A ZIF-8 magnetic cellulose aerogel and its preparation method and application

Abstract

The present invention belongs to the field of material technology, and discloses a ZIF-8 magnetic cellulose aerogel, a preparation method thereof and an application. Preparation method: Mix cellulose, a magnetic material and an inorganic zinc salt, and obtain the magnetic cellulose aerogel through freeze-drying; soak the magnetic cellulose aerogel in an organic solution of the inorganic zinc salt first to form a mixed system; then add an organic solution of 2-methylimidazole to the mixed system for soaking treatment to activate ZIF-8, and dry to obtain the ZIF-8 magnetic cellulose aerogel. The present invention also provides the ZIF-8 magnetic cellulose aerogel prepared according to the above preparation method; and also provides a filtering medium, which comprises the above ZIF-8 magnetic cellulose aerogel. The ZIF-8 magnetic cellulose aerogel prepared by the present invention has a relatively high adsorption efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, and particularly relates to a ZIF-8 magnetic cellulose aerogel and a preparation method and application thereof. Background Art

[0002] In recent years, with the development of national industrialization and urbanization, the rapid development of the national economy has been driven, and people's living standards have been improved. However, a series of industrial activities such as metal electroplating, mining, building materials decoration, etc. inevitably accompany the discharge of wastewater and waste gas. Volatile organic compounds (VOCs) are dangerous species with low boiling points, high vapor pressures, and reactivity at room temperature, including alkanes, aromatic hydrocarbons, aldehydes, etc.; they are mainly released into the environment through anthropogenic sources, such as oil refining, petrochemical processing, improper solvent treatment, and industrial activities. Most volatile organic compounds can lead to the formation of secondary pollutants, such as tropospheric ozone and secondary organic aerosols, which are toxic and carcinogenic to human health. Heavy metals usually refer to elements with high toxicity in agricultural and chemical production, such as mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr), zinc (Zn), copper (Cu), cobalt (Co), etc. These elements generally come from textile chemical printing and dyeing wastewater, sewage irrigation, metallurgical and electroplating wastewater, and directly or indirectly flow into streams, lakes, rivers or the ocean, which will cause heavy metal soil pollution. Many sediments are formed in road and construction areas, loaded with heavy metal compounds, and are easily transported by rainwater, which will further cause great harm to the human body.

[0003] Based on this, it is of great significance to develop materials with high efficiency, low cost, and sustainability for sewage treatment. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this purpose, the present invention provides a preparation method of a ZIF-8 magnetic cellulose aerogel, which can prepare a ZIF-8 magnetic cellulose aerogel with a high adsorption efficiency.

[0005] The present invention also provides a ZIF-8 magnetic cellulose aerogel prepared according to the above preparation method.

[0006] The present invention also provides a filter medium.

[0007] According to one aspect of the present invention, a preparation method of a ZIF-8 magnetic cellulose aerogel is provided, including the following steps:

[0008] S1: Mix cellulose, a magnetic material, and an inorganic zinc salt to obtain a mixed solution; perform freeze-drying on the mixed solution to obtain a magnetic cellulose aerogel;

[0009] S2: Immerse the magnetic cellulose aerogel in an organic solution of an inorganic zinc salt to form a mixed system; then add an organic solution of 2-methylimidazole to the mixed system and continue to immerse it to activate ZIF-8, and obtain the ZIF-8 magnetic cellulose aerogel after drying; in the organic solution of the inorganic zinc salt, the molar ratio of the inorganic zinc salt to the D-glucose unit of the cellulose is 1:1 to 20.

[0010] According to a preferred embodiment of the present invention, it has at least the following beneficial effects:

[0011] Cellulose aerogel has abundant hydroxyl functional groups, has high adsorption and multi-functional adsorption capabilities, and has low cost. It is a good green and environmentally friendly adsorption material. Metal-organic framework compounds (MOFs) are porous materials self-assembled from metal ions and organic ligands. Due to their large specific surface area (SSA), various adjustable functionalized surfaces and pore structures, they are endowed with high adsorption capacity and fast adsorption characteristics, and can be used for gas / water purification to combat various pollutants, such as volatile organic compounds (VOCs) and heavy metal ions. In the present invention, by loading the MOF material ZIF-8 on the magnetic cellulose aerogel, the obtained ZIF-8 magnetic cellulose aerogel has a high adsorption efficiency.

