Nitrogen-doped zinc-based adsorbent, preparation method thereof and application of nitrogen-doped zinc-based adsorbent in radioactive cesium removal

Abstract

The invention belongs to the field of material chemistry, and discloses a nitrogen-doped zinc-based adsorbent, a preparation method of the nitrogen-doped zinc-based adsorbent and application of the nitrogen-doped zinc-based adsorbent in radioactive cesium removal, and the preparation method of the nitrogen-doped zinc-based adsorbent comprises the following steps: step 1, preparing a ZIF-8 precursor with a dodecahedron structure; step 2, preparation of HNZOR or HNZSS: dispersing the ZIF-8 precursor obtained in the step 1 in a solvent, carrying out a low-temperature hydrothermal reaction at 150-200 DEG C, collecting a product after the reaction is completed, washing and carrying out vacuum drying to obtain HNZOR; the preparation method comprises the following steps: dispersing HNZOR in water, carrying out secondary low-temperature hydrothermal reaction in an ammonium hydroxide environment at 120-180 DEG C, collecting a product after the reaction is completed, washing and carrying out vacuum drying to obtain HNZSS; and 3, activating the HNZOR or HNZOR obtained in the step 2 by using potassium salt containing K < + >, and after activation is completed, washing and drying to obtain the nitrogen-doped zinc-based adsorbent. The adsorbent disclosed by the invention can be widely applied to removal and enrichment of Cs < + > in nuclear power plant wastewater, accident emergency water bodies and high-salt complex waste liquid.

Description

Technical Field

[0001] This invention relates to the field of materials chemistry, and in particular to a nitrogen-doped zinc-based adsorbent, its preparation method, and its application in the removal of radioactive cesium. Background Technology

[0002] Cesium-137 ( 137 Cs (chloroform) is a major and persistent source of gamma radiation in high-level liquid waste. It easily accumulates in human soft tissues through the food chain, causing serious health risks such as cell damage, cancer, and even death. Meanwhile, 137 Cs is also an important gamma-ray source in medical, agricultural irradiation, and industrial measurement applications. Therefore, efficient and selective separation and purification of radioactive cesium is crucial for the safe disposal and resource recovery of high-level radioactive waste. However, actual waste often contains a large number of competing cations (such as K+). + Na + Ca² + Mg² + ) and fission products, significantly interfering with Cs + The identification and extraction of these features greatly increases the difficulty of selectively separating them.

[0003] Currently, ion exchange and adsorption are widely recognized as ideal methods for separating radioactive cesium. Existing adsorbents include zeolites, layered hydrogen hydroxides (LDHs), and metal-organic frameworks (MOFs).

