Ionic liquid-cellulose-based carbon material and application thereof in gaseous iodine adsorption

Abstract

The invention discloses an ionic liquid-cellulose-based carbon material and application thereof in gaseous iodine adsorption. The carbon material is prepared from cellulosic fibers and ionic liquid as raw materials. The preparation method comprises the following steps: mixing and stirring cellulose fibers and an ionic liquid to form a gel-like solid-liquid two-phase mixture, then carrying out high-temperature carbonization at 350-500 DEG C under the protection of inert gas, carrying out constant-temperature carbonization for 1-2 hours, cooling to room temperature, and collecting a blocky product, namely a target carbon material; the diameter of the cellulose fiber is 20-70 nm, the length of the cellulose fiber is 1-10 [mu] m, and the ionic liquid is cyano-containing ionic liquid; the dosage mass ratio of the cellulose fiber to the ionic liquid is (6-9): 10. The carbon material is simple in preparation method and low in energy consumption, iodine-loving active groups are introduced into the carbon material in the preparation process, and the carbon material has efficient and large-capacity iodine adsorption performance when being used as an iodine adsorbent.

Description

Technical Field

[0001] This invention relates to the field of radioactive iodine adsorption carbon materials, and in particular to an ionic liquid-cellulose-based carbon material and its application in gaseous iodine adsorption. Background Technology

[0002] With the ever-increasing demand for energy due to societal development, nuclear energy, characterized by its cleanliness, efficiency, and stability, is one of the important energy sources for addressing current and future energy shortages. However, while the development and utilization of nuclear energy has solved the energy crisis and brought enormous economic and social benefits, it also results in the generation and release of radioactive nuclear waste (nuclides). Among these, radioactive iodine is considered one of the most hazardous radionuclides due to its high yield, high radioactivity, high chemical toxicity, and high mobility. Environmental monitoring following major nuclear accidents has consistently shown that radioactive iodine exists primarily in gaseous form and as elemental iodine (I2) as its final chemical state. Iodine is easily volatilized at high temperatures, diffuses, and settles on soil surfaces or dissolves in water, damaging the environment and biological tissues. It can also enter the human body through the food chain or respiration, selectively accumulating in the thyroid gland and causing various thyroid diseases and even cancer. To prevent radioactive iodine generated during nuclear energy utilization from harming the environment and humans, it is essential to enrich and properly dispose of it.

[0003] Currently, liquid absorption and solid adsorption methods are mainly used for the enrichment of radioactive iodine. Among these, solid adsorption is widely studied and applied due to its ease of operation and post-processing. Researchers are continuously exploring green and environmentally friendly preparation methods to prepare new solid adsorption materials with excellent iodine adsorption performance, such as carbon materials, covalent organic frameworks (COFs), and metal-organic frameworks (MOFs). Carbon materials, compared to other materials, have advantages such as low cost, wide availability of raw materials, ease of modification, and ease of mass production. Traditional preparation methods for carbon materials mainly include template methods, sol-gel methods, and impregnation methods. These methods involve post-processing steps such as template and solvent removal, which can easily generate secondary pollution and are energy-intensive. Furthermore, the adsorption rate and capacity of the prepared carbon materials for radioactive iodine still need improvement. Especially in emergency iodine treatment scenarios requiring rapid response, carbon materials must have a very high adsorption rate for iodine in the initial adsorption stage. Therefore, exploring strategies to effectively reduce energy consumption and secondary pollution while improving the iodine adsorption rate of carbon materials is of great significance. Summary of the Invention

[0004] To address the problems of high energy consumption and low iodine adsorption rate in the preparation process of current carbon materials for radioactive iodine adsorption, this invention provides an ionic liquid-cellulose-based carbon material, which is a doped carbon material for gaseous iodine adsorption.

[0005] The ionic liquid-cellulose-based carbon material provided by this invention is prepared from cellulose fiber (CF) and ionic liquids (ILs) as raw materials. Renewable biomass cellulose fiber serves as the carbon source, and the green solvent ionic liquid serves as the nitrogen source and dispersion medium. Utilizing the characteristic that a hydrogen bond network can be formed between cellulose fiber and ionic liquid, a gel-like solid-liquid two-phase mixture is obtained through physical mixing. This mixture consists of a cellulose fiber skeleton and ionic liquid filling the gaps between the cellulose fiber skeleton. Further carbonization of this mixture yields a doped carbon material.

