An NH2-AC / Fe MOFs material, its preparation method and application

Abstract

This invention discloses an NH2-AC / Fe MOFs material, its preparation method, and its applications. The preparation method includes the following steps: adding an amino-containing organic compound to an alcohol solution and stirring; adding activated carbon and stirring continuously; performing a water bath reaction to functionalize the activated carbon surface with amino groups, obtaining amino-functionalized activated carbon; adding NH2-AC to a mixture formed by iron salts and fumaric acid dispersed in a solvent, and heating to obtain the NH2-AC / Fe-MOFs material. The NH2-AC / Fe MOFs material prepared by this invention has a large specific surface area and abundant adsorption sites. Its surface active sites, such as iron, oxygen-containing functional groups, and amino groups, can adsorb fluoride ions through surface complexation, hydrogen bonding, electrostatic adsorption, ligand exchange, and ion exchange, exhibiting excellent fluoride ion adsorption performance.

Description

Technical Field

[0001] This invention belongs to the field of drinking water treatment technology, and specifically relates to an amino-functionalized activated carbon-supported iron metal-organic framework material (NH2-AC / Fe MOFs material), its preparation method, and its application. Background Technology

[0002] my country's "Standards for Drinking Water Quality" (GB5749-2022) clearly stipulates that the fluoride content in drinking water should be less than 1.0 mg / L; the World Health Organization (WHO) drinking water standards stipulate that the fluoride content should not exceed 1.5 mg / L. Fluoride ion concentrations in water are generally below 5 mg / L. Removing such low concentrations of fluoride ions is difficult, and there is an urgent need to develop efficient and low-cost treatment technologies.

[0003] Traditional technologies for removing fluoride ions from drinking water include coagulation and sedimentation, adsorption, membrane separation, ion exchange, and electrochemical methods. Among these, adsorption is considered one of the most effective methods for removing fluoride from water due to its low cost, simple operation, and mature development. Conventional adsorbent materials include metal-organic frameworks (MOFs), metal oxides, layered bimetallic hydroxides (LDHs), and porous carbon materials. Activated carbon is a low-cost adsorbent with a large specific surface area, but its adsorption performance is relatively poor. Therefore, surface functionalization can be used to improve its adsorption selectivity and rate. MOFs have attracted widespread attention due to their extremely large specific surface area and the large number of functional groups on their surface. MOFs are crystalline composite materials formed by the coordination of metal ions or metal clusters with organic ligands. They consist of a metal center and organic molecules, forming a structured network through coordination bonds with metal ions. The formation of the porous structure in MOFs can be adjusted by regulating the arrangement of these networks. Fluoride ions can be removed through electrostatic interactions with the surface of MOFs; interactions with oxygen-containing functional groups on the surface of MOFs; ion exchange between fluoride ions and hydroxyl groups; and metal-fluoride interactions with metal centers in MOFs (such as Fe, Al, La, etc.) to form metal-fluoride compounds. Summary of the Invention

[0004] In view of the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide an NH2-AC / Fe MOFs material, its preparation method and application. This material can greatly improve the number and activity of surface groups of adsorbent materials, solve the problems of poor adsorption capacity and low adsorption rate of fluoride ions in traditional adsorbent materials, and the preparation method is simple and easy to implement.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The first objective of this invention is to provide a method for preparing NH2-AC / Fe MOFs materials, which includes the following steps:

[0007] S1. Add the amino-containing organic compound to the alcohol solution and stir to obtain mixture A;

[0008] S2. Add activated carbon to mixture A and stir continuously to obtain mixture B;

[0009] S3. Mixture B is subjected to a water bath reaction to functionalize the surface of activated carbon with amino groups, resulting in amino-functionalized activated carbon NH2-AC.

[0010] S4. Disperse the iron salt and fumaric acid in a solvent and stir to form a mixture C;

[0011] S5. After adding NH2-AC to the mixed solution C and stirring, the mixture is heated to obtain NH2-AC / Fe-MOFs material.

