Method for synthesizing metal-organic framework material by using acid etching solution of aluminous clay mineral

Abstract

The present invention discloses a method for synthesizing metal-organic framework materials by using an acid-etched solution of aluminous clay minerals. This method uses the aluminous waste liquid generated during the production of nano-silica by acid etching nano-clay as the raw material and reaction medium, and synthesizes aluminum metal-organic framework materials through a one-step hydrothermal reaction. While harmlessly disposing of the waste liquid, it realizes the utilization of valuable resources and the production of new materials, truly achieving the sustainable development goal of "turning waste into materials". The prepared metal-organic framework materials have good crystallinity, excellent performance, stable batches, a specific surface area of up to 477.91 m² / g, the adsorption of organic molecules is not affected by coexisting ions, and the removal rate of organic pollutants (such as p-nitrophenol) in real water bodies such as seawater, the Yangtze River water, the Yellow River water, and tap water is high, with strong practical applicability.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing metal-organic framework materials using an acid-etched solution of aluminous clay minerals, belonging to the technical fields of deep processing of natural clay minerals, recycling of waste resources, and preparation of porous materials. Background Art

[0002] Nanosilica is indispensable in the fields of adsorption separation, catalysis, coatings, polymer composites, etc. However, it is difficult to synthesize porous silica with one-dimensional or two-dimensional nano-morphologies at low cost through artificial synthesis methods. Therefore, the preparation of nanosilica using natural nano-clays with one-dimensional or two-dimensional morphologies has become the focus of attention in recent years. Through acid leaching treatment, metal ions in the octahedral layer of clay minerals can be dissolved out, and then nanosilica can be obtained. However, a large amount of waste acid containing metal ions such as aluminum is generated during the acid leaching process, which is difficult to treat and easily causes environmental pollution. Therefore, the harmless disposal of acid leaching wastewater and the rational utilization of valuable metal resources in the water have become hot topics in the industry. For example, Chinese Patent CN214714567U discloses a device that can recover and concentrate the acid water generated in the production of activated clay, aiming to save materials, reduce production costs, and improve efficiency. Chinese Patent CN110950371B discloses a method for recovering valuable components in the waste liquid from the production of activated clay by adjusting the acidity of the acid solution, enabling the resource utilization of valuable components such as aluminum, iron, and calcium in the recovered waste liquid and reducing the cost of wastewater treatment. Chinese Patent CN212370201U discloses a high-efficiency waste acid resource recovery and utilization system for the production of activated clay, which can effectively solve the problem of pump damage during the solid-liquid separation of waste acid recovery and utilization. Chinese Patent CN112225241A discloses a method for preparing aluminum sulfate at low cost using the waste liquid from the production of activated clay. However, these patented technologies tend to separate aluminum in the waste liquid to obtain chemical raw materials such as aluminum salts, or improve equipment to enhance the separation effect. In recent years, with the continuous penetration of the concept of "from waste to materials", people more expect to directly convert waste into applicable materials, which can not only harmlessly treat wastewater but also obtain high-performance new materials. Metal-organic framework materials are porous materials with regular pore structures and have broad application prospects in many fields such as adsorption separation and catalysis. Currently, most of them are synthesized from pure aluminum salts in organic solvents, with relatively high costs. Through comprehensive literature and patent analysis, there is no literature report or application precedent on synthesizing metal-organic framework materials using the acid-etched solution of clay minerals so far. Summary of the Invention

[0003] Based on the above background, the present invention provides a method for synthesizing metal-organic framework materials using an acid-etched solution of aluminous clay minerals, using the waste liquid as the reaction solvent and the aluminum in the waste liquid as the aluminum source to prepare metal-organic framework materials that can be used for the adsorption of organic pollutants (such as p-nitrophenol).

