One-step preparation method of MOFs (Metal-Organic Frameworks) adsorption material based on bimetallic synergistic coordination and deep fluorine removal application of MOFs adsorption material

Abstract

The invention discloses a one-step preparation method of an MOFs (Metal-Organic Frameworks) adsorption material based on bimetallic synergistic coordination and deep defluorination application of the MOFs adsorption material. The method comprises the following specific steps: performing ultrasonic dispersion on a rare earth metal salt M1, an alkaline earth metal salt M2, an organic ligand B1 and a mixed solution of an organic solvent and a regulator according to a ratio, performing solvothermal reaction, and then performing separation, purification and drying. The novel adsorption material M1-MOF-M2 is obtained. The method has the following advantages: the one-step synthesis process simplifies the operation flow, and the yield is increased to 92% or above; the adsorption capacity of the material to fluorine ions is high due to the synergistic effect of double metals, and the removal efficiency is high within 15 minutes; the material keeps stable adsorption performance in a wide pH value range of 4-10 and in a complex ion environment. The method can provide an innovative solution for deep fluorine removal of industrial wastewater generated in industries such as lithium battery production and recovery or efficient removal of trace fluoride in drinking water, and shows a wide commercial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental functional materials and water treatment, and relates to a one-step preparation method of a MOFs adsorption material based on bimetallic coordinated coordination and its deep fluorine removal application. Background Art

[0002] With the rapid development of industry, the application of fluorine resources in chemical, electronic electroplating, photovoltaic and other industries has increased, and with it a surge in fluorine-containing wastewater. These wastewaters are highly acidic and contain high amounts of fluoride, posing a serious threat to the environment and health. Industrial fluoride-containing wastewater has significant characteristics, including huge water volume, large fluctuations in fluoride ion concentration, and various forms of fluoride ions. In response to the treatment of fluoride-containing industrial wastewater, people have developed a variety of fluoride removal technologies, including chemical precipitation, membrane separation, ion exchange, electrochemistry and adsorption, in order to ensure that the wastewater meets discharge standards or is recycled. Generally speaking, the treatment of high-concentration fluoride-containing wastewater (greater than 10 mg·L -1 ) is relatively easy to handle, while low concentrations (less than 10 mg·L -1 ) is even more challenging.

[0003] Adsorption has gradually become one of the mainstream methods for treating fluoride-containing wastewater due to its simple operation and low cost. A wide variety of adsorbents exist, including carbon-based materials, metals and their hydroxides or oxides, natural materials, and ion exchange resins. However, these traditional adsorbents have some shortcomings in practical applications. For example, when treating low-concentration fluoride-containing wastewater, traditional adsorbents suffer from limited adsorption capacity, low selectivity, poor regeneration performance, and poor stability over a wide pH range.

[0004] To comply with the national green development strategy and improve environmental quality, researchers have gradually turned their attention to metal organic frameworks (MOFs), which are more environmentally friendly and simple to prepare, and are applying them to wastewater treatment. Currently, MOFs and their derived carbon materials, such as La-MOFs and Zr-MOFs, have been proven to be effective adsorbents for removing fluoride ions and have been applied in the treatment of fluoride-containing wastewater. Despite this, research on the use of a one-step method based on bimetallic coordinated coordination to prepare new MOF adsorbent materials for the treatment of fluoride-containing wastewater is relatively scarce. Summary of the Invention

[0005] In response to the above technical problems, the purpose of the present invention is to provide a bimetallic coordinated MOFs adsorption material, a one-step preparation method and its application in deep fluoride removal from fluoride-containing wastewater. The novel adsorption material of the present invention adopts a convenient one-step preparation process, and realizes the directional growth of rare earth metal salt M1 and alkaline earth metal salt M2 on an organic ligand substrate through a regulated bimetallic coordinated strategy, thereby constructing a hierarchical porous M1-MOF-M2 structure with a heterogeneous interface. It has the advantages of simple synthesis method, high adsorption capacity, fast adsorption rate and wide working range. It is suitable for treating low-concentration and high-concentration fluoride-containing wastewater. The fluoride ion concentration after treatment can be as low as 1 mg / L, achieving deep fluoride removal; it can work in a wide pH range of 4 to 10, with a removal efficiency of more than 99% within 15 minutes, and an initial fluoride ion concentration of 500 mg·L -1 The maximum adsorption capacity reached 234.58 mg·g -1 , and has good potential for industrial promotion and application.

