A zif-67 loaded thiol-modified chitosan gel adsorbent and preparation and application thereof

Abstract

The application discloses a ZIF-67 loaded thiol-modified chitosan gel adsorbent and a preparation method and application thereof, and the preparation method of the ZIF-67 loaded thiol-modified chitosan gel adsorbent is as follows: after chitosan, concentrated hydrochloric acid and water are uniformly mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution, mercaptoacetic acid solution and hydroxysuccinimide solution are added, a thiol-modified chitosan solution is obtained through reaction, then, cobalt nitrate and sodium hydroxide are added, a thiol-modified chitosan gel containing cobalt ions is obtained, and finally, 2-methylimidazole solution is added, so that the ZIF-67 loaded thiol-modified chitosan gel adsorbent is obtained. The ZIF-67 loaded thiol-modified chitosan gel adsorbent can be used for treating heavy metal ions in wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanocomposite functional materials, and particularly relates to a ZIF-67 loaded thiol-modified chitosan gel adsorbent and a preparation and application thereof. BACKGROUND

[0002] Heavy metal wastewater is generally produced in the production processes of mechanical manufacturing, chemical industry, electroplating and metallurgy, and especially, a large amount of chromium, cadmium, copper, zinc, nickel and cyanide are discharged in the rinsing wastewater and plating tank wastewater in the electroplating process. These heavy metal wastewater has great harm to the environment, and therefore, the heavy metals in the wastewater need to be adsorbed and treated to meet the discharge standard.

[0003] At present, the methods for treating heavy metals include membrane separation, chemical precipitation, adsorption and electrochemistry. The membrane separation includes electrodialysis, ultrafiltration, reverse osmosis and the like, and the principle is to separate and purify the heavy metals in the wastewater by using pressure, but the treatment capacity of the membrane separation is small, and the pretreatment requirement of the wastewater is high. The chemical precipitation is to add a precipitant, alkali or sulfide into the heavy metal wastewater, generate a difficultly soluble compound through chemical reaction, and then separate the difficultly soluble solid through filtration, centrifugation and the like. Although the method has a wide removal range and high efficiency, the cost is high, and the precipitate needs to be discharged and treated. The electrochemistry includes electrocoagulation, micro-electrolysis and electro-reduction, and the heavy metals in the wastewater are removed by using the electrolysis principle. Although the heavy metals can be recycled and the process is basically pollution-free, the electrolysis equipment needs to be regularly maintained, and the power consumption increases the production cost. The adsorption includes physical adsorption, chemical adsorption and biological adsorption, and the resin, diatomite, activated carbon, chitosan and the like are generally used to adsorb the heavy metal ions in the wastewater, and the method has the advantages of energy saving, environmental protection and simple operation.

[0004] Chitosan is a natural alkaline polymer polysaccharide extracted from marine organisms such as shrimps and crabs, and is a product of deacetylation of chitin. The chitosan molecular structure contains a large number of -OH and -NH2, and forms a network cage structure through hydrogen bonds. Chitosan is rich in source, non-toxic and easy to biodegrade, and is an environmentally friendly adsorption material. However, chitosan has the defects of instability and easy dissolution, which limits its application. Therefore, the chitosan is often modified and loaded to increase its mechanical strength, specific surface area, adsorption site and selectivity and the like.

[0005] Different modification groups and particle loadings can improve the structure and adsorption performance of chitosan adsorbents. CN114749155A discloses a thiol-modified chitosan material and its preparation method and application in adsorbing mercury ions in wastewater, and the thiol-modified chitosan has an adsorption capacity of 128.4 mg / g for mercury ions in wastewater; CN113122938A discloses a preparation method and application of a chitosan / polyvinyl alcohol nanofiber membrane containing MOFs, and the chitosan is loaded with MOFs, and the application mainly reflects on the removal of phosphate, and the removal rate is 128 mg / g; CN115709054A discloses a chitosan-covalent organic framework composite material and its preparation method, and the chitosan gel beads with micro-mesoporous structure formed by chitosan and ZIF-8 have an adsorption capacity of 124.14 mg / g for mercury ions in water and a removal rate of 99.56%; CN113019332B discloses a chitosan / ZIF-8 composite material and its preparation method and application, and the ZIF-8 nanoparticles are uniformly loaded on the three-dimensional network structure of chitosan to form a composite material, which is used for wastewater treatment.

