Lanthanum modified MOFs material and preparation method and application thereof

Abstract

The invention relates to the field of environmental functional materials, in particular to a lanthanum modified MOFs material and a preparation method and application thereof. The preparation method comprises the following steps: dissolving zirconium chloride, 2-aminoterephthalic acid and lanthanum chloride heptahydrate in DMF (Dimethyl Formamide), fully dissolving under magnetic stirring, pouring into a reaction kettle, carrying out heating reaction by utilizing a drying oven, cooling to room temperature, pouring into a centrifugal tube for centrifuging, then sequentially washing the precipitate with DMF and methanol for many times, and finally pouring into a beaker for drying, thereby obtaining the zirconium-zirconium-lanthanum composite material. The lanthanum modified MOFs material is obtained; the metal lanthanum is introduced, so that the adsorption efficiency of the prepared material is improved, and the material has better selectivity and higher adsorption capacity; according to adsorption kinetics, the adsorption rate can reach 91.2% in 5 min, and the adsorption equilibrium can reach 94.5% in 20 min. According to an isothermal adsorption model, the maximum adsorption capacity can reach 344.93 mg / g at the temperature of 35 DEG C, and a Langmuir isothermal adsorption model is met.

Description

Technical Field

[0001] The present invention relates to the field of environmental functional materials, and particularly to a lanthanum-modified MOFs material, a preparation method thereof, and an application thereof. Background Art

[0003] For common phosphorus removal methods, chemical phosphorus removal requires a large amount of chemical agents to be added, generating a large amount of chemical sludge, which is difficult to treat and may contain harmful substances such as heavy metals. Although the microbial method has no secondary pollution, it is greatly affected by environmental factors, has a long treatment cycle, slow effect, and complex operation, etc. The physical adsorption method has the advantages of small floor area, simple process, and low cost, etc. However, traditional adsorbents such as biochar, graphene, LDHs adsorbents, metal oxides, and hydroxides have poor adsorption performance, are greatly affected by other anions and organic matter in water bodies, and have a slow adsorption rate, affecting the treatment efficiency. Therefore, it is very necessary to study the preparation of materials and methods for efficient treatment of phosphorus pollution. Summary of the Invention

[0004] In order to solve the technical problems that traditional adsorbents have low adsorption performance for phosphorus, poor selectivity, are greatly affected by the environment, and metal oxides and hydroxides will have metal spillage, causing secondary pollution to the environment, the present invention provides a lanthanum-modified MOFs material.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a preparation method of a lanthanum-modified MOFs material, zirconium chloride, 2-aminoterephthalic acid, and lanthanum chloride heptahydrate are dissolved in DMF, and are fully dissolved under magnetic stirring, poured into a reaction kettle, heated and reacted by an oven, then cooled to room temperature, poured into a centrifuge tube for centrifugation, and then the precipitate is washed with DMF and methanol multiple times in sequence, and finally poured into a beaker for drying, thus obtaining the lanthanum-modified MOFs material.

[0006] As a further limitation of the technical solution of the present invention, the molar ratio of zirconium chloride, 2-aminoterephthalic acid, and lanthanum chloride heptahydrate is 2:2:1.

[0007] As a further limitation of the technical solution of the present invention, the molar volume ratio of zirconium chloride to DMF used for dissolution is 1 mmol:5 mL; the volume ratio of DMF used for dissolution to DMF used for washing the precipitate is 2:1; the volume ratio of DMF used for washing the precipitate to methanol is 1:1.

[0008] As a further limitation of the technical solution of the present invention, the conditions for heating and reaction are 120 °C for 24 h.

[0009] As a further limitation of the technical solution of the present invention, the centrifugation conditions are 9000 rpm for 10 min.

[0010] The present invention also provides a lanthanum-modified MOFs material prepared by the above preparation method.

[0011] In addition, the present invention also provides the application of the above lanthanum-modified MOFs material in the adsorption and removal of phosphorus in water bodies.

