An acid-regulated copper-based prussian blue analogue and a preparation method and application thereof

Abstract

This invention relates to the field of cesium ion adsorption materials, specifically to an acid-controlled copper-based Prussian blue analogue, its preparation method, and its application. The invention provides a method for preparing an acid-controlled copper-based Prussian blue analogue, comprising: adding potassium ferrocyanide solution to a mixture of polyvinylpyrrolidone and a copper salt solution, followed by stirring and aging to obtain particulate copper-based Prussian blue analogue; adding the particulate copper-based Prussian blue analogue to a mixture of acid and N,N-dimethylformamide, followed by heating to obtain an acid-controlled copper-based Prussian blue analogue. This invention utilizes acid control to induce new structures and more adsorption sites in the copper-based Prussian blue analogue, thereby achieving selective and efficient adsorption of cesium ions in water, significantly reducing the interference of sodium ions on cesium ion adsorption, and making it more stable in solution.

Description

Technical Field

[0001] This invention relates to the field of cesium ion adsorption materials technology, specifically to an acid-controlled copper-based Prussian blue analogue, its preparation method, and its application. Background Technology

[0002] In the global energy transition, on the one hand, the expansion of nuclear energy applications and the increase in production activities in the new energy industry chain have led to a significant increase in the discharge of cesium-containing wastewater, which poses a major threat to the ecological environment and human health. On the other hand, with the rapid development of emerging industries, cesium, as a key strategic resource, is in urgent market demand. Therefore, developing efficient cesium ion adsorption and cesium sodium separation technologies is crucial for nuclear safety and resource recycling.

[0003] Adsorption has become the mainstream technology for cesium treatment due to its low cost and environmental friendliness. However, conventional materials (such as zeolite and ordinary resin) have limited adsorption capacity and slow kinetics, making it difficult to meet the needs of advanced treatment. Cesium ions have similar properties to sodium ions, but the concentration of sodium in actual water bodies is much higher than that of cesium. Sodium will compete for adsorption sites, inhibiting the selective adsorption of cesium and making it impossible to achieve the separation standard.

[0004] Some novel materials (such as crown ether polymers) are expensive and prone to contamination. Although Prussian blue analogues (PBAs) are relatively mature, they still have drawbacks such as poor stability and insufficient active sites.

[0005] Therefore, structural modulation of copper-based Prussian blue analogues is expected to further enhance their adsorption performance for cesium ions. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide an acid-regulated copper-based Prussian blue analogue, its preparation method, and its application. The method provided by this invention is simple to prepare, and the resulting adsorbent has good selective adsorption of cesium ions, greatly reducing the adsorption effect of sodium ions on cesium ions.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing an acid-regulated copper-based Prussian blue analogue, comprising: S1. Add potassium ferrocyanide solution to a mixture of polyvinylpyrrolidone and copper salt solution, then stir and age to obtain particulate copper-based Prussian blue analogue; S2. Particulate copper-based Prussian blue analogues were added to a mixture of acid and N,N-dimethylformamide, followed by heating to obtain acid-regulated copper-based Prussian blue analogues.

[0008] Currently, ordinary particulate Prussian blue and its analogues are widely used to remove cesium ions from water; however, they are susceptible to interference from other ions and have limited adsorption capacity, making it difficult to meet the needs of advanced treatment in practical applications. This invention significantly improves the adsorption capacity and selectivity of copper-based Prussian blue analogues for cesium ions by acid-modulating their structural characteristics, thereby enhancing their anti-interference performance in complex ionic environments.

[0009] Preferably, in S1, the copper salt in the copper salt solution is copper chloride, copper sulfate, copper nitrate, copper carbonate, or basic copper carbonate; and / or, the molar ratio between copper ions in the copper salt solution and ferrous ions in the potassium ferrocyanide solution is (1.8~2.2):1.

[0010] Preferably, in S1, the stirring conditions are: stirring at 500~800 r for 6~10 h, and the aging time is 8~24 h.

[0011] Preferably, in S1, the concentration of the particulate copper-based Prussian blue analogue is 0.5~1 g / L.

[0012] Preferably, in S2, the acid is hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid; and / or, the concentration of the acid is 0.1~2 mol / L.

