavalent uranium;

[0048] Figure 5 Variation diagram of the adsorption amount of the material prepared in Example 1 for hexavalent uranium with the adsorption time;

[0049] Figure 6 Adsorption performance diagram of the material prepared in Example 1 for hexavalent uranium at different pH values;

[0050] Figure 7 Adsorption performance diagram of the material prepared in Example 1 for hexavalent uranium in solutions with different initial uranium concentrations;

[0051] Figure 8 The material recycling performance diagram prepared for Example 1;

[0052] Figure 9 The uranium adsorption amount diagram of the material prepared for Example 1 in real seawater. Detailed implementation manners

[0053] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0054] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0055] Unless otherwise specified, the raw materials in the embodiments of the present invention are all obtained through commercial channels;

[0056] Among them, natural enteromorpha comes from Qingdao, Shandong Province; real seawater is taken from the Yellow Sea around Qingdao; 1H-imidazole-4-carbonitrile is purchased from Macklin Biochemical Co., Ltd.; hydrochloric acid is purchased from Yantai Far East Fine Chemical Co., Ltd.; other reagents are all purchased from Sinopharm Chemical Reagent Co., Ltd.

[0057] The solutions containing hexavalent uranium are all uranyl nitrate solutions.

[0058] Unless otherwise specified, the room temperature or normal temperature in the embodiments of the present invention both refer to 25 ± 3 °C.

[0059] Example 1

[0060] A preparation method of amidoximated MOF enteromorpha cellulose / sodium alginate aerogel, comprising the following steps:

[0061] (1) Add 10 g of natural enteromorpha into a mixed solution of 160 mL of deionized water and 40 mL of glacial acetic acid, then add a total of 12 g of sodium chlorite in four portions, react at 70 °C for 1 h, then wash with deionized water until neutral, dry and crush to obtain enteromorpha cellulose, and set aside.

[0062] (2) Weigh 0.5 g of the enteromorpha cellulose obtained in step (1) and 0.5 g of sodium alginate, add them into 19 mL of deionized water, and stir to dissolve at 90 °C. Then use a syringe to extract the mixed solution of enteromorpha cellulose and sodium alginate, and dropwise add it into a 0.2 mol / L zinc chloride solution, and let it stand for crosslinking for 24 h to obtain zinc ion-crosslinked gel beads.

[0063] (3) Immerse the zinc ion-crosslinked gel beads in methanol solution for solvent exchange for 8 h, and then immerse the obtained gel in a methanol solution containing ligands (2-methylimidazole and 1H-imidazole-4-carbonitrile), where the concentration of ligand 2-methylimidazole is 0.2 mol / L and the concentration of 1H-imidazole-4-carbonitrile ligand is 0.2 mol / L. After reacting at room temperature for 12 h, rinse it three times with methanol, then freeze it for 24 h and dry it to obtain the cyanated MOF composite porous material for standby.

[0064] (4) Disperse 0.05 g of the cyanated MOF composite porous material, 0.1 g of hydroxylamine hydrochloride, and 0.1 g of potassium carbonate into 15 mL of 90 vol.% ethanol solution. Under nitrogen protection, react at 80 °C for 8 h. After the reaction, cool and collect the sample, and wash the sample three times with water and ethanol in sequence. Finally, dry it under vacuum at 60 °C for 12 h to obtain the amidoxime-functionalized MOF Enteromorpha cellulose / sodium alginate aerogel.

[0065] Example 2

[0066] A preparation method of Enteromorpha cellulose / sodium alginate aerogel, which is different from Example 1 only in that it does not include steps (3) and (4), that is, it includes the following steps:

[0067] (1) Add 10 g of natural Enteromorpha to a mixed solution of 160 mL of deionized water and 40 mL of glacial acetic acid, then add a total of 12 g of sodium chlorite in four portions, react at 70 °C for 1 h, then wash it with deionized water until neutral, dry and crush it to obtain Enteromorpha cellulose for standby.

[0068] (2) Weigh 0.5 g of the Enteromorpha cellulose obtained in step (1) and 0.5 g of sodium alginate, add them to 19 mL of deionized water, and stir and dissolve at 90 °C. Then use a syringe to extract the mixed solution of Enteromorpha cellulose and sodium alginate, and dropwise add it to 0.2 mol / L zinc chloride solution, and let it stand for crosslinking for 24 h to obtain zinc ion-crosslinked gel beads, that is, Enteromorpha cellulose / sodium alginate aerogel.

