A method for preparing a cadmium (II) complex single crystal and adsorbing UO2 2+ Application

Abstract

The application discloses a preparation method of cadmium (II) complex single crystal and application of the cadmium (II) complex single crystal in adsorbing UO2 2+ The application belongs to the fields of coordination chemistry and adsorption removal of pollutants in water, and belongs to the field of coordination chemistry and adsorption removal of pollutants in water. The preparation method of the cadmium complex single crystal comprises the following steps: mixing a cadmium source, 5,11,17,23-tetra[(m-carboxyl phenyl)azo]-25,26,27,28-tetrahydroxyl calix[4]arene and 1,4-bis(1-imidazolyl)benzene in a solvent, and reacting to obtain the cadmium complex single crystal. The three-dimensional framework structure of the cadmium (II) complex single crystal prepared by the application is modified with rich carboxylic acid groups, azo groups and imidazole groups, and active adsorption sites are rich, so that the cadmium (II) complex single crystal is more conducive to the action with UO2 2+ , thereby effectively removing UO2 2+ in the aqueous solution. Moreover, the Cd (II) complex single crystal has good stability and can maintain a certain crystallinity in the aqueous solution.

Description

Technical Field

[0001] This invention relates to the fields of coordination chemistry and adsorption removal of pollutants in water, and particularly to a method for preparing single crystals of cadmium(II) complexes and adsorbing UO2. 2+ application. Background Technology

[0002] Nuclear power, as a high-energy-density energy source, plays a crucial role in energy security and carbon emission reduction. However, the use of nuclear energy inevitably generates large amounts of radioactive industrial wastewater containing hexavalent uranium (U(VI)). Radioactive uranium primarily exists as soluble UO2. 2+ UO2 exists in the aquatic environment in its extremely high chemical mobility and bioaccumulation potential. Once it enters the human body, it can cause irreversible damage to vital organs such as the kidneys and bones, increase the risk of diseases such as cancer, and seriously threaten the ecosystem and human health. Therefore, how to control UO2 is a crucial issue. 2+ Precise separation and enrichment are crucial for environmental protection and sustainable energy development.

[0003] Currently, it is used to remove UO2 from uranium-containing media. 2+ The main methods include precipitation, solvent extraction, electrochemical treatment, membrane separation, and adsorption. Among these, adsorption is preferred due to its good adaptability and environmental friendliness. 2+ Effective methods for uranium capture. In recent years, various porous adsorbents for uranium extraction have been developed, including nanomaterials and polymer materials; however, their simple composition, lack of structural and functional tunability, slow adsorption kinetics, low selectivity, and low adsorption capacity have hindered their further application. Therefore, developing novel adsorbent materials that combine structural tunability with excellent adsorption performance is crucial for capturing UO2 in aqueous phases. 2+ The efficient removal of [the substance] has become an urgent need.

[0004] Metal-organic frameworks (MOFs), as porous crystalline materials formed by the self-assembly of metal ions or clusters with organic ligands through strong coordination bonds, possess unique structural designability and tunable chemical composition. Therefore, designing a suitable MOF for the separation of radionuclides to achieve the separation of UO2 in aqueous solution is a key challenge. 2+ Its efficient adsorption has great research value. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing single crystals of cadmium(II) complexes and for adsorbing UO2. 2+ This invention addresses the aforementioned problems in the background art. The three-dimensional framework structure of the cadmium(II) complex single crystal prepared by this invention is modified with abundant carboxylic acid, azo, and imidazole functional groups, resulting in abundant active adsorption sites, which is more conducive to adsorption by UO2.2+ This mechanism effectively removes UO2 from aqueous solutions. 2+ Furthermore, this Cd(II) complex single crystal exhibits good stability and can maintain a certain degree of crystallinity in aqueous solution.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One of the technical solutions of this invention is to provide a cadmium complex single crystal, wherein the chemical formula of the cadmium complex single crystal is: {[Cd2L(bimb)(DMA)(H2O)]·5DMA} n Where bimb is 1,4-bis(1-imidazolyl)benzene, and L is deprotonated H4L.

[0008] This invention utilizes coordination interactions to achieve the synthesis of UO2 in aqueous solutions by introducing MOFs materials with functional groups such as carboxylic acid groups, imidazole groups, and azo groups. 2+ Highly efficient adsorption.

[0009] Preferably, the cadmium complex single crystal belongs to the triclinic crystal system with space group . α=84.3650(10)°, β=69.4020(10)°, γ=62.9920(10)°,

[0010] The second technical solution of the present invention provides a method for preparing single crystals of the above-mentioned cadmium complex, comprising the following steps:

[0011] A cadmium source, 5,11,17,23-tetratetra[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene and 1,4-bis(1-imidazolyl)benzene were mixed in a solvent and reacted to obtain the cadmium complex single crystal.

