Adsorbent, method for preparing the same, and use thereof

Abstract

This invention relates to the field of adsorbent technology, and discloses an adsorbent, its preparation method, and its application. The adsorbent comprises a copper metal-organic framework (MOF), in which copper is linked to carboxylic acid groups to form a porous structure; graphitic carbon nitride is supported on the surface of the MOF; and bismuth is doped on the surface and within the porous structure of the MOF. The adsorbent obtained by this invention exhibits good adsorption capacity for radioactive iodine.

Description

Technical Field

[0001] This invention relates to the field of adsorbent technology, and in particular to an adsorbent, its preparation method, and its application. Background Technology

[0002] With social and economic development, nuclear energy has become one of the most powerful and important energy sources, and the safe and efficient discharge and disposal of nuclear waste has become a critical issue. This makes nuclear power an option for countries seeking to reduce fuel shortages and fuel consumption while minimizing their impact on climate change. Radioactive iodine, produced by the nuclear fission of uranium-235, is used worldwide for nuclear accident protection, underground mineral discovery and pipeline leak detection, medical diagnosis and treatment, and food preservation. Clearly, radioactive iodine plays a significant role; however, it can also accumulate through the food chain, ultimately leading to cell mutations and increased cancer risk, posing a serious threat to human health.

[0003] Radioactive waste management remains a challenge, requiring innovative solutions to minimize its harmful environmental and health impacts. To this end, several different types of adsorbents have been developed to effectively capture and store volatile radioactive iodine, including activated carbon, silver-exchanged zeolite (AgZ), aerogels, layered double hydroxides, covalent organic frameworks, and metal-organic frameworks (MOFs). However, their ability to capture radioactive iodine remains relatively poor. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an adsorbent, its preparation method, and its application. The adsorbent obtained by this invention exhibits good adsorption capacity for radioactive iodine.

[0005] This invention provides an adsorbent comprising a copper metal-organic framework, wherein copper in the copper metal-organic framework is linked with carboxylic acid groups to form a porous structure; graphitic carbon nitride (g-C3N4) is supported on the surface of the copper metal-organic framework; and bismuth is doped on the surface and within the porous structure of the copper metal-organic framework.

[0006] Furthermore, the bismuth is doped on the surface and within the porous structure of the copper metal-organic framework, existing in the form of Bi-N bonds.

[0007] The present invention also provides a method for preparing the adsorbent, the method comprising:

[0008] A copper source solution and a 1,3,5-benzenetricarboxylic acid solution were mixed to obtain a mixed solution. Graphite-phase carbon nitride was added to the mixed solution and mixed thoroughly. Solid-liquid separation was performed, followed by a single washing. The solid was then dried to obtain an intermediate product (Cu-BTC@g-C3N4). The intermediate product was placed in an organic solvent, and then a bismuth source was added. The mixture was ultrasonically treated, followed by solid-liquid separation, a second washing, and drying to obtain the adsorbent (Bi / Cu-BTC@g-C3N4).

[0009] Furthermore, the molar concentration of the copper source solution, calculated as copper ions, is 0.3 mol / L.

[0010] Furthermore, the mass concentration of the 1,3,5-benzenetricarboxylic acid solution is 35 g / L.

[0011] Furthermore, the volume ratio of the copper source solution to the 1,3,5-benzenetricarboxylic acid solution is 1:1.

[0012] Furthermore, the specific preparation method of the 1,3,5-benzenetricarboxylic acid solution includes: dissolving 1,3,5-benzenetricarboxylic acid in anhydrous ethanol.

[0013] Furthermore, the specific preparation method of the copper source solution includes: dissolving the copper source in deionized water.

[0014] Furthermore, after the mixture is homogeneous, the mass concentration of graphitic carbon nitride is 20 mg / 24 mL to 35 mg / 24 mL.

[0015] Furthermore, after the mixture is homogeneous, the mass concentration of graphitic carbon nitride is 24 mg / 24 mL to 26 mg / 24 mL.

[0016] Furthermore, the drying temperature is 50℃-70℃, and the drying time is 17h-19h.

[0017] Furthermore, the drying process employs a vacuum drying oven.

[0018] Those skilled in the art should understand that solid-liquid separation can be carried out by centrifugation. Therefore, those skilled in the art can adjust the centrifugation speed and time according to actual needs, as long as the effect of solid-liquid separation can be achieved.

[0019] Furthermore, each wash involves washing with deionized water and anhydrous ethanol 3-5 times in sequence.

[0020] Furthermore, the mass ratio of the bismuth source to the intermediate product is 30%-50%.

[0021] Furthermore, the intermediate product has a mass concentration of 0.1 g / 20 mL in the organic solution.

[0022] Furthermore, the ultrasonic treatment time is 10-15 minutes.

[0023] Furthermore, the secondary washing involves rinsing with methanol at least three times.

[0024] Furthermore, the organic solvent includes methanol.

[0025] Furthermore, the copper source includes one or more of copper nitrate and copper nitrate trihydrate.

[0026] Furthermore, the bismuth source includes bismuth nitrate pentahydrate (Bi(NO3)3·5H2O).

[0027] The present invention also provides the application of the adsorbent in the adsorption of radioactive iodine.

[0028] The embodiments of the present invention have the following technical effects:

[0029] 1. The adsorbent of this invention exhibits good adsorption effect on radioactive iodine. Firstly, the copper metal-organic framework serves as the substrate of the adsorbent structure, ensuring the stability of the entire adsorbent structure. The copper metal-organic framework has a porous structure, which increases the specific surface area of ​​the adsorbent. 1,3,5-phenyltricarboxylic acid in the porous structure can capture iodine molecules through hydrogen bonds, thereby enhancing the adsorbent's adsorption capacity for iodine. The graphitic carbon nitride supported on the copper metal-organic framework increases the adsorption space of the entire adsorbent, enhancing its physical adsorption. Bismuth is doped into the plane of the copper metal-organic framework, existing not only as Bi-N bonds, which enhances the adsorbent's chemical adsorption but also its thermal stability.