[0006] Therefore, it is necessary to modify and load the chitosan aerogel to obtain an adsorbent material with simple preparation and large adsorption capacity for the treatment of heavy metal ions in wastewater. SUMMARY

[0007] In view of the above prior art, the purpose of the present application is to provide a ZIF-67 loaded thiol-modified chitosan gel adsorbent and its preparation method and application.

[0008] To achieve the above purpose, the present application adopts the following technical solutions:

[0009] In the first aspect of the present application, a preparation method of a ZIF-67 loaded thiol-modified chitosan gel adsorbent is provided, which comprises the following steps:

[0010] (1) mixing chitosan, concentrated hydrochloric acid and water to obtain a first mixed solution, adding 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution, mercaptoacetic acid solution and hydroxysuccinimide solution to the first mixed solution, and reacting to obtain a thiol-modified chitosan solution;

[0011] (2) adding cobalt nitrate to the thiol-modified chitosan solution to obtain a second mixed solution, adding the second mixed solution to a sodium hydroxide solution, and solidifying and washing to obtain a thiol-modified chitosan gel containing cobalt ions, and adding the thiol-modified chitosan gel containing cobalt ions to a 2-methylimidazole solution, and washing and drying after reaction to obtain the ZIF-67 loaded thiol-modified chitosan gel adsorbent.

[0012] Preferably, in step (1), the mass ratio of chitosan, concentrated hydrochloric acid and water is 1:(0.1-1):(50-100).

[0013] Preferably, in step (1), the mass ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide in the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution, water, mercaptoacetic acid in the mercaptoacetic acid solution, water, and hydroxysuccinimide in the hydroxysuccinimide solution is 1:(20-50):(20-50):(20-50).

[0014] Preferably, in step (1), the mass ratio of chitosan, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, mercaptoacetic acid and hydroxysuccinimide is 1:(0.1-1):(0.1-1):(0.1-1).

[0015] Preferably, in step (1), the reaction temperature is 25-55℃, and the reaction time is 2-10h.

[0016] Preferably, in step (2), the mass ratio of the mercapto-modified chitosan solution, cobalt nitrate and sodium hydroxide is 1:(0.1-1):(0.1-0.5).

[0017] Preferably, in step (2), the mass ratio of sodium hydroxide and water in the sodium hydroxide solution is 1:(5-20).

[0018] Preferably, in step (2), the solidification time is 6-12h.

[0019] Preferably, in step (2), the mass ratio of the mercapto-modified chitosan gel containing cobalt ions and 2-methylimidazole is 1:(0.1-1).

[0020] Preferably, in step (2), the mass ratio of 2-methylimidazole and water in the 2-methylimidazole aqueous solution is 1:(50-200).

[0021] Preferably, the drying is freeze-drying, the freeze-drying temperature is-65℃, and the freeze-drying time is 6-24h.

[0022] In a second aspect of the present application, a ZIF-67 loaded mercapto-modified chitosan gel adsorbent is provided.

[0023] In a third aspect of the present application, the application of the ZIF-67 loaded mercapto-modified chitosan gel adsorbent in the treatment of heavy metal ions in wastewater is provided.

[0024] Preferably, the heavy metal ions are mercury ions and arsenic ions.