[0012] In the ZIF-8 magnetic cellulose aerogel of the present invention, due to the addition of magnetic materials, it is easier to collect whether it is crushed in a gas environment or in a turbid and opaque liquid environment; and if ZIF-8 is not loaded on a certain solid carrier (such as aerogel), most of ZIF-8 exists in the form of powder, and it is difficult to form crystal grains, resulting in a low recovery rate of ZIF-8 after adsorption. Therefore, in the present invention, ZIF-8 is loaded on the magnetic cellulose aerogel to form a ZIF-8 crystal grain structure, thereby improving the recovery rate of ZIF-8. Moreover, the presence of the ZIF-8 crystal grain structure greatly improves the adsorption rate of the magnetic cellulose aerogel. Secondly, the ZIF-8 magnetic cellulose aerogel is soluble and combustible, and is easier to handle after use. In addition, when the molar ratio of the inorganic zinc salt to the D-glucose unit of the cellulose is in the range of 1:(1 to 20), the magnetic cellulose aerogel can effectively load ZIF-8.

[0013] In some embodiments of the present invention, the cellulose is carboxymethyl cellulose (CMC).

[0014] In some embodiments of the present invention, the magnetic material includes at least one of iron tetroxide, cobalt ferrite or samarium cobalt.

[0015] In some preferred embodiments of the present invention, the magnetic material is selected from iron tetroxide.

[0016] In some embodiments of the present invention, the inorganic zinc salt includes any one of zinc acetate, zinc nitrate, and zinc chloride.

[0017] In some preferred embodiments of the present invention, the inorganic zinc salt is selected from zinc acetate.

[0018] Specifically, an inorganic zinc salt is used in step S1, and the zinc ions in the inorganic zinc salt are used for crosslinking reaction with cellulose.

[0019] More specifically, zinc acetate is used in step S1, and the zinc ions in zinc acetate carry out crosslinking reaction with carboxymethyl cellulose. Compared with zinc nitrate and zinc chloride, the zinc ions of zinc acetate have the best effect on synthesizing ZIF-8.

[0020] In some embodiments of the present invention, the magnetic cellulose aerogel is prepared by a one-pot method in step S1.

[0021] In some embodiments of the present invention, in step S1, the cellulose and the magnetic material are first mixed and dissolved, and then the inorganic zinc salt is added, and the mixed solution is obtained after mixing.

[0022] In some embodiments of the present invention, in step S1, the cellulose and the magnetic material are added to water and mixed and dissolved.

[0023] In some preferred embodiments of the present invention, in step S1, carboxymethyl cellulose and magnetite are first added to deionized water, and stirred at 58 - 63 °C until completely dissolved to obtain a carboxymethyl cellulose solution (CMC solution); then zinc acetate is dissolved in deionized water and slowly added dropwise to the CMC solution, and stirred at room temperature for 2 - 2.5 h to obtain a black viscous solution.

[0024] In some embodiments of the present invention, in the mixed solution of step S1, the mass ratio of the cellulose to the magnetic material is 1:2 - 2:1; the molar ratio of the inorganic zinc salt to the D-glucose unit of the cellulose is 1:1 - 20.

[0025] In some preferred embodiments of the present invention, in the mixed solution of step S1, the mass ratio of the cellulose to the magnetic material is 1:1; the molar ratio of the inorganic zinc salt to the D-glucose unit of the cellulose is 1:10.

[0026] In some embodiments of the present invention, before the soaking treatment in step S2, the magnetic cellulose aerogel is placed in ethanol for washing to remove the excess inorganic zinc salt.

[0027] In some embodiments of the present invention, the concentration of the organic solution of the inorganic zinc salt is 0.45 - 18 mmol / L.

[0028] In some embodiments of the present invention, in the organic solution of the inorganic zinc salt in step S2, the molar ratio of the inorganic zinc salt to the D-glucose unit of the cellulose is 1:4 to 5. At this time, the loading rate of the magnetic cellulose aerogel for ZIF-8 is relatively high.