[0006] The present invention is achieved through the following technical solutions.

[0007] The present invention provides a one-step preparation method of a bimetallic coordinated MOFs adsorption material, comprising the following steps: (1) fully mixing a rare earth metal salt M1, an alkaline earth metal salt M2, an organic ligand B1, a regulator, and an organic solvent at room temperature to obtain a reaction solution; (2) The reaction solution of step (1) is subjected to a hot solvent reaction. After the reaction is completed, the reaction is separated, purified and dried to obtain a bimetallic coordinated MOFs adsorption material M1-MOF-M2.

[0008] In the present invention, in step (1), the rare earth metal salt M1 is any one of sulfates, nitrates or chlorides of cerium, lanthanum, europium, neodymium or praseodymium; the alkaline earth metal salt M2 is any one of sulfates, nitrates or chlorides of beryllium, magnesium, calcium or barium; and the organic ligand B1 is any one of terephthalic acid or trimesic acid or a mixture thereof.

[0009] In the present invention, in step (1), the molar number of the rare earth metal salt M1 is x , the number of moles of alkaline earth metal salt M2 y , the number of moles of organic ligand B1 z satisfy x : y = (0.5~2.5): 1、( x + y ): z = (1-3): 1. More preferably, x : y =(1~2): 1, ( x +y ): z = (1~1.5): 1.

[0010] In the present invention, in step (1), the rare earth metal salt M1, the alkaline earth metal salt M2, and the organic ligand B1 are first dispersed in an organic solvent, and after being uniformly dispersed by ultrasonication at room temperature, a regulator is added and mixed at room temperature to obtain a reaction solution.

[0011] In the present invention, in step (1), the regulator is formic acid, the organic solvent is N,N-dimethylformamide; the feed ratio of rare earth metal salt M1 to N,N-dimethylformamide and formic acid is 1 mmol: (10-20) mL: (5-20) mL.

[0012] In the present invention, in step (2), the solvent thermal reaction temperature is 100-150°C, and the solvent thermal reaction time is 10-30 hours. More preferably, the solvent thermal reaction temperature is 110-130°C, and the solvent thermal reaction time is 12-24 hours.

[0013] In the present invention, the specific steps of separation, purification and drying are: first centrifugation or vacuum filtration separation of the hot solvent product, then repeatedly washing the obtained precipitate with ethanol for multiple times, and then drying it under vacuum at a drying temperature of 40°C to 80°C for 12 h to 24 h.

[0014] The present invention provides a bimetallic coordinated MOFs adsorption material prepared by the one-step preparation method.

[0015] Furthermore, the present invention provides an application of the above-mentioned bimetallic coordinated MOFs adsorption material in deep defluorination of fluorine-containing wastewater; the fluorine-containing wastewater includes fluorine-containing industrial wastewater generated by lithium battery production and recycling industries, and drinking water source water containing trace fluoride.

[0016] The present invention utilizes the synergistic effects of electrostatic adsorption, ion exchange, or complexation on fluoride ions in wastewater through the novel M1-MOF-M2 adsorption material, achieving efficient removal of fluoride ions from both high- and low-concentration fluoride-containing wastewater. This material exhibits high adsorption capacity, rapid adsorption rate, and a wide operating range, demonstrating its potential for industrialization and application. Compared to existing technologies, the present invention exhibits the following advantages: The present invention provides a novel adsorption material of MOFs based on bimetallic coordinated coordination, which is prepared by a one-step method and has simple synthesis, efficient reaction and high yield.