[0030] 2. In this invention, to improve the adsorption effect of the adsorbent without damaging its structure, the physical adsorption capacity of the adsorbent is enhanced. This is achieved by adjusting the content of graphitic carbon nitride adsorbed on the surface of the copper metal-organic framework. The addition of graphitic carbon nitride in this method significantly improves the physical adsorption capacity of the adsorbent without damaging the binding sites on the surface of the copper metal-organic framework, thus ensuring bismuth doping. Furthermore, the bismuth doping amount is further adjusted to improve the chemical adsorption capacity and thermal stability of the adsorbent.

[0031] 3. The method of the present invention is simple and easy to implement, and can be industrialized. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 (a)- Figure 1 (b) is the XRD pattern provided in the embodiments and comparative examples of the present invention.

[0034] Figure 2 (a)- Figure 2 (b) is the Fourier transform infrared spectrum provided in the embodiments and comparative examples of the present invention.

[0035] Figure 3 (a) shows the morphology of Cu-BTC. Figure 3 (b) shows the morphology of g-C3N4. Figure 3 (c) shows the morphology of g-C3N4 loaded on the Cu-BTC surface. Figure 3 (c1)- Figure 3 (c3) is the morphology of g-C3N4 loaded on the Cu-BTC surface.

[0036] Figure 4 (a)- Figure 4 (d) shows the morphology of Embodiment 1 of the present invention.

[0037] Figure 5 This is the EDS elemental analysis chromatogram after iodine adsorption in Example 1, where, Figure 5 (d1) is the distribution map of element O. Figure 5 (d2) is the distribution map of Cu element. Figure 5 (d3) is the distribution map of element N. Figure 5 (d4) is the distribution map of Bi element. Figure 5 (d5) is the distribution diagram of C elements. Figure 5 (d6) is the distribution map of element I. Figure 5 (d7) is a distribution map of all elements.

[0038] Figure 6 (a) shows the thermogravimetric analysis (TGA), differential thermal analysis (DTA), and derivative thermogravimetric analysis (DTG) of Cu-BTC; Figure 6 (b) Thermogravimetric analysis (TGA), differential thermal analysis (DTA), and derivative thermogravimetric analysis (DTG) of 40%Bi-CNM-25; Figure 6 (c) shows the thermogravimetric analysis (TGA), differential thermal analysis (DTA), and derivative thermogravimetric analysis (DTG) of Cu-BTC after iodine adsorption. Figure 6 (d) shows the thermogravimetric analysis (TGA), differential thermal analysis (DTA), and derivative thermogravimetric analysis (DTG) of 40% Bi-CNM-25 after iodine adsorption.

[0039] Figure 7 These are nitrogen adsorption / desorption isotherm data for the examples and comparative examples.

[0040] Figure 8 This is the XPS spectrum of 40% Bi-CNM-25 before adsorption of iodine ions, where... Figure 8 (a) is the XPS spectrum of O 1S. Figure 8 (b) is the XPS spectrum of C1S. Figure 8 (c) is the XPS spectrum of Cu 2P. Figure 8 (d) is the XPS spectrum of Bi 4f.

[0041] Figure 9 (a) shows the XPS spectra of 40% Bi-CNM-25 before and after adsorption of iodine ions. Figure 9 (b) is the XPS plot of I 3d.

[0042] Figure 10 (a) shows the iodine removal rate in the examples and comparative examples. Figure 10 (b) shows the adsorption capacity of the examples and comparative examples for iodine. Figure 10 (c) shows the adsorption capacity of the examples and comparative examples for iodine in iodine solutions of different concentrations.

[0043] Figure 11 (a) shows the adsorption capacity of the examples and comparative examples for iodine. Figure 11 (b) shows the adsorption capacity of the examples and comparative examples for iodine.

[0044] Figure 12 (a) is the capacity of iodine adsorbed in each adsorption-desorption experiment using 40% Bi-CNM-25; Figure 12 (b) is a physical diagram of the adsorption-desorption experiment.

[0045] Figure 13 (a) shows the adsorption capacity of 40% Bi-CNM-25 for iodine under different pH conditions. Figure 13 (b) shows the effect of anions on the adsorption of iodine by 40% Bi-CNM-25. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0047] In a first aspect, some embodiments of the present invention provide an adsorbent comprising a copper metal-organic framework, wherein copper in the copper metal-organic framework is connected with carboxylic acid groups to form a porous structure; graphitic carbon nitride is loaded on the surface of the copper metal-organic framework; and bismuth is doped on the surface and within the porous structure of the copper metal-organic framework.

[0048] In some embodiments, bismuth is doped on the surface and within the porous structure of a copper metal-organic framework, existing in the form of Bi-N bonds.

[0049] In this invention, bismuth exists in the form of Bi-N bonds, which can enhance the chemical adsorption capacity of the adsorbent.

[0050] Secondly, some embodiments of the present invention also provide a method for preparing the adsorbent, the preparation method comprising:

[0051] A copper source solution and a 1,3,5-benzenetricarboxylic acid solution were mixed to obtain a mixed solution. Graphite-phase carbon nitride was added to the mixed solution and mixed thoroughly. Solid-liquid separation was performed, followed by a first washing. The solid was then dried to obtain an intermediate product. The intermediate product was placed in an organic solvent, and then a bismuth source was added. The mixture was ultrasonically treated, followed by solid-liquid separation, a second washing, and drying to obtain the adsorbent.

[0052] In some embodiments, the molar concentration of the copper source solution, calculated as copper ions, is 0.3 mol / L.

[0053] In some embodiments, the mass concentration of the 1,3,5-benzenetricarboxylic acid solution is 35 g / L.

[0054] In some embodiments, the volume ratio of the copper source solution to the 1,3,5-benzenetricarboxylic acid solution is 1:1.

[0055] In some embodiments, the specific preparation method of the 1,3,5-benzenetricarboxylic acid solution includes: dissolving 1,3,5-benzenetricarboxylic acid in anhydrous ethanol.

[0056] In some embodiments, the specific preparation method of the copper source solution includes: dissolving the copper source in deionized water.

[0057] In some embodiments, after uniform mixing, the mass concentration of graphitic carbon nitride is 20 mg / 24 mL to 35 mg / 24 mL.

[0058] In some embodiments, after uniform mixing, the mass concentration of graphitic carbon nitride is 24 mg / 24 mL to 26 mg / 24 mL.

[0059] At this dosage, not only can the surface of the copper metal frame be kept unaffected, but the adsorption capacity of the adsorbent can also be improved.