[0029] In some preferred embodiments of the present invention, in the organic solution of the inorganic zinc salt in step S2, the molar ratio of the inorganic zinc salt to the D-glucose unit of the cellulose is 1:4. At this time, the loading rate of the magnetic cellulose aerogel for ZIF-8 is the highest.

[0030] In some embodiments of the present invention, the concentration of the organic solution of 2-methylimidazole is 1 to 40 mmol / L.

[0031] In some embodiments of the present invention, the organic solution is methanol or isopropanol.

[0032] In some preferred embodiments of the present invention, the organic solution is methanol.

[0033] In some embodiments of the present invention, in step S2, the magnetic cellulose aerogel is first placed in the organic solution of the inorganic zinc salt and sonicated at 2 to 8 °C for 15 to 20 min to form the mixed system; then the organic solution of 2-methylimidazole is added to the mixed system and sonicated at 2 to 8 °C for 30 to 45 min.

[0034] Specifically, the magnetic cellulose aerogel will absorb zinc ions, enabling more ZIF-8 to be synthesized on the magnetic cellulose aerogel. In step S2, first placing the magnetic cellulose aerogel in the organic solution of the inorganic zinc salt and then adding the organic solution of 2-methylimidazole to the mixed system for soaking treatment can avoid the loss of the synthesized product ZIF-8 in the solvent system caused by adding the organic solution of 2-methylimidazole first.

[0035] In some embodiments of the present invention, after adding the organic solution of 2-methylimidazole in step S2, the mixed system includes the inorganic zinc salt and 2-methylimidazole, and the molar ratio of the inorganic zinc salt to 2-methylimidazole is 1:2.1 to 4. Preferably, the molar ratio of the inorganic zinc salt to 2-methylimidazole is 1:2.4.

[0036] In some embodiments of the present invention, after completing the soaking treatment in step S2, it further includes shaking the soaked system at 4 to 6 °C for 6 to 8 h.

[0037] In some embodiments of the present invention, the types of the inorganic zinc salts in step S1 and step S2 are the same, which can reduce unnecessary variables and save raw materials.

[0038] In some embodiments of the present invention, before step S2 of activating the ZIF-8, it further includes a step of washing the magnetic cellulose aerogel after the soaking treatment, and the detergent used is methanol or isopropanol.

[0039] In some embodiments of the present invention, the method of activation in step S2 includes: encapsulating the magnetic cellulose aerogel after the soaking treatment in a high-pressure reactor, and heating it at 115 - 125 °C for 6 - 8 h to activate the ZIF-8.

[0040] In some embodiments of the present invention, the drying temperature in step S2 is 80 - 85 °C.

[0041] According to the second aspect of the present invention, there is provided a ZIF-8 magnetic cellulose aerogel prepared according to the preparation method, which includes ZIF-8 and magnetic cellulose aerogel, the magnetic cellulose aerogel loads the ZIF-8, and the magnetic cellulose aerogel includes a magnetic material.

[0042] According to the third aspect of the present invention, there is provided a filter medium, which includes the ZIF-8 magnetic cellulose aerogel.

[0043] Specifically, the filter medium can be used for gas pollution prevention or water pollution prevention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below with reference to the drawings and embodiments, where:

[0045] Figure 1 It is a physical picture and a scanning electron microscope micrograph of the magnetic carboxymethyl cellulose aerogel prepared in Example 1 of the present invention; among them, the left is the physical picture and the right is the scanning electron microscope micrograph;

[0046] Figure 2 It is a physical picture of the magnetic carboxymethyl cellulose aerogel prepared in Example 1 of the present invention being attracted by a magnet;

[0047] Figure 3 It is a structure and component detection diagram of the ZIF-8 magnetic cellulose aerogel 1# in Example 2 of the present invention; among them, A is the scanning electron microscope micrograph, B is the FTIR detection result diagram, and C is the XPS detection result diagram; 1# - ZIF-8 magnetic cellulose aerogel 1#, CMC - magnetic carboxymethyl cellulose aerogel;

[0048] Figure 4This is the structure and component detection diagram of ZIF-8 magnetic cellulose aerogel 2# in Example 3 of the present invention; wherein, A is the scanning electron microscope micrograph, B is the FTIR detection result diagram, and C is the XPS detection result diagram; 2# - ZIF-8 magnetic cellulose aerogel 2#, CMC - magnetic carboxymethyl cellulose aerogel;