[0017] The present invention uses cerium salts, lanthanum salts, europium salts, neodymium salts and praseodymium salts among rare earth metals with good affinity for fluoride ions, as well as beryllium salts, magnesium salts, calcium salts and barium salts among alkaline earth metals with strong ionization as metal bases, and trimesic acid and terephthalic acid containing carbonyl and hydroxyl groups as organic ligands, which are more likely to form hydrogen bonds and can well carry out coordination reactions with rare earth metal salts and alkaline earth metal salts, thereby enhancing the skeleton stability of MOF.

[0018] The novel M1-MOF-M2 adsorption material prepared by the present invention has the structure of two MOF materials at the same time, can better combine the advantages of the two MOFs, and produce a synergistic effect, thereby increasing the acid-base stability and the adsorption capacity for fluoride ions, so that the novel M1-MOF-M2 adsorption material exhibits good adsorption performance for fluoride ions in a wide pH range of 4 to 10.

[0019] The present invention provides a one-step method for preparing a new MOFs adsorption material based on bimetallic cooperative coordination and its application in deep defluorination of fluoride-containing wastewater, which solves the problem of difficulty in completely adsorbing fluoride ions in fluoride-containing wastewater and has the advantages of low reagent consumption, high adsorption capacity, fast adsorption rate and wide working range.

[0020] The present invention provides a one-step method for preparing a new MOFs adsorption material based on bimetallic coordinated coordination and its application in deep fluoride removal from fluoride-containing wastewater. The material simultaneously performs electrostatic adsorption, ion exchange and complexation on fluoride ions in the fluoride-containing wastewater, and can efficiently and thoroughly adsorb fluoride in high-concentration and low-concentration fluoride-containing wastewater, reducing the fluoride concentration to below 1 mg / L (1 ppm). The material has broad prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the preparation process of the new M1-MOF-M2 adsorption material of the present invention.

[0022] Figure 2 This is the XRD pattern of the new La-MOF-Mg adsorption material prepared in Example 1 of the present invention.

[0023] Figure 3 This is the SEM image of the new La-MOF-Mg adsorption material prepared in Example 1 of the present invention.

[0024] Figure 4 This is the XRD pattern of the new La-MOF-Fe adsorption material prepared in Comparative Example 1 of the present invention.

[0025] Figure 5 This is the SEM spectrum of the La-MOF-Fe novel adsorption material prepared in Comparative Example 1 of the present invention.

[0026] Figure 6XRD patterns of the new adsorption materials La-MOF-Mg, Ce-MOF-Mg, La-MOF-Ce, Ce-MOF-Fe, Zr-MOF-Fe and Zr-MOF-Mg prepared in the present invention.

[0027] Figure 7 These are the SEM images of the new adsorption materials La-MOF-Mg, Ce-MOF-Mg, La-MOF-Ce, Ce-MOF-Fe, Zr-MOF-Fe, and Zr-MOF-Mg prepared in the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0029] like Figure 1 As shown, the present invention provides a one-step preparation method of a novel MOFs adsorption material based on bimetallic coordinated coordination, and the specific steps are as follows: (1) Add rare earth metal salt M1, alkaline earth metal salt M2 and organic ligand B1 to formic acid and N,N -dimethylformamide mixed solution, performing ultrasonic dispersion to obtain a reaction solution; (2) subjecting the reaction solution of step (1) to a hot solvent reaction at 100-150° C., followed by separation, purification and drying to obtain the M1-MOF-M2 adsorption material; In the present invention, the molar number of the rare earth metal salt M1 added in step (1) is set to x , the number of moles of alkaline earth metal salt M2 added is y , the number of moles of organic ligand B1 added is z , x : y = (0.5~2.5): 1, ( x + y ): z = (1~3):1.

[0030] In the present invention, in step (1), the rare earth metal salt M1 is selected from one of cerium salt, lanthanum salt, europium salt, neodymium salt or praseodymium salt.

[0031] In the present invention, in step (1), the alkaline earth metal salt M2 is selected from one of beryllium salt, magnesium salt, calcium salt or barium salt.

