A thiol polymer nanogel and its preparation method and application

Abstract

The present invention discloses a thiol-modified polymer nanogel, its preparation method, and application. The preparation method comprises: dissolving a halogenated olefin monomer, a crosslinking agent, and an initiator in a mixed solution to obtain an oil phase; and an aqueous solution of a surfactant to obtain an aqueous phase. Under nitrogen protection, the oil phase is added to the aqueous phase and stirred to obtain an oil-in-water microemulsion. The halogenated polymer nanogel is then heated to induce free radical polymerization. Furthermore, under nitrogen protection, a sulfhydride reacts with the halogenated polymer nanogel to thiolate the halogenated polymer nanogel, thereby obtaining the thiol-modified polymer nanogel. The preparation method of the present invention is simple, low-cost, and does not use toxic reagents. The prepared thiol-modified polymer nanogel has good stability and selectivity and can efficiently remove mercury from water.

Description

Technical Field

[0001] The invention belongs to the field of material technology, relates to a material for efficiently removing mercury from water, and particularly relates to a thiol polymer nanogel and a preparation method and application thereof. Background Art

[0002] Mercury has attracted widespread global attention due to its high toxicity, high diffusion rate, and high bioaccumulation. Anthropogenic sources of mercury include gold mining, fossil fuel combustion, metal production, cement production, waste incineration, and the chlor-alkali industry. Countries are continuously working to reduce mercury emissions, such as adopting cleaner or alternative processes, developing novel mercury capture technologies to reduce mercury emissions, and establishing stricter mercury emission standards. The mobility and diffusion of mercury are closely linked to the movement of natural water. Because water is essential to life and contributes significantly to the mercury cycle in the environment, remediation of mercury contamination in water is a critical issue.

[0003] The international community has established strict limits on mercury concentrations in water. For example, the U.S. Environmental Protection Agency sets a limit of 2 μg / L for mercury in drinking water and 10 μg / L for mercury in industrial wastewater. Current methods for remediating mercury in water include precipitation, flocculation, adsorption, ion exchange, and solvent extraction. Adsorption, among other methods, is simple, efficient, easy to operate, produces no byproducts, and is reproducible, and has garnered widespread attention in the field.

[0004] However, traditional adsorbents such as activated carbon, zeolite, mesoporous silica and resins lack sufficient mercury-philic functional groups, and have defects such as slow kinetics, low capacity, poor selectivity and large material consumption in the removal of mercury from water, making it difficult to meet the needs of rapid and high-standard remediation of mercury-contaminated water bodies. Researchers have attempted to improve the mercury removal efficiency by modifying the surface of traditional materials with soft base ligands such as sulfur / selenium, but due to the number of intrinsic active functional groups and pore distribution defects of traditional materials, the number of soft base functional ligands modified on the surface is small, and the improvement in the adsorption efficiency of traditional materials for mercury after modification is limited. In addition, the surface modification chemical reagents will block some pores, inhibit the diffusion of mercury into the interior of the material, resulting in slow mercury removal kinetics.