[0012] Preferably, the cadmium source is cadmium nitrate.

[0013] Preferably, the molar ratio of the cadmium source, 5,11,17,23-tetratetra[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene and 1,4-bis(1-imidazolyl)benzene is 1.8-2:1:4.5-5.

[0014] Preferably, the solvent contains N,N'-dimethylacetamide (DMA) and water.

[0015] Single-crystal diffraction analysis results show that DMA does not only exist as a reaction solvent. Some DMA molecules participate in the construction of the single-crystal structure through coordination bonds, forming stable coordination with the central metal ion and becoming part of the crystal structure.

[0016] Preferably, the volume ratio of N,N'-dimethylacetamide to water is 1:1.

[0017] Preferably, the reaction is carried out at a temperature of 100°C for 48 hours.

[0018] The third technical solution of the present invention: provides a single crystal of the above-mentioned cadmium complex for adsorbing UO2. 2+ Applications in the field.

[0019] Fourth technical solution of the present invention: providing a method for adsorbing UO2 in water 2+ The method involves adding the aforementioned cadmium complex single crystal to water.

[0020] The beneficial technical effects of the present invention are as follows:

[0021] The cadmium(II) complex single crystal prepared in this invention has a three-dimensional framework structure modified with abundant carboxylic acid, azo, and imidazole functional groups, resulting in a rich number of active adsorption sites, which is more conducive to its adsorption by UO2. 2+ This mechanism effectively removes UO2 from aqueous solutions. 2 + Furthermore, this Cd(II) complex single crystal exhibits good stability and can maintain a certain degree of crystallinity in aqueous solution. Under pH=5 conditions, this single crystal resists UO2... 2+ The adsorption removal rate can reach 89.35%, while achieving a high adsorption capacity of 128.56 mg / g. Furthermore, the synthesis process of this invention is simple and has excellent application prospects. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a diagram of the coordination environment of cadmium in the single crystal of the cadmium complex of Example 1 of the present invention.

[0024] Figure 2 This is a structural diagram of the cadmium complex single crystal of Example 1 of the present invention.

[0025] Figure 3 Simulated powder diffraction pattern, experimental powder diffraction pattern, and powder diffraction pattern after soaking in an aqueous solution at pH 5 for 12 hours are shown for single crystals of cadmium complexes.

[0026] Figure 4The cadmium complex single crystal of Example 1 of this invention exhibits its effect on UO2 in water bodies with different pH values. 2+ The adsorption effect diagram.

[0027] Figure 5 The cadmium complex single crystals of Example 1 of this invention, control product 1, and control product 2 were tested for their effects on UO2 in water at pH 5. 2+ A comparison chart of adsorption effects.

[0028] Figure 6 The cadmium complex single crystal of Example 1 of this invention adsorbs UO2 in water. 2+ The dynamic diagram.

[0029] Figure 7 This invention demonstrates the adsorption of different concentrations of UO2 in water by a single crystal of a cadmium complex, as described in Example 1 of this invention. 2+ Adsorption isotherm diagram. Detailed Implementation

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0031] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0032] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. It should be noted that any aspects of this invention not described in detail are conventional practices in the art and are not the focus of this invention.

[0033] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0034] This invention discloses a method for preparing a cadmium(II) complex single-crystal adsorbent, comprising the following steps:

[0035] Cadmium nitrate tetrahydrate, 5,11,17,23-tetra[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene (abbreviated as H4L) and 1,4-bis(1-imidazolyl)benzene (abbreviated as bimb) were dissolved in a mixed solvent of N,N'-dimethylacetamide (abbreviated as DMA) and distilled water, then sealed in a reaction flask, sonicated at room temperature, and stored in a constant temperature oven at 100℃ for 48 hours. After being taken out, the mixture was cooled to room temperature to obtain orange-yellow block crystals. After filtration and drying, the target product was obtained, which is Cd(II) single crystal adsorbent.

[0036] Unless otherwise specified, "room temperature" in this invention refers to 10-30°C.