[0004] Zeolite is a common natural mineral with good ion exchange properties. However, its selectivity and adsorption capacity are limited, especially in complex wastewater environments, where it is easily interfered with by other cations. Layered hydrogen hydroxides (LDHs): Due to their layered structure and tunable interlayer anionic properties, LDHs exhibit excellent performance in the adsorption of heavy metal ions. However, they are relatively unstable in aquatic environments and are prone to structural collapse. Metal-organic frameworks (MOFs): MOFs are considered ideal adsorbent candidates due to their excellent porosity and specific surface area. However, in practical applications, they face problems such as particle aggregation, difficulty in post-adsorption separation, and limited reusability. Furthermore, traditional MOF calcination conversion methods often lead to a reduction in specific surface area and coverage of active sites, affecting adsorption performance. The preparation of traditional MOF-derived adsorbents largely relies on high-temperature calcination processes (typically 800–1400℃). The method has the following defects: (1) High temperature causes structural collapse: During the calcination process, the MOF framework decomposes violently, causing particle sintering, grain coarsening and pore collapse, resulting in a significant decrease in specific surface area and porosity, which is not conducive to the diffusion and adsorption of target ions; (2) Loss of active sites: High temperature easily causes the surface functional groups to decompose and the dopant elements to volatilize, making it difficult to retain active centers that can be used for ion exchange; (3) Uncontrollable morphology: Under high temperature conditions, the material growth kinetics are difficult to control, and it is impossible to achieve the topological inheritance from MOF precursor to target product, which limits the directional design of the micromorphology of the adsorbent. The above defects directly restrict the high capacity, fast kinetics, strong selectivity and renewability required for adsorbents in actual radioactive waste liquid treatment. MOF-derived transition metal oxides / sulfides (TMOs / TMSs): Transition metal oxides / sulfides (TMOs / TMSs) derived from metal-organic frameworks (MOFs) have become promising next-generation materials in many research fields due to their highly controllable morphology, tunable porosity, and good water stability. However, TMOs / TMSs ​​prepared by traditional high-temperature calcination methods still suffer from reduced specific surface area and coverage of active sites. Although these materials exhibit good adsorption performance under laboratory conditions, many problems remain in practical applications, such as insufficient selectivity: In complex wastewaters, the presence of multiple competing cations severely affects the adsorption of Cs. + Selective adsorption. Structural instability: Many materials easily lose their original structure in an aqueous environment, leading to a decline in adsorption performance. Difficult regeneration: Some adsorbents exhibit poor regeneration when adsorbing Cs. + Its inability to be effectively regenerated limits its large-scale application. Summary of the Invention

[0005] The purpose of this invention is to address the technical deficiencies in existing technologies by providing a nitrogen-doped zinc-based adsorbent, its preparation method, and its application in the removal of radioactive cesium. Using ZIF-8 as a precursor, nitrogen-doped ZnO nanorods or ZnS microspheres with controllable structures are prepared without high-temperature calcination. This method avoids pore structure damage and loss of active sites through mild reaction conditions, and achieves precise morphology control and surface functionalization through the synergistic effect of solvents and additives, thereby obtaining adsorbents with both high Cs content and high Cs content. +A novel adsorbent material with adsorption capacity, excellent selectivity and good cycling stability.

[0006] The technical solution adopted to achieve the purpose of this invention is: A method for preparing a nitrogen-doped zinc-based adsorbent includes the following steps: Step 1: Prepare the ZIF-8 precursor with a dodecahedral structure; Step 2: Prepare nitrogen-doped ZnO nanorods or nitrogen-doped ZnS microspheres; The preparation steps of the nitrogen-doped ZnO nanorods are as follows: the ZIF-8 precursor obtained in step 1 is dispersed in a solvent and subjected to a low-temperature hydrothermal reaction at 150~200℃. After the reaction is completed, the product is collected, washed and vacuum dried to obtain nitrogen-doped ZnO nanorods HNZOR. The preparation steps of the nitrogen-doped ZnS microspheres are as follows: the nitrogen-doped ZnO nanorods HNZOR are dispersed in water, and then a second low-temperature hydrothermal reaction is carried out in an ammonium hydroxide environment at 120~180℃. After the reaction is completed, the product is collected, washed and vacuum dried to obtain nitrogen-doped ZnS microspheres HNZSS. Step 3, Preparation of nitrogen-doped zinc-based adsorbent: using K-containing... + The nitrogen-doped ZnO nanorods (HNZOR) or nitrogen-doped ZnS microspheres (HNZOR) obtained in step 2 of potassium salt activation are washed and dried to obtain nitrogen-doped zinc-based adsorbents.

[0007] In the above technical solution, the method for preparing the ZIF-8 precursor in step 1 is as follows: Zinc nitrate hexahydrate and 2-methylimidazole in a molar ratio of 1:(4~5) were dissolved in methanol, mixed, and reacted at 50~80℃ for 12~48h. The resulting precipitate was washed and vacuum dried to obtain the ZIF-8 precursor with a dodecahedral structure.