[0049] Figure 5 This is the structure and component detection diagram of ZIF-8 magnetic cellulose aerogel 4# in Example 4 of the present invention; wherein, A is the scanning electron microscope micrograph, B is the FTIR detection result diagram, and C is the XPS detection result diagram; 4# - ZIF-8 magnetic cellulose aerogel 4#, CMC - magnetic carboxymethyl cellulose aerogel;

[0050] Figure 6 This is the structure and component detection diagram of ZIF-8 magnetic cellulose aerogel 8# in Example 5 of the present invention; wherein, A is the scanning electron microscope micrograph, B is the FTIR detection result diagram, and C is the XPS detection result diagram; 8# - ZIF-8 magnetic cellulose aerogel 8#, CMC - magnetic carboxymethyl cellulose aerogel;

[0051] Figure 7 This is the structure and component detection diagram of ZIF-8 magnetic cellulose aerogel 16# in Example 6 of the present invention; wherein, A is the scanning electron microscope micrograph, B is the FTIR detection result diagram, and C is the XPS detection result diagram; 16# - ZIF-8 magnetic cellulose aerogel 16#, CMC - magnetic carboxymethyl cellulose aerogel. Detailed implementation manners

[0052] The embodiments of the present invention will be described in detail below. The embodiments described by referring to the attached drawings are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention.

[0053] In the description of the present invention, unless otherwise clearly defined, words such as ultrasonic and washing should be understood in a broad sense. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0054] In the description of the present invention, the description referring to terms such as "one embodiment" and "some embodiments" means that the specific features, materials or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment. Moreover, the specific features, materials or characteristics described can be combined in any one or more embodiments in a suitable manner.

[0055] Unless otherwise specified, the test methods used in the embodiments are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are all reagents and materials that can be obtained from commercial channels.

[0056] The materials used in the following examples are as follows:

[0057] Carboxymethyl cellulose (CMC, CAS: 9004-32-4, Shanghai Ron Reagent Co., Ltd.), with a molecular weight of 250,000 and a degree of substitution of 0.9; zinc acetate ((CH3COO)2Zn, CAS: 557-34-6, Shanghai Aladdin Biochemical Technology Co., Ltd.); iron oxide nanoparticles (Fe3O4, CAS: 1317-61-9, Shanghai Macklin Biochemical Co., Ltd.), with a particle size of 20 nm; the experimental water used is deionized water.

[0058] Example 1

[0059] In this example, magnetic carboxymethyl cellulose aerogel was prepared. The specific process is as follows:

[0060] The magnetic carboxymethyl cellulose aerogel was prepared by a one-pot method. 5 g of CMC and 5 g of iron oxide nanoparticles were added to 180 mL of deionized water, and stirred at 60 °C until completely dissolved to obtain a CMC solution; then 0.75 g of zinc acetate was dissolved in 20 mL of deionized water and slowly added dropwise to the CMC solution, and stirred at room temperature for 2 h to obtain about 200 g of a black viscous solution. Among them, the black viscous solution contains CMC and iron oxide nanoparticles, and their respective concentrations are both 2.5 wt%, and the molar ratio of zinc acetate to the D-glucose unit of CMC is 1:10. Finally, the obtained black viscous solution was transferred to a petri dish and freeze-dried to obtain a black magnetic carboxymethyl cellulose aerogel. The physical picture and scanning electron microscope micrograph of the magnetic carboxymethyl cellulose aerogel are as Figure 1 shown. From Figure 1 it can be seen that the magnetic carboxymethyl cellulose aerogel has a porous structure, and the microstructure of the magnetic carboxymethyl cellulose aerogel presents an irregular shape. From Figure 2 it can be seen that the magnetic carboxymethyl cellulose aerogel can be easily attracted by a magnet, indicating that it has magnetism.

[0061] After the above-mentioned magnetic carboxymethyl cellulose aerogel was prepared, it was placed in an appropriate amount of ethanol and ultrasonicated to remove the excess zinc acetate for use in the subsequent preparation of ZIF-8 magnetic cellulose aerogel.