[0060] In some embodiments, the drying temperature is 50°C-70°C, and the drying time is 17h-19h.

[0061] In some embodiments, the drying is performed using a vacuum drying oven.

[0062] Those skilled in the art should understand that solid-liquid separation can be carried out by centrifugation. Therefore, those skilled in the art can adjust the centrifugation speed and time according to actual needs, as long as the effect of solid-liquid separation can be achieved.

[0063] In some embodiments, a single wash involves washing with deionized water and anhydrous ethanol 3-5 times in sequence.

[0064] In some embodiments, the mass ratio of the bismuth source to the intermediate product is 30%-50%.

[0065] In some embodiments, the intermediate product has a mass concentration of 0.1 g / 20 mL in the organic solution.

[0066] In some embodiments, the ultrasonic treatment time is 10-15 minutes.

[0067] In some embodiments, the secondary washing involves rinsing with methanol at least three times.

[0068] In some embodiments, the organic solvent includes methanol.

[0069] In some embodiments, the copper source includes one or more of copper nitrate and copper nitrate trihydrate.

[0070] In some embodiments, the bismuth source includes bismuth pentahydrate.

[0071] Thirdly, some embodiments of the present invention also provide the application of the adsorbent in the adsorption of radioactive iodine.

[0072] Analysis will be conducted in conjunction with specific embodiments:

[0073] Example 1:

[0074] 0.875 g of Cu(NO3)2·3H2O was added to 12 mL of water to form solution A. 0.42 g of 1,3,5-benzenetricarboxylic acid was added to 12 mL of anhydrous ethanol, followed by 25 mg of graphitic carbon nitride under stirring for 30 minutes to form solution B. The solution was centrifuged at 8000 rpm for 4 minutes, washed four times with water and ethanol, and then vacuum-dried at 60 °C for 18 hours to obtain an intermediate. 0.1 g of the intermediate was placed in 20 mL of methanol, and then bismuth nitrate pentahydrate (30% by mass of the intermediate) was added to the above solution. The solution was ultrasonically dispersed for 15 minutes, and the precipitate obtained by centrifugation was washed three times with methanol and then vacuum-dried at 60 °C for 18 hours. This was denoted as 30%Bi-CNM-25.

[0075] Example 2:

[0076] Example 2 is the same as Example 1, except that bismuth nitrate pentahydrate is added in Example 2 at a mass ratio of 40% to the intermediate. This is denoted as: 40%Bi-CNM-25.

[0077] Example 3:

[0078] Example 3 is the same as Example 1, except that in Example 2, bismuth nitrate pentahydrate was added at a mass ratio of 50% to the intermediate. This is denoted as: 50%Bi-CNM-25.

[0079] Comparative Example 1:

[0080] 20g of melamine powder (99%, Sigma Aldrich) was calcined at 550℃ for 4 hours at a heating rate of 8℃ / min. After cooling to ambient temperature, the powder was collected and ground into a light yellow graphitic carbon nitride powder, denoted as g-C3N4.

[0081] Comparative Example 2:

[0082] Solution A was prepared by dissolving 1.94 g of Cu(NO3)2·3H2O in 24 mL of deionized water. Solution B was prepared by dissolving 0.84 g of 1,3,5-benzenetricarboxylic acid in 24 mL of anhydrous ethanol. The two solutions (A+B) were mixed and stirred at room temperature until a suspension was formed. The resulting mixture was then transferred to a Teflon-lined stainless steel autoclave and heated at 120 °C for 18 hours, followed by natural cooling to room temperature. The mixture was centrifuged at 8000 rpm for 4 minutes to separate the blue powder, which was then thoroughly washed four times with deionized water and ethanol, respectively. The powder was then vacuum dried at 60 °C for 18 hours. This is denoted as Cu-BTC.

[0083] Comparative Example 3:

[0084] 0.875 g of Cu(NO3)2·3H2O was added to 12 mL of water to form solution A. 0.42 g of 1,3,5-benzenetricarboxylic acid was added to 1 mL of anhydrous ethanol, followed by the addition of 20 mg of graphitic carbon nitride under stirring for 30 minutes to form solution B. The solution was then washed four times with water and ethanol, centrifuged at 8000 rpm for 4 minutes, and dried under vacuum at 60 °C for 18 hours. This solution is designated CNM-20.

[0085] Comparative Example 4:

[0086] 0.875 g of Cu(NO3)2·3H2O was added to 12 mL of water to form solution A. 0.42 g of 1,3,5-benzenetricarboxylic acid was added to 1 mL of anhydrous ethanol, followed by the addition of 25 mg of graphitic carbon nitride under stirring for 30 minutes to form solution B. The solution was centrifuged at 8000 rpm for 4 minutes, washed four times with water and ethanol, and then vacuum-dried at 60 °C for 18 hours. This solution is designated CNM-25.

[0087] Comparative Example 5:

[0088] 0.875 g of Cu(NO3)2·3H2O was added to 12 mL of water to form solution A. 0.42 g of 1,3,5-benzenetricarboxylic acid was added to 1 mL of anhydrous ethanol, followed by the addition of 30 mg of graphitic carbon nitride under stirring for 30 minutes to form solution B. The solution was centrifuged at 8000 rpm for 4 minutes, washed 3-5 times with water and ethanol, and then vacuum dried at 60 °C for 18 hours. This solution is designated CNM-30.

[0089] Comparative Example 6:

[0090] 0.875 g of Cu(NO3)2·3H2O was added to 12 mL of water to form solution A. 0.42 g of 1,3,5-benzenetricarboxylic acid was added to 1 mL of anhydrous ethanol, followed by the addition of 35 mg of graphitic carbon nitride under stirring for 30 minutes to form solution B. The solution was centrifuged at 8000 rpm for 4 minutes, washed four times with water and ethanol, and then vacuum-dried at 60 °C for 18 hours. This solution is designated CNM-35.