[0008] In the above technical solution, in step 2, the time for the first low-temperature hydrothermal reaction is 150~200h, and the time for the second low-temperature hydrothermal reaction is 120~180h.

[0009] In the above technical solution, in step 2, the nitrogen-doped ZnO nanorods are in the shape of a flower-like hierarchical structure formed by the self-assembly of nanorods, and the length of the nanorods is 1~5μm.

[0010] In the above technical solution, in step 2, the ammonium hydroxide environment is provided by ammonia water and thiourea in a mass ratio of (0.8~1.5):1.

[0011] In the above technical solution, in step 2, the diameter of the nitrogen-doped ZnS microspheres is 50~300nm.

[0012] In the above technical solution, in step 3, the potassium salt is potassium chloride, potassium sulfate, potassium nitrate, and potassium carbonate.

[0013] In the above technical solution, in step 3, K in the potassium salt + The concentration is 1~5 mol / L, and the activation time is 12~48 h.

[0014] Another aspect of the present invention includes a nitrogen-doped zinc-based adsorbent obtained using the preparation method described above.

[0015] Another aspect of the present invention includes the application of the nitrogen-doped zinc-based adsorbent in the removal of radioactive cesium.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. The preparation method of the nitrogen-doped zinc-based adsorbent of this invention is a scalable solvothermal in-situ etching process. This process uses rhombic dodecahedral ZIF-8 particles as a precursor, first converting them into high specific surface area, carbon-free ZnO nanorods under mild conditions; then, converting them into ZnS microspheres through a sulfidation reaction in an ammonium hydroxide environment; finally, the material is activated with potassium ions using KCl solution. This process achieves in-situ nitrogen doping during synthesis, introducing exchangeable cation sites to enhance Cs. + The trapping ability is enhanced by preserving abundant amorphous regions and open channels under low-temperature conditions, which facilitates the rapid diffusion of target metal ions within the adsorbent. Furthermore, KCl activation significantly improves the material's performance in environments with high concentrations of coexisting ions (such as Na+). + K + Mg 2+ Ca 2+ In complex systems of Cs + Selective adsorption properties.

[0017] 2. This invention successfully constructed a morphology-tunable MOF-derived inorganic adsorbent rich in active sites, retaining a hierarchical porous structure and a moderate specific surface area, which is conducive to ion diffusion; the surface is enriched with nitrogen doping and coordination unsaturated sites (O / N or S / N), enhancing Cs + Affinity; K + After pre-activation, it can be activated by K + / Cs + Efficient Cs capture by ion exchange + It also possesses high adsorption capacity (>270 mg / g), rapid kinetics (reaching equilibrium in <50 min), and strong anti-interference properties (Na). + / Cs + (Still highly efficient at a ratio of >300:1), excellent irradiation / acid-base stability and good regenerability; suitable for continuous operation with a fixed bed column, with a penetration volume >450 BV.

[0018] 3. This invention provides a new approach and feasible pathway for the efficient and selective removal of radioactive cesium and other target nuclides. The adsorbent of this invention can be widely applied to the removal of Cs from nuclear power plant wastewater, emergency water bodies, and high-salt complex waste liquids. + Removal and enrichment. Attached Figure Description

[0019] Figure 1 (a) is a schematic diagram of the synthesis route of nitrogen-doped zinc-based adsorbent, (b) is a scanning electron microscope (SEM) image of ZIF-8 precursor, (c) and (d) are SEM images of HNZOR, and (e) is a SEM image of HNZSS.

[0020] Figure 2 (a)HNZSS removes Cs at pH 4 + Dynamics ( C o =16 mg / L, (b) HNZOR removes Cs at pH 8 + Dynamics ( C o =16 mg / L, (c) ZIF-8 removes Cs at pH 7 + Dynamics ( C o =16mg / L).