[0062] Example 2

[0063] In this example, ZIF-8 magnetic cellulose aerogel 1# was prepared. In the methanol solution of zinc acetate, the molar ratio of zinc acetate to the D-glucose unit of CMC is 1:1. The specific process is as follows:

[0064] Take 0.8 g of zinc acetate and dissolve it in 30 mL of methanol to form a methanol solution of zinc acetate. Immerse 1 g of the magnetic carboxymethyl cellulose aerogel cleaned with ethanol in Example 1 into the methanol solution of zinc acetate, and ultrasonicate it at 4 °C for 15 min. Take 0.82 g of 2-methylimidazole and dissolve it in 20 mL of methanol to form a methanol solution of 2-methylimidazole, then add it to the magnetic carboxymethyl cellulose aerogel and the methanol solution of zinc acetate and mix evenly to form a suspension system, and ultrasonicate it at 4 °C for 30 min. Then transfer it to a constant temperature shaker at 4 °C and shake it at a speed of 200 rpm for 6 h. Finally, take out the black solid from the suspension system, ultrasonically wash it with methanol 3 times, and then encapsulate the black solid in a 100 mL capacity autoclave with 50 mL of methanol, and heat it at 120 °C for 6 h to activate ZIF-8. Cool down, take out the black solid and dry it thoroughly in a forced-air drying oven at 80 °C to obtain ZIF-8 magnetic cellulose aerogel 1#.

[0065] The single-point surface area of ZIF-8 magnetic cellulose aerogel 1# at P / P0 is 30.5968 m 2 / g, and the BET surface area is 31.1468 m 2 / g. The structure and components of ZIF-8 magnetic cellulose aerogel 1# were detected, and the detection results are as Figure 3 shown. Among them, the scanning electron microscope micrograph of A shows that the cubic grains are ZIF-8, and the particle size is about 0.5 - 1 μm; the powder of the magnetic carboxymethyl cellulose aerogel after grinding is irregular in shape relative to ZIF-8, and ZIF-8 adheres to the pores and surface of the magnetic carboxymethyl cellulose aerogel. In addition, it is found that less ZIF-8 is loaded, which is because a small part of ZIF-8 did not form a cubic grain structure and has been washed away during the preparation process. The Fourier transform infrared spectroscopy (FTIR) detection result graph of B shows that ZIF-8 magnetic cellulose aerogel 1# includes ZIF-8 and magnetic carboxymethyl cellulose aerogel. The X-ray photoelectron spectroscopy (XPS) detection result graph of C shows that no N element is detected in the magnetic carboxymethyl cellulose aerogel, but N element can be detected in ZIF-8 magnetic cellulose aerogel 1#, indicating that ZIF-8 is indeed loaded in ZIF-8 magnetic cellulose aerogel 1#.

[0066] Example 3

[0067] In this example, ZIF-8 magnetic cellulose aerogel 2# was prepared. In the methanol solution of zinc acetate, the molar ratio of zinc acetate to the D-glucose unit of CMC is 1:2. The specific process is as follows:

[0068] Take 0.4 g of zinc acetate and dissolve it in 30 mL of methanol to prepare a methanol solution of zinc acetate. Immerse 1 g of the magnetic carboxymethyl cellulose aerogel cleaned with ethanol in Example 1 into the methanol solution of zinc acetate, and ultrasonicate it at 4 °C for 15 min. Take 0.41 g of 2-methylimidazole and dissolve it in 20 mL of methanol to prepare a methanol solution of 2-methylimidazole, then add it to the magnetic carboxymethyl cellulose aerogel and the methanol solution of zinc acetate, mix evenly to form a suspension system, and ultrasonicate it at 4 °C for 30 min. Then transfer it to a constant temperature shaker at 4 °C and shake it at a speed of 200 rpm for 6 h. Finally, take out the black solid from the suspension system, ultrasonically wash it with methanol 3 times, and then encapsulate the black solid in a 100 mL autoclave with 50 mL of methanol, and heat it at 120 °C for 6 h to activate ZIF-8. Cool it, take out the black solid and dry it thoroughly in a forced-air drying oven at 80 °C to obtain ZIF-8 magnetic cellulose aerogel 2#.