[0013] Etching particulate copper-based Prussian blue analogs with hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid not only transformed the particulate state into a porous state but also revealed XRD peaks distinct from those before etching, demonstrating the emergence of new structures in acid-regulated copper-based Prussian blue analogs. However, etching with hydrofluoric acid failed to produce any new structural features, resulting in low cesium ion adsorption. Further analysis of the deeper structural information revealed that the increased content of mesopores in the structure reduces steric hindrance, allowing hydrated cesium ions with larger hydration radii to more easily enter the interior of the acid-regulated copper-based Prussian blue analogs, thus achieving selective adsorption of cesium ions.

[0014] Preferably, in S2, the mass-to-volume ratio of the particulate copper-based Prussian blue analog to the mixture of acid and N,N-dimethylformamide is 0.8~1 mg / mL; and / or, in the mixture of acid and N,N-dimethylformamide, the volume ratio of acid to N,N-dimethylformamide is (0.4~0.6):1.

[0015] Preferably, in S2, the heating reaction is carried out at 60-80°C for 20-50 h.

[0016] This invention provides acid-regulated copper-based Prussian blue analogs.

[0017] This invention provides the application of acid-regulated copper-based Prussian blue analogues in the adsorption of cesium ions in water.

[0018] The acid-regulated copper-based Prussian blue analogue provided in this invention can be used for the treatment of radioactive wastewater and the removal of cesium ions from industrial wastewater.

[0019] This invention provides a cesium ion adsorbent, including the acid-regulated copper-based Prussian blue analog proposed in this invention.

[0020] Therefore, the present invention has the following beneficial effects: the present invention utilizes acid regulation of copper-based Prussian blue analogues to enable the copper-based Prussian blue analogues to exhibit new structures and more adsorption sites; thereby achieving selective and efficient adsorption of cesium ions in water, greatly reducing the interference of sodium ions on the adsorption of cesium ions and making it more stable in solution. Attached Figure Description

[0021] Figure 1 XRD patterns of CupP after different acid regulation.

[0022] Figure 2 This is a graph showing the adsorption capacity of five Prussian blue analogues for Cs(I) aqueous solution.

[0023] Figure 3 The kinetic curves of five Prussian blue analogues to Cs(I) aqueous solution are shown.

[0024] Figure 4 This is a graph showing the adsorption capacity of six Prussian blue analogues for Cs(I) aqueous solution.

[0025] Figure 5 This is a selective adsorption diagram of sodium cesium.

[0026] Figure 6 The diagram shows the pore size distribution of six Prussian blue analogues, where a is CupB, b is CupB-HCl, c is CupB-HNO3, d is CupB-HF, e is CupB-H2SO4, and f is CupB-H3PO4.

[0027] Figure 7 This is a graph showing the specific surface area and mesopore volume ratio of six Prussian blue analogues.

[0028] Figure 8 The images show TEM images of CupPb and CupPb-HNO3, where a is CupPb and b is CupPb-HNO3. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0030]

Example

[0031] ② Add 1 mmol of potassium ferrocyanide to 50 mL of water, stir thoroughly to dissolve, and record as solution B.

[0032] ③ Slowly and evenly add solution B to solution A, stir at 500 r for 6 h, let stand and age for 12 h, centrifuge at 6000 rpm, wash and dry to obtain particulate copper-based Prussian blue analogue, denoted as CupB.

[0033] (2) Hydrochloric acid etching ① Add 30 mg of granular Prussian blue (CuPB) to a mixed solution of 35 mL hydrochloric acid and N,N-dimethylformamide (DMF). The concentration of hydrochloric acid in the mixed solution is 0.1 mol / L, and the volume concentration of DMF is 71%.

[0034] ② The powder was ultrasonically dispersed and stirred until homogeneous. The mixture was then placed in an 80℃ oven and reacted for 24 h to obtain the product etched with hydrochloric acid. The product was washed with pure water and ethanol, and then freeze-dried to obtain a hydrochloric acid-controlled copper-based Prussian blue analogue, denoted as CupB-HCl-0.1.