[0021] Figure 3 (a) shows the X-ray diffraction (XRD) patterns of ZIF-8, HNZOR, and HNZSS; (b) shows the X-ray absorption near-edge structure (XANES) pattern of Zn K-edge; and (c) shows the Zn K-edge k-edge structure. 2 Weighted Fourier transform extended X-ray absorption fine structure (FT-EXAFS) spectrum.

[0022] Figure 4 (a) shows the Cs after KNZSS and KNZOR were irradiated with 100 kGy γ. + Removal efficiency and distribution coefficient (K) d (b) are Cs after KNZSS and KNZOR were irradiated with 200 kGy γ. + Removal efficiency and distribution coefficient (K) d (c) are the XRD patterns of HNZSS and HNZOR after soaking in pH 0-10 solution for 24 hours, and (d) are the Zn concentrations of HNZSS and HNZOR after soaking in pH 0-10 solution for 24 hours. 2+ Dissolution concentration, (e) is the Cs of KNZSS and KNZOR under different pH conditions. +Removal efficiency, (f) is the Cs of KNZSS and KNZOR in four consecutive adsorption-desorption cycles. + Removal efficiency (g) is the KNZSS removal efficiency at high Na+ concentrations. + or K + Under coexistence conditions (molar ratio > 170:1), the effect of Cs + The allocation coefficient (K) d The removal efficiency (h) of KNZOR at high concentrations of Na + or K + Under coexistence conditions (molar ratio > 170:1), the effect of Cs + The allocation coefficient (K) d ) and removal efficiency, (i) are Cs of KNZSS and KNZOR in real water bodies (salt lake water, river water, tap water). + Removal efficiency.

[0023] Figure 5 In (a), Cs is the KNZSS in the fixed bed column. + The penetration curve (b) is the Cs of KNZOR in a fixed bed column. + Breakthrough curves, (c) show the Cs values ​​of each fraction during the elution process of a fixed-bed column containing KNZSS. + Concentration and cumulative elution efficiency, (d) represents the Cs of each fraction during the elution process of a fixed-bed column containing KNZOR. + Concentration and cumulative elution efficiency. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0025] Example 1 Preparation methods of activated nitrogen-doped ZnO nanorod adsorbents (KNZOR), such as Figure 1 As shown in (a), the steps include: Step 1: Synthesize the ZIF-8 precursor; Zinc nitrate hexahydrate (3.39 g, 11.3 mmol) was dissolved in 150 mL of methanol, and 2-methylimidazole (3.94 g, 47.9 mmol) was dissolved in 150 mL of methanol. The two solutions were mixed and reacted at 60 °C for 24 h. The resulting precipitate was washed with ethanol and deionized water and dried under vacuum at 60 °C to obtain a ZIF-8 precursor with a dodecahedral structure and a particle size of approximately 150 nm.

[0026] like Figure 1(b) Scanning electron microscope (SEM) image of the ZIF-8 precursor, showing its typical dodecahedral morphology and a particle size of about 150 nm, indicating that the precursor has a uniform structure and is suitable for subsequent transformation.

[0027] Step 2: Prepare nitrogen-doped ZnO nanorods (HNZOR); 0.2 g of ZIF-8 precursor was dispersed in 40 mL of ethanol-water mixed solvent (volume ratio 1:1), and sonicated for 20 min to form a homogeneous suspension. The suspension was then transferred to a polytetrafluoroethylene-lined high-pressure reactor and reacted at 160 °C for 2 h. After natural cooling, the product was collected, washed with water / ethanol, and dried under vacuum at 60 °C to obtain HNZOR. SEM showed that it consisted of sharp-tipped nanorods with a length of approximately 1.13 μm, which self-assembled into a flower-like hierarchical structure.

[0028] Step 3, using K + Preparation of KNZOR by activating HNZOR; 0.5 g of HNZOR was added to 500 mL of 2 mol / L KCl aqueous solution, and the mixture was stirred continuously for 24 h. The product was washed with water and dried in air to obtain K. + Activated KNZOR.