[0025] The present application has the following beneficial effects:

[0026] The ZIF-67 loaded thiol modified chitosan gel adsorbent prepared by the present application improves the content of active sites in the adsorbent through the modification of thiol, thereby improving the adsorption capacity of the adsorbent to heavy metal ions. Meanwhile, the thiol groups can be grafted on the molecules of the adsorbent by the present application, which can improve the grafting content of the thiol groups, and the thiol groups can coordinate with the heavy metal ions to adsorb the heavy metal ions in the wastewater to the gel adsorbent, thereby improving the adsorption capacity of the gel adsorbent,

[0027] In the preparation of the synthetic ZIF-67, the present application uses deionized water instead of the commonly used solvent methanol, which meets the requirements of clean production. In addition, the in-situ synthesis method is used to load a large amount of ZIF-67 on the thiol modified chitosan gel adsorbent. Meanwhile, the ZIF-67 loaded thiol modified chitosan gel adsorbent can be prepared at room temperature, and the reaction conditions are simple and easy to operate. In addition, the freeze-drying method is used to ensure the activity and structure of the adsorbent. By loading ZIF-67 on chitosan, the active sites of cobalt ions on ZIF-67 and the organic framework sites of ZIF-67 can increase the active adsorption points of chitosan, thereby increasing the adsorption capacity of the adsorbent.

[0028] The present application improves the content of thiol groups in the adsorbent and provides more active sites for the adsorbent by chemical grafting thiol modification and ZIF-67 loading, which can improve the adsorption effect of the chitosan gel adsorbent on heavy metal ions. In addition, the loading of ZIF-67 can solve the defects of high cost and difficult recovery of ZIF powder used alone. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 X-ray diffraction spectrum of the ZIF-67 loaded thiol modified chitosan gel adsorbent prepared in Examples 1-3;

[0030] Figure 2 Infrared spectrum of the ZIF-67 loaded thiol modified chitosan gel adsorbent prepared in Examples 1-3;

[0031] Figure 3 Adsorption effect diagram of the ZIF-67 loaded thiol modified chitosan gel adsorbent prepared in Examples 1-3 and the materials prepared in Comparative Examples 1-2 on heavy metal ions Hg(II) and As(V). DETAILED DESCRIPTION

[0032] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0033] As described in the background, in the heavy metal treatment process, the membrane separation method is high in cost and needs post-treatment, the electrochemical method needs electrolytic equipment and is high in cost, and chitosan is an environmentally friendly adsorbent material, but chitosan has defects of instability and easy dissolution.

[0034] Therefore, in order to exert the adsorption performance of chitosan, the chitosan is modified and loaded in the application. Firstly, the thiol modification of chitosan is realized by using chemical grafting modification technology. The chemical grafting technology can increase the grafting content of thiol in the adsorbent molecules, thereby increasing the adsorption performance of the adsorbent.

[0035] Meanwhile, the chitosan is loaded with ZIF-67. Compared with the chitosan loaded with ZIF-8 in the prior art, ZIF-8 is a crystal structure formed by the combination of Zn ions and 2-methyl imidazole, and ZIF-67 is a crystal structure formed by the combination of Co ions and 2-methyl imidazole. Therefore, the central metal atoms in the crystal structures of the two are different. In the same conditions, ZIF-67 has a better removal effect on heavy metal pollutants. ZIF-67 itself can interact with heavy metal ions and remove them efficiently. The more ZIF-67 loaded in the adsorbent, the more active sites the adsorbent can provide, thereby greatly improving the removal effect of the composite adsorbent. Loading ZIF-67 on chitosan can also solve the problem of difficult recovery and reduce the adsorption cost.

[0036] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0037] The test materials used in the embodiments of the present application are all conventional test materials in the art and can be purchased through commercial channels.

[0038] Example 1: Preparation method of ZIF-67 loaded thiol modified chitosan gel adsorbent

[0039] (1) chitosan, concentrated hydrochloric acid and water were mixed in a mass ratio of 1:0.6:75 to obtain a first mixed solution, 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide solution, mercaptoacetic acid solution and hydroxysuccinimide solution were added to the first mixed solution, and the mixture was reacted at 40℃ for 7h to obtain a thiol modified chitosan solution;

[0040] In the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution, the mass ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide to water is 1:35; in the mercaptoacetic acid solution, the mass ratio of mercaptoacetic acid to water is 1:35; in the hydroxysuccinimide solution, the mass ratio of hydroxysuccinimide to water is 1:35; and in the chitosan, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, mercaptoacetic acid, and hydroxysuccinimide mass ratio is 1:0.5:0.6:0.6.