[0012] In a further embodiment, the amino-containing organic compound is at least one of polyethyleneimine (PEI) and ethylenediamine (EDA);

[0013] The alcohol solution is methanol or ethanol;

[0014] The volume ratio of the amino-containing organic compound to the alcohol solution is 1:8-12.

[0015] In a further embodiment, the volume ratio of amino organic matter in the mixture B to the mass ratio of activated carbon (AC) is 1:1-2.

[0016] In a further embodiment, the water bath reaction is carried out at a temperature of 80-90℃ for a duration of 12-24 hours.

[0017] In a further embodiment, the iron salt is at least one of nitrates and chlorides;

[0018] The solvent is at least one of N,N-dimethylformamide and pure water.

[0019] In a further embodiment, the molar ratio of the iron salt to fumaric acid is 1:1.

[0020] In a further embodiment, the heating reaction is carried out at a temperature of 65-85°C for a duration of 6-12 hours.

[0021] The mass ratio of NH2-AC added to the volume ratio of the mixed solution C is 10-20 g / L.

[0022] In a further embodiment, the product after the heating reaction in step S5 needs to be naturally cooled, and then separated and dried to obtain an iron-metal-organic framework material supported on amino-functionalized activated carbon. The separation is carried out by centrifugation, and the drying temperature is 60-80℃.

[0023] The second objective of this invention is to provide NH2-AC / Fe MOFs materials prepared by the above-described method.

[0024] NH2-AC / Fe MOFs are iron-metal-organic framework materials supported on amino-functionalized activated carbon. These materials possess a large specific surface area and abundant adsorption sites. The iron, oxygen-containing functional groups, and amino groups on their surface can adsorb fluoride ions through surface complexation, hydrogen bonding, electrostatic adsorption, ligand exchange, and ion exchange, thus exhibiting excellent fluoride ion adsorption performance. More importantly, NH2-AC / Fe MOFs are environmentally friendly materials; they do not produce any substances harmful to human health during fluoride ion adsorption, making them a highly efficient and green water treatment material.

[0025] The third objective of this invention is to provide the application of the above-mentioned NH2-AC / Fe MOFs material in the removal of fluoride ions from water.

[0026] This material can adsorb and remove fluoride ions from an initial concentration of about 5 mg / L in water to below 1 mg / L within 10 minutes, so that the treated water meets the drinking water hygiene standards.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) The metal-organic framework (MOF) material in the NH2-AC / Fe MOFs material prepared in this invention has a larger specific surface area and more tunable microporous structures compared to metal oxides, thus possessing more adsorption sites and producing better adsorption effects. In addition, this material can adsorb and remove fluoride ions through surface electrostatic interactions (Formulas 1-4), hydroxyl exchange (Formulas 1 and 5), and hydrogen bonding with surface amino groups (Formula 6). Therefore, the NH2-AC / Fe MOFs material prepared in this invention has excellent fluoride ion adsorption performance and does not produce any substances harmful to the human body during the removal of fluoride ions, making it a novel, efficient, and green water treatment material.

[0029] The specific reaction process is as follows:

[0030] ≡FeOH (surface-hydroxylated iron) + H + →≡FeOH2 + Formula 1

[0031] ≡FeOH2 + +F -→≡FeOH2 + F - Equation 2

[0032] R-NH2+H + →R-NH3 + Formula 3

[0033] R-NH3 + +F - →R-NH3 + F - Formula 4

[0034] ≡FeOH2 + +F - →≡FeF+H2O, formula 5

[0035] R-NH2 + HF → R-NH2 HF, equation 6

[0036] (2) In the preparation method of this application, trans-butenedioic acid is added. Its trans configuration and the synergistic effect of the carboxylic acid group not only promote the uniform dispersion and stable coordination of iron ions, but also obtain a composite material with high specific surface area and high adsorption activity by regulating the pore structure and pyrolysis behavior.