[0029] Example 2 Preparation method of activated nitrogen-doped ZnS microsphere adsorbent (KNZSS), such as Figure 1 As shown in (a), the steps include: Step 1: Synthesize the ZIF-8 precursor, the specific steps are the same as Step 1 in Example 1; Step 2: Prepare nitrogen-doped ZnO nanorods (HNZOR), the specific steps are the same as step 2 in Example 1; Step 3: Prepare nitrogen-doped ZnS microspheres (HNZSS); Disperse 0.2 g of HNZOR in 30 mL of deionized water, sonicate for 20 min, add 0.5 mL of 30% ammonia solution, stir for 10 min, then add thiourea (0.4 g, 5.2 mmol), and continue stirring for 20 min. Transfer to a high-pressure reactor, react at 150 °C for 4 h, cool, centrifuge to collect the product, wash with water, and vacuum dry to obtain HNZSS.

[0030] Step 4, using K + Preparation of KNZSS by activating HNZSS; 0.5 g HNZSS was added to 500 mL of 2 mol / L KCl aqueous solution and stirred continuously for 24 h. The product was washed with water and dried in air to obtain KNZSS.

[0031] Test case like Figure 1SEM images of HNZOR in (c) and (d) show the flower-like hierarchical structure formed by the self-assembly of ZnO nanorods. The rods can reach a length of 1.13 μm and have sharp tips, which reflects the characteristics of one-dimensional directional growth.

[0032] like Figure 1 SEM images of HNZSS (e) show that it is a regular solid microsphere with abundant internal channels. This indicates that ZnO nanorods are completely transformed into smooth ZnS microspheres after sulfidation, confirming the effectiveness of the topological transformation. Compared with HNZOR, HNZSS has a microsphere structure with more abundant channels and a larger specific surface area. HNZOR is Zn-O / N, while a Zn-S / N coordination environment is formed in HNZSS. 2- It has stronger soft alkalinity and is compatible with Cs. + There are more favorable soft and hard acid-base interactions or stronger coordination abilities between (soft acids), thereby improving adsorption selectivity and capacity.

[0033] To investigate the effects of HNZSS, HNZOR and their precursor ZIF-8 on low concentrations of Cs under different pH conditions. + The adsorption kinetics of Cs were studied, and the preparation of Cs was carried out. + initial concentration ( C o All solutions were prepared at 16 mg / L, and the pH values ​​of the HNZSS, HNZOR, and ZIF-8 systems were adjusted and controlled at 4, 8, and 7, respectively, for adsorption kinetic experiments. Their adsorption performance is as follows: Figure 2 As shown, HNZSS achieved a removal rate of 97.6% at pH 4 in just 150 minutes, demonstrating excellent adsorption activity. In contrast, HNZOR achieved a removal rate of 87.5% at pH 8 in 200 minutes, while ZIF-8 remained unequilibrated at pH 7 for 250 minutes, with a removal rate of 87.1%. These data indicate that HNZSS exhibits a faster adsorption rate and higher removal efficiency under acidic conditions. Compared to its precursor ZIF-8, HNZOR significantly broadens the applicable pH range of the material, better meeting the treatment needs of practical industrial alkaline wastewater. This confirms the excellent performance and engineering application potential of the synthesized HNZOR and HNZSS in treating cesium-containing wastewater in complex water environments.

[0034] like Figure 3 In (a), XRD analysis of HNZOR confirmed that ZIF-8 was completely oxidized to hexagonal ZnO; XRD analysis of HNZSS confirmed that it was pure hexagonal ZnS. HNZOR was completely sulfided to hexagonal ZnS with no ZnO residue, indicating high phase purity.

[0035] like Figure 3In (b), the Zn K-edge X-ray absorption near-edge structure (XANES) spectrum shows that the absorption edge position of zinc in HNZOR and HNZSS is consistent with that of standard ZnO, and is significantly higher than that of metallic zinc foil, confirming that zinc exists stably in the +2 valence state.