[0032] In the present invention, in step (2), the specific steps of separation, purification and drying are: first centrifugation or vacuum filtration separation of the product, collecting the precipitate, repeatedly washing it with ethanol for multiple times, and then drying it under vacuum at a drying temperature of 40°C to 80°C for 12 h to 24 h.

[0033] Example 1

[0034] This embodiment provides a one-step method for preparing a novel La-MOF-Mg adsorption material, comprising the following steps: (1) In molar ratio, n(LaCl3): n(MgCl2) = 1: 1, n(LaCl3+MgCl2): n(BTC) = 2: 1, 4mmol LaCl3· x H2O, 4 mmol MgCl2·6H2O, and 4 mmol H3BTC were added to 60 mL DMF and ultrasonically dispersed at room temperature for 30 min to fully mix the substances to obtain reaction solution 1.

[0035] (2) Add 60 mL of FA to the reaction solution 1 in step (1), and stir at 850 rpm for 5 min at room temperature to mix the solution evenly to obtain reaction solution 2.

[0036] (3) The reaction solution 2 in step (2) was placed in a sealed reactor and reacted at 120°C for 24 h. After the reaction was completed, the reaction solution 2 was cooled to room temperature and then solid-liquid separation was performed. The obtained solid was washed with ethanol several times to obtain product 1.

[0037] (4) The product 1 in step (3) was placed in a vacuum drying oven at 60°C for 24 hours, and the obtained product was the new bimetallic coordinated adsorption material La-MOF-Mg.

[0038] (5) Take 0.01 g of the new bimetallic coordinated adsorption material La-MOF-Mg in step (4) and place it in 50 mL of fluoride with a concentration of 50 mg·L at 25 °C. -1 Fluoride was adsorbed from fluoride-containing wastewater for 15 minutes at a solution pH of 4.5. After adsorption, the supernatant was taken and the fluoride ion concentration was measured to be 3.08 mg·L -1 The maximum adsorption capacity of fluoride ions by the adsorbent was calculated to be 234.58 mg·g -1 , indicating that the adsorbent can achieve efficient adsorption of fluoride in wastewater with low initial fluoride ion concentration. The XRD patterns and SEM patterns of the materials before and after adsorption are shown in Figure 2. Figure 2 and Figure 3 As shown; the results show that the adsorption material of the present invention has higher structural stability during the adsorption process.

[0039] Example 2

[0040] The difference between this embodiment and embodiment 1 is that in step (5), 0.1 g of the novel bimetallic coordinated adsorption material La-MOF-Mg is used, and the rest is the same as in embodiment 1. After the adsorption is completed, the supernatant is taken and the fluoride ion concentration is measured to be 0.67 mg·L -1 The removal rate was 98.66%, indicating that the adsorbent can achieve deep removal of fluoride in wastewater with lower initial fluoride ion concentration.

[0041] Example 3

[0042] The difference between this embodiment and embodiment 1 is that the fluoride concentration in the fluoride-containing wastewater in step (5) is 500 mg / L -1 , and the rest were the same as in Example 1. After the adsorption was completed, the supernatant was taken and the fluoride ion concentration was measured to be 455.05 mg·L -1 The maximum adsorption capacity of fluoride ions by the adsorbent was calculated to be 224.90 mg·g -1 , indicating that the adsorbent can achieve efficient adsorption of fluoride in wastewater with higher initial fluoride ion concentration.

[0043] Example 4

[0044] The difference between this embodiment and embodiment 1 is that the fluoride concentration in the fluoride-containing wastewater in step (5) is 500 mg / L -1 0.2 g of the novel bimetallic coordinated adsorption material La-MOF-Mg was taken, and the other properties were the same as those in Example 1. After the adsorption was completed, the supernatant was taken and the fluoride ion concentration was measured to be 0.90 mg·L -1 The fluoride ion removal rate of the adsorbent was 99.82%, indicating that the adsorbent can achieve deep removal of fluoride in wastewater with higher initial fluoride ion concentration.