[0006] The specific preparation steps are as follows: Cellulose fibers are mixed with an ionic liquid and stirred at 40-70 rpm for 10-15 min to form a gel-like solid-liquid two-phase mixture. The solid-liquid two-phase mixture is then carbonized at high temperature under an inert gas atmosphere at 350-500℃ for 1-2 h. After cooling to room temperature, the product is collected and ground into powder, which is the carbon material.

[0007] The ionic liquid is a cyanide-containing ionic liquid.

[0008] The cellulose fibers have a diameter of 20-70 nm and a length of 1-10 μm.

[0009] The mass ratio of the cellulose fiber to the ionic liquid is (6-9):10.

[0010] Preferably, the ionic liquid is 1-(3-cyanopropyl)-3-methylimidazolium dicyandiamide salt ([C3CNmim][N(CN)2]), 1-cyanomethyl-3-methylimidazolium dicyandiamide salt ([MCNIM][N(CN)2]), 1-(3-cyanopropyl)-3-methylpyridinium dicyandiamide salt ([C3CNpy][N(CN)2]), 1-cyanomethyl-3-methylpyridinium dicyandiamide salt ([MCNpy][N(CN)2]), or 1-cyanomethyl-3-methylimidazolium chloride salt ([C3CNpy][N(CN)2]). MCNIM-Cl), 1-cyanomethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt (MCNIM-Tf2N), 1,3-bis(cyanomethyl)imidazolium chloride salt (BCNIM-Cl), 1,3-bis(cyanomethyl)imidazolium bis(pentafluoroethylsulfonyl)imine salt (BCNIM-beti), 1,3-bis(cyanomethyl)imidazolium bis(trifluoromethanesulfonyl)imine salt (BCNIM-Tf2N), 1-ethyl-3-methylimidazolium dicyanamide salt (EMIM-dca), 1-butanediol 3-methylpyridinium dicyanamide (3MBP-dca), 1-ethyl-3-methylimidazolium tricyanomethane (EMIM-tcm), 1-butyl-3-methylimidazolium tricyanomethane (BMIM-tcm), 1-ethyl-3-methylimidazolium tetracyanoborate (EMIM-tcb), 3-cyanomethylthiazolium bromide (CNThia-Br), 3-methylthiazolium dicyanamide (MThia-dca), 1-vinyl-3-ethylimidazolium dicyanamide (EVIM- The following are all of the following: dca), poly(1-vinyl-3-ethylimidazolium) dicyandiamide (PEVIM-dca), poly(1-allyl-3-vinylimidazolium) dicyandiamide (PAVIM-dca), poly(1-allyl-4-vinylpyridinium) dicyandiamide (PAV-dca), poly(1-cyanomethyl-3-vinylimidazolium) bromide (PCMVIM-Br), and poly(1-cyanomethyl-3-vinylimidazolium) bis(trifluoromethanesulfonyl)imide (PCMVIM-Tf2N).

[0011] These ionic liquids facilitate the formation of hydrogen bond networks between cellulose fibers. The heteroatom content in carbon materials can be controlled by changing the chemical structure of the ionic liquid.

[0012] Preferably, the cellulose fibers are carboxylated cellulose nanofibers with a diameter of 50 nm and a length of 1-3 μm, and the ionic liquid is [C3CNmim][N(CN)2]. The mass ratio of carboxylated cellulose nanofibers to ionic liquid is 4:5.

[0013] The preparation method of the ionic liquid [C3CNmim][N(CN)2] is as follows: 4-Chloroprene was added to 1-methylimidazole and refluxed at 80°C for 24 h. Then, ethyl acetate was added to the mixed solution to wash away the residual raw material. Finally, the residual solvent was removed by vacuum drying to obtain a reddish-brown solid intermediate [C3CNmim][Cl]. [C3CNmim][Cl] was dissolved in deionized water and sodium dicyandiamide was added under stirring. The reaction was continued for 4 h. After the reaction, acetonitrile was used to precipitate the solution. The filtrate was filtered and vacuum dried to remove the residual solvent to obtain the ionic liquid [C3CNmim][N(CN)2].