[0041] (2) Cobalt nitrate was added to the thiol-modified chitosan solution to obtain a second mixture. This mixture was then added to a sodium hydroxide solution and cured for 8 hours. After washing, a cobalt ion-containing thiol-modified chitosan gel was obtained. The cobalt ion-containing thiol-modified chitosan gel was added to a 2-methylimidazole solution. After the reaction, the mixture was washed and dried at -65℃ for 12 hours to obtain ZIF-67 loaded thiol-modified chitosan gel adsorbent.

[0042] The mass ratio of the thiol-modified chitosan solution, cobalt nitrate, and sodium hydroxide is 1:0.6:0.3; the mass ratio of sodium hydroxide to water in the sodium hydroxide solution is 1:12; the mass ratio of the second mixture to 2-methylimidazole is 1:0.6; and the mass ratio of 2-methylimidazole to water in the aqueous solution of 2-methylimidazole is 1:120.

[0043] The X-ray diffraction pattern of the ZIF-67-supported thiol-modified chitosan gel adsorbent prepared in this embodiment is shown in the figure below. Figure 1 As shown, by Figure 1 It can be seen that ZIF-67 loading was successful; the infrared spectrum of the ZIF-67-loaded thiol-modified chitosan gel adsorbent prepared in this embodiment is as follows. Figure 2 As shown, by Figure 2 It can be seen that the thiol group was successfully grafted onto the chitosan molecule.

[0044] Example 2: Preparation method of ZIF-67 supported thiol-modified chitosan gel adsorbent

[0045] (1) Chitosan, concentrated hydrochloric acid and water are mixed in a mass ratio of 1:0.1:50 to obtain a first mixture. 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution, mercaptoacetic acid solution and hydroxysuccinimide solution are added to the first mixture and reacted at 25°C for 10 h to obtain a mercapto-modified chitosan solution.

[0046] In the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution, the mass ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide to water is 1:20; in the mercaptoacetic acid solution, the mass ratio of mercaptoacetic acid to water is 1:20; in the hydroxysuccinimide solution, the mass ratio of hydroxysuccinimide to water is 1:20; and in the chitosan, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, mercaptoacetic acid, and hydroxysuccinimide mass ratio is 1:0.1:0.1:0.1.

[0047] (2) Cobalt nitrate was added to the thiol-modified chitosan solution to obtain a second mixture. This mixture was then added to a sodium hydroxide solution and cured for 12 hours. After washing, a cobalt ion-containing thiol-modified chitosan gel was obtained. The cobalt ion-containing thiol-modified chitosan gel was added to a 2-methylimidazole solution. After the reaction, the mixture was washed and dried at -65°C for 24 hours to obtain ZIF-67 loaded thiol-modified chitosan gel adsorbent.

[0048] The mass ratio of thiol-modified chitosan solution, cobalt nitrate and sodium hydroxide is 1:0.1:0.1, the mass ratio of sodium hydroxide to water in sodium hydroxide solution is 1:5, the mass ratio of the second mixture to 2-methylimidazole is 1:0.1, and the mass ratio of 2-methylimidazole to water in aqueous solution of 2-methylimidazole is 1:50.

[0049] The X-ray diffraction pattern of the ZIF-67-supported thiol-modified chitosan gel adsorbent prepared in this embodiment is shown in the figure below. Figure 1 As shown, by Figure 1 It can be seen that ZIF-67 loading was successful; the infrared spectrum of the ZIF-67-loaded thiol-modified chitosan gel adsorbent prepared in this embodiment is as follows. Figure 2 As shown, by Figure 2 It can be seen that the thiol group was successfully grafted onto the chitosan molecule.

[0050] Example 3: Preparation method of ZIF-67 supported thiol-modified chitosan gel adsorbent

[0051] (1) Chitosan, concentrated hydrochloric acid and water are mixed in a mass ratio of 1:1:100 to obtain the first mixture. 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution, mercaptoacetic acid solution and hydroxysuccinimide solution are added to the first mixture and reacted at 55°C for 2 hours to obtain a mercapto-modified chitosan solution.