[0005] In recent years, some nanomaterials such as graphene, metal organic frameworks (MOFs), porous organic polymers (POPs), covalent organic frameworks (COFs), nanometal sulfides, etc. have been developed for the remediation of mercury in water. Through reasonable pore size regulation and functional ligand modification, these nanomaterials show high affinity and high enrichment efficiency for mercury in water. For example, Ma et al. constructed a thiol-functionalized COFs mercury "nano-trap". Based on its high density of strong mercury chelating groups, large surface area and stable molecular skeleton, this nanomaterial showed ultra-high removal efficiency for mercury in water, with a maximum adsorption capacity of over 1000 mg / g, and can reduce the mercury concentration in water to below 0.4 μg / L. Zhang et al. prepared a MOF-808-SH by replacing the polyacid ligands on MOF-808 with thioglycolic acid, which has ultra-fast adsorption kinetics for the removal of mercury in water, with a rate constant of k As high as 36.89 g / (mg·min), dozens of times faster than existing mercury adsorbents. Despite significant progress in the use of nano-adsorbent materials for mercury remediation in water, several key challenges remain. First, the high cost stems from the expensive precursor modules / monomers used to construct nanomaterials such as POPs and COFs. Second, the complex synthesis process often involves the use of large amounts of toxic reagents. For example, graphene synthesis requires large amounts of acid and oxidants, while the polymerization of COFs and POPs requires large amounts of organic solvents. Third, some nano-adsorbent materials suffer from poor chemical stability. For example, MOFs exhibit poor stability in water, particularly in alkaline solutions, and nano-metal sulfides dissolve in acid, releasing heavy metals. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a thiol-polymer nanogel and a preparation method thereof. The preparation method of the present invention is simple, low-cost, and does not use toxic reagents. The prepared thiol-polymer nanogel has good stability and selectivity and can effectively remove mercury from water.

[0007] The technical solution of the present invention is achieved as follows:

[0008] A method for preparing a thiolated polymer nanogel comprises the following steps: a mixed solution obtained by dissolving a halogenated olefin monomer, a crosslinking agent and an initiator is mixed and dissolved as an oil phase, an aqueous solution of a surfactant is used as an aqueous phase, the oil phase is added to the aqueous phase under nitrogen protection, and stirred to obtain an oil-in-water microemulsion, which is then heated to initiate free radical polymerization to obtain a halogenated polymer nanogel, and then under nitrogen protection, a sulfhydride reacts with the halogenated polymer nanogel to thiolate the halogenated polymer nanogel, thereby obtaining the thiolated polymer nanogel.

[0009] Furthermore, the method specifically includes the following steps:

[0010] (1) A halogenated olefin monomer, a crosslinking agent, and an initiator are mixed and dissolved to obtain an oil phase, a surfactant is dissolved in water to obtain an aqueous phase, and then the oil phase is added to the aqueous phase, nitrogen is introduced to exclude air, and the mixture is stirred for 10-60 min to obtain an oil-in-water microemulsion; the molar ratio of the halogenated olefin monomer, the crosslinking agent, and the initiator in the oil phase is 100:0.1:1-100:1:1: the mass concentration of the surfactant in the aqueous phase is 0.4%; and the volume ratio of the oil phase to the aqueous phase is 1:10;

[0011] (2) The oil-in-water microemulsion was heated to 60-80 °C and reacted for 4 h, and then centrifuged, washed, and dried to obtain the halogenated polymer nanogel;

[0012] (3) Under nitrogen protection, the halogenated polymer nanogel and the hydrosulfide are dissolved in anhydrous ethanol, and then reacted at 75°C to convert the halogenated hydrocarbons in the halogenated polymer nanogel into thiol groups. After the reaction, the thiolated polymer nanogel is obtained by centrifugation, washing, and drying. In specific applications, the anhydrous ethanol must ensure that the hydrosulfide is completely dissolved to achieve a good dispersion effect with the halogenated polymer nanogel. The amount of anhydrous ethanol used is 18 to 25 times the total mass of the hydrosulfide and the halogenated polymer nanogel.

[0013] Furthermore, in step (3), a phase transfer catalyst is added during the reaction of the hydrosulfide and the halogenated polymer nanogel. The phase transfer catalyst is tetrabutylammonium bromide, and the amount of the phase transfer catalyst is 0.4-1 wt% of the total mass of the hydrosulfide and the halogenated polymer nanogel.

[0014] Furthermore, the halogenated olefin monomer is chloromethylstyrene.

[0015] Furthermore, the cross-linking agent is one or more of divinylbenzene, allyl methacrylate and triallyl isocyanurate, preferably divinylbenzene.

[0016] Furthermore, the initiator is one or more of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate and methyl ethyl ketone peroxide, preferably azobisisobutyronitrile.