[0091] The examples and comparative examples were tested:

[0092] (1) Iodine capture and adsorption:

[0093] Considering radioactive iodine isotopes ( 131 I and 129 I) The strong radiation emitted; studies on iodine absorption and adsorption used non-radioactive methods. 127I (I2) was used as a substitute. Gravimetric analysis was employed to evaluate iodine vapor adsorption. Here, the Cu-BTC and CNM-25 complexes were activated at 120°C before weighing. Following a predetermined protocol, 50 mg of each of Examples 1-3 (x%Bi-CNM-25 (x = 30, 40, 50)) was placed in a weighing pan within a sealed glass container. Under ambient pressure, an excess of 2-3 g of iodine crystals in each sealed container was heated to 350 K (80°C) until saturation. After a specific exposure time, the cooled sample was recorded as x%Bi-CNM-25-I2 (x = 30, 40, 50) and weighed again. The amount of iodine vapor captured was calculated using the following formula:

[0094] q e =((m f -m i ) / m i )×1000;

[0095] Where q e Iodine adsorption capacity (mg / g), m i (mg) and m f (mg) represents the mass of x%Bi-CNM-25 samples (x is 30, 40, 50) before and after iodine adsorption.

[0096] (2) Adsorption of iodine in solution:

[0097] The adsorption performance of Cu-BTC and x%Bi-CNM-25 (x = 30, 40, 50) nanocomposites for iodine in cyclohexane solution was evaluated using an iodine / cyclohexane solution. The x%Bi-CNM-25 (x = 30, 40, 50) nanocomposites were pretreated and vacuum-dried at 120 °C for 6 hours to remove adsorbed moisture. The iodine solution (0.5 g / L cyclohexane solution) used in the adsorption experiments was prepared by dissolving precisely weighed iodine. 20 mg of Cu-BTC and x%Bi-CNM-25 (x = 30, 40, 50) were dispersed in 20 mL of the solution, and stirred at 150 rpm for 30 hours under isothermal conditions. Calibration curves were constructed using UV-Vis spectroscopy to correlate solution concentration with absorbance at the maximum adsorption wavelength. After adsorption, the samples were separated by centrifugation or filtration, and the residual iodine concentration in the filtrate was determined by UV-Vis spectroscopy. The adsorption capacity at equilibrium (q) was calculated. e (mg / g) is calculated using the following formula:

[0098] q e =((C0-C e )V) / M;

[0099] Among them, C0 and C eV represents the initial and post-adsorption concentrations of I2 in the cyclohexane solution (mg / L); V represents the volume of the solution (L); and M represents the mass of the adsorbent (mg).

[0100] (3) Iodine release experiment:

[0101] Iodine-containing substances are immersed in provided ethanol, and pure ethanol is used to adsorb and desorb them.

[0102] (4) Material characterization:

[0103] The morphology of the synthesized materials was examined using a scanning electron microscope (SEM, JSM-IT500HR, Japan) with an accelerating voltage of 15 kV. Elemental analysis was performed using energy-dispersive X-ray spectroscopy (EDX) on the JSM-IT500HR scanning microscope. Phase analysis was conducted using X-ray diffraction (XRD, Bruker-AS D8 Advance, Germany) with Cu-Kα as the radiation source. Infrared spectroscopy was performed using a Fourier transform infrared spectrometer (FTIR, NICOLETIS10, USA) and KBr particle technique. The chemical composition and elemental valence of the adsorbent were determined using X-ray photoelectron spectroscopy (XPS, PHI Quantera II electron spectrometer, Japan). BET surface area and pore size distribution were measured by nitrogen adsorption / desorption using a TriStar II 3020 surface area and porosity analyzer (Micromeritics, USA). All samples were degassed overnight under vacuum at 120 °C (BELSORP-MAX, Japan) before analysis. Thermogravimetric analysis (TGA) was performed on an SDTA851E thermogravimetric analyzer (Mettler-Toledo, USA) using a nitrogen flow and a heating rate of 10 °C / min. The iodine concentration in the eluent was measured using a UV-Vis spectrometer (Specord 50plus, Germany).

[0104] Results and Analysis:

[0105] Table 1. Parameters of products from Comparative Example 2 and Comparative Example 4

[0106]

[0107] Table 2 Comparison of the iodine adsorption capacity of the adsorbents in Example 3 and existing technologies

[0108]

[0109] Table 3 Model parameters of pseudo-first-order and pseudo-second-order dynamic models

[0110]

[0111] Table 4 Model parameters for Langmuir and Freundlich models

[0112]

[0113] Figure 1 (b) shows the X-ray diffraction (XRD) characterization results of the adsorbents in Comparative Examples 1-2, Comparative Example 4, and Examples 1-3. Figure 1 (a)- Figure 1 As shown in (b), the characteristic peak positions of Cu-BTC are 6.70°, 9.49°, 11.65°, 13.5°, 15.06°, 16.52°, 17.51°, 19.22°, 26.02°, and 29.39°, corresponding to the

[200] ,

[220] ,

[222] ,

[400] ,

[422] ,

[333] ,

[440] ,

[040] ,

[600] , and

[553] crystal planes, respectively, indicating that Cu-BTC was successfully prepared with high crystallinity. The diffraction patterns show that Cu-BTC material is isomorphic to copper-based MOFs (standard card CCDC 846570).

[14] The results showed that during the composite preparation process of Cu-BTC and g-C3N4, g-C3N4 did not affect Cu. 2+ and BTC 3- Coordination. Furthermore, CNM-20, CNM-25, CNM-30, and CNM-35 all exhibit strong diffraction peak intensities, from... Figure 1 (a) shows that the diffraction peak intensity of CNM-25 is more prominent than others, indicating that CNM-25 has better coordination. Therefore, CNM-25 can be used for further Bi doping to prepare the best composite material for iodine adsorption. The diffraction peaks of g-C3N4 are consistent with the standard card (JCPDS No. 87-1526). The diffraction peaks at 13.3° and 27.6° correspond to the

[100] crystal plane and the

[002] crystal plane, respectively, indicating that the preparation of g-C3N4 was successful. It is worth noting that... Figure 1 In (b), no diffraction peaks corresponding to the bismuth-based compound were found in the XRD pattern, indicating that the doped bismuth is uniformly distributed across the entire surface of the composite material, or uniformly doped within the interstices of the composite framework. The overall diffraction intensity of the adsorbent decreases with increasing bismuth content, especially in the 40%Bi-CNM-25 and 50%Bi-CNM-25 samples. These results suggest that bismuth is embedded in the plane and exists as Bi-N bonds.