[0014] This invention also provides applications of the above-mentioned ionic liquid-cellulose-based carbon material: acting as a gaseous iodine adsorbent, especially for rapid and efficient adsorption of radioactive iodine in emergency radioactive iodine treatment scenarios requiring rapid response.

[0015] Compared with the prior art, the advantages of the present invention are: (1) In the carbon material preparation method of the present invention, the cellulose fiber has a certain aspect ratio. By mixing and stirring the cellulose fiber and the ionic liquid, the cellulose fiber builds a three-dimensional network structure with each other. At the same time, the ionic liquid molecules fully penetrate and fill the three-dimensional network structure of the cellulose fiber, that is, the ionic liquid is "locked" in the network structure, which lays a uniform precursor foundation for subsequent synergistic high-temperature carbonization.

[0016] (2) This invention provides a post-process for preparing heteroatom-doped carbon materials with high iodine adsorption performance without post-processing. This process eliminates post-processing steps such as template removal and solvent removal, which are prone to secondary pollution and high energy consumption. Compared with traditional carbon material preparation methods, the preparation method of this invention simplifies the preparation steps, reduces pollution and energy consumption, and is a greener and more environmentally friendly method for preparing carbon materials.

[0017] (3) While simplifying the carbon material preparation process, this invention introduces uniformly distributed heteroatoms and abundant π-conjugated systems into the carbon material to obtain doped carbon materials with rapid and efficient iodine adsorption performance.

[0018] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 SEM images of carbon materials prepared at different carbonization temperatures are shown. (a), (b), (c), and (d) are SEM images of products C-350, C-400, C-450, and C-500, respectively.

[0020] Figure 2 This is an elemental surface scan of carbon material C-350.

[0021] Figure 3 This is an elemental surface scan of carbon material C-400.

[0022] Figure 4 This is an elemental surface scan of carbon material C-450.

[0023] Figure 5 This is an elemental surface scan of carbon material C-500.

[0024] Figure 6 Fourier transform infrared spectra of ionic liquids and cellulose fibers.

[0025] Figure 7 Fourier transform infrared spectra of carbon materials prepared under different carbonization conditions.

[0026] Figure 8 Raman spectra of carbon materials prepared under different carbonization conditions.

[0027] Figure 9 Curves showing the change in gaseous iodine adsorption capacity over time for carbon materials prepared under different carbonization conditions.

[0028] Figure 10 The graphs show the changes in gaseous iodine adsorption capacity over time for single cellulose char and single ionic liquid char.

[0029] Figure 11 The images show the Raman spectra of carbon material C-400 before and after adsorption of gaseous iodine.

[0030] Figure 12 This is a graph showing the recyclability and adsorption performance of carbon material C-400. Detailed Implementation

[0031] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0032] Example 1 Preparation method of ionic liquid [C3CNmim][N(CN)2]: Step (1): Add 4-chlorobutyronitrile to 1-methylimidazole, reflux and stir at 80°C for 24 h, then add ethyl acetate to the mixed solution to wash away the residual raw material, and finally vacuum dry to remove the residual solvent to obtain the reddish-brown solid intermediate [C3CNmim][Cl].

[0033] Step (2): Dissolve [C3CNmim][Cl] in deionized water, add sodium dicyandiamide while stirring, and continue stirring for 4 h. After the reaction, precipitate with acetonitrile, filter, and dry the filtrate under vacuum to remove residual solvent, obtaining the ionic liquid [C3CNmim][N(CN)2]. The molar ratio of 1-methylimidazole, 4-chlorobutyronitrile, and sodium dicyandiamide is 1:1.2:1.2.

[0034] The chemical reactions involved in the two steps are as follows:

[0035]

[0036] Example 2 A method for preparing ionic liquid-cellulose-based carbon materials: Step (1): At room temperature, 0.80 g of carboxylated cellulose nanofibers with a diameter of 50 nm and a length of 1-3 μm were dispersed in 1.00 g of [C3CNmim][N(CN)2] prepared in Example 1, and stirred at 50 rpm for 10 min to obtain a gel-like solid-liquid two-phase mixture, which was used as a precursor and named ILs-CF. This step ensured that the ionic liquid fully penetrated and filled the three-dimensional network formed by the cellulose fibers, laying the foundation for obtaining uniform heteroatom doping in the subsequent carbonization.