[0012] As a further limitation of the above application, when the lanthanum-modified MOFs material removes phosphorus in water, the adsorption rate reaches 91.2% in 5 minutes and the adsorption equilibrium reaches 94.5% in 20 minutes.

[0013] Compared with the prior art, the present invention has the following beneficial effects: MOFs are porous materials constructed by the coordination of metal ions and organic bridging ligands. MOFs materials have the advantages of high specific surface area, rich adsorption sites, adjustable pore size, etc., thus enhancing the binding affinity and adsorption capacity. The present invention introduces lanthanum metal to prepare a lanthanum-modified MOFs material, which improves the adsorption efficiency of the material, has better selectivity and higher adsorption capacity.

[0014] According to the adsorption kinetics, the adsorption rate of the lanthanum-modified MOFs material reaches 91.2% at 5 minutes and the adsorption equilibrium reaches 94.5% at 20 minutes.

[0015] According to the isothermal adsorption model, it shows that the maximum adsorption capacity can reach 344.93 mg / g at 35 °C and conforms to the Langmuir isothermal adsorption model.

[0016] The presence of most coexisting ions has little effect on phosphorus adsorption. In the experiment of actual water bodies, the phosphorus concentration is 0.386 mg / L after adsorption, which meets the WHO standard of 0.5 mg / L.

[0017] In the experiment of organic matter humic acid, even when the humic acid concentration reaches 25 mg / l, it has little effect on adsorption. Description of the Drawings

[0018] Figure 1 It is the adsorption kinetics simulation diagram of the lanthanum-modified MOFs material.

[0019] Figure 2 It is the isothermal adsorption model of the lanthanum-modified MOFs material.

[0020] Figure 3 It is the influence diagram of coexisting ions on the phosphorus adsorption effect of the lanthanum-modified MOFs material.

[0021] Figure 4 It is the test diagram of the lanthanum-modified MOFs material for removing phosphorus in real water bodies.

[0022] Figure 5 It is the influence diagram of organic matter humic acid on the phosphorus adsorption removal rate of the lanthanum-modified MOFs material. Detailed implementation mode

[0023] The present invention will be further described below in conjunction with specific embodiments. Example 1

[0024] Preparation of lanthanum-modified MOFs material Take 4 mmol of zirconium chloride (ZrCl4), 4 mmol of 2-aminoterephthalic acid (NH2-H2BDC), and 2 mmol of lanthanum chloride heptahydrate (LaCl3·7H2O), with a molar mass ratio of Zr:La = 2:1. The above three reagents are dissolved in 20 ml of DMF, fully dissolved under magnetic stirring, poured into a reaction kettle, heated to 120 °C in an oven for 24 h; then cooled to room temperature, poured into a centrifuge tube for centrifugation (9000 rpm, 10 min). After centrifugation, the supernatant is removed to leave the precipitate, and the precipitate is washed repeatedly with 10 ml of DMF and 10 mL of methanol, and then poured into a beaker to dry for 12 h, thus completing the preparation of the lanthanum-modified MOFs material.

[0025] The prepared lanthanum-modified MOFs material is subjected to the following phosphorus adsorption and removal experiments in Examples 2-6. Considering the application in the actual water environment, the following adsorption experiments were carried out by the test method of the present invention at pH = 7.0. All adsorption tests were carried out in three parallel experiments to obtain the average value. Example 2

[0026] Adsorption kinetics experiment of lanthanum-modified MOFs material Immerse 0.5 g of the lanthanum-modified MOFs material prepared in Example 1 into 1 L of a phosphate solution containing 10 mg / L, keep the reaction at 25 °C, extract about 1.5 mL of the suspension at different time intervals, and filter it using a 0.45 μm filter membrane. The remaining concentration of phosphate in the filtrate was determined by the ammonium molybdate spectrophotometric method. The results are as Figure 1 shown. According to the adsorption kinetics, the adsorption rate reached 91.2% at 5 min and the adsorption equilibrium reached 94.5% at 20 min. Example 3