[0036] like Figure 3 In the middle (c), Zn K edge k 2 The weighted Fourier transform extended X-ray absorption fine structure (FT-EXAFS) spectra show that zinc in HNZOR is mainly coordinated with O / N atoms, while zinc in HNZSS is mainly coordinated with S / N atoms. No Zn–Zn metallic bond signal (~2.30 Å) was detected in either spectrum, indicating that the zinc species are highly dispersed. In addition, the absence of Zn–O characteristic peaks in HNZSS confirms that the ZnO precursor has been completely converted to ZnS.

[0037] Application Example 1 Cs + Adsorption.

[0038] Cs⁺ adsorption was performed using the Langmuir model. 5 mg of KNZOR or KNZSS was placed in 10 mL of a 100 mg / L CsCl solution (pH ≈ 5.6-6.0). Adsorption equilibrium was reached after 50 minutes (KNZOR) or 30 minutes (KNZSS). The static adsorption capacity of KNZOR was 289.01 mg / g, and the adsorption capacity of Cs⁺ within 50 minutes was [not specified in the original text]. + The removal rate reached 87.06%; the static adsorption capacity of KNZSS was 314.46 mg / g, the removal rate was 68.93% within 5 min and 97.62% within 30 min.

[0039] The irradiation stability experiment used the exact same test conditions as conventional static adsorption (5 mg adsorbent + 10 mL 100 mg / L CsCl, 24 h), except that the material was irradiated with 100-200 kGy of γ-rays before adsorption. The results are as follows: Figure 4 As shown in (a) and (b), Cs after KNZSS and KNZOR were irradiated with γ (100–200 kGy) + Removal efficiency and distribution coefficient (K) d The results show that its performance remains essentially unchanged after irradiation, demonstrating excellent radiation resistance. After irradiation with 200 kGy gamma rays, HNZOR exhibits a removal efficiency of 83.6%, K... d >1×10 3 mL / g; After irradiation with 200 kGy γ rays, the removal efficiency of KNZSS was 96.5%, K d >1×10 3 mL / g.

[0040] like Figure 4 As shown in (c) and (d), the XRD patterns of KNZSS and KNZOR after soaking in pH 0-10 solution for 24 hours are compared with those of Zn. 2+ The leaching concentration proves that it is structurally stable and does not corrode significantly under extreme acid and alkaline conditions.

[0041] like Figure 4 As shown in (e), 5 mg of KNZOR or KNZSS adsorbent was added to 10 mL of CsCl solution with an initial concentration of 100 mg / L. The pH of the solution was pre-adjusted to the target value within the range of 1-10 using 0.1 mol / L HCl or 0.1 mol / L NaOH. After adsorption with shaking at room temperature for 24 hours, the Cs concentration was measured. + Removal efficiency. The results showed that KNZOR achieved a removal rate of over 81% in the pH range of 3-9 (76.2% at pH 10), while KNZSS achieved a removal rate of over 95% in the pH range of 3-8 and maintained a stable removal capacity of 55%-84.4% throughout the pH range of 1-10, demonstrating excellent wide pH adaptability.

[0042] like Figure 4 As shown in (f), 5 mg of KNZOR or KNZSS adsorbent was added to 10 mL of a 100 mg / L CsCl solution (pH≈6). After adsorption at room temperature with shaking for 24 hours, Cs was recovered by elution with 0.5 mol / L NH4Cl solution. + The adsorbent was then reactivated with 0.2 mol / L KCl solution, completing one adsorption-desorption cycle. After four consecutive cycles, the Cs content of KNZOR... + The removal efficiency remained stable at 81.9%–85.6%, while the removal efficiency of KNZSS consistently remained at 96.2%–97.5%, indicating that both exhibit excellent structural stability and regeneration capability, with KNZSS demonstrating superior cycling performance. These results confirm that the prepared nitrogen-doped zinc-based adsorbent possesses good reusability in practical applications.