[0035] Example 2 This embodiment is basically the same as Example 1, except that the hydrochloric acid concentrations are 0.5 mol / L, 1.0 mol / L, and 1.5 mol / L, and the obtained products are denoted as CuPB-HCl-X (X=0.5, 1.0, 1.5).

[0036] Example 3 This embodiment is basically the same as Example 1, except that 0.1 mol / L hydrochloric acid is replaced with 1.0 mol / L nitric acid (HNO3), sulfuric acid (H2SO4), and phosphoric acid (H3PO4), respectively, and the obtained product is denoted as CupB-X (X=HNO3, H2SO4, H3PO4).

[0037] Comparative Example 1 ① Add 0.3 g of polyvinylpyrrolidone (PVP) and 2 mmol of copper chloride to 100 mL of water, stir thoroughly to dissolve, and record as solution A.

[0038] ② Add 1 mmol of potassium ferrocyanide to 50 mL of water, stir thoroughly to dissolve, and record as solution B.

[0039] ③ Slowly and evenly add solution B to solution A, stir at 500 r for 6 h, let stand and age for 12 h, centrifuge at 6000 rpm, wash and dry to obtain particulate copper-based Prussian blue analogue, denoted as CupB.

[0040] Comparative Example 2 This comparative example is basically the same as Example 1, except that 0.1 mol / L hydrochloric acid is replaced with 1.0 mol / L hydrofluoric acid (HF), and the resulting product is denoted as CupB-HF.

[0041] [Performance Testing] 1. XRD XRD analysis was performed on CupP and CupP-X (X = HCl, HNO3, HF, H2SO4, H3PO4), and the obtained XRD patterns are shown below. Figure 1 As shown, after etching CuPB with HCl, HNO3, H2SO4, and H3PO4, new crystal planes appear at 16° and 21°, and the 200° peak of CuPB weakens and the crystal plane disappears. This indicates that the structure has changed. This proves that a new structure appears after etching CuPB with HCl, HNO3, H2SO4, and H3PO4.

[0042] 2. Adsorption performance (1) Determination of adsorption capacity CupB and CupB-HCl-X (X=0.1, 0.5, 1.0, 1.5) were selected for adsorption capacity determination. The method is as follows: 2 mg of adsorbent was weighed and added to a sample bottle containing 10 mL of a 250 mg / L Cs(I) solution. The sample bottle was placed in a constant temperature shaker and shaken at 25℃ and 180 rpm for 24 h. The supernatant was then aspirated with a syringe and filtered through a 0.45 μm polyethersulfone membrane to obtain the adsorbed liquid. After dilution, the Cs(I) concentration in the solution was measured, and the adsorption capacity was calculated. The experiment was repeated twice.

[0043] Figure 2 This is a graph showing the adsorption capacity of five Prussian blue analogues for Cs(I) aqueous solution. Based on... Figure 2It can be seen that the adsorption capacity of copper-based Prussian blue was significantly improved after hydrochloric acid regulation; and when the hydrochloric acid concentration rose to 1.0 mol / L, it was close to the maximum adsorption capacity, so 1.0 mol / L can be determined as the optimal acid concentration.

[0044] (2) Adsorption kinetics determination Adsorption kinetics were determined using CuPB and CuPB-HCl-X (X = 0.1, 0.5, 1.0, 1.5). The method was as follows: 8 mg of adsorbent was weighed and added to a beaker containing 100 mL of a 10 mg / L Cs(I) solution. The beaker was shaken at 25 ℃ and 500 rpm. At time intervals of 10 s, 30 s, 1, 2, 5, 10, 15, 20, 30, 45, 60, and 120 min, 4 mL of liquid was drawn using a syringe and filtered through a 0.45 μm polyethersulfone membrane to obtain the adsorbed liquid. The Cs(I) concentration in the solution was then measured after dilution. The experiment was repeated twice.

[0045] Figure 3 The kinetic curves of five Prussian blue analogues to Cs(I) aqueous solution are shown. Figure 3 It can be seen that CuPB-HCl basically reaches adsorption equilibrium after 60 min. Compared with CuPB, the adsorption rate of Prussian blue after hydrochloric acid regulation is greatly improved. Based on the adsorption capacity and adsorption kinetics results, the optimal acid concentration of 1 mol / L hydrochloric acid was selected as the one with better effect.