[0017] Furthermore, the surfactant is one or more of sodium dodecyl sulfate, Tween 80 and dodecyltrimethylammonium bromide, preferably sodium dodecyl sulfate.

[0018] Furthermore, the hydrosulfide is one of sodium hydrosulfide and potassium hydrosulfide; and the mass ratio of the hydrosulfide to the halogenated polymer nanogel is 2-6:1.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention uses chloromethylstyrene as a monomer to directly initiate free radical copolymerization to prepare chlorinated polymer nanogels, so that the surface of the chlorinated polymer nanogels has a large number of active functional groups -Cl. At the same time, chloromethylstyrene has a benzene ring, so that the molecular skeleton of the chlorinated polymer nanogels has good stability. Then, the chlorinated polymer nanogels react with excess hydrogen sulfide, and the active functional groups -Cl are completely converted into thiol groups. As a result, the thiol-containing polymer nanogels have a large number of thiol groups and structural stability, which is conducive to the efficient removal of mercury in water.

[0021] 2. The present invention adopts a microemulsion polymerization strategy. Under the action of surfactants, the halogenated olefin monomers in the oil phase can be evenly and stably dispersed in the aqueous phase to form extremely small oil droplets. The reaction then proceeds, with each oil droplet serving as a reaction site. As a result, the resulting nanogel has a small and evenly distributed particle size, a large specific surface area, and good dispersibility, fully exposing the thiol functional groups and facilitating improved mercury adsorption efficiency.

[0022] 3. The thiol polymer nanogel prepared by the present invention has good adsorption efficiency for mercury in the pH range of 2-12 and has good chemical stability. After 10 cycles, the removal rate of Hg exceeds 99%; it also has good selectivity and resistance to ion interference. + Mg 2+ , Ca 2+ 、Cu 2+ , Pb 2+ Various cations and Cl - 、SO4 2- 、NO3 - 、HPO4 2- When multiple anions coexist, mercury can still be removed efficiently and selectively.

[0023] 4. The raw materials used in the present invention are all commercial olefin monomers, which are low in cost, simple in preparation method, mild in reaction conditions, thorough in polymerization process, and high in monomer utilization rate, reaching 95.2%; no toxic organic solvents are involved in the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 -Actual picture of PVB-SH in Example 1.

[0025] Figure 2 -SEM image and particle size distribution of PVB-Cl in Example 1.

[0026] Figure 3 -SEM image and particle size distribution of PVB-SH in Example 1.

[0027] Figure 4 -XPS spectra of PVB-Cl and PVB-SH in Example 1.

[0028] Figure 5 -Specific surface area and pore size distribution of PVB-Cl and PVB-SH in Example 1.

[0029] Figure 6 - Kinetic test of mercury adsorption by PVB-Cl and PVB-SH in Example 1.

[0030] Figure 7 - Mercury removal efficiency of PVB-SH under different pH conditions in Example 1.

[0031] Figure 8 -Isothermal characteristics of mercury adsorption on PVB-SH at different temperatures in Example 1.

[0032] Figure 9 -Effect of coexisting metal cations on mercury adsorption by PVB-SH in Example 1.

[0033] Figure 10 - Adsorption distribution coefficient of PVB-SH for different metal ions in Example 1.

[0034] Figure 11 -Effect of coexisting anions on mercury adsorption by PVB-SH in Example 1.

[0035] Figure 12 -Images of PVB-SH before and after long-term immersion in different corrosive solutions in Example 1 and their effects on mercury removal efficiency.

[0036] Figure 13 -XPS spectrum analysis of PVB-SH after immersion in different etching solutions in Example 1.

[0037] Figure 14 - Mercury removal efficiency of PVB-SH after different regeneration times in Example 1.