[0043] like Figure 4 As shown in (g) and (h), under conditions of high concentration of competing ions coexisting, 5 mg of KNZOR or KNZSS was added to 10 mL of solution containing 100 mg / L Cs. + In a solution (using CsCl as the source), Na is introduced respectively. + (1000 mg / L, Na) + / Cs + Molar ratio = 321:1) or K + (500mg / L, K) + / Cs +The molar ratio was 173:1, and the performance was measured after adsorption by shaking at room temperature for 24 hours. The results showed that KNZSS in Na + / Cs + =321:1 for Cs + The allocation coefficient (K) d ) reached 5.7×10 3 mL / g, at K + / Cs + When the ratio is 173:1, it is further increased to 1.4 × 10. 4 mL / g; KNZOR in K + / Cs + =K under the condition of 173:1 d (Cs) is 5.7 × 10 3 mL / g, corresponding Cs + The removal efficiency remained at a high level. These results fully demonstrate that KNZSS and KNZOR still possess excellent selectivity and anti-interference ability under extreme ion interference environments, and are particularly suitable for cesium separation in high-salt and complex wastewater.

[0044] like Figure 4 As shown in (i), to evaluate the potential for practical application, 5 mg of KNZOR or KNZSS adsorbent was added to 10 mL of a solution containing 100 mg / L Cs. + In real water bodies (using CsCl as the source), including salt lake water, river water, and tap water, Cs was measured after 24 hours of shaking adsorption at room temperature. + Removal efficiency. Experimental results show that KNZSS has good removal efficiency for Cs in saline lake water, river water, and tap water. + The removal rates reached 72.05%, 75.52%, and 84.67%, respectively; KNZOR also showed good performance under the same conditions, with removal rates of 67.34%, 70.59%, and 73.14%, respectively. Although real water bodies contain high concentrations of coexisting ions (such as Na+), + K + Ca 2+ Mg 2+ Both adsorbents (such as natural organic matter) can effectively capture Cs. + This fully demonstrates its applicability in complex real-world aquatic environments, with KNZSS exhibiting superior overall performance.

[0045] Application Example 2 Column experiments were conducted using the nitrogen-doped zinc-based adsorbent prepared in Example 1 or 2.

[0046] In the fixed-bed column adsorption experiment, KNZOR and KNZSS were directly packed as dry powders into a glass chromatography column with an inner diameter of 0.8 cm. The bed height was 1.5 cm, and the packing amounts were 0.12 g (KNZOR) and 0.13 g (KNZSS), respectively. After packing, the column was moistened with deionized water and air bubbles were removed to ensure a uniform bed.

[0047] like Figure 5 As shown in (a) and (b), in the fixed-bed column experiment, 0.12 g of KNZOR or 0.13 g of KNZSS dry powder was packed into a glass column with an inner diameter of 0.8 cm and a bed height of 1.5 cm, and a solution containing 10 mg / L of KNZSS was continuously introduced at a flow rate of 0.5 mL / min. + The dynamic adsorption performance of simulated wastewater (using CsCl as the source) was investigated. The results showed that KNZSS and KNZOR could treat up to 532 BV (bed volume) and 450 BV (based on the breakthrough point C), respectively. t The dynamic adsorption capacities of cesium-containing wastewater (calculated as C0=0.05) were 238.86 mg / g and 172.34 mg / g, respectively, which fully demonstrates that both have excellent dynamic adsorption capacity, with KNZSS showing superior treatment efficiency and application potential.