[0069] The single-point surface area of ZIF-8 magnetic cellulose aerogel 2# at P / P0 is 121.3653 m 2 / g, and the BET surface area is 124.4152 m 2 / g. The structure and components of ZIF-8 magnetic cellulose aerogel 2# were detected, and the detection results are as Figure 4 shown. Among them, the scanning electron microscope micrograph of A shows that the cubic grains are ZIF-8, with a particle size of about 0.5 - 1 μm; the powder of the magnetic carboxymethyl cellulose aerogel after grinding is irregular in shape relative to ZIF-8 (including the gray layered structure, which is caused by insufficient grinding of carboxymethyl cellulose), and ZIF-8 adheres to the pores and surface of the magnetic carboxymethyl cellulose aerogel. In addition, it was found that less ZIF-8 was loaded, which is because a small part of ZIF-8 did not form a cubic grain structure and was washed away during the preparation process. The FTIR detection result diagram of B shows that ZIF-8 magnetic cellulose aerogel 2# includes ZIF-8 and magnetic carboxymethyl cellulose aerogel. The XPS detection result diagram of C shows that no N element was detected in the magnetic carboxymethyl cellulose aerogel, but N element can be detected in ZIF-8 magnetic cellulose aerogel 2#, indicating that ZIF-8 is indeed loaded in ZIF-8 magnetic cellulose aerogel 2#.

[0070] Example 4

[0071] In this example, ZIF-8 magnetic cellulose aerogel 4# was prepared. In the methanol solution of zinc acetate, the molar ratio of zinc acetate to the D-glucose unit of CMC is 1:4. The specific process is as follows:

[0072] Take 0.2 g of zinc acetate and dissolve it in 30 mL of methanol to form a methanol solution of zinc acetate. Immerse 1 g of the magnetically modified carboxymethyl cellulose aerogel cleaned with ethanol in Example 1 into the methanol solution of zinc acetate, and ultrasonicate it at 4 °C for 15 min. Take 0.21 g of 2-methylimidazole and dissolve it in 20 mL of methanol to form a methanol solution of 2-methylimidazole. Then add it to the magnetically modified carboxymethyl cellulose aerogel and the methanol solution of zinc acetate, mix well to form a suspension system, and ultrasonicate it at 4 °C for 30 min. Then transfer it to a constant temperature shaker at 4 °C and shake it at a speed of 200 rpm for 6 h. Finally, take out the black solid from the suspension system, wash it ultrasonically with methanol three times, and then encapsulate the black solid in a 100 mL autoclave with 50 mL of methanol and heat it at 120 °C for 6 h to activate ZIF-8. Cool it, take out the black solid and dry it thoroughly in a forced-air drying oven at 80 °C to obtain ZIF-8 magnetically modified cellulose aerogel 4#.

[0073] The single-point surface area of ZIF-8 magnetically modified cellulose aerogel 4# at P / P0 is 94.2980 m 2 / g, and the BET surface area is 96.5020 m 2 / g. The structure and components of ZIF-8 magnetically modified cellulose aerogel 4# were detected, and the detection results are as Figure 5 shown. Among them, the scanning electron microscope micrograph of A shows that the cubic grains are ZIF-8, with a particle size of about 0.5 - 1 μm; the powder of the magnetically modified carboxymethyl cellulose aerogel after grinding is irregular in shape compared to ZIF-8, and ZIF-8 adheres to the pores and surface of the magnetically modified carboxymethyl cellulose aerogel. In addition, it was found that compared with Examples 2 and 3, more ZIF-8 was loaded in this example, indicating that more ZIF-8 cubic grain structures were formed in this example. The FTIR detection result diagram of B shows that ZIF-8 magnetically modified cellulose aerogel 4# includes ZIF-8 and magnetically modified carboxymethyl cellulose aerogel. The XPS detection result diagram of C shows that no N element was detected in the magnetically modified carboxymethyl cellulose aerogel, but N element can be detected in ZIF-8 magnetically modified cellulose aerogel 4#, indicating that ZIF-8 is indeed loaded in ZIF-8 magnetically modified cellulose aerogel 4# and the content of N element is relatively high.