[0069] Example 3

[0070] A preparation method of cyanated MOF composite porous material, which is different from Example 1 only in that it does not include step (4), that is, it includes the following steps:

[0071] (1) Add 10 g of natural Enteromorpha to a mixed solution of 160 mL of deionized water and 40 mL of glacial acetic acid, then add a total of 12 g of sodium chlorite in four portions, react at 70 °C for 1 h, then wash it with deionized water until neutral, dry and crush it to obtain Enteromorpha cellulose for standby.

[0072] (2) Weigh 0.5 g of the Enteromorpha cellulose obtained in step (1) and 0.5 g of sodium alginate, add them to 19 mL of deionized water, stir and dissolve at 90 °C, then use a syringe to extract the mixed solution of Enteromorpha cellulose and sodium alginate, and dropwise add it to a 0.2 mol / L zinc chloride solution, and let it stand for crosslinking for 24 h to obtain zinc ion-crosslinked gel beads.

[0073] (3) Place the zinc ion-crosslinked gel beads in a methanol solution for solvent exchange for 8 h, then immerse the obtained gel in a methanol solution containing ligands (2-methylimidazole and 1H-imidazole-4-carbonitrile), where the concentration of the ligand 2-methylimidazole is 0.2 mol / L and the concentration of the 1H-imidazole-4-carbonitrile ligand is 0.2 mol / L. After reacting at room temperature for 12 h, rinse it three times with methanol, then freeze it for 24 h and dry it to obtain a cyanated MOF composite porous material.

[0074] Example 4

[0075] A preparation method of an amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel, which is different from Example 1 only in that the concentration of the zinc chloride solution in step (2) is 0.25 mol / L. Other process steps and parameters are the same as those in Example 1.

[0076] Example 5

[0077] A preparation method of an amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel, which is different from Example 1 only in that the concentration of the zinc chloride solution in step (2) is 0.3 mol / L. Other process steps and parameters are the same as those in Example 1.

[0078] Example 6

[0079] A preparation method of an amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel, which is different from Example 1 only in that the concentration of the ligand 2-methylimidazole in step (3) is 0.3 mol / L and the concentration of the 1H-imidazole-4-carbonitrile ligand is 0.1 mol / L. Other process steps and parameters are the same as those in Example 1.

[0080] Example 7

[0081] A preparation method of an amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel, which is different from Example 1 only in that the concentration of the ligand 2-methylimidazole in step (3) is 0.1 mol / L and the concentration of the 1H-imidazole-4-carbonitrile ligand is 0.4 mol / L. Other process steps and parameters are the same as those in Example 1.

[0082] Example 8

[0083] A preparation method of amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel, which is different from Example 1 only in that the concentration of ligand 2-methylimidazole in step (3) is 0.4 mol / L. Other process steps and parameters are the same as those in Example 1.

[0084] Comparative Example 1

[0085] A preparation method of sodium alginate aerogel, comprising the following steps:

[0086] Add 0.5 g of sodium alginate to 19 mL of deionized water, stir and dissolve at 90 °C, then use a syringe to extract the sodium alginate solution and dropwise add it to 0.2 mol / L zinc chloride solution. After standing for crosslinking for 24 h, freeze for 24 h and then dry to obtain sodium alginate aerogel.

[0087] Comparative Example 2

[0088] A preparation method of amidoximated MOF sodium alginate aerogel, which is different from Example 1 in that Enteromorpha cellulose is not added, and specifically includes the following steps:

[0089] (1) Weigh 0.5 g of sodium alginate and add it to 19 mL of deionized water, stir and dissolve at 90 °C, then use a syringe to extract the mixed solution of Enteromorpha cellulose and sodium alginate and dropwise add it to 0.2 mol / L zinc chloride solution. Stand for crosslinking for 24 h to obtain zinc ion-crosslinked gel beads.

[0090] (3) Place the zinc ion-crosslinked gel beads in a methanol solution for solvent exchange for 8 h, then immerse the obtained gel in a methanol solution containing ligands (2-methylimidazole and 1H-imidazole-4-carbonitrile), wherein the concentration of ligand 2-methylimidazole is 0.2 mol / L and the concentration of 1H-imidazole-4-carbonitrile ligand is 0.2 mol / L. React at room temperature for 12 h, wash three times with methanol, then freeze for 24 h and dry to obtain a cyanated MOF composite porous material for standby.