[0037] Step (2): Transfer the obtained ILs-CF to an alumina crucible and heat it in a tube furnace under a nitrogen atmosphere (flow rate 60 mL·min). 1 ) at 2℃·min 1 The heating rate was increased from room temperature to 350℃ and held constant for 60 min. After cooling to room temperature, the block product was collected, which is the target product, ionic liquid-cellulose-based carbon material, i.e., a doped carbon material, named C-350.

[0038] In step (2), the carbonization temperature was changed to 400℃, 450℃ and 500℃ respectively, and the carbon materials were finally named C-400, C-450 and C-500 respectively.

[0039] In this embodiment, the preferred mass ratio of cellulose fiber to ionic liquid is 4:5. From the perspective of preparing gel-like solid-liquid two-phase mixtures, if the ratio is lower than 3:5, the mixture has low viscosity and is in a fluid state, making it difficult to form and separate from the mixing container. If the ratio is higher than 9:10, the amount of cellulose fiber exceeds the saturated dispersion of the ionic liquid, causing the cellulose fiber to aggregate, and the resulting two-phase mixture system is prone to breakage and collapse.

[0040] The performance of the carbon material prepared in Example 2 was tested as follows: (1) Figure 1 SEM images of carbon materials prepared at different carbonization temperatures are shown, where (a), (b), (c), and (d) are SEM images of products C-350, C-400, C-450, and C-500, respectively. The C-350 surface is smooth and dense, indicating that the precursor mainly underwent a homocrystalline transformation and partial carbonization at this temperature. When the temperature rises to 400℃, the precursor material undergoes violent pyrolysis, releasing a large amount of small-molecule gas, thus forming a rough surface composed of numerous carbon nanoparticles. With further increases in temperature, these carbon nanoparticles exhibit a tendency to increase in size and melt (Figures c and d). Therefore, the SEM results show that the carbonization process (carbonization temperature) affects the surface structure of the carbon material.

[0041] (2) Figure 2-5 These are elemental surface scans of carbon materials prepared at different carbonization temperatures. The figures show that the C, N, and O signals are uniformly distributed in all carbonization products. This indicates that the solid-liquid two-phase mixture formed by the ionic liquid and cellulose fibers successfully and uniformly fixes N and O heteroatoms onto the carbon framework after carbonization, proving that the preparation strategy of direct carbonization of solid-liquid two-phase mixtures can effectively achieve uniform doping of heteroatoms.

[0042] (3) Figure 6 These are Fourier transform infrared spectra of the two raw materials (ionic liquid and cellulose fiber). Figure 7 These are Fourier transform infrared spectra of carbon materials prepared at different carbonization temperatures. It can be seen that after high-temperature carbonization, at 1449 cm⁻¹... 1 The appearance of new bands, attributed to the vibration of the CNC skeleton, indicates the presence of a CN-loop network. At 1049 cm⁻¹ 1 The peak at 1616 cm⁻¹ corresponds to the stretching vibration of CO, inherited from the cellulose cellulose polysaccharide backbone. 1 The nearby peaks belong to the C=C / C=N stretching vibrations in the heterocyclic network. The above analysis indicates that the carbonization of cellulose fibers and ionic liquids together forms a nitrogen- and oxygen-containing heterocyclic network. When the carbonization temperature exceeds 400℃, the peak shapes of the aforementioned main characteristic peaks no longer change drastically, indicating that the molecular structure of the carbon material tends to stabilize.

[0043] (4) Doping carbon materials with N and O atoms will introduce defects. Defect information is usually analyzed using Raman spectroscopy. The relative intensity ratio of the D band and the G band is usually determined by the difference between the two bands. D / I G Assess the degree of structural defects in carbon materials. Figure 8These are Raman spectra of carbon materials prepared at different carbonization temperatures. It can be seen that C-350, C-400, C-450, and C-500 show high values ​​at 1350 and 1565 cm⁻¹. 1 The vicinity shows D and G bands. The D and G band signal intensities of the C-350 sample are extremely weak, indicating incomplete carbonization at 350℃ and insufficient carbon framework formation, making it difficult to accurately calculate its Ig. D / I G The ratio. Samples C-400, C-450, and C-500 all exhibit typical Raman characteristic peaks of carbon materials, with I... D / I G The ratios were 1.31, 1.20, and 1.16, respectively, i.e., I D / I G The ratio gradually decreases with increasing temperature. The C-400 sample has the highest Ig ratio. D / I G The ratio (1.31) indicates that its carbon framework is rich in edge defects and heteroatom doping sites, although I increases with increasing carbonization temperature. D / I G The value gradually decreased to 1.16, but remained greater than 1, indicating that defect-rich doped carbon materials were successfully prepared within the temperature range of 400–500 °C. Raman spectroscopy analysis also showed that the carbonization temperature significantly affected the degree of defects in the doped carbon materials.