[0037] (3) In this application, polyethyleneimine and ethylenediamine are selected to modify the surface amino groups of activated carbon, so that the product has a rougher surface and a larger specific surface area, which is conducive to the adsorption of fluoride ions; at the same time, the product surface has more amino active groups, which promotes the removal of fluoride ions.

[0038] (4) When the NH2-AC / Fe MOFs material prepared in this invention is added to fluoride-containing water, it can treat the fluoride-containing water with an initial fluoride concentration of about 5 mg / L to below 1 mg / L of drinking water within 10 minutes.

[0039] (5) The preparation method of the present invention is simple and easy to operate, and is suitable for large-scale industrial production. Attached Figure Description

[0040] Figure 1 The image shows the SEM morphology of the NH2-AC / Fe MOFs material prepared in Example 1. Detailed Implementation

[0041] The present invention will be further described below with reference to embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0042] 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 this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0043] Example 1

[0044] A method for preparing NH2-AC / Fe MOFs includes the following steps:

[0045] S1. Stir 4 mL of PEI and 40 mL of methanol in a beaker for 1 hour to obtain mixture A;

[0046] S2. Add 4g of activated carbon (AC) to mixture A and stir continuously for 1 hour to obtain mixture B;

[0047] S3. Place the mixture B in a water bath and carry out the polymerization reaction at 85°C for 24 hours to functionalize the surface of the activated carbon with amino groups. Filter the obtained product, wash it with pure water, and dry it to obtain amino-functionalized activated carbon NH2-AC solid.

[0048] S4. Disperse ferric chloride hexahydrate and fumaric acid in a molar ratio of 1:1 (1.352 g ferric chloride hexahydrate and 0.580 g fumaric acid) in 50 mL of pure water and stir vigorously for 30 min to form mixture C.

[0049] S5. Add 1g of solid NH2-AC to the mixture C and stir. Then place it in a high-pressure reactor and react at 65℃ for 6h. After the reaction is completed, let it cool naturally. Then centrifuge the product and dry it at 60℃ to obtain the NH2-AC / FeMOFs material.

[0050] Detection Example 1:

[0051] The morphology of the NH2-AC / Fe MOFs material prepared in Example 1 was characterized by scanning electron microscopy, such as... Figure 1 As shown, the prepared material is an AC-loaded rod-shaped structure.

[0052] Detection Example 2:

[0053] 0.15 g of NH2-AC / Fe MOFs material prepared in Example 1 was added to 500 mL of fluoride-containing water with a fluoride concentration of 5 mg / L and stirred for 30 minutes. The fluoride concentration in the water was measured and calculated to be 0.402 mg / L using a fluoride ion electrode.

[0054] The test results show that when NH2-AC / Fe MOFs material is added to fluoride-containing water at a concentration of 0.3 g / L, the fluoride concentration in the water can be reduced from an initial concentration of 5 mg / L to below 1 mg / L, thus meeting the drinking water standard.

[0055] Example 2

[0056] A method for preparing NH2-AC / Fe MOFs materials includes the following steps:

[0057] S1. Stir 4 mL of EDA and 32 mL of ethanol in a beaker for 1 h to obtain mixture A;

[0058] S2. Add 8g of AC to mixture A and stir the mixture continuously for 1 hour to obtain mixture B;

[0059] S3. Place the mixture B in a water bath and carry out the polymerization reaction at 80°C for 20 hours to functionalize the surface of activated carbon with amino groups. Filter the obtained product, wash it with pure water, and dry it to obtain solid NH2-AC.

[0060] S4. Disperse ferric chloride hexahydrate and fumaric acid in a 1:1 molar ratio (1.352 g ferric chloride hexahydrate and 0.580 g fumaric acid) in 50 mL DMF and stir vigorously for 30 min to form mixture C.

[0061] S5. Add 1g of solid NH2-AC to the mixture C and stir for 2h. Then place it in a high-pressure reactor and react at 85℃ for 12h. After the reaction is completed, let it cool naturally. Then centrifuge the product and dry it at 80℃ to obtain the NH2-AC / Fe MOFs material.