[0004] The technical solution of the present invention is as follows:

[0005] A method for synthesizing metal-organic framework materials using an acid-etched solution of aluminous clay minerals, comprising the following steps:

[0006] (1) Disperse the aluminous clay minerals into an acid solution, then carry out hydrothermal treatment at 120-200 °C for 1-12 h. After naturally cooling to room temperature, perform solid-liquid separation, collect the liquid, and obtain the acid-etched solution of aluminous clay minerals; the aluminous clay minerals are at least one of kaolinite, calcined kaolinite, illite, montmorillonite, halloysite, and dickite; the acid is at least one of hydrochloric acid, nitric acid, oxalic acid, sulfuric acid, phosphoric acid, and ethylenediaminetetraacetic acid, and the concentration of the acid solution is 0.25 mol / L - 3.5 mol / L.

[0007] (2) Add elemental aluminum or aluminum salts to the acid-etched solution obtained in step (1). On the one hand, neutralize the excessive acid to increase the pH of the solution; on the other hand, increase the molar concentration of aluminum in the solution to obtain a reaction precursor solution for preparing metal-organic framework materials; the elemental aluminum includes one of aluminum pellets, aluminum wires, aluminum sheets, and aluminum powders; the aluminum salts include at least one of aluminum hydroxide, sodium aluminate, and aluminum nitrate. The concentration of aluminum in the finally obtained reaction precursor solution is 10-15 g / L.

[0008] (3) Load the reaction precursor solution obtained in step (2) into a reaction kettle, add ligand powder, adjust the pH value of the solution to 2.5-4.5 with a base, and stir to disperse evenly; then seal the reaction kettle and heat it to 160-220 °C for reaction for 12-36 h, and naturally cool to room temperature; the ligand is nitroterephthalic acid, and the molar ratio of aluminum element to ligand in the reaction precursor solution is 1:0.5 - 1:1; the volume of the reaction precursor solution is 30-50 mL.

[0009] (4) Perform solid-liquid separation on the suspension obtained after the reaction in step (3), wash the solid successively with methanol and deionized water, dry it at a temperature of 80-100 °C, and grind it into powder to obtain metal-organic framework materials.

[0010] The synthesis mechanism of the present invention: The acid dissolution method is used to dissolve aluminum ions in aluminous natural clay minerals as the reaction precursor solution. The aluminous waste liquid generated during the production of nano-silica is used as the metal source and reaction medium. By adding elemental aluminum or aluminum salts to neutralize the excess acid and increase the aluminum ion concentration, the pH is adjusted to a suitable value for synthesizing metal-organic frameworks with a base. Nitroterephthalic acid and aluminum ions in the acid-etched solution are coordinated and synthesized into aluminum metal-organic framework mesoporous materials through a one-step hydrothermal reaction.

[0011] The metal-organic framework material synthesized by the acid etching solution of aluminous clay minerals in the present invention can be used as an adsorbent in sewage treatment. The prepared adsorbent is environmentally friendly and has good adsorption effect, which not only realizes the harmless disposal and resource utilization of strong acid wastewater, but also provides a new material for efficiently removing pollutants in water.

[0012] In summary, the present invention has the following advantages:

[0013] 1) Using the aluminous waste liquid generated in the process of producing nano-silica by acid etching nano-clay as the raw material and reaction medium, an aluminum metal-organic framework material is synthesized through a one-step hydrothermal reaction. While harmlessly disposing of the waste liquid, it realizes the utilization of valuable resources and the production of new materials, truly achieving the sustainable development goal of "turning waste into materials";

[0014] 2) The prepared metal-organic framework material has good crystallinity, excellent performance, stable batches, and the specific surface area can reach 477.91 m 2 / g. The adsorption of organic molecules is not affected by coexisting ions, and it has a high removal rate of organic pollutants (such as p-nitrophenol) in real water bodies such as seawater, the Yangtze River water, the Yellow River water, and tap water, and has strong practical applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the infrared spectrum of the metal-organic framework material prepared in Example 1 of the present invention. Among them, a is nitroterephthalic acid, and b is the metal-organic framework material;

[0016] Figure 2 are the scanning electron microscope and transmission electron microscope pictures of the metal-organic framework material prepared in Example 1 of the present invention. Among them, a is the scanning electron microscope picture, and b is the transmission electron microscope picture;

[0017] Figure 3 is the XRD pattern of the metal-organic framework material prepared in Example 1 of the present invention;

[0018] Figure 4 is the specific surface area and pore size distribution diagram of the metal-organic framework material prepared in Example 1 of the present invention. Among them, a is the N2 adsorption-desorption specific surface area, and b is the pore size distribution diagram.