[0044] (5) Test of gaseous iodine adsorption performance For safety reasons, non-radioactive materials are used. 127 I. To simulate radioactive iodine isotopes, a gaseous iodine adsorption experiment was conducted using a gravimetric method, employing a triple parallel experiment to reduce experimental error. Approximately 20 mg of carbon material and excess elemental iodine particles were placed separately into two open-mouthed small glass bottles (5 mL each). These two small glass bottles were then placed into a screw-top glass bottle (100 mL). The screw-top bottle was sealed and placed in an 80°C, atmospheric pressure oven for a certain period of adsorption. After cooling the screw-top bottle to room temperature, the small glass bottle containing the sample was removed and weighed. The above operation was repeated.

[0045] The gaseous iodine adsorption properties of carbon materials obtained at different carbonization temperatures and the original cellulose fibers (CF) are as follows: Figure 9 As shown, the iodine saturation adsorption capacities of cellulose fibers (CF), C-350, C-400, C-450, and C-500 are 0.07 g·g⁻¹. 1 6.71 g·g 1 6.16 g·g 1 5.74 g·g 1 and 5.48 g·g 1 The carbon materials reached adsorption equilibrium within 48 hours. Although C-350 exhibited the highest adsorption performance, the carbon particles transformed into a high-viscosity crystalline state after adsorption, indicating incomplete carbonization, which is consistent with the aforementioned Raman spectroscopy characterization results. C-400, on the other hand, maintained a good solid state while exhibiting good adsorption performance. Considering all factors, the carbonization conditions of C-400 were selected as the optimal process conditions for preparing this type of carbon material, and C-400 was used for subsequent cyclic experiments and adsorption mechanism characterization.

[0046] In comparison, in this embodiment, single carboxylated cellulose nanofibers and single [C3CNmim][N(CN)2] were used as raw materials and carbonized at 400°C to prepare cellulose char (denoted as CF-400) and ionic liquid char (denoted as ILs-400), respectively. The gaseous iodine adsorption performance of these two char materials was tested, and the results are shown in […]. Figure 10 The saturated adsorption capacities of CF-400 and ILs-400 for gaseous iodine were 7.70 g·g⁻¹, respectively. 1 and 6.82 g·g 1 Although the iodine adsorption capacities of CF-400 and ILs-400 are higher than those of the carbon material prepared in Example 1, during the rapid adsorption phase (0-0.5 h), the adsorption capacities of CF-400 and ILs-400 are 1.85 g·g⁻¹. 1 and 2.33 g·g 1 The adsorption capacities of C-350, C-400, C-450, and C-500 during the rapid adsorption phase were 2.90 g·g⁻¹. 1 3.41 g·g 1 2.62 g·g 1 2.15 g·g 1 It is significantly better than the CF-400.

[0047] Furthermore, a pseudo-second-order kinetic model was used to fit and analyze the adsorption curves of C-350, C-400, C-450, C-500, CF-400, and ILs-400. The pseudo-second-order kinetic model is typically used to evaluate whether an adsorbent conforms to chemisorption as the dominant adsorption mode and to obtain the adsorption rate constant. k 2 (unit: g·g) 1 ·h 1 ). k A higher correlation coefficient indicates a higher adsorption rate of the adsorbent for the adsorbate (the adsorbed substance, in this case, iodine). R 2 The larger the value, the more the adsorption process conforms to the pseudo-second-order kinetic model; therefore, it is considered that the adsorption process is mainly chemisorption. The formula for the pseudo-second-order kinetic model is as follows:

[0048] in, t Adsorption time (h) q t for t The amount of adsorbent adsorbed at time (g·g) 1 ), q This represents the amount of adsorbent adsorbed at equilibrium. k 2 is the pseudo-second-order kinetic rate constant (g·g 1 ·h 1 ).