[0038] Figure 15 -SEM images and XPS spectra of PVB-SH after 10 regenerations in Example 1. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] A method for preparing thiol-modified polymer nanogel:

[0042] (1) Dissolve 0.12 g of sodium dodecylsulfonate in 30 mL of deionized water and stir to dissolve to obtain an aqueous phase; mix and dissolve 0.0288 mL of crosslinker divinylbenzene (0.2 mmol), 0.04 g of initiator azobisisobutyronitrile and 2.82 mL of functional monomer chloromethylstyrene (20 mmol) to obtain an oil phase; pour the oil phase into the aqueous phase and stir rapidly at 1000 rpm for 30 min under nitrogen protection to obtain an oil-in-water microemulsion;

[0043] (2) The oil-in-water microemulsion was heated to 75°C and reacted for 4 h. After cooling to room temperature, the solid was collected by centrifugation, washed with deionized water, and dried to obtain 2.84 g of chlorinated polymer nanogel PVB-Cl with a yield of 95.17%.

[0044] (3) Then, 0.5 g of PVB-Cl, 1.5 g of NaHS and 0.3 g of tetrabutylammonium bromide (phase transfer catalyst) were weighed and dissolved in 50 mL of anhydrous ethanol. Nitrogen was introduced to remove air, and then stirred at 75 °C for 24 h. After the reaction, the solid was collected by centrifugation, washed with deionized water and dried to obtain 0.12 g of light yellow thiol polymer nanogel PVB-SH (such as Figure 1 shown).

[0045] Example 2

[0046] This embodiment is the same as embodiment 1, except that the amount of the cross-linking agent divinylbenzene in this embodiment is 0.00288 g.

[0047] Example 3

[0048] This example is the same as Example 1, except that the amount of sodium hydrosulfide in this example is 3 g.

[0049] Example 4

[0050] This example is the same as Example 1, except that the amount of sodium hydrosulfide in this example is 2 g.

[0051] Example 5

[0052] This example is the same as Example 1, except that the amount of sodium hydrosulfide in this example is 1 g.

[0053] Example 6

[0054] This embodiment is the same as embodiment 1, except that the amount of the cross-linking agent divinylbenzene in this embodiment is 0.0144 g.

[0055] Comparative Example 1

[0056] This embodiment is the same as embodiment 1, except that 2-ethyl chloromethylacrylate is used instead of chloromethylstyrene.

[0057] Comparative Example 2

[0058] This example is the same as Example 1, except that the amount of the cross-linking agent divinylbenzene in this example is 0.144 g.

[0059] Comparative Example 3

[0060] This example is the same as Example 1, except that the amount of the cross-linking agent divinylbenzene in this example is 0.288 g.

[0061] Comparative Example 4

[0062] This example is the same as Example 1, except that the amount of sodium hydrosulfide in this example is 0.5 g.

[0063] 1. The SEM images and particle size distribution diagrams of PVB-Cl and PVB-SH in Example 1 are as follows: Figure 1 and Figure 2 As shown in the figure, the SEM image shows that the chlorinated polymer nanogel PVB-Cl has uniformly distributed nanoparticles. The particle size statistics of the chlorinated polymer nanogel PVB-Cl were performed using Nano Measure software, and the average particle size of PVB-Cl was 40.69 nm. The microscopic morphology of the PVB-SH nanogel obtained by NaHS treatment did not show significant changes, and the average particle size was slightly larger than that of PVB-Cl, about 41.94 nm. The chemical composition of PVB-Cl and PVB-SH nanogels was analyzed using X-ray photoelectron spectroscopy (XPS). The results showed that PVB-Cl was mainly composed of three elements: C, O and Cl. After NaSH treatment, the characteristic peak of Cl 2p at 200.3 eV disappeared, and a new characteristic peak of S 2p appeared at 163.7 eV, corresponding to the -SH composition; the XPS C1s fine structure spectrum also showed that after NaHS treatment, the C-Cl peak in PVB-Cl disappeared, and a new C-SH characteristic peak appeared ( Figure 4 ), these results all prove that NaHS treatment successfully converts Cl in PVB-Cl into -SH. The specific surface area analysis results show that both PVB-Cl and PVB-SH have large specific surface areas, with PVB-Cl having a specific surface area of ​​81.52 m 2 / g, porosity of about 0.7411 cm 3 / g, with an average pore size of 36.78 nm. After treatment with NaHS, the specific surface area of ​​PVB-SH slightly decreased to 73.22 m 2 / g, the porosity is reduced to 0.2729cm 3 / g, the average pore size is reduced to 15.92nm ( Figure 5 ), the main reason is that the Cl atoms are occupied by the larger -SH, but PVB-SH still has a large specific surface area, which is conducive to the full exposure of the -SH functional group and improves the removal efficiency of mercury in water.