[0037] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0038] Example 1

[0039] A method for preparing a single crystal of a cadmium(II) complex, comprising the following steps:

[0040] Cd(NO3)2·4H2O (0.02 mmol, 6.17 mg), H4L (0.01 mmol, 10.44 mg), 1,4-bis(1-imidazolyl)benzene (0.05 mmol, 10.50 mg), and a mixed solvent (DMA:water = 4.5 mL:4.5 mL) were added to a 10 mL glass bottle. After sonication at room temperature for 10 minutes, the bottle was sealed and stored in a 100°C oven for 48 hours. After cooling to room temperature, orange-yellow blocky Cd-MOF crystals were obtained. The product was washed with a DMA / water solution (1 / 1, V / V) and dried at room temperature to obtain a single crystal of the cadmium complex ({[Cd2L(bimb)(DMA)(H2O)]·5DMA}). n ).

[0041] Figure 1 This is a diagram of the coordination environment of cadmium in the single crystal of the cadmium complex of Example 1 of the present invention.

[0042] Figure 2 This is a structural diagram of the cadmium complex single crystal of Example 1 of the present invention.

[0043] Figure 3 Simulated powder diffraction pattern, experimental powder diffraction pattern, and powder diffraction pattern after soaking in an aqueous solution at pH 5 for 12 hours are shown for single crystals of cadmium complexes.

[0044] Figure 3 In the diagram, 1 is a simulated powder diffraction pattern of a cadmium complex single crystal, 2 is an experimental powder diffraction pattern of a cadmium complex single crystal of Example 1 of the present invention, and 3 is a powder diffraction pattern of a cadmium complex single crystal of Example 1 of the present invention after being soaked in an aqueous solution at pH=5 for 12 hours.

[0045] Depend on Figure 3 The single-crystal simulated powder diffraction pattern is consistent with the actual powder diffraction pattern of the cadmium complex, proving that the material was successfully synthesized. The powder diffraction pattern after soaking in an aqueous solution at pH 5 for 12 hours is also consistent with the actual powder diffraction pattern of the cadmium complex, demonstrating that the material structure possesses a certain degree of stability.

[0046] Comparative Example 1

[0047] The only difference from Example 1 is that H4L in Example 1 is replaced with an equimolar amount of bimb, and the resulting product is referred to as Control Product 1.

[0048] Comparative Example 2

[0049] The only difference from Example 1 is that bimb in Example 1 is replaced with an equimolar amount of H4L, and the resulting product is referred to as Control Product 2.

[0050] Effect verification

[0051] Cadmium complex adsorption of UO2 2+ test:

[0052] 1. UO2 at different pH conditions (pH = 3, 5, 7, 9) with a concentration of 5 ppm in 15 mL. 2+ 5 mg of the orange-yellow blocky cadmium complex single crystals prepared in Example 1 were added to the aqueous solution, and the mixture was stirred thoroughly at room temperature for 12 hours before sampling. After filtration through a 0.22 μm filter membrane, the UO2 in the supernatant was analyzed using a UV-Vis spectrophotometer. 2+ The remaining concentration was detected. The test results are as follows: Figure 4 As shown.

[0053] Figure 4 The cadmium complex single crystal of Example 1 of this invention exhibits its effect on UO2 in water bodies with different pH values. 2+ The adsorption effect diagram.

[0054] Depend on Figure 4 It can be seen that at pH 5, the cadmium complex single crystal has a certain effect on UO2. 2+ The adsorption and removal effect is optimal, reaching a removal rate of 89.35%.

[0055] Figure 5 The cadmium complex single crystals of Example 1 of this invention, control product 1, and control product 2 were tested for their effects on UO2 in water at pH 5. 2+ A comparison chart of adsorption effects.

[0056] Depend on Figure 5 It can be seen that the cadmium complex single crystal in Example 1 is effective for UO2. 2+The adsorption and removal effect of the product was the best, reaching a removal rate of 89.35%, while the removal rate of control product 1 was 56.68% and control product 2 was 50.63%.

[0057] 2. In 15 mL of UO2 with a concentration of 5 ppm and a pH of 5 2+ 5 mg of the orange-yellow blocky cadmium complex single crystals prepared in Example 1 were added to an aqueous solution and stirred at room temperature for different times (0-600 min) before sampling. After filtration through a 0.22 μm filter membrane, the UO2 in the supernatant was analyzed using a UV-Vis spectrophotometer. 2+ The remaining concentration was detected. The test results are as follows: Figure 6 As shown.

[0058] Figure 6 The cadmium complex single crystal of Example 1 of this invention adsorbs UO2 in water. 2+ The dynamic diagram.

[0059] Figure 6 The experimental results show that 89.35% of UO2 is present at adsorption equilibrium. 2+ It is adsorbed and removed.