[0019] Figure 5 is the performance of the metal-organic framework material prepared in Example 1 of the present invention for repeated adsorption of p-nitrophenol.

[0020] Figure 6 is the adsorption performance of the metal-organic framework material prepared in Example 1 of the present invention for p-nitrophenol in the Yangtze River water, the Yellow River water, and seawater.

[0021] Figure 7 is the performance of the metal-organic framework material prepared in Example 1 of the present invention for adsorbing p-nitrophenol in the coexistence of phenol. Detailed implementation manners

[0022] The present invention will be explained and described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] Disperse the aluminum-rich kaolinite mineral into 2 mol / L hydrochloric acid aqueous solution, and then carry out hydrothermal treatment at 180 °C for 6 h. After natural cooling to room temperature, perform solid-liquid separation, collect the liquid, and obtain the acid etching solution of the aluminum-rich clay mineral. Add aluminum powder to the acid etching solution. On the one hand, neutralize the excessive acid to increase the pH of the solution; on the other hand, increase the molar concentration of aluminum in the solution to obtain the reaction precursor solution for preparing the metal-organic framework material. Load the reaction precursor solution into a hydrothermal reaction kettle, add the ligand powder nitroterephthalic acid (molar ratio 1:0.5), mix evenly, adjust the pH value of the solution to 3 with an alkali, stir and disperse evenly to obtain a uniform mixed solution. Seal the reaction kettle, heat it to 200 °C and react for 36 h, and then naturally cool to room temperature. Perform solid-liquid separation on the obtained suspension, wash the solid successively with methanol and deionized water, dry it at 100 °C, and grind it into powder to obtain the metal-organic framework adsorbent material (named Nitro-MIL-53(Al)).

[0025] Structure characterization and performance evaluation of the metal-organic framework material prepared in Example 1:

[0026] As can be seen from the attached Figure 1 figures, typical vibration bands representing carboxyl groups appear in the range of 1300 - 1710 cm -1 for nitroterephthalic acid, proving that carboxylic acid groups exist in the structure of the prepared metal-organic framework adsorbent. The characteristic absorption peak at 756 cm -1 represents the C-H bending vibration on the benzene ring of the organic ligand. The characteristic absorption peak at 595 cm -1 represents the formation of the Al 3+ -O bond between Al and the organic ligand. The characteristic absorption peak at 1354 cm −1 represents the symmetric stretching vibration of the nitro group. These results indicate that the metal ions are successfully connected to the carboxyl groups on the organic ligand, and the metal-organic framework adsorbent is successfully synthesized.

[0027] As can be seen from the attached Figure 2 figures, the metal-organic framework material synthesized using the acid etching solution of the aluminum-rich clay mineral has smaller crystal grains, showing a short rod or block crystal morphology, with a uniform and smooth surface, sharp edges, and good dispersibility.

[0028] As can be seen from the attached Figure 3It can be seen that the adsorbent prepared by the present invention has basically the same diffraction peak positions as those reported in the literature, and the diffraction peaks are clear and sharp, indicating the successful synthesis of the aluminum metal-organic framework material.

[0029] From the attached Figure 4 It can be seen that the nitrogen adsorption-desorption specific surface area of the adsorbent prepared by the present invention is 477.91 m 2 / g, and the average pore diameter is 2.58 nm, belonging to mesoporous materials.

[0030] From the attached Figure 5 It can be seen that after the adsorbent is regenerated 4 times, the removal rate of p-nitrophenol can still reach more than 90%, indicating that the aluminum metal-organic framework material synthesized from the acid etching solution of aluminum-rich clay minerals is a reusable adsorbent.

[0031] From the attached Figure 6 It can be seen that the adsorbent prepared by the present invention has good adsorption performance in the actual water bodies of the Yellow River, the Yangtze River and seawater.

[0032] From the attached Figure 7 It can be seen that in the mixed system composed of phenol / p-nitrophenol, the adsorption capacity of the adsorbent of the present invention has no obvious change compared with that when p-nitrophenol is adsorbed alone, indicating that the adsorbent has good selectivity for p-nitrophenol.