[0052] In the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution, the mass ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide to water is 1:50; in the mercaptoacetic acid solution, the mass ratio of mercaptoacetic acid to water is 1:50; in the hydroxysuccinimide solution, the mass ratio of hydroxysuccinimide to water is 1:50; and in the chitosan, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, mercaptoacetic acid, and hydroxysuccinimide, the mass ratio is 1:1:1:1.

[0053] (2) Cobalt nitrate was added to the thiol-modified chitosan solution to obtain a second mixture. This mixture was then added to a sodium hydroxide solution and cured for 6 hours. After washing, a cobalt ion-containing thiol-modified chitosan gel was obtained. The cobalt ion-containing thiol-modified chitosan gel was added to a 2-methylimidazole solution. After the reaction, the mixture was washed and dried at -65°C for 6 hours to obtain ZIF-67 supported thiol-modified chitosan gel adsorbent.

[0054] The mass ratio of thiol-modified chitosan solution, cobalt nitrate and sodium hydroxide is 1:1:0.5, the mass ratio of sodium hydroxide to water in sodium hydroxide solution is 1:20, the mass ratio of the second mixture to 2-methylimidazole is 1:1, and the mass ratio of 2-methylimidazole to water in aqueous solution of 2-methylimidazole is 1:200.

[0055] The X-ray diffraction pattern of the ZIF-67-supported thiol-modified chitosan gel adsorbent prepared in this embodiment is shown in the figure below. Figure 1 As shown, by Figure 1 It can be seen that ZIF-67 loading was successful; the infrared spectrum of the ZIF-67-loaded thiol-modified chitosan gel adsorbent prepared in this embodiment is as follows. Figure 2 As shown, by Figure 2 It can be seen that the thiol group was successfully grafted onto the chitosan molecule.

[0056] Comparative Example 1: Preparation method of ZIF-67 supported chitosan adsorbent

[0057] Cobalt nitrate was added to the chitosan solution. After the cobalt nitrate dissolved, a second mixture was obtained. This mixture was then added to a sodium hydroxide solution and solidified for 8 hours. After washing, a chitosan gel containing cobalt ions was obtained. The chitosan gel containing cobalt ions was added to a 2-methylimidazole solution. After the reaction, the mixture was washed and dried at -65°C for 12 hours to obtain ZIF-67 supported chitosan gel adsorbent.

[0058] The mass ratio of chitosan solution, cobalt nitrate and sodium hydroxide is 1:0.6:0.3, the mass ratio of sodium hydroxide to water in the sodium hydroxide solution is 1:12, the mass ratio of the second mixture to 2-methylimidazole is 1:0.6, and the mass ratio of 2-methylimidazole to water in the aqueous solution of 2-methylimidazole is 1:120.

[0059] Preparation method of thiol-modified chitosan adsorbent

[0060] The chitosan, concentrated hydrochloric acid and water were mixed in a mass ratio of 1:0.6:75 to obtain a first mixed solution. A 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution, a mercaptoacetic acid solution and a hydroxysuccinimide solution were added to the first mixed solution, and the mixture was reacted at 40°C for 7h to obtain a thiol-modified chitosan solution.

[0061] The mass ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide to water in the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide solution was 1:35; the mass ratio of mercaptoacetic acid to water in the mercaptoacetic acid solution was 1:35; the mass ratio of hydroxysuccinimide to water in the hydroxysuccinimide solution was 1:35; and the mass ratio of chitosan to 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide to mercaptoacetic acid to hydroxysuccinimide was 1:0.5:0.6:0.6.

[0062] Test Example 1: Adsorption performance test

[0063] 1. 0.05g of the adsorbents of Examples 1-3 and Comparative Examples 1-2 and chitosan powder were respectively added to 150mL conical flasks, and then 100mL of wastewater containing Hg(II) at a concentration of 100ppm was added to each conical flask. The pH of the solution was maintained at 6, the stopper was tightly capped, and the conical flask was shaken at 25°C for 24h. The adsorption capacity of Hg(II) was measured, and the results are shown in Table 1 and Figure 3 .