[0049] In this invention, we desire that the adsorbent used for iodine adsorption is primarily chemisorption, with physically adsorbed iodine still existing in the form of I₂, and chemisorbed iodine mainly existing in the form of I₃. and I5 Iodine exists in the form of physical adsorption. Because physically adsorbed iodine is more susceptible to desorption due to changes in the environment (such as temperature and pressure) than chemically adsorbed iodine, it can cause secondary pollution.

[0050] The results of fitting analysis of the adsorption curves of C-350, C-400, C-450, C-500, CF-400 and ILs-400 using a pseudo-second-order kinetic model are shown in Table 1.

[0051] Table 1. Results of fitting analysis of adsorption curves of C-350, C-400, C-450, C-500, CF-400, and ILs-400 using the pseudo-second-order kinetic model.

[0052] As shown in Table 1, although CF-400 exhibits the highest saturation adsorption capacity, its second-order kinetic fitting data indicates that the process is not primarily dominated by chemisorption. The high saturation adsorption capacity is likely a result of the synergistic effect of physical and chemisorption. In practical applications, physically adsorbed components are more susceptible to desorption due to changes in environmental conditions (such as temperature and pressure) compared to chemisorbed components, posing a risk of secondary pollution. Furthermore, CF-400's lower... k The 2-value also indicates that it is not suitable for emergency iodine adsorption scenarios. Additionally, the correlation coefficient of ILs-400... R 2 Although it is relatively large, its adsorption rate constant is... k The adsorption rate of the carbon materials prepared in this invention is smaller than that of the four carbon materials (C-350, C-400, C-450, and C-500) prepared in Example 2 of this invention. This indicates that, compared to ILs-400, the carbon materials prepared in this invention have a higher adsorption rate and superior chemisorption performance for iodine. Among them, C-400 has the largest adsorption rate constant, indicating that its iodine adsorption rate is the highest among this series of materials, and that it is mainly chemisorbed iodine. Therefore, in the face of iodine leakage scenarios, the carbon materials prepared in this invention (especially C-400) have the ability to respond quickly and saturate quickly, which is a key advantage of emergency adsorption materials. This is a technical effect that cannot be achieved by CF-400 and ILs-400 prepared by single materials.

[0053] In addition, the Raman spectra of carbon material C-400 before and after iodine adsorption (C-400-I2) are as follows: Figure 11 As shown, the locations are 109, 141, and 165 cm. 1 The characteristic peaks indicate that the electron-rich system of C-400 induces polarization of iodine molecules, forming a charge-transfer complex I3 through charge-transfer interactions. and I5 This further proves that the carbon material prepared by the present invention mainly adsorbs iodine by chemical adsorption.

[0054] (6) Reusability test of carbon materials The iodine release assay was performed using a gravimetric method. The carbon material, saturated with iodine adsorption, was placed in a 100°C oven. Sample vials containing the iodine were removed at different time points, cooled to room temperature, and weighed. The sample was then re-adsorbed in an 80°C oven (similar to the gaseous iodine adsorption process), and this cycle was repeated five times. The C-400's recyclability is as follows: Figure 12 As shown, after 5 desorption-resorption cycles, C-400 still maintained a concentration of 5.27 g·g⁻¹. 1The iodine adsorption capacity was 85.6% of the original, indicating that it has good recycling performance.

[0055] In summary, the iodophilic groups, including nitrogen-containing, oxygen-containing functional groups and aromatic heterocyclic rings, introduced during the carbon material preparation process of this invention can effectively improve the iodine adsorption capacity of the carbon material. Compared with traditional carbon material preparation processes, this method avoids post-processing steps such as template removal, solvent removal, and post-doping, which are prone to secondary pollution and high energy consumption, making it a relatively greener and more environmentally friendly carbon material preparation method.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An ionic liquid-cellulose-based carbon material, characterized in that, The preparation method is as follows: Cellulose fibers and ionic liquids are mixed and stirred to form a gel-like solid-liquid two-phase mixture. Then, high-temperature carbonization is carried out under inert gas protection at a carbonization temperature of 350-500℃ for 1-2 hours. After cooling to room temperature, the blocky product is collected, which is the ionic liquid-cellulose-based carbon material. The ionic liquid is a cyanide-containing ionic liquid; The mass ratio of the cellulose fiber to the ionic liquid is (6-9):

10.