[0027] Isothermal adsorption experiment of lanthanum-modified MOFs material Add 50 mg of the lanthanum-modified MOFs material to phosphate solutions with different concentrations (10 - 1000 mg / L), then oscillate the mixture for 2 h to reach the adsorption equilibrium, keep pH = 7, and select 15 °C, 25 °C, and 35 °C for three groups of experiments respectively to measure the remaining concentration of phosphate. The results are as Figure 2 shown. According to the isothermal adsorption model, it shows that the maximum adsorption capacity can reach 344.93 mg / g at 35 °C and conforms to the Langmuir isothermal adsorption model. Example 4

[0028] Effect of coexisting ions on phosphorus adsorption of lanthanum-modified MOFs materials Four typical interfering substances (chloride ion, sulfate, carbonate and nitrate) at two different concentrations (0.01 M and 0.1 M) were respectively added to 10 mg / L phosphate solution, and the dosage of lanthanum-modified MOFs materials was fixed at 0.5 g / L to test the phosphorus adsorption effect. The results are as Figure 3 shown. In the experiment of coexisting ions, the presence of most coexisting ions had little effect on phosphorus adsorption, and there was only a slight effect when the concentration of SO3 2- was 0.1 M. Example 5

[0029] Phosphorus adsorption test of lanthanum-modified MOFs materials in real water The water sample from the upper reaches of the Fenhe River in Taiyuan was filtered with a 0.45 μm filter membrane. 1 L of the filtered water sample was added with 35.12 mg of potassium dihydrogen phosphate and divided into three 100 ml solutions. 50 mg of lanthanum-modified MOFs materials were added to each solution and placed in a shaker for reaction (25 °C, 200 rpm, 2 h). The results are as Figure 4 shown. In the experiment of actual water, the phosphorus concentration after adsorption was 0.386 mg / L, meeting the WHO standard of 0.5 mg / L. Example 6

[0030] Removal rate of phosphorus adsorption of lanthanum-modified MOFs materials by organic matter humic acid Three different concentrations (5 mg / L, 15 mg / L, 25 mg / L) of humic acid were respectively added to 10 mg / L phosphate solution, and the dosage of lanthanum-modified MOFs materials was fixed at 0.5 g / L to determine the removal rate of phosphorus adsorption of lanthanum-modified MOFs materials. The results are as Figure 5 shown. In the experiment on organic matter humic acid, even when the humic acid concentration reached 25 mg / L, it had little effect on adsorption.

Claims

1. A method for preparing a lanthanum-modified MOFs material, characterized in that: Zirconium chloride, 2-aminoterephthalic acid and lanthanum chloride heptahydrate were dissolved in DMF, fully dissolved under magnetic stirring, poured into a reactor, heated in an oven for reaction, then cooled to room temperature, poured into a centrifuge tube for centrifugation, and then washed with DMF and methanol for multiple times, and finally poured into a beaker for drying to obtain lanthanum-modified MOFs material.

2. The method for preparing a lanthanum-modified MOFs material according to claim 1, characterized in that: The molar ratio of the zirconium chloride, 2-aminoterephthalic acid and lanthanum chloride heptahydrate is 2:2:

1.

3. The method for preparing a lanthanum-modified MOFs material according to claim 2, characterized in that: The molar volume ratio of the zirconium chloride to the DMF used for dissolution is 1 mmol:5 mL; the volume ratio of the DMF used for dissolution to the DMF used for washing the precipitate is 2:1; the volume ratio of the DMF used for washing the precipitate to methanol is 1:

1.

4. The method for preparing a lanthanum-modified MOFs material according to claim 1, characterized in that: The heating reaction condition was 120°C for 24 h.

5. The method for preparing a lanthanum-modified MOFs material according to claim 1, characterized in that: The centrifugation condition was 9000 rpm for 10 min.

6. A lanthanum-modified MOFs material prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the lanthanum-modified MOFs material according to claim 6 in the adsorption and removal of phosphorus in water.

8. The use according to claim 7, characterized in that: When the lanthanum-modified MOFs material removes phosphorus in water, the adsorption rate reaches 91.2% in 5 minutes and reaches the adsorption equilibrium of 94.5% in 20 minutes.

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