[0033] In summary, the metal-organic framework material prepared in Example 1 of the present invention can effectively remove organic pollutants (such as p-nitrophenol) in sewage.

[0034] Example 2

[0035] Disperse the aluminum-rich clay mineral illite into the oxalic acid solution, and then carry out hydrothermal treatment at 180 °C for 12 h. After natural cooling to room temperature, carry out solid-liquid separation, collect the liquid, and obtain the acid etching solution of the aluminum-rich clay mineral. Add aluminum hydroxide powder to the acid etching solution. On the one hand, neutralize the excessive acid to increase the pH of the solution; on the other hand, increase the molar concentration of aluminum in the solution to obtain the reaction precursor solution for preparing the metal-organic framework material. Load the reaction precursor solution into a hydrothermal reaction kettle, add the ligand powder nitrophthalic acid (molar ratio 1:1), mix evenly, adjust the pH value of the solution to 4.5 with alkali, stir and disperse evenly to obtain a uniform mixed solution. Seal the reaction kettle, heat it to 200 °C and react for 12 h, and then naturally cool to room temperature. Carry out solid-liquid separation on the obtained suspension, wash the solid with methanol and deionized water in sequence, dry it at 80 °C, and grind it into powder to obtain the metal-organic framework adsorbent material.

[0036] Example 3

[0037] Disperse the aluminous clay mineral calcined kaolinite into nitric acid solution, and then carry out hydrothermal treatment at 200 °C for 1 h. After natural cooling to room temperature, carry out solid-liquid separation, collect the liquid, and obtain the acid etching solution of the aluminous clay mineral. Add sodium aluminate into the acid etching solution. On the one hand, neutralize the excessive acid and increase the pH of the solution; on the other hand, increase the molar concentration of aluminum in the solution to obtain the reaction precursor solution for preparing metal-organic framework materials. Load the reaction precursor solution into a hydrothermal reaction kettle, add the ligand powder nitroterephthalic acid (molar ratio 1:0.5), mix evenly, adjust the pH value of the solution to 2.5 with alkali, stir and disperse evenly to obtain a homogeneous mixed solution. Seal the reaction kettle, heat it to 200 °C and react for 24 h, and then naturally cool to room temperature. Carry out solid-liquid separation on the obtained suspension, wash the solid successively with methanol and deionized water, dry it at 100 °C, and grind it into powder to obtain the metal-organic framework adsorbent material.

[0038] Example 4

[0039] Disperse the aluminous clay mineral dickite into phosphoric acid solution, and then carry out hydrothermal treatment at 120 °C for 10 h. After natural cooling to room temperature, carry out solid-liquid separation, collect the liquid, and obtain the acid etching solution of the aluminous clay mineral. Add aluminum nitrate salt into the acid etching solution. On the one hand, neutralize the excessive acid and increase the pH of the solution; on the other hand, increase the molar concentration of aluminum in the solution to obtain the reaction precursor solution for preparing metal-organic framework materials. Load the reaction precursor solution into a hydrothermal reaction kettle, add the ligand powder nitroterephthalic acid (molar ratio 1:1), mix evenly, adjust the pH value of the solution to 3.5 with alkali, stir and disperse evenly to obtain a homogeneous mixed solution. Seal the reaction kettle, heat it to 160 °C and react for 36 h, and then naturally cool to room temperature. Carry out solid-liquid separation on the obtained suspension, wash the solid successively with methanol and deionized water, dry it at 100 °C, and grind it into powder to obtain the metal-organic framework adsorbent material.