[0046] (3) Determination of cesium adsorption capacity CupB and CupB-X (X = HCl, HNO3, HF, H2SO4, H3PO4) were selected for adsorption capacity determination. The method is as follows: 2 mg of adsorbent was weighed and added to a sample bottle containing 10 mL of a 250 mg / L Cs(I) solution. The sample bottle was placed in a constant temperature shaker and shaken at 25℃ and 180 rpm for 24 h. The supernatant was then aspirated with a syringe and filtered through a 0.45 μm polyethersulfone membrane to obtain the adsorbed liquid. After dilution, the Cs(I) concentration in the solution was measured, and the adsorption capacity was calculated. The experiment was repeated twice.

[0047] Figure 4 This is a graph showing the adsorption capacity of six Prussian blue analogues for Cs(I) aqueous solutions. It can be observed that after etching CuPB with HCl, HNO3, H2SO4, and H3PO4, the adsorption capacity of CuPB-X (X = HCl, HNO3, H2SO4, H3PO4) for cesium ions was significantly increased; while the adsorption capacity of CuPB-HF was even lower than that of untreated CuPB, which is speculated to be related to the fact that the structural characteristics did not change after HF etching in the XRD results. Combined with... Figure 1 and Figure 4 The results show that the structure of CupB changes when treated with a specific acid, and this special structure enhances the selective adsorption of Cs(I).

[0048] (4) Selectivity determination of cesium sodium Selective adsorption of Cs(I) and Na(I) was performed using CupB and CupB-X (X = HCl, HNO3, HF, H2SO4, H3PO4). The method was as follows: 2 mg of adsorbent was weighed and added to a sample vial containing 10 mL of solution A (100 mg / L Cs(I), 100 mg / L Na(I)) and solution B (100 mg / L Cs(I), 1000 mg / L Na(I)). The sample vial was placed in a constant temperature shaker and shaken at 25℃ and 180 rpm for 24 h. The supernatant was then aspirated with a syringe and filtered through a 0.45 μm polyethersulfone membrane to obtain the adsorbed liquid. After dilution, the concentrations of Cs(I) and Na(I) in the solution were measured, and the selectivity coefficient was calculated. The experiment was repeated twice.

[0049] Figure 5 The chart shows the selective adsorption of cesium ions by six Prussian blue analogues at different sodium ion concentrations. It can be seen that etching with acids other than HF (HCl, HNO3, H2SO4, H3PO4) significantly improves the material's selectivity for cesium ions. Even in the presence of high-concentration sodium ions (Group B), the selectivity coefficient of CuPB-HNO3 for Cs(I) remains above 150.

[0050] 3. Mechanism Analysis CupB and CupB-X (X = HCl, HNO3, HF, H2SO4, H3PO4) were selected for BET determination. Figure 6 The diagram shows the pore size distribution of six Prussian blue analogues, and it can be seen that the pore size increases after etching with acid (except HF). Figure 7 This is a graph showing the specific surface area and mesopore volume ratio of Prussian blue analogues. Figure 7 The higher the content of mesopores (2~50 nm), the smaller the specific surface area. Figure 4 The adsorption capacity of six Prussian blue analogues and Figure 7 It can be seen that increasing the specific surface area does not improve the adsorption of cesium ions. The high specific surface area mainly comes from micropores (<2 nm). The increase in mesopore content helps to reduce steric hindrance, making it easier for hydrated cesium ions with larger hydration radii to enter the interior of the material. Micropores, on the other hand, cause blockage. CuPB-HF has the highest micropore content and the lowest adsorption capacity, while CuPB-HCl, CuPB-HNO3, and CuPB-H3PO4 have high mesopore content and high adsorption capacity.

[0051] The increase in mesoporous content only reduces the diffusion resistance of Cs ions in the material; further analysis of the material structure is required. Elemental analysis was performed on CuPB and CuPB-X (X = HCl, HNO3, HF, H2SO4, H3PO4) using the following method: 3 mg of the adsorbent and 2 mL of aqua regia were added to a 50 mL reaction vessel. The reaction was carried out at 180℃ for 6 h. After natural cooling, the solution was completely removed and diluted to volume with a 50 mL volumetric flask. The contents of Cu, Fe, and K in the adsorbent were determined and calculated.