[0091] (4) Disperse 0.05 g of the cyanated MOF composite porous material, 0.1 g of hydroxylamine hydrochloride and 0.1 g of potassium carbonate in 15 mL of 90 vol.% ethanol solution. Under nitrogen protection, react at 80 °C for 8 h. After the reaction, cool and collect the sample, wash the sample three times with water and ethanol in sequence, and finally vacuum dry at 60 °C for 12 h to obtain the amidoxime-functionalized MOF Enteromorpha cellulose / sodium alginate aerogel.

[0092] Technical effects:

[0093] 1. Structural characterization

[0094] Figure 1SEM images of the aerogels prepared in Example 1, Example 2, Example 3 and Comparative Example 1, where a is Comparative Example 1, b is Example 2, c is Example 3, and d is Example 1; it can be seen that compared with the Enteromorpha cellulose / sodium alginate aerogel without in-situ growth (Example 2), a regular crystal structure appears on the surface of the aerogel prepared in Example 1, proving the successful in-situ growth of MOF on the surface of Enteromorpha cellulose / sodium alginate.

[0095] The infrared spectra of the aerogels prepared in Example 1 and Example 3 are shown in Figure 2 , it can be seen that the presence of cyano groups in Example 3 proves the presence of cyano ligands in MOF. After amidoximation, the disappearance of the cyano peak and the appearance of the N-O peak in Example 1 prove the success of amidoximation and the successful preparation of the material.

[0096] The X-ray diffraction pattern of the aerogel prepared in Example 1 is shown in Figure 3 , it can be seen that compared with the simulated sample ZIF-8, the characteristic peaks appear in the aerogel prepared in Example 1, indicating the successful synthesis of MOF.

[0097] 2. Adsorption performance

[0098] 2.1 Test the adsorption performance of the adsorbents prepared in Example 1, Example 4, Example 5, Example 6, Example 7 and Example 8. The experimental steps are as follows: Add 2 mg of different aerogels to the solution containing hexavalent uranium, where the concentration of uranium ions is 100 mg / L, the adsorption time is 180 min, the adsorption pH is 4.5, and the adsorption temperature is 25 °C.

[0099] The adsorption performance diagrams of the aerogels prepared in Example 1, Example 4, Example 5, Example 6, Example 7 and Example 8 for hexavalent uranium are shown in Figure 4 , it can be seen that compared with 2-methylimidazole and 1H-imidazole-4-carbonitrile in other ratios, the aerogel prepared in Example 1 shows more excellent adsorption performance, indicating that an appropriate ligand ratio can effectively promote the uranium adsorption performance of the material.

[0100] 2.2 Explore the relationship between the adsorption performance of the aerogel prepared in Example 1 and time. The experimental steps are as follows: Add 2 mg of the aerogel to the solution containing hexavalent uranium, where the pH is 4.5, the initial uranium concentration is 100 mg / L, the adsorption temperature is 25 °C, and the adsorption time is 5 - 180 minutes.

[0101] The relationship diagram between the adsorption amount of the adsorbent prepared in Example 1 for hexavalent uranium and time is shown in Figure 5, it can be seen that the aerogel prepared in Example 1 can reach the adsorption equilibrium within 90 minutes, and the adsorption capacity for hexavalent uranium is as high as 523.4 mg / L, indicating that this material has rapid adsorption kinetics and excellent uranium adsorption performance.

[0102] 2.3 To explore the adsorption performance of the aerogel prepared in Example 1 for hexavalent uranium at different pH values, the experimental steps are as follows: Add 2 mg of the aerogel to the solution containing hexavalent uranium, where the pH range is 3 - 8, the initial uranium concentration is 100 mg / L, the adsorption temperature is 25 °C, and the adsorption time is 3 h.

[0103] The adsorption performance graph of the aerogel prepared in Example 1 for hexavalent uranium at different pH values is shown in Figure 6 , it can be seen that as the pH increases, the adsorption amount of the adsorbent for hexavalent uranium first increases and then decreases, and the maximum adsorption amount appears at pH = 5, with the maximum adsorption amount being 761.7 mg / g, indicating that the solution pH will significantly affect the adsorption performance of the adsorbent.

[0104] 2.4 To investigate the adsorption performance of the aerogel prepared in Example 1 for hexavalent uranium in uranium solutions with different initial concentrations, the experimental steps are as follows: Add 2 mg of the aerogel to the solution containing hexavalent uranium, where the pH is 5, the initial uranium concentration is 25 - 175 mg / L, the adsorption temperature is 25 °C, and the adsorption time is 3 h.