[0040] Example 5

[0041] Disperse halloysite, a clay mineral rich in aluminum, into sulfuric acid solution, and then conduct hydrothermal treatment at 180 °C for 8 h. After natural cooling to room temperature, perform solid-liquid separation, collect the liquid, and obtain the acid-etched solution of the aluminum-rich clay mineral. Add aluminum sheets to the acid-etched solution. On the one hand, neutralize the excessive acid to increase the pH of the solution; on the other hand, increase the molar concentration of aluminum in the solution to obtain a reaction precursor solution for preparing metal-organic framework materials. Load the reaction precursor solution into a hydrothermal reactor, add the ligand powder nitroterephthalic acid (molar ratio 1:1), mix evenly, adjust the pH value of the solution to 2.5 with alkali, stir and disperse evenly to obtain a homogeneous mixed solution. Seal the reactor, heat it to 180 °C and react for 36 h, and then naturally cool to room temperature. Perform solid-liquid separation on the obtained suspension, wash the solid successively with methanol and deionized water, dry it at 100 °C, and grind it into powder to obtain the metal-organic framework adsorbent material.

[0042] Example 6

[0043] Disperse montmorillonite, a clay mineral rich in aluminum, into hydrochloric acid solution, and then conduct hydrothermal treatment at 180 °C for 6 h. After natural cooling to room temperature, perform solid-liquid separation, collect the liquid, and obtain the acid-etched solution of the aluminum-rich clay mineral. Add aluminum wire to the acid-etched solution. On the one hand, neutralize the excessive acid to increase the pH of the solution; on the other hand, increase the molar concentration of aluminum in the solution to obtain a reaction precursor solution for preparing metal-organic framework materials. Load the reaction precursor solution into a hydrothermal reactor, add the ligand powder nitroterephthalic acid (molar ratio 1:0.5), mix evenly, adjust the pH value of the solution to 3 with alkali, stir and disperse evenly to obtain a homogeneous mixed solution. Seal the reactor, heat it to 220 °C and react for 36 h, and then naturally cool to room temperature. Perform solid-liquid separation on the obtained suspension, wash the solid successively with methanol and deionized water, dry it at 100 °C, and grind it into powder to obtain the metal-organic framework adsorbent material.

Claims

1. A method for synthesizing metal-organic framework materials using an acid etching solution of aluminous clay minerals, characterized in that, It includes the following steps: (1) Disperse the aluminum-rich clay minerals into an acid solution, then carry out hydrothermal treatment at 120-200 °C for 1-12 h. After naturally cooling to room temperature, perform solid-liquid separation, collect the liquid, and obtain the acid etching solution of the aluminum-rich clay minerals; (2) Add elemental aluminum or aluminum salts to the acid etching solution obtained in step (1) to obtain a reaction precursor solution for preparing metal-organic framework materials; (3) Load the reaction precursor solution obtained in step (2) into a reaction kettle, add ligand powder, adjust the pH value of the solution to 2.5-4.5 with an alkali, and stir to disperse evenly; then seal the reaction kettle and heat it to 160-220 °C for reaction for 12-36 h, and naturally cool to room temperature; (4) Perform solid-liquid separation on the suspension obtained after the reaction in step (3), wash the solid successively with methanol and deionized water, dry it at a temperature of 80-100 °C, and grind it into powder to obtain the metal-organic framework material.

2. The method for synthesizing metal-organic framework materials using an acid etching solution of aluminous clay minerals according to claim 1, characterized in that, The aluminum-rich clay minerals are at least one of kaolinite, calcined kaolinite, illite, montmorillonite, halloysite, and dickite.

3. The method for synthesizing metal-organic framework materials using an acid etching solution of aluminous clay minerals according to claim 1, characterized in that, The acid is at least one of hydrochloric acid, nitric acid, oxalic acid, sulfuric acid, and phosphoric acid, and the concentration of the acid solution is 0.25 mol / L - 3.5 mol / L.

4. The method for synthesizing metal-organic framework materials using an acid etching solution of aluminous clay minerals according to claim 1, characterized in that, The elemental aluminum includes one of aluminum pellets, aluminum wires, aluminum sheets, and aluminum powders; the aluminum salts include at least one of aluminum hydroxide, sodium meta-aluminate, and aluminum nitrate; the concentration of aluminum in the finally obtained reaction precursor solution is 10-15 g / L.

5. The method for synthesizing metal-organic framework materials using an acid etching solution of aluminous clay minerals according to claim 1, characterized in that, The ligand is nitroterephthalic acid, and the molar ratio of aluminum element to ligand in the reaction precursor solution is 1:0.5 - 1:1.

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