[0064] 2. Mercury adsorption test of PVB-Cl and PVB-SH in Example 1

[0065] (1) Differences in the adsorption efficiency of mercury between PVB-Cl and PVB-SH

[0066] The adsorbent addition amount was 0.2 g / L, the mercury concentration was 10 mg / L, the test temperature was 25°C, and the solution pH was adjusted to 5. The adsorption test showed that PVB-Cl hardly adsorbed mercury. After 360 minutes of adsorption, the mercury removal rate of PVB-Cl in water was only 0.5%. PVB-Cl can quickly and efficiently remove mercury from water. Within 0.5 minutes of adsorption, the mercury concentration in the solution quickly decreased from 10.03 mg / L to 1.21 mg / L, with a removal rate of 87.94%; after 10 minutes, the mercury concentration decreased to 0.19 mg / L, with a removal rate of 98.10%; after 240 minutes of adsorption, the residual mercury concentration in the solution decreased to below 0.002 mg / L, which is lower than the limit value of mercury content in drinking water set by the US Environmental Protection Agency ( Figure 6 ).

[0067] (2) Effect of pH on mercury adsorption by PVB-SH

[0068] The adsorbent addition amount was 0.2 g / L, the mercury concentration was 10 mg / L, the test temperature was 25°C, and the adsorption time was 24 hours. Changes in the pH value of the solution can change the surface charge of the adsorbent and the adsorbate, thereby affecting adsorption. Adsorption tests under different pH conditions are as follows: Figure 7 As shown, PVB-SH exhibits extremely high mercury adsorption efficiency within the pH range of 2-11, with residual mercury concentrations below 1 μg / L and a removal rate exceeding 99.99%. At pH 12, mercury removal efficiency decreases slightly, reaching 89.96%.

[0069] (3) Mercury removal efficiency of PVB-SH at different temperatures

[0070] The adsorbent addition amount was 0.2 g / L, the mercury concentration was 5-300 mg / L, the adsorption time was 24 h, the solution pH was 5, and the test temperatures were 25°C, 35°C, and 45°C. Figure 8 As shown in Figure 2, under the condition of 25℃, the adsorption efficiency of PVB-SH nanogel for mercury gradually increased with the increase of mercury concentration. ce In the range from 0 to 50 mg / L, the adsorption capacity of mercury by PVB-SH increased rapidly from 0 to 258.45 mg / g. c e With further increases in temperature, the mercury adsorption capacity slowly increases until it reaches equilibrium, reaching a maximum adsorption capacity of 342.02 mg / g. Increasing temperature promotes mercury adsorption. When the temperature is increased from 25°C to 45°C, the maximum mercury adsorption capacity of PVB-SH increases to 380.55 mg / g, indicating that mercury adsorption by PVB-SH is an endothermic reaction. The disorder of the solid-liquid system is thermodynamically favorable, and adsorption can be promoted by increasing temperature.

[0071] (4) Influence of coexisting ions

[0072] For the interference test of coexisting metal ions, the amount of adsorbent added was 0.2 g / L, the concentration of each heavy metal was 10 mg / L, the adsorption time was 24 h, the solution pH was 5, and the test temperature was 25°C. Figure 9 As shown, in Na + , Ca 2+ Mg 2+ , Pb 2+ 、Cu 2+ 、Cd 2+ 、Ni 3+ 、Zn 2+ and Mn 2+ When 9 common metal ions coexist, PVB-SH can still effectively remove mercury from water, with a removal rate of 99.98%. PVB-SH shows extremely high selectivity for the adsorption of mercury, with a distribution coefficient of K d Up to 3.07×10 7 , 3 orders of magnitude higher than other metal ions ( Figure 10 ).