[0114] Fourier transform infrared spectroscopy (FT-IR) was used to determine the specific functional groups of the adsorbents prepared in the examples and comparative examples. The test results are as follows: Figure 2(a)- Figure 2 As shown in (b), the adsorption band (1730 cm⁻¹) generated by the vibration of non-ionized carboxyl groups. -1 -1690cm -1 This indicates that metal ions (Cu) 2+ It binds to 1,3,5-benzenetricarboxylic acid rather than to H. 690cm -1 -900cm -1 The absorption band at 1620 cm⁻¹ represents the out-of-plane bending vibration of the aromatic hydrocarbon CH₄. -1 -1380cm -1 The new absorption bands may be due to the asymmetric and symmetric stretching vibrations of the carboxylic acid groups. These findings confirm that the carboxylic acid groups in organic ligands interact with copper ions to form porous structures. Typically, the 1641 cm⁻¹ band... -1 The position corresponds to the stretching vibration peak of -COOH, at 1364 cm⁻¹. -1 The position corresponds to the in-plane bending vibration peak of -OH. 1107 cm⁻¹ -1 and 727cm -1 This is a stretching vibration belonging to the -CO-Cu bond. 488 cm⁻¹ -1 and 730cm -1 The absorption band at 1364 cm⁻¹ is attributed to Cu-O stretching vibration characteristics. -1 and 1448cm -1 The strong peak appearing nearby is due to the symmetrical stretching of the carboxylic acid group (COOH) in BTC. At 1646 cm⁻¹ -1 The newly recorded peak at 2700 cm⁻¹ is due to the asymmetric stretching vibration of 1,3,5-benzenetricarboxylic acid. -1 -3500cm -1 The broadband width in the region is due to the presence of carboxylic acid groups and adsorbed water in the sample. 3000 -1 -3400cm -1 The peak at this location corresponds to the stretching vibrations of NH and OH. It is located at 1100 cm⁻¹. -1 and 1800cm -1 The multiple Fourier transform infrared peaks between the peaks represent stretching vibrations of the aromatic CN groups in the triazine ring of the g-C3N4 structure. (806 cm⁻¹) -1 The wavelength at this point is related to the bending of triazine or heptaazine units. (1637 cm⁻¹ in the g-C₃N₄ spectrum) -1 and 1240cm -1 The characteristic peaks at this location are attributed to the C=N and CN stretching vibrations. Similarly, the absence of characteristic peaks for bismuth-based oxides indicates that bismuth is well integrated into the CNM-25 structure without forming Bi-O bonds.

[0115] The adsorbents Cu-BTC, g-C3N4, and CNM-25, along with their surface morphology and structure, were analyzed using scanning electron microscopy and thermogravimetric analysis, respectively. Figure 3 (a) and Figure 3 As shown in (b), Cu-BTC and g-C3N4 have clear lamellar structures and thicknesses, with Cu-BTC exhibiting a typical octahedral morphology. Figure 3 (c) Figure 3 (c1)- Figure 3 (c3) shows the adhesion of g-C3N4 to the surface of the Cu-BTC structure. With increasing g-C3N4 content, g-C3N4 can increase the specific surface area of ​​the Cu-BTC@g-C3N4 composite material, thereby improving its adsorption capacity. However, with further addition of g-C3N4, the structure of the Cu-BTC@g-C3N4 composite material is damaged at certain points, resulting in a rough and irregular surface. Therefore, considering the above factors, the mass concentration of graphitic carbon nitride in this invention is 20 mg / 24 mL to 35 mg / 24 mL. More preferably, the mass concentration of graphitic carbon nitride is 24 mg / 24 mL to 26 mg / 24 mL.

[0116] Bismuth was incorporated into the Cu-BTC@g-C3N4 composite material. Scanning electron microscopy, EDS, and spectra revealed the morphology of the incorporated bismuth, such as... Figure 4 (a)- Figure 4 As shown in (d). Bismuth doping did not alter or destroy any structural morphology; the composite material surface was smooth, and the size ranged from 10 μm to 50 μm. Figure 5 (d1)- Figure 5 As shown in (d7), all the composite elements can be clearly seen and identified, and the amount of iodine that the adsorbent can adsorb is also very high.

[0117] Taking Example 1 as an example, further investigation was conducted. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study the thermal decomposition behavior of the adsorbents (Cu-BTC, 40%Bi-CNM-25) in the range of 25℃-800℃. TGA measured the mass change of the material as a function of temperature, thereby gaining a deeper understanding of the material's thermal stability. Figure 6 The image shows the raw data, including TGA, DTA, and derivative thermogravimetric analysis (DTG). From... Figure 6 The data shows the decomposition of the raw material at three different thermal degradation stages. The TGA and DTG curves for Cu-BTC and 40% Bi-CNM-25 are shown below. Figure 6 (a) and Figure 6As shown in (b), the derivative thermogravimetric curve shows a significant peak, indicating that the weight loss rate is significant at this temperature. Based on the comprehensive analysis of the TGA and DTG curves, the decomposition process can be divided into three stages: (1) solvent evaporation; (2) thermal stabilization; and (3) structural collapse. The first stage occurs in the range of (30℃-90℃), with weight losses of approximately 4.36% and 17.20%, respectively. This is due to the removal of water molecules coordinated with Cu(II) in Cu-BTC and solvent molecules on the surface of Cu-BTC materials. This can be seen from... Figure 6 (a) and Figure 6 The exothermic peak obtained in (b) at (350℃-360℃) was confirmed. The second stage considered thermal stability; 40%Bi-CNM-25 showed stability in the 100℃-300℃ range with slow weight loss (15.35%). However, in the second stage, the Cu-BTC material experienced a weight loss of 36.50% in the temperature range of 90℃-330℃. TGA curves showed that in the final stage, Cu-BTC and 40%Bi-CNM-25 experienced weight losses of 24.22% and 16.48%, respectively, in the temperature range of 331℃-390℃. This indicates that the adsorbent obtained in this invention has significantly greater structural stability compared to the comparative example.