[0060] 3. In 30 mL of UO2 at different concentrations with a pH of 5 2+ 5 mg of the orange-yellow blocky cadmium complex single crystals prepared in Example 1 were added to aqueous solutions (5, 50, 100, 150, 200, and 250 ppm), respectively. After thorough stirring at room temperature and reaching adsorption equilibrium, the solution was filtered through a 0.22 μm filter membrane. The UO2 in the supernatant was analyzed using a UV-Vis spectrophotometer. 2+ The remaining concentration was detected. The test results are as follows: Figure 7 As shown.

[0061] Figure 7 This invention demonstrates the adsorption of different concentrations of UO2 in water by a single crystal of a cadmium complex, as described in Example 1 of this invention. 2+ Adsorption isotherm diagram.

[0062] Figure 7 In the figure, the horizontal axis represents the concentration C of uranyl residue in the solution after adsorption. e This is not the initial concentration C0 of the solution.

[0063] Depend on Figure 7It is known that the adsorption capacity of the cadmium complex single crystal in Example 1 of this invention can reach 128.56 mg / g. This adsorption capacity is significantly higher than that of previously reported adsorbents such as activated carbon (28.3 mg / g) (J. Colloid Interface Sci. 2006, 296, 2, 434-441), nanoporous alumina (2.76 mg / g) (Sep. Purif. Technol. 2011, 83, 196-203), magnetic graphene / iron oxide composite material (69.49 mg / g) (Chem. Eng. J. 2013, 220, 45-52), and polypropylene nanofibers (83.24 mg / g) (Ecotoxicol. Environ. Saf. 2019, 186, 109746). This adsorption capacity for UO2 is significantly higher. 2+ The excellent removal performance can be attributed to the presence of numerous accessible carboxylic acid oxygens and nitrogen-containing adsorption sites within the adsorbent framework, demonstrating the effectiveness of the novel cadmium complex single crystals of this invention for UO2 removal. 2+ It has a good adsorption effect.

[0064] 4. Select a single crystal of appropriate size and perform X-ray diffraction experiments at room temperature under a microscope. The specific testing method is as follows: On a Bruker SmartApex-IICCD diffractometer, use a Mo-K crystal monochromated with a graphite monochromator. α ray by Diffraction data were collected using [method name missing]. Data reconstruction was performed using the Bruker SAINT program. Absorption correction was performed on the diffraction data of some structures using the SADABS program. The crystal structure was obtained by direct method combined with Fourier difference synthesis. All non-hydrogen atom coordinates and anisotropy parameters were corrected using full-matrix least squares method, and the CH atom positions were determined according to theoretical models. The coordination environment of metallic cadmium in the cadmium complex single crystal is shown in [reference missing]. Figure 1 The crystal structure of a single crystal of cadmium complex is shown in [reference needed]. Figure 2 Detailed crystal measurement data are shown in Table 1.

[0065] Table 1. Main crystallographic data of the coordination compounds of the present invention

[0066]

[0067] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A cadmium complex single crystal, characterized by, The chemical formula of the cadmium complex single crystal is: {[Cd2L(bimb)(DMA)(H2O)]·5DMA} n wherein, bimb is 1,4-bis(1-imidazolyl)benzene, and L is 5,11,17,23-tetra[(m-carboxylphenyl)azo]-25,26,27,28-tetrahydroxyl calix[4]arene after deprotonation. The cadmium complex single crystal belongs to triclinic system, and the space group is P , a = 17.9172(7) Å, b = 18.2534(6) Å, c = 18.4083(7) Å, α = 84.3650(10) °, β = 69.4020(10) °, γ = 62.9920(10) °, V = 5007.3(3) Å 3 .

2. A method for producing the cadmium complex single crystal according to claim 1, characterized by, The method comprises the following steps: mixing a cadmium source, 5,11,17,23-tetra[(m-carboxylphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene and 1,4-bis(1-imidazolyl)benzene in a solvent, and reacting to obtain the cadmium complex single crystal; the cadmium source is cadmium nitrate.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the cadmium source, 5,11,17,23-tetra[(m-carboxylphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene and 1,4-bis(1-imidazolyl)benzene is 1.8-2:1:4.5-5.

4. The production method according to claim 2, characterized by, The solvent comprises N,N'-dimethylacetamide and water.

5. The production method according to claim 4, characterized by, The volume ratio of the N,N'-dimethylacetamide and water is 1:

1.

6. The preparation method according to claim 2, characterized in that, The temperature of the reaction is 100 DEG C, and the time is 48 hours.

7. Use of the cadmium complex single crystal of claim 1 in adsorbing UO2 2+ of the art.

8. A method of adsorbing UO2 in water, characterized in that, 2+ adding the cadmium complex single crystal in claim 1 in water. ​

Images