[0105] The adsorption performance graph of the aerogel prepared in Example 1 for hexavalent uranium in uranium solutions with different initial concentrations is shown in Figure 7 , it can be seen that the adsorption amount of the aerogel prepared in Example 1 for uranium gradually increases with the increase of the initial concentration, and the adsorption amount is 844.7 mg / g when the initial concentration is 175 mg / L.

[0106] 2.5 To investigate the cyclic regeneration performance of the aerogel prepared in Example 1, the experimental steps are as follows: Add 2 mg of the adsorbent to 50 mL of the hexavalent uranium solution, where the initial uranium concentration is 50 mg / L, the adsorption pH is 5, and the adsorption time is 3 h. After adsorption, desorb with 0.05 M hydrochloric acid solution for 3 h. After desorption, soak and rinse with ultrapure water, and then air-dry naturally before the next adsorption.

[0107] The cyclic regeneration performance of the aerogel prepared in Example 1 is shown in Figure 8 , it can be seen that after five cycles of regeneration, the regeneration rate of the sample is still as high as 91.6% (reaching 91.6% of the initial adsorption amount), indicating that the aerogel structure is stable and has excellent cyclic regeneration performance.

[0108] 2.6 Investigation of the adsorption selectivity performance of the sample prepared in Example 1. The experimental procedure is as follows: Add 2 mg of the adsorbent to 50 L of real seawater samples, and take samples on the 1st, 7th, 14th, 21st, and 30th days after dosing. Use ICP-MS to measure the uranium concentration in seawater before and after adsorption, and calculate the adsorption capacity based on the concentration change.

[0109] The adsorption selectivity performance of the sample prepared in Example 1 is shown in Figure 9 . It can be seen that after 30 days of adsorption in real seawater, the adsorption capacity of the adsorbent for uranium is as high as 19.8 mg / g, indicating that the aerogel has excellent adsorption selectivity for uranium in real seawater and can preferentially adsorb uranium in complex seawater.

[0110] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A preparation method of amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel, characterized in that, It includes the following steps: After mixing ulva cellulose and sodium alginate in water, it is gradually added dropwise into a metal ion solution for crosslinking. Then, after solvent exchange of the obtained gel, it is placed in a ligand solution for in-situ growth to obtain a cyanated MOF composite porous material. Finally, amidoximation treatment is carried out to obtain the amidoximated MOF ulva cellulose / sodium alginate aerogel.

2. The preparation method of the amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel according to claim 1, characterized in that, The ulva cellulose is extracted from natural ulva, and the specific preparation method includes the following steps: Mix natural ulva and inorganic salts in a solvent for reaction. After the reaction is completed, the obtained product is washed to neutrality, dried and crushed to obtain the ulva cellulose.

3. The preparation method of the amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel according to claim 2, wherein The inorganic salt is sodium chlorite; and / or, The solvent is a mixed solvent of glacial acetic acid and water.

4. The preparation method of an amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel according to claim 2, characterized in that, The temperature of the mixed reaction is 70 °C and the time is 0.5 - 2 h.

5. The preparation method of an amidoximated MOF enteromorpha cellulose / sodium alginate aerogel according to claim 1, characterized in that, The metal ions in the metal ion solution include Zr 4+ , Fe 3+ , Cu 2+ and Zn 2+ , one or more of which, with a concentration of 0.15 - 3 mol / L.

6. The preparation method of an amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel according to claim 1, wherein, The total concentration of the ligand in the ligand solution is 0.4 mol / L.

7. The preparation method of the amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel according to claim 6, characterized in that, The ligand is 2-methylimidazole and 1H-imidazole-4-carbonitrile, and the molar ratio of 2-methylimidazole to 1H-imidazole-4-carbonitrile is 1:(0 - 3).

8. The preparation method of an amidoximated MOF Enteromorpha cellulose / sodium alginate aerogel according to claim 1, characterized in that, The amidoximation treatment specifically includes the following steps: Mix the cyanated MOF composite porous material, hydroxylamine hydrochloride and potassium carbonate uniformly in an ethanol solution, and react at 60 - 90 °C for 6 - 12 h under a nitrogen atmosphere.

9. The amidoximated MOF ulva cellulose / sodium alginate aerogel prepared by the preparation method according to any one of claims 1 - 8.

10. Application of the amidoximated MOF ulva cellulose / sodium alginate aerogel according to claim 9 in adsorbing uranium elements.

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