[0045] Example 5

[0046] The difference between this embodiment and embodiment 1 is that the ratio of n(LaCl3): n(MgCl2) in step (1) is 2:1, and the rest is the same as embodiment 1. After the adsorption is completed, the supernatant is taken and the fluoride ion removal rate is measured to be 98.31%, and the maximum fluoride ion adsorption capacity is 180.78 mg·g -1 , that is, the efficient removal of fluoride in fluoride-containing wastewater is achieved.

[0047] Example 6

[0048] The difference between this embodiment and embodiment 1 is that the rare earth metal salt selected in step (1) is CeCl3, and n(CeCl3): n(MgCl2) = 1:1. The other conditions are the same as those in embodiment 1, and the obtained material is Ce-MOF-Mg. After the adsorption is completed, the supernatant is taken and the fluoride ion removal rate is measured to be 98.92%, and the maximum fluoride ion adsorption capacity is 199.58 mg·g-1 , that is, the efficient removal of fluoride in fluoride-containing wastewater is achieved.

[0049] Example 7

[0050] The difference between this embodiment and embodiment 1 is that the pH value of the fluorine-containing wastewater in step (5) is 7, and the rest is the same as embodiment 1. After the adsorption is completed, the supernatant is taken and the fluoride ion removal rate is measured to be 94.38%, and the maximum fluoride ion adsorption capacity is 189.64 mg·g -1 , that is, the efficient removal of fluoride in fluoride-containing wastewater is achieved.

[0051] Example 8

[0052] The difference between this embodiment and embodiment 1 is that the pH value of the fluorine-containing wastewater in step (5) is 10, and the rest is the same as embodiment 1. After the adsorption is completed, the supernatant is taken and the fluoride ion removal rate is measured to be 91.57%, and the maximum fluoride ion adsorption capacity is 156.45 mg·g -1 , that is, the efficient removal of fluoride in fluoride-containing wastewater is achieved.

[0053] Comparative Example 1 The difference between this comparative example and Example 1 is that the metal salts selected in step (1) are La(NO3)3 and Fe(NO3)3, the other steps are the same as Example 1, and the obtained material is La-MOF-Fe.

[0054] After adsorption, the supernatant was taken and the fluoride ion removal rate was measured to be 97.48%, and the maximum fluoride ion adsorption capacity was 92.42 mg·g -1 The adsorbent achieved efficient removal of fluoride from fluoride-containing wastewater, but the maximum adsorption capacity decreased significantly. The XRD and SEM spectra of the materials before and after adsorption are shown in Figure 2. Figure 4 and Figure 5 The results show that when rare earth metals and Fe are used as ligands, impurity peaks appear in the adsorbed materials, indicating that there are defects in their structural stability.

[0055] Comparative Example 2 The difference between this comparative example and Example 1 is that the metal salts selected in step (1) are Ce(NO3)3 and Fe(NO3)3, and the other steps are the same as in Example 1. The obtained material is Ce-MOF-Fe, and its XRD spectrum and SEM spectrum are as follows: Figure 6 and Figure 7 shown.

[0056] After adsorption, the supernatant was taken and the fluoride ion removal rate was measured to be 96.58%, and the maximum fluoride ion adsorption capacity was 91.69 mg g -1, the adsorbent achieved efficient removal of fluoride in fluoride-containing wastewater, but the maximum adsorption capacity decreased significantly.

[0057] Comparative Example 3 The difference between this comparative example and Example 1 is that the metal salts selected in step (1) are Zr(NO3)3 and Mg(NO3)3, and the other steps are the same as in Example 1. The obtained material is Zr-MOF-Mg, and its XRD spectrum and SEM spectrum are as follows: Figure 6 and Figure 7 shown.

[0058] After adsorption, the supernatant was taken and the fluoride ion removal rate was measured to be 84.04%, and the maximum fluoride ion adsorption capacity was 40.35 mg·g -1 , the adsorbent achieved effective removal of fluoride in fluoride-containing wastewater, but the maximum adsorption capacity decreased significantly.

