Cadmium (II) complex single crystal preparation method and UO2 < 2 + > adsorption application

Abstract

The invention discloses a preparation method of a cadmium (II) complex single crystal and application of the cadmium (II) complex single crystal to UO2 < 2 + > adsorption, 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-tetrahydroxy 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 frame structure of the prepared cadmium (II) complex single crystal is modified with abundant carboxylic acid group, azo group and imidazolyl functional groups, active adsorption sites are abundant, and the cadmium (II) complex single crystal is more beneficial to action with UO2 < 2 + >, so that UO2 < 2 + > in an aqueous solution is effectively removed. In addition, the Cd (II) complex single crystal has good stability and can keep a certain crystallinity in an aqueous solution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coordination chemistry and adsorption removal of pollutants in water, in particular to a preparation method of cadmium (II) complex single crystal and adsorption of UO2 2+ application. BACKGROUND

[0002] Nuclear power, as a high energy density energy carrier, plays a key role in energy security and carbon emission reduction. However, a large amount of radioactive industrial wastewater containing hexavalent uranium U(VI) is inevitably produced in the process of nuclear energy utilization. Among them, radioactive uranium mainly exists in the form of soluble UO2 2+ in the water environment. Due to its extremely high chemical mobility and biological accumulation potential, once entering the human body, it will cause irreversible damage to important organs such as kidneys and bones, increase the risk of diseases such as cancer, and seriously threaten the ecology and human health. Therefore, how to realize the accurate separation and enrichment of UO2 2+ is of great importance to environmental protection and sustainable development of energy.

[0003] At present, the methods for removing UO2 2+ from uranium-containing media mainly include precipitation method, solvent extraction method, electrochemical treatment method, membrane separation method and adsorption method, etc. Among them, the adsorption method has become an effective method for UO2 2+ capture due to its good adaptability and environmental protection. In recent years, a variety of porous adsorbents for extracting uranium have been developed, including nano-carbon materials, polymer materials, etc.; but due to its simple composition, lack of structural and functional adjustability, slow adsorption kinetics, low selectivity and adsorption capacity, etc., its further application is hindered. Therefore, how to develop new adsorbent materials with structural adjustability and excellent adsorption performance to realize the efficient removal of UO2 2+ in water phase has become an urgent need.

[0004] Metal-organic framework (MOFs) material is a kind of porous crystalline material formed by self-assembly of metal ions or clusters and organic ligands through strong coordination bond, which has unique structural designability and chemical composition controllability. Therefore, how to design a kind of metal-organic framework material suitable for the field of radioactive nuclide separation to realize the efficient adsorption of UO2 2+ in aqueous solution has good research value. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of cadmium (II) complex single crystal and adsorption of UO2 2+ application, to solve the above problems in the background art. The three-dimensional framework structure of the cadmium (II) complex single crystal prepared by the present application is modified with rich carboxylic acid group, azo group and imidazole group functional groups, and the active adsorption sites are rich, which is more conducive to the adsorption of UO22+ The Cd(II) coordination complex single crystal can effectively remove UO2 in an aqueous solution 2+ The Cd(II) coordination complex single crystal has good stability and can maintain a certain crystallinity in an aqueous solution.

[0006] To achieve the above object, the application provides the following technical scheme.

[0007] The Cd(II) coordination complex single crystal has the chemical formula: {[Cd2L(bimb)(DMA)(H2O)]·5DMA} n wherein bimb is 1,4-bis(1-imidazolyl)benzene, and L is H4L after deprotonation.

[0008] The MOFs material designed by introducing carboxylic acid groups, imidazole groups and azo groups and the like can realize high-efficiency adsorption of UO2 in an aqueous solution by using coordination. 2+

[0009] Preferably, the Cd(II) coordination complex single crystal belongs to a triclinic system, and the space group is α=84.3650(10)°, β=69.4020(10)°, γ=62.9920(10)°,

[0010] The application also provides a preparation method of the Cd(II) coordination complex single crystal.

