Preparation method of carbonated apatite-metal organic framework composite material and application of carbonated apatite-metal organic framework composite material to adsorption and removal of heavy metal ions in water

Abstract

The invention provides a preparation method of a carbonated apatite-metal organic framework composite material, which comprises the following steps: mixing carbonated apatite with a zinc salt solution to form a uniform solution; and adding an organic ligand into the mixed solution, carrying out thermal reaction, centrifuging, washing and drying to obtain the carbonated apatite-metal organic framework composite material. According to the application of the carbonated apatite-metal organic framework composite material in adsorption removal of heavy metal ions in water, the heavy metal ions comprise at least one of Cd < 2 + >, Pb < 2 + >, Hg < 2 + >, Cu < 2 + >, Cr < 3 + >, Cr < 6 + >, Zn < 2 + >, As < 3 + >, Ni < 2 + >, Mn < 2 + > and Sr < 2 + >. The obtained product selectively captures heavy metal ions on metal ions, meanwhile, nucleation sites are provided to avoid agglomeration of the metal organic framework, and the capacity is improved.

Description

Technical Field

[0001] This invention relates to a method for preparing a metal-organic framework composite for the efficient adsorption and removal of heavy metal ions from water, belonging to the field of chemical technology. Background Technology

[0002] Water pollution is considered a global problem and is rapidly increasing due to industrialization and other human activities. Untreated heavy metal ions emitted from various industries are a major source of water pollution. Therefore, the removal of heavy metal ions from wastewater has attracted the scientific community's attention to addressing this environmental issue. Existing technologies face multiple core technical challenges in the adsorption and treatment of heavy metal ions, making it difficult to balance efficiency, stability, and economy. Adsorbent performance has significant bottlenecks; traditional materials lack selectivity and are susceptible to calcium ions. 2+ Mg 2+ Interference from coexisting ions and organic matter limits the removal efficiency of target heavy metals; natural adsorbents have low capacity, while synthetic adsorbents are prone to saturation in high-concentration wastewater and slow adsorption kinetics in low-concentration wastewater; and nano-adsorbents are also prone to aggregation, leading to activity decay.

[0003] The adsorbent exhibits poor adaptability to complex water conditions. Heavy metals in wastewater, in their complexed and colloidal forms, are difficult to remove with conventional adsorbents, requiring additional pretreatment. pH changes alter the form of heavy metals, and high-salt environments compress the electric double layer, further reducing adsorption efficiency. Regeneration and recycling face significant challenges. Conventional regeneration methods, such as acid and alkali treatments, easily damage the material, resulting in a sharp decrease in capacity after multiple cycles. Furthermore, the regenerated wastewater contains high concentrations of heavy metals, posing a high risk of secondary pollution, and the disposal of exhausted adsorbents as hazardous waste is costly.

[0004] In engineering applications, solid-liquid separation of fine-particle materials such as nano-adsorbents is difficult, requiring additional equipment and increasing costs; single processes are difficult to adapt to switching between high and low concentration wastewater, the preparation and maintenance costs of high-performance adsorbents are relatively high, and there is a lack of on-site rapid monitoring technology for low-concentration heavy metals, making it difficult to accurately control process parameters.

[0005] Metal-organic frameworks (MOFs) possess extremely high surface areas and porous internal structures, making them highly promising for the adsorption and removal of heavy metals. The synthesis of MOFs is central to this technology. The surface properties of MOFs largely depend on the synthetic route. By controlling the metals, ligands, and solvents, and simultaneously adding apatite as a substrate support and nucleation site inducer, nucleation sites are provided to induce in-situ growth of MOFs, forming composite materials. Furthermore, by controlling the particle size and dispersibility of MOFs, these composite materials exhibit rapid and higher heavy metal ion removal efficiencies. Summary of the Invention

[0006] The purpose of this invention is to solve the problems in the prior art and provide a method for preparing a metal-organic framework for adsorbing and efficiently removing heavy metal ions from water.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a carbonate apatite-metal-organic framework composite material includes the following steps: (1) After mixing the carbonate apatite with the zinc salt solution, a homogeneous solution is formed; (2) The organic ligands are added to the mixed solution in step (1), and after thermal reaction, the mixture is centrifuged, washed and dried to obtain the carbonate apatite-metal-organic framework composite material.

[0008] The zinc salt is any one of zinc nitrate hexahydrate, zinc chloride, and zinc sulfate; The mass ratio of carbonate apatite to zinc salt is 0.1-1:5-10.

[0009] The zinc salt solution is miscible with at least one of methanol, water or N,N-dimethylformamide; Carbonate apatite is mixed with 0.5 M to 1.0 M acetate-sodium acetate buffer solution.