[0073] The adsorbent addition amount for the coexisting anion interference test was 0.2 g / L, the anion concentration was 10-1000 mg / L, the adsorption time was 24 h, the solution pH was 5, and the test temperature was 25°C. Figure 11 As shown, PVB-SH showed little impact on mercury removal under low anion coexistence conditions (10 mg / L), achieving a removal efficiency exceeding 99.9%. However, under high anion coexistence conditions (1000 mg / L), PVB-SH's mercury removal efficiency decreased slightly, but remained above 96%. Coexisting ion interference tests demonstrated that PVB-SH exhibited excellent resistance to interference from metal cations and common anions in mercury removal.

[0074] (5) Stability analysis

[0075] 50 mg of PVB-SH was immersed in 10 mL of tap water, 1 mmol / L NaOH, 10 mmol / L NaOH, 0.1 mol / L NaCl, 1 mol / L NaCl, 0.1 mol / L HCl, and 1 mol / L HCl solutions for 45 days, and then the mercury removal efficiency was tested. The results showed that PVB-SH maintained a high mercury removal efficiency of over 99.9% ( Figure 12 XPS chemical composition analysis showed that the elemental composition and thiol functional groups of PVB-SH did not change significantly after long-term exposure to tap water and corrosive fluid, indicating that PVB-SH has strong stability ( Figure 13 ).

[0076] (6) Renewability

[0077] The good chemical stability of PVB-SH gives it excellent regeneration. After adsorbing mercury, PVB-SH can be efficiently regenerated in an acidic solution of thiourea. Figure 14 As shown in the figure, after 10 regenerations, the mercury removal efficiency of PVB-SH was almost unchanged, with a removal rate of 99.58%. After 10 regenerations, the microstructure and chemical composition of PVB-SH changed significantly ( Figure 15 ), demonstrating its good reproducibility and structural stability.

[0078] 3. The thiol-polymer nanogel PVB-SH prepared in Examples 1 to 5 and Comparative Examples 1 to 5 was used as an adsorbent to adsorb mercury. The amount of adsorbent added was 0.2 g / L, the mercury concentration was 5-300 mg / L, the adsorption time was 24 h, the solution pH was 5, and the adsorption equilibrium was reached at 25°C. The maximum adsorption capacity of mercury by the thiol-polymer nanogel PVB-SH prepared in each Example is as follows:

[0079]

[0080] From the above table, we can see that (1) excess sodium hydrosulfide is beneficial to increase the adsorption capacity of mercury by the adsorbent, and at the same time, the adsorption capacity of mercury by the adsorbent increases with the increase of the mass of sodium hydrosulfide. Figure 4 It can be seen that when the chlorinated hydrocarbons in Example 1 are completely converted into thiol groups, when the mass ratio of sodium hydrosulfide to PVB-Cl is greater than 3:1, the mercury adsorption amount is slightly increased. This is because sodium hydrosulfide has a certain degradation effect on the thiol-modified polymer nanogel PVB-SH, which can increase its specific surface area and porosity. After research, it was found that when the mass ratio of sodium hydrosulfide to PVB-Cl exceeds 6:1, the solubility of sodium hydrosulfide reaches a supersaturated state, and the mercury adsorption amount of the obtained thiol-modified polymer nanogel PVB-SH no longer increases significantly.

[0081] (2) Excessive cross-linking agent will affect the adsorption effect of the adsorbent on mercury, because excessive cross-linking agent will hinder the diffusion of mercury into the adsorbent, thereby affecting the adsorption amount of mercury.