[0062] Similar to Example 2, the NH2-AC / Fe MOFs material prepared in Example 2 was subjected to a defluoridation test on fluoride-containing water. The results showed that the addition of 0.3 g / L of NH2-AC / Fe MOFs material could reduce the fluoride concentration from an initial concentration of 5 mg / L to below 1 mg / L (the fluoride concentration after treatment was 0.862 mg / L), meeting the drinking water standard.

[0063] Example 3

[0064] A method for preparing NH2-AC / Fe MOFs materials includes the following steps:

[0065] S1. Stir 2 mL of PEI and 2 mL of EDA with 48 mL of methanol in a beaker for 1 h to obtain mixture A;

[0066] S2. Add 6g AC to mixture A and stir continuously for 1 hour to obtain mixture B;

[0067] S3. Place the mixture B in a water bath and carry out the polymerization reaction at 90°C for 12 hours to functionalize the surface of activated carbon with amino groups. Filter the obtained product, wash it with pure water, and dry it to obtain solid NH2-AC.

[0068] S4. Ferric chloride hexahydrate and fumaric acid were dispersed in 50 mL of solvent (a mixture of 25 mL of pure water and 25 mL of N,N-dimethylformamide) at a 1:1 molar ratio (1.352 g of ferric chloride hexahydrate and 0.580 g of fumaric acid) and stirred vigorously for 30 min to obtain mixture C.

[0069] S5. Add 0.5g of NH2-AC solid to the mixture C and stir for 2h. Then place it in a high-pressure reactor and react at 80℃ for 10h. After the reaction is completed, let it cool naturally. Centrifuge the product and dry it at 80℃ to obtain the NH2-AC / Fe MOFs material.

[0070] Similar to Example 2, the NH2-AC / Fe MOFs material synthesized in Example 3 was subjected to a defluoridation test on fluoride-containing water. The results showed that the addition of 0.3 g / L of NH2-AC / Fe MOFs material could reduce the fluoride concentration from an initial concentration of 5 mg / L to below 1 mg / L (the fluoride concentration after treatment was 0.637 mg / L), meeting the drinking water standard.

[0071] Example 4

[0072] A method for preparing NH2-AC / Fe MOFs includes the following steps:

[0073] S1. Stir 4 mL of EDA and 40 mL of methanol in a beaker for 1 h to obtain mixture A;

[0074] S2. Add 4g AC to mixture A and stir the mixture continuously for 1 hour to obtain mixture B;

[0075] S3. Place the obtained mixture B in a water bath and carry out a polymerization reaction at 85°C for 24 hours to functionalize the surface of activated carbon with amino groups. Filter, wash with pure water and dry the obtained product to obtain solid NH2-AC.

[0076] S4. Disperse ferric nitrate nonahydrate and fumaric acid in a 1:1 molar ratio (2.020 g ferric nitrate nonahydrate and 0.580 g fumaric acid) in 50 mL of pure water and stir vigorously for 30 min to obtain mixture C.

[0077] S5. Add 1g of NH2-AC solid to the mixture C and stir for 2h. Then place it in a high-pressure reactor and react at 65℃ for 6h. After the reaction is completed, let it cool naturally. Centrifuge the product and dry it at 80℃ to obtain the NH2-AC / Fe MOFs material.

[0078] Similar to Example 2, the NH2-AC / Fe MOFs synthesized in Example 4 were subjected to a defluoridation test on fluoride-containing water. The results showed that the addition of 0.3 g / L of NH2-AC / Fe MOFs material could reduce the fluoride concentration from an initial concentration of 5 mg / L to below 1 mg / L (the fluoride concentration after treatment was 0.509 mg / L), meeting the drinking water standard.