[0010] The organic ligand is any one of thiophene-2,5-dicarboxylic acid, thiazolyl-2,4-dicarboxylic acid, and dithiophene[3,2-b:2',3'-d]thiophene-2,6-dicarboxylic acid; the mass ratio of zinc salt to organic ligand is 1:1 to 1:5.

[0011] In step (2), the thermal reaction temperature is 130-180℃ and the reaction time is 12-24h.

[0012] In step (2), the centrifugation speed is 5000 to 10000 rpm and the centrifugation time is 5 to 15 minutes; the drying temperature is 60 to 100℃ and the drying time is 6 to 24 hours.

[0013] The application of the carbonate apatite-metal-organic framework composite material described above in the adsorption and removal of heavy metal ions in water is characterized in that the heavy metal ions include Cd. 2+ Pb 2+ Hg 2+ Cu 2+ At least one of them.

[0014] The adsorption is carried out under conditions of pH 4-8 and temperature 20-40℃, the dosage of the metal-organic framework material is 0.1-2 g / L, and the adsorption time is 10-300 minutes.

[0015] A water treatment agent comprising a carbonate apatite-metal-organic framework composite material obtained by the method.

[0016] A wastewater treatment method includes adding the carbonate apatite-metal-organic framework composite material obtained by the method to wastewater containing heavy metal ions for adsorption treatment, followed by solid-liquid separation.

[0017] The core technology for adsorbing heavy metal ions using carbonate apatite-metal-organic framework composites focuses on the construction and precise regulation of synergistic mechanisms. Key points are as follows: This application employs a thermal reaction between carbonate apatite and zinc salt under the organic ligands of this application to promote the formation of a product with a coordination structure between the zinc salt and the ligands. This results in a product that selectively captures heavy metal ions and provides nucleation sites to prevent the aggregation of metal-organic frameworks, thereby increasing capacity.

[0018] The pH can be controlled at 4-7, the dosage is 0.1-2 g / L, the contact time is 10-300 min, and extreme acid and alkaline environments should be avoided.

[0019] After ultrasonic elution with methanol or ethanol for 30 minutes and 5-8 cycles, the adsorption capacity is still high, improving engineering applicability. It can be prepared into granules, membranes and other molded materials, and is compatible with mainstream processes such as fixed bed and fluidized bed. After integrating pre-filtration and post-pH adjustment processes, wastewater can be discharged in compliance with standards. Moreover, saturated materials can be disposed of in a standardized manner after high-temperature calcination and solidification, without secondary pollution. Attached Figure Description

[0020] Figure 1 These are scanning electron microscope (SEM) images of the carbonate-metal-organic framework composite material prepared in Example 1 of this invention. (a) 100 nm; (b) 500 nm; (c) 1 μm; (d) 5 μm. Detailed Implementation

[0021] Example 1 (1) Dissolve 1g of carbonate apatite in 0.5M acetic acid-sodium acetate buffer solution; (2) Dissolve 5g of zinc nitrate hexahydrate in 50 mL of methanol solution; (3) Add the solution from step (1) to the solution from step (2) and stir to form a homogeneous mixed solution; (4) Thiophene-2,5-dicarboxylic acid was added to the mixed solution in step (3), and the reaction was carried out in a polytetrafluoroethylene reactor at 150°C for 12 hours. After the reaction was completed, the mixture was centrifuged at 5000 rpm and dried at 80°C for 8 hours to obtain carbonate apatite-metal-organic framework composite material-1.

[0022] Example 2 The steps are the same as in Example 1, except that the ligand is replaced with thiazoline-2,4-dicarboxylic acid to obtain carbonate apatite-metal-organic framework composite material-2.

[0023] Example 3 The steps are the same as in Example 1, except that the ligand is replaced with dithiophene[3,2-b:2',3'-d]thiophene-2,6-dicarboxylic acid, to obtain carbonate apatite-metal-organic framework composite material-3.

[0024] Example 4 The steps are the same as in Example 1, except that the thermal reaction temperature is 180°C and the reaction time is 20 h, to obtain carbonate apatite-metal-organic framework composite material-4.

[0025] Example 5 The steps are the same as in Example 1, except that the mass of carbonate apatite is 0.1g, resulting in carbonate apatite-metal-organic framework composite material-5.

[0026] Example 6 To simulate the experimental process, this case proposes to configure a system containing Cd. 2+ Pb 2+ Hg 2+ Cu 2+ Cr 6+ The mixed solution in which Cd 2 + Pb 2+ Hg 2+ Cu 2+ Cr 6+ The concentrations were all 50 mg / L.

[0027] Weigh 5 mg of the carbonate-metal-organic framework composite material prepared in Examples 1-5 and add it to 50 mL of mixed solution. The mixture is shaken and adsorbed at 200 rpm in a constant temperature water bath shaker. After 60 min, collect 1 mL of sample from the solution and remove the adsorbent powder through a 0.45 μm needle filter. Then, detect residual Cd using ICP-OES. 2+ concentration.