[0059] Comparative Example 4 The difference between this comparative example and Example 1 is that the metal salts selected in step (1) are Zr(NO3)3 and Fe(NO3)3, and the other steps are the same as in Example 1. The obtained material is Zr-MOF-Fe, and its XRD spectrum and SEM spectrum are as follows: Figure 6 and Figure 7 shown.

[0060] After adsorption, the fluoride ion removal rate was measured to be 75.36%, and the maximum fluoride ion adsorption capacity was 35.60 mg·g -1 , the adsorbent achieved effective removal of fluoride in fluoride-containing wastewater, but the maximum adsorption capacity decreased significantly.

[0061] The basic principles, main features and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention, which is defined by the appended claims and their equivalents.

Claims

1. A one-step preparation method based on bimetallic coordinated MOFs adsorption material, characterized in that: The steps include: (1) fully mixing a rare earth metal salt M1, an alkaline earth metal salt M2, an organic ligand B1, a regulator, and an organic solvent at room temperature to obtain a reaction solution; (2) The reaction solution of step (1) is subjected to a hot solvent reaction. After the reaction is completed, the reaction is separated, purified and dried to obtain a bimetallic coordinated MOFs adsorption material M1-MOF-M2.

2. The one-step preparation method based on bimetallic coordinated MOFs adsorption material according to claim 1, characterized in that: In step (1), the rare earth metal salt M1 is any one of sulfates, nitrates or chlorides of cerium, lanthanum, europium, neodymium or praseodymium; the alkaline earth metal salt M2 is any one of sulfates, nitrates or chlorides of beryllium, magnesium, calcium or barium; and the organic ligand B1 is any one of terephthalic acid or trimesic acid or a mixture thereof.

3. The one-step preparation method based on bimetallic coordinated MOFs adsorption material according to claim 1, characterized in that: In step (1), the molar number of the rare earth metal salt M1 is x , the number of moles of alkaline earth metal salt M2 y , the number of moles of organic ligand B1 z satisfy x : y = (0.5~2.5): 1、( x + y ): z = (1~3):

1.

4. The one-step preparation method based on bimetallic coordinated MOFs adsorption material according to claim 1, characterized in that: In step (1), the rare earth metal salt M1, the alkaline earth metal salt M2, and the organic ligand B1 are first dispersed in an organic solvent, and after being uniformly dispersed by ultrasonication at room temperature, a regulator is added and mixed at room temperature to obtain a reaction solution.

5. The one-step preparation method based on bimetallic coordinated MOFs adsorption material according to claim 1, characterized in that: In step (1), the regulator is formic acid, the organic solvent is N,N-dimethylformamide; the feed ratio of rare earth metal salt M1 to N,N-dimethylformamide and formic acid is 1 mmol: (10-20) mL: (5-20) mL.

6. The one-step preparation method based on bimetallic coordinated MOFs adsorption material according to claim 1, characterized in that: In step (2), the solvent thermal reaction temperature is 100-150°C, and the solvent thermal reaction time is 6-30h.

7. The one-step preparation method based on bimetallic coordinated MOFs adsorption material according to claim 1, characterized in that: In step (2), the specific steps of separation, purification and drying are as follows: first, the hot solvent product is centrifuged or filtered under reduced pressure, and then the obtained precipitate is repeatedly washed with ethanol for multiple times, and then dried under vacuum at a drying temperature of 40°C to 80°C for 12 h to 24 h.

8. A bimetallic coordinated MOFs adsorption material prepared according to the one-step preparation method according to claim 1.

9. Use of the bimetallic coordinated MOFs adsorption material according to claim 1 in deep defluorination of fluorine-containing wastewater.

10. The use according to claim 9, characterized in that Fluoride-containing wastewater includes fluoride-containing industrial wastewater generated by the lithium battery production and recycling industries, as well as drinking water sources containing trace amounts of fluoride.

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