[0079] Comparative Example 1

[0080] A method for preparing NH2-AC includes the following steps:

[0081] S1. Stir 4 mL of EDA and 40 mL of methanol in a beaker for 1 hour to obtain mixture A;

[0082] S2. Add 4g AC to mixture A and stir the mixture continuously for 1 hour to obtain mixture B;

[0083] S3. Place the mixture B in a water bath and carry out the polymerization reaction at 85°C for 24 hours to functionalize the surface of the activated carbon with amino groups. Filter the resulting product, wash it with pure water, and dry it to obtain solid NH2-AC.

[0084] Similar to Example 2, the NH2-AC synthesized in Comparative Example 1 was used to conduct a fluoride removal test on a fluoride-containing water sample. The results showed that the dosage of NH2-AC material of 0.3 g / L could reduce the fluoride concentration from an initial concentration of 5 mg / L to 3.137 mg / L. Its fluoride removal effect was significantly lower than that of NH2-AC / Fe MOFs in the above four examples.

[0085] Comparative Example 2

[0086] A method for preparing AC / Fe MOF includes the following steps:

[0087] S1. Ferric chloride hexahydrate and fumaric acid were dispersed in a 1:1 molar ratio (1.352 g ferric chloride hexahydrate and 0.580 g fumaric acid) in 50 mL of solvent (a mixture of 25 mL pure water and 25 mL N,N-dimethylformamide), and stirred vigorously for 30 min to obtain mixture C;

[0088] S2. Add 1g of solid AC to the mixture C and stir for 2 hours. Then place it in a high-pressure reactor and react at 65°C for 6 hours. After the reaction is completed, allow it to cool naturally. Then centrifuge the product, wash it with deionized water and ethanol, and dry it at 80°C to obtain AC / Fe MOFs material.

[0089] The AC / Fe MOF synthesized in Comparative Example 2 was subjected to a defluorination test in fluoride-containing water. The results showed that the addition of AC / Fe MOFs material at a dosage of 0.3 g / L could reduce the fluoride concentration from an initial concentration of 5 mg / L to 2.516 mg / L. The defluorination effect was lower than that of NH2-AC / Fe MOFs prepared in Example 4.

[0090] Comparative Example 3

[0091] A method for preparing A-NH2-AC / Fe MOF by modifying AC with ammonia water includes the following steps:

[0092] S1. Add 10g AC to 100mL of 15% ammonia water, heat and stir in a water bath at 60℃ for 3h, cool and centrifuge, wash with deionized water, and dry the obtained solid at 60℃ to obtain A-NH2-AC.

[0093] S2. Ferric chloride hexahydrate and fumaric acid were dispersed in 50 mL of solvent (a mixture of 25 mL of pure water and 25 mL of N,N-dimethylformamide) at a 1:1 molar ratio (1.352 g of ferric chloride hexahydrate and 0.580 g of fumaric acid) and stirred vigorously for 30 min to obtain mixture C.

[0094] S3. Add 1g of A-NH2-AC solid to the mixture C and stir for 2h. Then place it in a high-pressure reactor and react at 65℃ for 6h. After the reaction is completed, let it cool naturally. Then centrifuge the product, wash it with deionized water, and dry it at 80℃ to obtain A-NH2-AC / Fe MOFs material.

[0095] Similar to test example 2, the A-NH2-AC / Fe MOF synthesized in comparative example 3 was subjected to a defluorination test in fluoride-containing water. The results showed that when the dosage of AC / Fe MOFs material was 0.3 g / L, the fluoride concentration was reduced from an initial concentration of 5 mg / L to 1.823 mg / L.

[0096] The low fluoride removal effect is because Comparative Example 3 is an activated carbon modified with ammonia (A-NH2-AC) combined with an iron metal-organic framework material. Its surface roughness and specific surface area are smaller than those of the NH2-AC / Fe MOFs material prepared in Example 4, so its adsorption and removal effect on fluoride ions is poor.