[0082] Finally, it should be noted that the above embodiments of the present invention are merely examples for illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations and modifications can be made based on the above description. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solution of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a thiol-polymer nanogel, characterized in that: The mixed liquid obtained by dissolving a halogenated olefin monomer, a crosslinking agent and an initiator is an oil phase, and an aqueous solution of a surfactant is an aqueous phase. Under nitrogen protection, the oil phase is added to the aqueous phase and stirred to obtain an oil-in-water microemulsion, which is then heated to initiate free radical polymerization to obtain a halogenated polymer nanogel. Under nitrogen protection, sulfhydride reacts with the halogenated polymer nanogel to thiolate the halogenated polymer nanogel, thereby obtaining a thiolated polymer nanogel.

2. The method for preparing a thiol-polymer nanogel according to claim 1, wherein: The specific steps include: (1) A halogenated olefin monomer, a crosslinking agent, and an initiator are mixed and dissolved to obtain an oil phase, a surfactant is dissolved in water to obtain an aqueous phase, and then the oil phase is added to the aqueous phase, nitrogen is introduced to exclude air, and the mixture is stirred for 10-60 min to obtain an oil-in-water microemulsion; the molar ratio of the halogenated olefin monomer, the crosslinking agent, and the initiator in the oil phase is 100:0.1:1-100:1:1; the mass concentration of the surfactant in the aqueous phase is 0.4%; and the volume ratio of the oil phase to the aqueous phase is 1:10; (2) The oil-in-water microemulsion was heated to 60-80 °C and reacted for 4 h, and then centrifuged, washed, and dried to obtain the halogenated polymer nanogel; (3) Under nitrogen protection, the halogenated polymer nanogel and sulfhydride are dissolved in anhydrous ethanol, and then reacted at 75°C to convert the halogenated hydrocarbons in the halogenated polymer nanogel into thiol groups. After the reaction is completed, the thiol-containing polymer nanogel is obtained by centrifugation, washing and drying.

3. The method for preparing a thiol-polymer nanogel according to claim 2, wherein: In step (3), a phase transfer catalyst is added during the reaction between the hydrosulfide and the halogenated polymer nanogel. The phase transfer catalyst is tetrabutylammonium bromide, and the amount of the phase transfer catalyst is 0.4-1 wt% of the total mass of the hydrosulfide and the halogenated polymer nanogel.

4. The method for preparing a thiol-polymer nanogel according to claim 1, 2 or 3, wherein: The halogenated olefin monomer is chloromethylstyrene.

5. The method for preparing a thiol-modified polymer nanogel according to claim 1, 2 or 3, wherein: The crosslinking agent is one or more of divinylbenzene, allyl methacrylate and triallyl isocyanurate.

6. The method for preparing a thiol-polymer nanogel according to claim 5, wherein: The cross-linking agent is divinylbenzene.

7. The method for preparing a thiol-polymer nanogel according to claim 1, 2 or 3, characterized in that: The initiator is one or more of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate and methyl ethyl ketone peroxide.

8. The method for preparing a thiol-polymer nanogel according to claim 7, wherein: The initiator is azobisisobutyronitrile.

9. The method for preparing a thiol-modified polymer nanogel according to claim 1, 2 or 3, wherein: The surfactant is one or more of sodium lauryl sulfate, Tween 80 and dodecyltrimethylammonium bromide.

10. The method for preparing a thiol-polymer nanogel according to claim 9, characterized in that: The surfactant is sodium lauryl sulfate.

11. The method for preparing a thiol-polymer nanogel according to claim 1, 2 or 3, characterized in that: The hydrosulfide is one of sodium hydrosulfide and potassium hydrosulfide; and the mass ratio of the hydrosulfide to the halogenated polymer nanogel is 2-6:

1.

12. A thiol-polymer nanogel, characterized in that: The nanogel is prepared by the method for preparing a thiol-polymer nanogel according to any one of claims 1 to 11.

13. Use of the thiol-polymer nanogel according to claim 12 in removing mercury from water.

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