[0074] The above results show that when the molar ratio of zinc acetate to the D-glucose unit of CMC is about 1:4, the loading rate of the magnetically modified carboxymethyl cellulose aerogel for ZIF-8 is the highest.

[0075] Example 5

[0076] In this example, ZIF-8 magnetically modified cellulose aerogel 8# was prepared, and the molar ratio of zinc acetate to the D-glucose unit of CMC in the methanol solution of zinc acetate was 1:8. The specific process is as follows:

[0077] Take 0.1 g of zinc acetate and dissolve it in 30 mL of methanol to prepare a methanol solution of zinc acetate. Immerse 1 g of the magnetic carboxymethyl cellulose aerogel cleaned with ethanol in Example 1 into the methanol solution of zinc acetate, and ultrasonicate it at 4 °C for 15 min. Take 0.11 g of 2-methylimidazole and dissolve it in 20 mL of methanol to prepare a methanol solution of 2-methylimidazole, then add it to the magnetic carboxymethyl cellulose aerogel and the methanol solution of zinc acetate, mix evenly to form a suspension system, and ultrasonicate it at 4 °C for 30 min. Then transfer it to a constant temperature shaker at 4 °C and shake it at a speed of 200 rpm for 6 h. Finally, take out the black solid from the suspension system, ultrasonically wash it with methanol 3 times, and then encapsulate the black solid in a 100 mL capacity autoclave with 50 mL of methanol, and heat it at 120 °C for 6 h to activate ZIF-8. Cool it, take out the black solid and dry it thoroughly in a forced air drying oven at 80 °C to obtain ZIF-8 magnetic cellulose aerogel 8#.

[0078] The single-point surface area of ZIF-8 magnetic cellulose aerogel 8# at P / P0 is 44.7544 m 2 / g, and the BET surface area is 45.7540 m 2 / g. The structure and components of ZIF-8 magnetic cellulose aerogel 8# were detected, and the detection results are as Figure 6 shown. Among them, the scanning electron microscope micrograph of A shows that the cubic grains are ZIF-8, and the particle size is about 0.5 - 1 μm; the powder of the magnetic carboxymethyl cellulose aerogel after grinding is irregular in shape relative to ZIF-8, and ZIF-8 adheres to the pores and surface of the magnetic carboxymethyl cellulose aerogel. In addition, it was found that less ZIF-8 was loaded, which is because a small part of ZIF-8 did not form a cubic grain structure and was washed away during the preparation process. The FTIR detection result diagram of B shows that ZIF-8 magnetic cellulose aerogel 8# includes ZIF-8 and magnetic carboxymethyl cellulose aerogel. The XPS detection result diagram of C shows that no N element was detected in the magnetic carboxymethyl cellulose aerogel, but N element can be detected in ZIF-8 magnetic cellulose aerogel 8#, indicating that ZIF-8 is indeed loaded in ZIF-8 magnetic cellulose aerogel 8#.

[0079] Example 6

[0080] In this example, ZIF-8 magnetic cellulose aerogel 16# was prepared. In the methanol solution of zinc acetate, the molar ratio of zinc acetate to the D-glucose unit of CMC is 1:16. The specific process is as follows:

[0081] Take 0.1 g of zinc acetate and dissolve it in 30 mL of methanol to prepare a methanol solution of zinc acetate. Immerse 2 g of the magnetic carboxymethyl cellulose aerogel cleaned with ethanol in Example 1 into the methanol solution of zinc acetate, and ultrasonicate it at 4 °C for 15 min. Take 0.11 g of 2-methylimidazole and dissolve it in 20 mL of methanol to prepare a methanol solution of 2-methylimidazole, then add it to the magnetic carboxymethyl cellulose aerogel and the methanol solution of zinc acetate, mix evenly to form a suspension system, and ultrasonicate it at 4 °C for 30 min. Then transfer it to a constant temperature shaker at 4 °C and shake it at a speed of 200 rpm for 6 h. Finally, take out the black solid from the suspension system, wash it ultrasonically with methanol three times, and then encapsulate the black solid in a 100 mL capacity autoclave with 50 mL of methanol, and heat it at 120 °C for 6 h to activate ZIF-8. Cool down, take out the black solid and dry it thoroughly in a forced-air drying oven at 80 °C to obtain ZIF-8 magnetic cellulose aerogel 16#.