[0118] Both Cu-BTC and 40%Bi-CNM-25 exhibited three-stage weight loss. Within the temperature range of 80℃-330℃, the maximum weight loss for Cu-BTC was 36.56%, and for 40%Bi-CNM-25, it was 17.20%. The DTA curves of Cu-BTC and 40%Bi-CNM-25 showed two very small internal thermal peaks near 80℃-90℃, and a very prominent exothermic peak near 350℃. After 450℃-550℃, no significant mass loss was observed in either Cu-BTC or 40%Bi-CNM-25. Figure 6 (c) shows the four thermal degradation processes of Cu-BTC-I2 as the temperature increases. The first stage shows that the removal rate of physically adsorbed water molecules reaches 49.07% in the range of (30℃-140.3℃), which is also the maximum value. The DTA curve also shows the exothermic reaction of rapid thermal degradation at 350℃. Figure 6The 40%Bi-CNM-25-I2 sample in (d) also exhibited four distinct thermal degradation processes, showing four stages of weight loss. The maximum weight loss occurred at (30℃-80℃), with a mass loss range of 38.33%. This loss may be due to phase transition formation or degradation of other groups used in nitrate synthesis. The results indicate that the stability of the adsorbent of this invention further increases after iodine adsorption, exhibiting good structural stability within the temperature range of 600℃-650℃. The DTG curves of all samples showed a major peak of exothermic reaction at 350℃. The weight loss rate can be ranked according to thermal stability; higher stability indicates less weight loss. The total weight loss rate of all samples can be divided into: Cu-BTC > 40%Bi-CNM-25 and Cu-BTC-I2 after iodine adsorption > 40%Bi-CNM-25-I2. Thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTG) results showed that the thermal stability of the 40%Bi-CNM-25 composite material was superior to that of the comparative example, and the structure of 40%Bi-CNM-25 remained stable at 320℃. Furthermore, the thermal behavior of 40%Bi-CNM-25 showed a significant difference compared to that of 40%Bi-CNM-25-I2 adsorbed with iodine. The temperature at which iodine molecules were released from the adsorbed state was 200℃, significantly lower than the decomposition temperature of the original 40%Bi-CNM-25 sample. This observation strongly demonstrates that there is a physical adsorption process between I2 molecules and the 40%Bi-CNM-25 nanocomposite material, allowing I2 molecules to be adsorbed into the porous structure. In addition, Figure 6 The TGA data shown in (a) highlights the excellent thermal stability of 40%Bi-CNM-25 (up to 320°C).

[0119] Understanding the texture properties of materials is crucial for predicting their ability to trap guest molecules such as iodine. These properties, including surface area, pore volume, and pore size distribution, significantly influence the adsorption capacity of Cu-BTC and CNM-25 composites. To gain a deeper understanding of these key properties, we performed nitrogen adsorption-desorption measurements at 77 K to evaluate the porous structure of the Cu-BTC and CNM-25 composites, and the results are shown in Table 1. The results revealed that loading graphitic carbon nitride onto the surface of the copper-based metal framework is beneficial for increasing the specific surface area of ​​the adsorbent material, thereby increasing the physical space for iodine molecule adsorption.

[0120] Figure 7The nitrogen adsorption / desorption isotherm data show that Cu-BTC exhibits a Type IV isotherm with an H3-type hysteresis loop, indicating that Cu-BTC possesses mesoporous properties. Furthermore, the coexistence of Type I and Type IV adsorption isotherms suggests the presence of both macroporous and mesoporous structures in all materials. Rapid nitrogen adsorption is observed in the low-pressure range (P / P0 < 0.04), while significant hysteresis is observed in the high-pressure range, indicating that the adsorbent possesses a rich microporous structure, and the presence of macropores provides favorable conditions for pollutant adsorption. The BET specific surface area (S) of Cu-BTC and CNM-25 is shown in Table 1. BET The values ​​are 1503.5683m respectively. 2 / g、1608.5211m 2 / g. The corresponding pore volume calculated using the "single-point method" is 0.6039 cm³. 3 / g, 0.6622cm 3 / g (P / P0=0.98), with average pore sizes of 2.45nm and 3.04nm, respectively. The physical surface properties of the material are beneficial to improving the adsorbent's ability to capture iodine.

[0121] The purpose of measuring the sample is to analyze its elemental composition and confirm the formation of the composite material. Figure 8 This is the XPS spectrum of 40% Bi-CNM-25 before iodine ion adsorption. Figure 9 The high-resolution spectrum of I3d showed the presence of iodide (I3) at (630.85 eV) and (619.36 eV), respectively. - The peaks are caused by iodine molecules (I2) and iodine molecules (I3d). The appearance of these two peaks indicates that the iodine capture process is a fusion of chemical and physical processes, and is the result of the combined effect of chemical and physical capture.

[0122] The enhanced iodine adsorption capacity observed in Cu-BTC and x%Bi-CNM-25 (x = 30, 40, 50) is due to several factors. The extensive open space within the Cu-BTC framework provides ample space for guest molecule interactions. Furthermore, the π-electron enrichment of g-C3N4 and the presence of bismuth (Bi) in the x%Bi-CNM-25 (x = 30, 40, 50) composites also play crucial roles. The relatively weak bonds in the x%Bi-CNM-25 (x = 30, 40, 50) structure facilitate the formation of new bonds with iodine molecules, thereby promoting the chemical capture of iodine. In addition, bismuth is well known to promote electron-hole pair separation and electron transfer processes, thus enhancing the adsorption capacity of the adsorbent for iodine.

[0123] like Figure 10As shown in (a), the I2 absorption capacity of the x%Bi-CNM-25 nanocomposite material (x = 30, 40, 50) is higher than that of Cu-BTC and Cu-BTC / g-C3N4. Within 30 hours, the weight of all samples increased sharply, indicating a rapid iodine adsorption rate. After 48 hours, the rate of weight increase slowed down. After 70 hours, no significant weight change was observed, indicating that absorption equilibrium had been reached. Under equilibrium conditions, Cu-BTC and g-C3N4 exhibited relatively low iodine absorption rates of 345 mg / g and 192 mg / g, respectively. In contrast, the 30%Bi-CNM-25, 40%Bi-CNM-25, and 50%Bi-CNM-25 of this invention demonstrated stronger iodine adsorption capabilities, with absorption rates of 378 mg / g, 425 mg / g, 512 mg / g, and 588 mg / g, respectively. This indicates that increasing the bismuth doping concentration enhances iodine adsorption; however, excessive bismuth doping can clog the pore structure, thus affecting the adsorption effect. Therefore, in this invention, the mass ratio of the intermediate product to the bismuth source solution is 30%-50%. It is worth noting that the x%Bi-CNM-25 (x is 30, 40, 50) composite material obtained in this invention has a significantly higher adsorption capacity for iodine than other materials. This is not only because the x%Bi-CNM-25 (x is 30, 40, 50) composite material has a higher specific surface area and porosity, which provides more binding sites and space for the adsorption of iodine molecules, but also because the x%Bi-CNM-25 (x is 30, 40, 50) composite material chemically captures iodine ions. The combined effect of chemical and physical processes enhances the adsorption capacity of the adsorbent of this invention for radioactive iodine.