[0028]

[0029] As can be seen from the table above, the technical solution of this application achieves an adsorption efficiency of over 70% for metal ions within approximately 60 minutes, and also achieves this efficiency for Cd. 2+ Pb 2+ Hg 2+ The adsorption rate can reach over 95%. The selective adsorption of carbonate apatite-metal-organic framework composites originates from the Ca in the carbonate apatite lattice. 2+ With Pb2+ Cd 2+ It has a high ionic radius matching degree, preferentially undergoes lattice substitution, and can interact with Pb. 2+ Cd 2+ The formation of sparingly soluble salt precipitates further enhances selectivity; secondly, the organic ligands of MOFs (-COOH, -SH, etc.) react with Hg. 2+ Cu 2+ Stable coordination bonds are formed, and sulfur-containing ligands pair with Hg. 2+ The composite material exhibits outstanding chelation specificity and is also effective for Cr. 6+ The adsorption of Cr is mainly through electrostatic adsorption and reduction. The organic ligands (-OH, -NH2) of MOF can adsorb Cr 6+ Reduced to Cr 3+ At a pH of 5-7, Cr in water 6+ With CrO4 2- / Cr2O7 2- The presence of Hg in its original form leads to electrostatic repulsion with the negatively charged carbonate-metal-organic framework composite material, significantly reducing its adsorption capacity. Therefore, the difference in competitive adsorption capacity among different ions determines the adsorption priority. 2+ >Pb 2+ >Cd 2+ >Cu 2+ >Cr 6+ .

[0030] Example 7 Taking Example 1 as an example, the obtained product was ultrasonically eluted with 95% methanol for 60 min, and the elution was repeated 5 times. Then, the relevant experiments as in Example 6 were performed again, and its Cd 2+ Pb 2+ Hg 2+ Cu 2+ Cr 6+ The final concentrations were 3.11 mg / L, 4.35 mg / L, 3.73 mg / L, 7.80 mg / L, and 17.03 mg / L, respectively.

[0031] The above embodiments are merely preferred examples of the present invention and therefore cannot be used to limit the scope of the present invention. Any modifications or changes made based on the embodiments and description of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing a carbonate apatite-metal-organic framework composite material, characterized in that, Includes the following steps: (1) After mixing carbonate apatite with zinc salt solution, a homogeneous solution is formed; (2) The organic ligands are added to the mixed solution in step (1), and after thermal reaction, the mixture is centrifuged, washed and dried to obtain the carbonate apatite-metal-organic framework composite material.

2. The preparation method according to claim 1, characterized in that, The zinc salt is any one of zinc nitrate hexahydrate, zinc chloride, and zinc sulfate; The mass ratio of carbonate apatite to zinc salt is 0.1-1:5-10.

3. The preparation method according to claim 1, characterized in that, The zinc salt solution is miscible with at least one of methanol, water or N,N-dimethylformamide; Carbonate apatite is mixed with 0.5 M to 1.0 M acetate-sodium acetate buffer solution.

4. The preparation method according to claim 1, characterized in that, The organic ligand is any one of thiophene-2,5-dicarboxylic acid, thiazolyl-2,4-dicarboxylic acid, and dithiophene[3,2-b:2',3'-d]thiophene-2,6-dicarboxylic acid; the mass ratio of zinc salt to organic ligand is 1:1 to 1:

5.

5. The preparation method according to claim 1, characterized in that, In step (2), the thermal reaction temperature is 130-180℃ and the reaction time is 12-24h.

6. The preparation method according to claim 1, characterized in that, In step (2), the centrifugation speed is 5000 to 10000 rpm and the centrifugation time is 5 to 15 minutes; the drying temperature is 60 to 100℃ and the drying time is 6 to 24 hours.

7. The application of the carbonate apatite-metal-organic framework composite material as described in any one of claims 1-6 in the adsorption and removal of heavy metal ions in water, characterized in that, The heavy metal ions include Cd. 2+ Pb 2+ Hg 2+ Cu 2+ Cr 3+ Cr 6 + Zn 2+ As 3+ Ni 2+ Mn 2+ 、Sr 2+ At least one of them.

8. The application according to claim 7, characterized in that, The adsorption was carried out at a pH of 4-8 and a temperature of 20-40℃, with the metal-organic framework material being added at a dosage of 0.1-2 g / L and the adsorption time being 10-300 min.

9. A water treatment agent, characterized in that, A carbonate-metal-organic framework composite material comprising the method described in any one of claims 1-6.

10. A wastewater treatment method, characterized in that, The method includes adding the carbonate-metal-organic framework composite material obtained by any one of claims 1-6 to wastewater containing heavy metal ions for adsorption treatment, followed by solid-liquid separation.

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