[0082] The single-point surface area of ZIF-8 magnetic cellulose aerogel 16# at P / P0 is 22.9297 m 2 / g, and the BET surface area is 23.3431 m 2 / g. The structure and components of ZIF-8 magnetic cellulose aerogel 16# were detected, and the detection results are as Figure 7 shown. Among them, the scanning electron microscope micrograph of A shows that the cubic grains are ZIF-8, and the particle size is about 0.5 - 1 μm; the powder of the magnetic carboxymethyl cellulose aerogel after grinding is irregular in shape relative to ZIF-8, and ZIF-8 adheres to the pores and surface of the magnetic carboxymethyl cellulose aerogel. In addition, it was found that less ZIF-8 was loaded, which is because a small part of ZIF-8 did not form a cubic grain structure and has been washed away during the preparation process. The FTIR detection result diagram of B shows that ZIF-8 magnetic cellulose aerogel 16# includes ZIF-8 and magnetic carboxymethyl cellulose aerogel. The XPS detection result diagram of C shows that no N element was detected in the magnetic carboxymethyl cellulose aerogel, but N element can be detected in ZIF-8 magnetic cellulose aerogel 16#, indicating that ZIF-8 is indeed loaded in ZIF-8 magnetic cellulose aerogel 16#.

[0083] The above has made a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge scope of those of ordinary skill in the art. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A preparation method of ZIF-8 magnetic cellulose aerogel, characterized in that, It includes the following steps: S1: Mix cellulose, magnetic material, inorganic zinc salt and water to obtain a mixed solution; freeze-dry the mixed solution to obtain magnetic cellulose aerogel; the cellulose is carboxymethyl cellulose; in the mixed solution, the molar ratio of the inorganic zinc salt to the D-glucose unit of the cellulose is 1:1 to 20; S2: First soak the magnetic cellulose aerogel in an organic solution of inorganic zinc salt to form a mixed system, wherein the soaking treatment is ultrasonic treatment at 2-8°C for 15-20 min; then add an organic solution of 2-methylimidazole to the mixed system and continue the soaking treatment, and the soaking treatment is ultrasonic treatment at 2-8°C for 30-45 min to activate ZIF-8, and the ZIF-8 magnetic cellulose aerogel is obtained after drying.

2. The preparation method according to claim 1, characterized in that, The magnetic material includes at least one of iron tetroxide, cobalt ferrite or samarium cobalt.

3. The preparation method according to claim 2, characterized in that, The inorganic zinc salt includes any one of zinc acetate, zinc nitrate, and zinc chloride.

4. The preparation method according to claim 1, characterized in that, In the organic solution of the inorganic zinc salt in step S2, the molar ratio of the inorganic zinc salt to the D-glucose unit of the cellulose is 1:4 to 5.

5. The preparation method according to claim 4, characterized in that, The organic solution is methanol or isopropanol.

6. The preparation method according to claim 1, wherein In step S1, the cellulose and the magnetic material are first added to water and mixed and dissolved, and then the inorganic zinc salt is added, and the mixed solution is obtained after mixing.

7. The preparation method according to claim 6, characterized in that, In the mixed solution of step S1, the mass ratio of the cellulose to the magnetic material is 1:2 to 2:

1.

8. The preparation method according to any one of claims 1 to 7, characterized in that, After the soaking treatment in step S2, it further includes shaking the soaked system at 4-6°C for 6-8 h.

9. The preparation method according to any one of claims 1 to 7, characterized in that Before activating the ZIF-8 in step S2, it further includes a step of washing the magnetic cellulose aerogel after the soaking treatment, and the detergent used is methanol or isopropanol.

10. The preparation method according to any one of claims 1 to 7, characterized in that, The activation temperature in step S2 is 115-125°C, and the time is 6-8 h.

11. A ZIF-8 magnetic cellulose aerogel prepared by the preparation method according to any one of claims 1 to 10, characterized in that, It includes ZIF-8 and magnetic cellulose aerogel, the magnetic cellulose aerogel loads the ZIF-8, and the magnetic cellulose aerogel includes a magnetic material.

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