[0124] Due to its Cu-BTC structure, the adsorbent of this invention ultimately forms a composite material with a layered porous structure. This structure is characterized by the presence of accessible free pores and open sites, which facilitate the diffusion of iodine molecules. The interconnected nature of these pores gives the adsorbent of this invention a high iodine adsorption capacity and rapid absorption kinetics, and the appropriate doping of bismuth further enhances the adsorption sites.

[0125] exist Figure 10 In (a), the maximum iodine absorption capacity of the 50%Bi-CNM-25 nanocomposite is 588 mg / g, which is much higher than that of other solid adsorbents, such as silver-based zeolites, MOFs, and CMPs (as shown in Table 2). Therefore, x%Bi-CNM-25 nanocomposite (x represents 30, 40, and 50) has great potential for gaseous iodine capture.

[0126] Kinetic experiments were conducted in an iodine / cyclohexane solution to investigate the adsorption behavior of the adsorbent over time. Figure 10(b) The adsorption process exhibits a clear biphasic trend. In the initial stage, the adsorption capacity increases rapidly, then gradually rises until reaching equilibrium after approximately 20 hours. The adsorption capacity of the CNM-25 composite material for iodine is significantly higher than that of Cu-BTC. With the doping of Bi into CNM-25, the adsorption capacity of the adsorbent for iodine increases with the increase of Bi doping amount. After 20 hours, the iodine adsorbed on Cu-BTC, CNM-25, 30%Bi-CNM-25, 40%Bi-CNM-25, and 50%Bi-CNM-25 are 85.32 mg / g, 91.21 mg / g, 124.34 mg / g, 141.11 mg / g, and 156.41 mg / g, respectively. Furthermore, the maximum clearance rate of the adsorbent of the present invention reaches an astonishing 79%, while the adsorption equilibrium of Cu-BTC and CNM-25 is rapidly reached within 15 hours. It is evident that the adsorbent of the present invention has a high adsorption capacity for iodine.

[0127] The study found that the x%Bi-CNM-25 composite material (x = 30, 40, 50) had slightly stronger adsorption capacity compared to pure Cu-BTC powder. This indicates a correlation or relationship between Cu-BTC and x%Bi-CNM-25.

[0128] Pseudo-first-order dynamic model: ;

[0129] Pseudo-second-order dynamic model: ;

[0130] Where q e (mg / g) represents the adsorption capacity of I2 at equilibrium, q t (mg / g) represents the adsorption capacity at a specific time t (hours), and k1 and k2 are the adsorption rate constants of the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, respectively. The kinetic parameters are shown in Table 3. The results in Table 3 show that, compared with the pseudo-first-order kinetic model, the nonlinear correlation coefficient (R²) values ​​of the adsorption data are higher (0.988-0.993), indicating that the adsorption data conforms to the pseudo-second-order kinetic model. Figure 10 In (c), as the adsorption time increases, the reaction gradually approaches equilibrium. After 20 hours of reaction, the q of Cu-BTC, CNM-25, and x%Bi-CNM-25 composite materials (x = 30, 40, 50) is... emax The removal values ​​were 100 mg / g, 109 mg / g, 165 mg / g, 176 mg / g, and 181 mg / g, respectively. This result confirms that the adsorption process of iodine in our study is governed by pseudo-second-order kinetics. The process by which iodine molecules are attracted and bind to x%Bi-CNM-25 (x being 30, 40, and 50) was determined to be chemisorption. Therefore, it can be inferred that the adsorption of I2 by Bi can be achieved through chemisorption.

[0131] Figure 10 (c) Adsorption isotherms of iodine on Cu-BTC and its x%Bi-CNM-25 composites (x = 30, 40, 50) were explored. Adsorption isotherms are crucial for understanding the maximum ability of an adsorbent to capture a specific molecule (iodine in this case). Figure 10 In (c), the maximum adsorption capacities of Cu-BTC, CNM-25, 30%Bi-CNM-25, and 40%Bi-CNM-25 were 131.5 mg / g, 145.8 mg / g, 163.0 mg / g, and 180.8 mg / g, respectively. Notably, the 50%Bi-CNM-25 composition exhibited the highest adsorption capacity of 191.2 mg / g. To elucidate the adsorption behavior of iodine (50 mg / L-300 mg / L) on different adsorbents, the Freundlich and Langmuir models were employed, described by the following formulas:

[0132] Langmuir model: ;

[0133] Freundlich model: ;

[0134] Where, q e q is the amount of iodine adsorbed at equilibrium (mg / g). m It is the calculated maximum iodine adsorption capacity (mg / g), K L and K f is the equilibrium constant of the Langmuir and Freundlich models, and n represents the strength coefficient related to the adsorption strength.

[0135] The results in Table 4 show that the Langmuir model is best suited for analyzing the adsorption of iodine by various adsorbents (R2). This indicates that the adsorption of iodine on the composite material is a monolayer adsorption, occurring at specific homogeneous sites on the surface. Figure 11 In this invention, the adsorption capacity of the adsorbent increases with the increase of Bi, and the adsorption active sites of the adsorbent also increase. Furthermore, the adsorbent of this invention still has good adsorption capacity in cyclohexane containing iodine molecules.

[0136] The adsorbent 40% Bi-CNM-25-I2 containing iodine and a vial containing ethanol were sealed at 25°C for 24 hours. Then, solid-liquid separation was performed. The solid material was dried and used again to capture vapor iodine at 80°C. Four to five adsorption-desorption experiments were conducted.