[0064] 2. 0.05g of the adsorbents of Examples 1-3 and Comparative Examples 1-2 and chitosan powder were respectively added to 150mL conical flasks, and then 100mL of wastewater containing As(V) at a concentration of 100ppm was added to each conical flask. The pH of the solution was maintained at 6, the stopper was tightly capped, and the conical flask was shaken at 25°C for 24h. The adsorption capacity of As(V) was measured, and the results are shown in Table 1 and Figure 3 .

[0065] The calculation formula of the adsorption capacity is: Q e = [(C0-C e )·V] / m.

[0066] The calculation formula of the removal rate is: R = [(C0-C e ) / C0]×100%.

[0067] In the formula, Q e is the adsorption capacity of the adsorbent for adsorbing Hg(II) or As(V) (mg / g), C0is the concentration of Hg(II) or As(V) in the adsorption solution (mg / L), and C eThe concentration of Hg(II) or As(V) in the solution after adsorption by the adsorbent (mg / L), V is the volume of the wastewater (L), m is the mass of the adsorbent, and R is the removal rate of Hg(II) or As(V) in the wastewater (%).

[0068] Table 1 Adsorption performance of As(V) and Hg(II) in wastewater

[0069]

[0070] From Table 1 and Figure 3 It can be seen that, by modifying the thiol group of chitosan and loading ZIF, the adsorption capacity of the adsorbent for As(V) and Hg(II) in wastewater can be significantly increased, wherein the adsorption capacity of the adsorbent for Hg(II) in wastewater can reach 199.6 mg / g, and the adsorption capacity of the adsorbent for As(V) in wastewater can reach 190.0 mg / g, while the adsorption capacity and removal rate of chitosan, chitosan modified only with thiol group, and chitosan loaded only with ZIF for As(V) and Hg(II) in wastewater are lower than those of the adsorbent prepared in the present application. It can be seen that, by simultaneously modifying the thiol group of chitosan and loading ZIF, the adsorption capacity of the adsorbent for As(V) and Hg(II) in wastewater can be significantly improved.

[0071] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Use of ZIF-67 loaded thiol-modified chitosan gel adsorbent in the treatment of heavy metal ions in wastewater, characterized in that, The ZIF-67 loaded thiol-modified chitosan gel adsorbent is prepared by the following method: (1) mixing chitosan, concentrated hydrochloric acid and water in a mass ratio of 1:(0.1-1):(50-100) to obtain a first mixed solution; adding 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide solution, mercaptoacetic acid solution and hydroxysuccinimide solution into the first mixed solution, and reacting at 25-55°C for 2-10h to obtain a thiol-modified chitosan solution; wherein the mass ratio of chitosan, 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide, mercaptoacetic acid and hydroxysuccinimide is 1:(0.1-1):(0.1-1):(0.1-1); (2) adding cobalt nitrate into the thiol-modified chitosan solution to obtain a second mixed solution, then adding the second mixed solution into a sodium hydroxide solution and solidifying for 6-12h, and then washing to obtain a cobalt ion-containing thiol-modified chitosan gel; adding the cobalt ion-containing thiol-modified chitosan gel into a 2-methylimidazole solution, and then washing and drying after reaction to obtain the ZIF-67 loaded thiol-modified chitosan gel adsorbent; wherein the mass ratio of the thiol-modified chitosan solution, cobalt nitrate and sodium hydroxide is 1:(0.1-1):(0.1-0.5); and the mass ratio of the cobalt ion-containing thiol-modified chitosan gel and 2-methylimidazole is 1:(0.1-1); The heavy metal ions are As(V) and Hg(II).

2. Use according to claim 1, wherein In step (1), the mass ratio of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide and water in the 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide solution is 1:(20-50); the mass ratio of mercaptoacetic acid and water in the mercaptoacetic acid solution is 1:(20-50); and the mass ratio of hydroxysuccinimide and water in the hydroxysuccinimide solution is 1:(20-50).

3. The use according to claim 1, wherein In step (2), the mass ratio of sodium hydroxide and water in the sodium hydroxide solution is 1:(5-20); and the mass ratio of 2-methylimidazole and water in the 2-methylimidazole aqueous solution is 1:(50-200).

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