[0052] Table 1 shows the main elemental contents of six Prussian blue analogues. It can be seen that the Cu:Fe ratio remains essentially unchanged after HF etching, while after etching with the other acids (HCl, HNO3, H2SO4, H3PO4), the Cu:Fe ratio decreases from 2.0 to 1.5-1.6. The reduced Cu content in CuPB-X (X = HCl, HNO3, H2SO4, H3PO4) indicates that these acids affect the Cu content during etching, leading to defects or vacancies, exposing more adsorption sites, and increasing adsorption capacity. This result verifies the XRD results, demonstrating that structural changes lead to changes in adsorption sites, thereby enhancing the selective adsorption of Cs(I).

[0053] Table 1 Elemental Content

[0054] CuPB and CuPB-HNO3 were selected for transmission electron microscopy (TEM) analysis, and the obtained TEM spectra are shown below. Figure 8 As shown. Combined with Figure 1 Data analysis showed that the HNO3-etched material exhibited good crystal diffraction peaks in XRD, proving that CuPB-HNO3 still retains the long-range ordered structure of CuPB. However, HRTEM revealed that due to the removal of a large number of Cu ions by acid etching, CuPB-HNO3 developed local defects, exhibiting a short-range disordered state. After etching, some regions of the material changed from a periodic arrangement and obvious lattice stripe structure before etching to a disordered arrangement and amorphous structure without obvious lattice stripes. This transformation exposed more adsorption sites, reduced ion diffusion steric hindrance, and promoted the adsorption of target ions by the material.

Claims

1. A method for preparing an acid-regulated copper-based Prussian blue analogue, characterized in that, include: S1. Add potassium ferrocyanide solution to a mixture of polyvinylpyrrolidone and copper salt solution, then stir and age to obtain particulate copper-based Prussian blue analogue; S2. Particulate copper-based Prussian blue analogues were added to a mixture of acid and N,N-dimethylformamide, followed by heating to obtain acid-regulated copper-based Prussian blue analogues.

2. The preparation method according to claim 1, characterized in that, In S1, the copper salt in the copper salt solution is copper chloride, copper sulfate, copper nitrate, copper carbonate, or basic copper carbonate; and / or, the molar ratio between copper ions in the copper salt solution and ferrous ions in the potassium ferrocyanide solution is (1.8~2.2):

1.

3. The preparation method according to claim 1, characterized in that, In S1, the stirring conditions are: stirring at 500~800 r for 6~10 h, and the aging time is 8~24 h.

4. The preparation method according to claim 1, characterized in that, In S1, the concentration of the particulate copper-based Prussian blue analogue is 0.5~1 g / L.

5. The preparation method according to claim 1, characterized in that, In S2, the acid is hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid; and / or, the concentration of the acid is 0.1~2 mol / L.

6. The preparation method according to claim 1, 3, or 5, characterized in that, In S2, the mass-to-volume ratio of the particulate copper-based Prussian blue analogue to the mixture of acid and N,N-dimethylformamide is 0.8~1 mg / mL; and / or, in the mixture of acid and N,N-dimethylformamide, the volume ratio of acid to N,N-dimethylformamide is (0.4~0.6):

1.

7. The preparation method according to claim 1, characterized in that, In S2, the heating reaction conditions are 60~80℃ for 20~50 h.

8. The acid-regulated copper-based Prussian blue analogue prepared by any one of the preparation methods described in claims 1 to 7.

9. The application of the acid-controlled copper-based Prussian blue analogue prepared by any one of the preparation methods described in claims 1 to 7, or the acid-controlled copper-based Prussian blue analogue as described in claim 8, in the adsorption of cesium ions in water.

10. A cesium ion adsorbent, characterized in that, This includes acid-regulated copper-based Prussian blue analogs prepared by any of the preparation methods described in claims 1 to 7, or acid-regulated copper-based Prussian blue analogs as described in claim 8.

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