[0137] The iodine recovery capacity of 40% Bi-CNM-25 and the color change of the filtrate in each cycle are shown in the figure. Figure 12Initially, the iodine capture capacity of the adsorbent 40% Bi-CNM-25 was 588 mg / g. After two washing cycles, the iodine capture capacity was 521 mg / g and 478 mg / g, respectively. With further cycling, the iodine capture capacity gradually decreased, reaching 258 mg / g by the fifth cycle. Zeolite-13X is a well-known iodine capture material with a capture capacity of 320 mg / g-380 mg / g.

[15] This indicates that, compared with other materials on the market, the x%Bi-CNM-25 (x is 30, 40, 50) adsorbent of the present invention has significant reusability in terms of vapor iodine absorption.

[0138] The effect of solution pH on the adsorption process was investigated using various acidic and alkaline solutions prepared with hydrochloric acid and NaOH, respectively. The initial iodine concentration was 100 mg / L. Figure 13 As shown in (a), the results indicate that the adsorbents of the present invention have a strong removal efficiency for iodine in the pH range of 5-10.

[0139] In the presence of F - Cl - ,Br - and I - In the presence of anionic sodium salt, I₂ in aqueous solution was adsorbed using 40% Bi-CNM-25 material. Adsorption experiments were conducted using 50 mL of iodine solution with a concentration of 100 mg / L. The adsorbent concentration used was 5 mg / L, and the anion concentration of the sodium salt was 20 mg / L. The adsorption process was carried out for 5 hours at room temperature (30°C) and pH 7. Figure 13 (b) The results showed that the anion (F) - ,Br - and Cl - The presence of I₂ stimulates the adsorption capacity of the adsorbent to increase that of iodine, thus making the adsorption capacity of I₂ greater than that of I₂. - The adsorption capacity is greater, thereby causing the adsorbent of the present invention to produce a higher adsorption capacity.

[0140] It should be noted that the terminology used in this invention is for describing specific embodiments only and is not intended to limit the scope of this application. As shown in this specification, unless the context clearly indicates otherwise, words such as "a," "an," "an," and / or "the" do not specifically refer to the singular and may include the plural. The terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, or apparatus that includes said element.

[0141] It should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," "linked," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components. For those skilled in the art, the specific meaning of the above terms in the present invention can be understood according to the specific circumstances.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

[0143] References:

[0144] [1]Sava, DF, et al., Capture of volatile iodine, a gaseous fissionproduct, by zeolitic imidazolate framework-8. J Am Chem Soc, 2011.133(32): p.12398-401.

[0145] [2]Valizadeh, B., et al., Porous Metal–Organic Framework@PolymerBeads for Iodine Capture and Recovery Using a Gas‐Sparged Column. AdvancedFunctional Materials, 2018. 28.

[0146] [3]Nandanwar, S.U., et al., Porous microsphere of magnesium oxide asan effective sorbent for removal of volatile iodine from off-gas stream.Adsorption, 2016. 22(3): p. 335-345.

[0147] [4]Mahdi, E.M., A.K. Chaudhuri, and J.-C. Tan, Capture andimmobilisation of iodine (I2) utilising polymer-based ZIF-8 nanocompositemembranes. Molecular Systems Design&Engineering, 2016. 1(1): p. 122-131.

[0148] [5]Liu, S., et al., Efficient capture and stable storage ofradioactive iodine by bismuth-based ZIF-8 derived carbon materials asadsorbents. Separation and Purification Technology, 2022. 302: p. 122151.

[0149] [6]Nenoff, T.M., et al., SILVER-MORDENITE FOR RADIOLOGIC GAS CAPTUREFROM COMPLEX STREAMS: DUAL CATALYTIC CH3I DECOMPOSITION AND I CONFINEMENT.Microporous and Mesoporous Materials, 2014. 200: p. 297-303.

[0150] [7]Yu, Q., et al., Millimeter-sized Bi2S3@polyacrylonitrile hybrid beads for highly efficient iodine capture. New Journal of Chemistry, 2020.44:p. 16759-16768.

[0151] [8]Tian, Z., et al., Comprehensive comparison of bismuth and silver functionalized nickel foam composites in capturing radioactive gaseous iodine. Journal of Hazardous Materials, 2021.417: p. 125978.

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Claims

1. An adsorbent, characterized in that, The adsorbent comprises a copper metal-organic framework, in which copper is linked to carboxylic acid groups to form a porous structure; graphitic carbon nitride is supported on the surface of the copper metal-organic framework; and bismuth is doped on the surface and within the porous structure of the copper metal-organic framework. The bismuth is doped on the surface and within the pore structure of the copper metal-organic framework and exists in the form of Bi-N bonds. The preparation method of the adsorbent includes: mixing a copper source solution and a 1,3,5-benzenetricarboxylic acid solution to obtain a mixed solution, adding graphite phase carbon nitride to the mixed solution, mixing evenly, separating the solid and liquid, washing once, and drying the solid to obtain an intermediate product; The intermediate product was placed in an organic solvent, and then a bismuth source was added. The mixture was then subjected to ultrasonic treatment, solid-liquid separation, secondary washing, and drying to obtain the adsorbent. The molar concentration of the copper source solution is 0.3 mol / L; The mass concentration of the 1,3,5-benzenetricarboxylic acid solution is 35 g / L; The volume ratio of the copper source solution to the 1,3,5-benzenetricarboxylic acid solution is 1:1; After the mixture is homogeneous, the mass concentration of graphitic carbon nitride is 20 mg / 24 mL to 35 mg / 24 mL. The mass ratio of the bismuth source to the intermediate product is 30%-50%. The intermediate product has a mass concentration of 0.1 g / 20 mL in the organic solution.

2. The adsorbent according to claim 1, characterized in that, The copper source in the copper source solution includes one or more of copper nitrate and copper nitrate trihydrate. The bismuth source in the bismuth source solution includes bismuth nitrate pentahydrate.

3. The adsorbent according to claim 1, characterized in that, The drying temperature is 50℃-70℃, and the drying time is 17h-19h.

4. The adsorbent according to claim 1, characterized in that, The organic solvent includes methanol.

5. The use of the adsorbent according to any one of claims 1-4 in the adsorption of radioactive iodine.

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