[0011] The Cd(II) coordination complex single crystal is obtained by mixing a cadmium source, 5,11,17,23-tetra[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxyl calix[4]arene and 1,4-bis(1-imidazolyl)benzene in a solvent and reacting.

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

[0013] Preferably, the molar ratio of the cadmium source, 5,11,17,23-tetra[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxyl calix[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] According to the single crystal diffraction analysis result, it can be seen that the DMA does not exist only as a reaction solvent. Part of the DMA molecules participate in the construction of the single crystal structure by coordination bonds, form stable coordination with the central metal ions and become a component of the crystal structure.​

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

[0017] Preferably, the temperature of the reaction is 100℃ and the time is 48 hours.

[0018] The third technical solution of the present application provides an application of the above-mentioned cadmium complex single crystal in adsorbing UO2 2+ in the field.

[0019] The fourth technical solution of the present application provides a method for adsorbing UO2 2+ in water, wherein the above-mentioned cadmium complex single crystal is added into the water.

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

[0021] The three-dimensional framework structure of the cadmium(II) complex single crystal prepared by the present application is modified with rich carboxylic acid groups, azo groups and imidazole groups, and the active adsorption sites are rich, which is more conducive to the reaction 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 degree of crystallinity in the aqueous solution. Under the condition of pH=5, the adsorption removal rate of the single crystal to UO2 2+ can reach 89.35%, and meanwhile, a high adsorption capacity can be achieved, which can reach 128.56mg / g. In addition, the synthesis process of the present application is simple and has a good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0023] Figure 1 It is a coordination environment diagram of cadmium in the cadmium complex single crystal of the embodiment 1 of the present application.

[0024] Figure 2 It is a structural diagram of the cadmium complex single crystal of the embodiment 1 of the present application.

[0025] Figure 3 It is a simulated powder diffraction pattern, an experimental powder diffraction pattern and a powder diffraction pattern after being soaked in the aqueous solution with pH=5 for 12h of the cadmium complex single crystal.

[0026] Figure 4Adsorption effect diagram of cadmium complex single crystal of embodiment 1 of the present application on UO2 2+ in different pH water bodies.

[0027] Figure 5 Adsorption effect comparison diagram of cadmium complex single crystal of embodiment 1 of the present application, control product 1 and control product 2 on UO2 2+ in water body with pH=5.

[0028] Figure 6 Kinetics diagram of cadmium complex single crystal of embodiment 1 of the present application adsorbing UO2 2+ in water.

[0029] Figure 7 Adsorption isotherm diagram of cadmium complex single crystal of embodiment 1 of the present application adsorbing UO2 2+ in water with different concentrations. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present application will now be described in detail, which should be considered to be illustrative of the present application and are not intended to limit the scope of the present application, and are to be understood as being merely descriptive of certain aspects, features and embodiments of the present application. It should be understood that the terminology used in the present application is merely for the purpose of describing particular embodiments and is not intended to limit the present application.

[0031] In addition, for numerical ranges in the present application, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value between any stated value or stated range, as well as any other stated value or intermediate value in the stated range is also encompassed within the present application. The upper and lower limits of these smaller ranges can be independently included or excluded from the ranges.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. It is to be noted that the present application is not limited to the materials or methods of their description unless otherwise specified.

[0033] As used in the present application, "comprise", "include", "have", "contain", and the like are open-ended terms, i.e., meaning "including but not limited to".

[0034] The present application discloses a preparation method of a cadmium(II) complex single crystal adsorbent, comprising the following steps:

[0035] Cd(NO3)2·4H2O, 5,11,17,23-tetra[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxyl calix[4]arene (H4L) and 1,4-bis(imidazol-1-yl)benzene (bimb) were dissolved in a mixed solvent of N,N'-dimethylacetamide (DMA) and distilled water, then were sealed in a reaction bottle, ultrasonic treatment at room temperature, stored in a constant temperature oven at 100℃ for 48 hours, after taking out, cooling to room temperature, orange yellow block crystal was obtained, after filtration and drying, the target product, Cd(II) single crystal adsorbent was obtained.