[0097] Comparative Example 4

[0098] A method for preparing NH2-AC / Fe3O4 includes the following steps:

[0099] S1. Stir 4 mL of EDA and 40 mL of methanol in a beaker for 1 h to obtain mixed solution A;

[0100] S2. Add 4g AC to mixture A and stir the mixture continuously for 1 hour to obtain mixture B;

[0101] S3. Place the mixture B in a water bath and carry out the polymerization reaction at 85°C for 24 hours. Filter the obtained product, wash it with pure water, and dry it to obtain NH2-AC solid.

[0102] S4. Dissolve 1.352g of FeCl3·6H2O and 0.924g of NaHCO3 together in 50 mL of ultrapure water and stir thoroughly for 30 min to form mixture C;

[0103] S5. Weigh 0.132g of VC and add it to 30 mL of ultrapure water to form mixture D;

[0104] S6. Add mixture D to mixture C and stir for 20 minutes to form mixture E;

[0105] S7. Disperse 1g of NH2-AC solid in 30mL of deionized water to form a mixture F; then add mixture F to mixture E and sonicate for 30min, transfer to a reaction vessel, and react at 150℃ for 5h; centrifuge the cooled mixture, wash with deionized water and ethanol, and dry at 60℃ for 24h to obtain NH2-AC / Fe3O4 solid.

[0106] Similar to test example 2, the NH2-AC / Fe3O4 synthesized in comparative example 4 was subjected to a defluorination test on fluoride-containing water. The results showed that the addition of 0.3 g / L of NH2-AC / Fe3O4 material could reduce the fluoride concentration from an initial concentration of 5 mg / L to 2.461 mg / L.

[0107] The low fluoride removal effect is because the NH2-AC / Fe MOFs material prepared in Example 4 contains metal-organic frameworks (MOFs), which have a larger specific surface area and more tunable microporous structures than the metal oxides in Comparative Example 4, thus having more adsorption sites and producing a better adsorption effect.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing NH2-AC / Fe MOFs material, characterized in that: Includes the following steps: S1. Add an amino-containing organic compound to an alcohol solution and stir to obtain a mixture A; the amino-containing organic compound is at least one of polyethyleneimine and ethylenediamine; S2. Add activated carbon to mixture A and stir continuously to obtain mixture B; the volume ratio of amino organic matter in mixture B to the mass ratio of activated carbon is 1:1-2. S3. The mixture B is subjected to a water bath reaction to functionalize the surface of the activated carbon with amino groups, resulting in amino-functionalized activated carbon NH2-AC. S4. Disperse the iron salt and fumaric acid in a solvent and stir to form a mixture C; S5. After adding NH2-AC to the mixed solution C and stirring, the mixture is heated to obtain NH2-AC / Fe-MOFs material; wherein the mass ratio of NH2-AC added to the volume of the mixed solution C is 10-20 g / L; the heating reaction temperature is 65-85℃ and the time is 6-12 h.

2. The preparation method according to claim 1, characterized in that: The alcohol solution is methanol or ethanol; The volume ratio of the amino-containing organic compound to the alcohol solution is 1:8-12.

3. The preparation method according to claim 1, characterized in that: The water bath reaction is carried out at a temperature of 80-90℃ for 12-24 hours.

4. The preparation method according to claim 1, characterized in that: The iron salt is at least one of nitrate, chloride, and hydrate; The solvent is at least one of N,N-dimethylformamide and pure water.

5. The preparation method according to claim 1, characterized in that: The molar ratio of the iron salt to fumaric acid is 1:

1.

6. The preparation method according to claim 1, characterized in that: The product after the heating reaction in step S5 needs to be cooled naturally, and then separated and dried to obtain an amino-functionalized activated carbon-supported iron-metal-organic framework material. The separation is carried out by centrifugation, and the drying temperature is 60-80℃.

7. NH2-AC / Fe MOFs material prepared by the preparation method according to any one of claims 1-6.

8. The application of the NH2-AC / Fe MOFs material as described in claim 7 in the removal of fluoride ions from water.

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