2. The ionic liquid-cellulose-based carbon material as described in claim 1, characterized in that, The ionic liquid is 1-(3-cyanopropyl)-3-methylimidazolium dicyanamide salt, 1-cyanomethyl-3-methylimidazolium dicyanamide salt, 1-(3-cyanopropyl)-3-methylpyridinium dicyanamide salt, 1-cyanomethyl-3-methylpyridinium dicyanamide salt, 1-cyanomethyl-3-methylimidazolium chloride salt, 1-cyanomethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1,3-bis(cyanomethyl)imidazolium chloride salt, 1,3-bis(cyanomethyl)imidazolium bis(pentafluoroethylsulfonyl)imine salt, 1,3-bis(cyanomethyl)imidazolium bis(trifluoromethanesulfonyl)imine salt, 1-ethyl-3-methylimidazolium dicyanamide salt, 1-butyl-3-methylpyridine Any one of the following: onium dicyandiamide salt, 1-ethyl-3-methylimidazolium tricyanomethane salt, 1-butyl-3-methylimidazolium tricyanomethane salt, 1-ethyl-3-methylimidazolium tetracyanoborate, 3-cyanomethylthiazolylium bromide salt, 3-methylthiazolylium dicyandiamide salt, 1-vinyl-3-ethylimidazolium dicyandiamide salt, poly(1-vinyl-3-ethylimidazolium) dicyandiamide salt, poly(1-allyl-3-vinylimidazolium) dicyandiamide salt, poly(1-allyl-4-vinylpyridinium) dicyandiamide salt, poly(1-cyanomethyl-3-vinylimidazolium) bromide salt, and poly(1-cyanomethyl-3-vinylimidazolium)bis(trifluoromethanesulfonyl)imide salt.

3. The ionic liquid-cellulose-based carbon material as described in claim 1, characterized in that, The cellulose fibers have a diameter of 20-70 nm and a length of 1-10 μm.

4. The ionic liquid-cellulose-based carbon material as described in claim 1, characterized in that, Cellulose fibers are mixed with ionic liquid and stirred at 40-70 rpm for 10-15 min to form a gel-like solid-liquid two-phase mixture.

5. The ionic liquid-cellulose-based carbon material as described in claim 1, characterized in that, The cellulose fibers are carboxylated cellulose nanofibers with a diameter of 50 nm and a length of 1-3 μm, and the ionic liquid is 1-(3-cyanopropyl)-3-methylimidazolium dicyandiamide salt.

6. The ionic liquid-cellulose-based carbon material as described in claim 5, characterized in that, The mass ratio of cellulose fiber to ionic liquid is 4:

5.

7. The ionic liquid-cellulose-based carbon material as described in claim 5, characterized in that, The preparation method of the ionic liquid 1-(3-cyanopropyl)-3-methylimidazolium dicyandiamide salt is as follows: 4-Chloroprene was added to 1-methylimidazolium, and the mixture was refluxed and stirred at 80 °C for 24 h. Then, ethyl acetate was added to the mixed solution to wash away the residual raw materials. Finally, the residual solvent was removed by vacuum drying to obtain the reddish-brown solid intermediate 1-(3-cyanopropyl)-3-methylimidazolium chloride. 1-(3-cyanopropyl)-3-methylimidazolium chloride was dissolved in deionized water, and sodium dicyandiamide was added under stirring. The reaction was continued for 4 h. After the reaction, acetonitrile was used to precipitate the solution. The filtrate was filtered and vacuum dried to remove the residual solvent to obtain the ionic liquid 1-(3-cyanopropyl)-3-methylimidazolium dicyandiamide.

8. An application of the ionic liquid-cellulose-based carbon material according to any one of claims 1-7, characterized in that, Used as a gaseous iodine adsorbent.

9. The application of the ionic liquid-cellulose-based carbon material as described in claim 8, characterized in that, Used to adsorb radioactive iodine.

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