[0036] The "room temperature" in the present application is 10-30℃ unless otherwise specified.

[0037] The raw materials used in the following examples and comparative examples of the present application are all commercially available products.

[0038] Example 1

[0039] A preparation method of a cadmium(II) complex single crystal, the steps are as follows:

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

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

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

[0043] Figure 3 It is a simulated powder diffraction pattern of the cadmium complex single crystal, an experimental powder diffraction pattern and a powder diffraction pattern after soaking in a pH = 5 aqueous solution for 12 hours.

[0044] Figure 3 In the figure, 1 is a simulated powder diffraction pattern of the cadmium complex single crystal, 2 is an experimental powder diffraction pattern of the cadmium complex single crystal of Example 1 of the present application, and 3 is a powder diffraction pattern of the cadmium complex single crystal of Example 1 of the present application after soaking in a pH = 5 aqueous solution 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 removal effect of the orange yellow block cadmium complex single crystal prepared in Example 1 is optimal, and the removal rate reaches 89.35%, while the removal rate of the control product 1 is 56.68%, and the removal rate of the control product 2 is 50.63%.

[0057] 2. 5 mg of the orange yellow block cadmium complex single crystal prepared in Example 1 was added into 15 mL of UO2 2+ solution with a concentration of 5 ppm and a pH value of 5, and samples were taken after stirring at room temperature for different time (0-600 min). After filtration by using a 0.22 μm filter membrane, the residual concentration of UO2 2+ in the supernatant was detected by using an ultraviolet visible spectrophotometer. The test results are shown in Table 1. Figure 6

[0058] Figure 6 The kinetic diagram of the cadmium complex single crystal prepared in Example 1 adsorbing UO2 2+ in water.

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

[0060] 3. 5 mg of the orange yellow block cadmium complex single crystal prepared in Example 1 was added into 30 mL of UO2 2+ solution with different concentrations (5, 50, 100, 150, 200, 250 ppm) and a pH value of 5, and the solution was fully stirred at room temperature until the adsorption equilibrium was reached. After filtration by using a 0.22 μm filter membrane, the residual concentration of UO2 2+ in the supernatant was detected by using an ultraviolet visible spectrophotometer. The test results are shown in Table 3. Figure 7

[0061] Figure 7 The adsorption isotherm diagram of the cadmium complex single crystal prepared in Example 1 adsorbing UO2 2+ in water with different concentrations.

[0062] Figure 7 In the adsorption isotherm diagram, the abscissa is expressed as the residual uranyl concentration C e in the solution after adsorption, not the initial concentration C0 of the solution.

[0063] The kinetic diagram of the cadmium complex single crystal prepared in Example 1 adsorbing UO2 2+ in water. 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 H4L after deprotonation.

2. The cadmium complex single crystal according to claim 1, characterized by The cadmium complex single crystal belongs to triclinic system, and the space group is P-1 α = 84.3650(10)°, β = 69.4020(10)°, γ = 62.9920(10)°, 3. A method for producing the cadmium complex single crystal according to any one of claims 1 to 2, characterized by, The method comprises the following steps: The 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 are mixed in a solvent, reacted to obtain the cadmium complex single crystal.

4. The production method according to claim 3, characterized by, The cadmium source is cadmium nitrate.

5. The preparation method according to claim 3, characterized in that, The molar ratio of the 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 is 1.8-2:1:4.5-5.

6. The preparation method according to claim 3, characterized in that, The solvent comprises N,N'-dimethylacetamide and water.

7. The production method according to claim 6, characterized by, The volume ratio of the N,N'-dimethylacetamide and water is 1:

1.

8. The preparation method according to claim 3, characterized in that, The reaction temperature is 100 DEG C and the reaction time is 48 hours.

9. Use of a single crystal of the cadmium complex of any one of claims 1-2 for adsorbing UO2 2+ in the field of nuclear medicine.

10. A method of adsorbing UO2 in water, characterized in that, 2+ The cadmium complex single crystal of any one of claims 1-2 is added in water. ​

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