[0048] like Figure 5 As shown in (c) and (d), in the elution experiment, 0.1 mol / L NH4Cl solution was used to desorb the adsorption-saturated KNZOR or KNZSS fixed bed column at a flow rate of 0.5 mL / min. The eluent was collected at each time point and Cs was measured. + Concentration. The results showed that Cs + Both adsorbents can be efficiently enriched in small amounts of eluent: KNZSS achieved a cumulative elution recovery of 95.72% within 140 minutes, while KNZOR achieved a recovery of 99.85% in just 110 minutes, with total recoveries exceeding 95%. These results confirm that the prepared adsorbent is not only easily regenerated but also capable of achieving Cs... + Its efficient concentration and recycling capabilities have great potential for recycling and resource utilization.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a nitrogen-doped zinc-based adsorbent, characterized in that, Includes the following steps: Step 1: Prepare the ZIF-8 precursor with a dodecahedral structure; Step 2: Prepare nitrogen-doped ZnO nanorods or nitrogen-doped ZnS microspheres; The preparation steps of the nitrogen-doped ZnO nanorods are as follows: the ZIF-8 precursor obtained in step 1 is dispersed in a solvent and subjected to a low-temperature hydrothermal reaction at 150~200℃. After the reaction is completed, the product is collected, washed and vacuum dried to obtain nitrogen-doped ZnO nanorods HNZOR. The preparation steps of the nitrogen-doped ZnS microspheres are as follows: the nitrogen-doped ZnO nanorods HNZOR are dispersed in water, and then a second low-temperature hydrothermal reaction is carried out in an ammonium hydroxide environment at 120~180℃. After the reaction is completed, the product is collected, washed and vacuum dried to obtain nitrogen-doped ZnS microspheres HNZSS. Step 3, Preparation of nitrogen-doped zinc-based adsorbent: using K-containing... + The nitrogen-doped ZnO nanorods (HNZOR) or nitrogen-doped ZnS microspheres (HNZOR) obtained in step 2 of potassium salt activation are washed and dried to obtain nitrogen-doped zinc-based adsorbents.

2. The method for preparing the nitrogen-doped zinc-based adsorbent as described in claim 1, characterized in that, In step 1, the method for preparing the ZIF-8 precursor is as follows: Zinc nitrate hexahydrate and 2-methylimidazole in a molar ratio of 1:(4~5) were dissolved in methanol, mixed, and reacted at 50~80℃ for 12~48h. The resulting precipitate was washed and vacuum dried to obtain the ZIF-8 precursor with a dodecahedral structure.

3. The method for preparing the nitrogen-doped zinc-based adsorbent as described in claim 1, characterized in that, In step 2, the time for the first low-temperature hydrothermal reaction is 150~200h, and the time for the second low-temperature hydrothermal reaction is 120~180h.

4. The method for preparing the nitrogen-doped zinc-based adsorbent as described in claim 1, characterized in that, In step 2, the nitrogen-doped ZnO nanorods are shaped as flower-like hierarchical structures formed by the self-assembly of nanorods, and the length of the nanorods is 1~5μm.

5. The method for preparing the nitrogen-doped zinc-based adsorbent as described in claim 1, characterized in that, In step 2, the ammonium hydroxide environment is provided by ammonia and thiourea in a mass ratio of (0.8~1.5):

1.

6. The method for preparing the nitrogen-doped zinc-based adsorbent as described in claim 1, characterized in that, In step 2, the diameter of the nitrogen-doped ZnS microspheres is 50~300 nm.

7. The method for preparing the nitrogen-doped zinc-based adsorbent as described in claim 1, characterized in that, In step 3, the potassium salt is potassium chloride, potassium sulfate, potassium nitrate, and potassium carbonate.

8. The method for preparing the nitrogen-doped zinc-based adsorbent as described in claim 1, characterized in that, In step 3, the potassium salt contains K + The concentration is 1~5 mol / L, and the activation time is 12~48 h.

9. A nitrogen-doped zinc-based adsorbent obtained by any one of the preparation methods described in claims 1 to 8.

10. The application of the nitrogen-doped zinc-based adsorbent as described in claim 9 in the removal of radioactive cesium.

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