NH2-AC / Fe MOFs material as well as preparation method and application thereof

Abstract

The invention discloses an NH2-AC / Fe MOFs material and a preparation method and application thereof, and the preparation method comprises the following steps: adding an amino-containing organic matter into an alcoholic solution, stirring and mixing, adding activated carbon, and continuously stirring; carrying out water bath reaction, and carrying out amino functionalization on the surface of the activated carbon to obtain amino-functionalized activated carbon; the preparation method comprises the following steps: adding NH2-AC into a mixed solution formed by dispersing ferric salt and fumaric acid into a solvent, and heating for reaction to obtain the NH2-AC / Fe-MOFs material. The prepared NH2-AC / Fe MOFs material has a large specific surface area and abundant adsorption sites, active sites such as iron, oxygen-containing functional groups and amino groups on the surface of the material can adsorb fluorine ions through surface complexation, hydrogen bonds, electrostatic adsorption, ligand exchange and ion exchange, and the material has excellent fluorine ion adsorption performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of drinking water treatment, and in particular relates to an amino-functionalized activated carbon-loaded iron metal organic framework material (NH2-AC / Fe MOFs material) and a preparation method and application thereof. Background Art

[0002] my country's "Standard for Drinking Water Quality" (GB5749-2022) clearly stipulates that the fluoride content in drinking water must be less than 1.0 mg / L; the drinking water standard formulated by the World Health Organization (WHO) stipulates that the fluoride content must not exceed 1.5 mg / L. Due to the wide range of fluoride pollution, fragmented pollution areas, complex environment, unclear removal mechanism, difficulty in treatment, and high cost, the problem of fluoride pollution in my country's drinking water has not yet been effectively solved. The fluoride ion concentration in water is generally below 5 mg / L. It is difficult to remove such a low concentration of fluoride ions, 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 precipitation, adsorption, membrane separation, ion exchange, and electrochemical methods. Among them, adsorption is considered to be one of the best and most effective means of removing fluoride from water because of its low cost, simple operation, and mature development. Conventional adsorption materials include metal organic frameworks (MOFs), metal oxides, layered double hydroxides (LDH), and porous carbon materials. Activated carbon is a low-cost adsorption material with a large specific surface area, but its adsorption performance is poor. Therefore, its adsorption selectivity and rate can be improved by surface functionalization. MOFs have attracted widespread attention due to their ultra-large specific surface area and a large number of functional groups on the surface. MOFs are crystalline composite materials formed by the coordination of metal ions or metal clusters with organic ligands. They are composed of metal centers and organic molecules, and form a structured network through coordination bonds with metal ions. The formation of porous structures in MOFs can be regulated by adjusting 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.). Summary of the invention

[0004] In view of the shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide an NH2-AC / Fe MOFs material and a preparation method and application thereof, which can greatly increase the number and activity of surface groups of the adsorption material, solve the problems of poor adsorption capacity and low adsorption rate of fluoride ions of traditional adsorption materials, and the preparation method is simple and easy to implement.

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

[0006] The first object of the present invention is to provide a method for preparing NH2-AC / Fe MOFs material, which comprises the following steps:

[0007] S1, adding an amino-containing organic compound to an alcohol solution and stirring to obtain a mixed solution A;

[0008] S2, adding activated carbon to the mixed solution A, and continuously stirring to obtain a mixed solution B;

[0009] S3, subjecting the mixed solution B to a water bath reaction to amino functionalization of the surface of the activated carbon to obtain amino functionalized activated carbon NH2-AC;

[0010] S4, dispersing the iron salt and fumaric acid in a solvent, and stirring to form a mixed solution C;

[0011] S5. Add NH2-AC to the mixed solution C, stir and mix, and then heat to react 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 matter to the alcohol solution is 1:8-12.

[0015] In a further embodiment, the mass ratio of the volume of the amino-containing organic matter in the mixed solution B to the 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° C. and for a time of 12-24 hours.

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

[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 temperature is 65-85°C and the time is 6-12h;

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

[0022] In a further solution, the product after the heating reaction in step S5 needs to be naturally cooled, and then separated and dried to obtain the amino-functionalized activated carbon-loaded iron metal organic framework material, wherein the separation is performed by centrifugation and the drying temperature is 60-80°C.

[0023] The second object of the present invention is to provide NH2-AC / Fe MOFs material prepared by the above preparation method.

[0024] NH2-AC / Fe MOFs material is an iron metal organic framework material supported by amino-functionalized activated carbon. The material has a large specific surface area and abundant adsorption sites. The active sites such as iron, oxygen-containing functional groups, and amino groups on its surface can adsorb fluoride ions through surface complexation, hydrogen bonding, electrostatic adsorption, ligand exchange, and ion exchange, so it has excellent fluoride ion adsorption performance. More importantly, NH2-AC / Fe MOFs material is an environmentally friendly material. It does not produce any substances harmful to the human body during the adsorption of fluoride ions. It is an efficient green water treatment material.

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

[0026] This material can adsorb and remove fluoride ions in water with an initial concentration of about 5 mg / L to below 1 mg / L within 10 minutes, making the treated water meet the sanitary standards for drinking water.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The metal organic framework (MOFs) material in the NH2-AC / Fe MOFs material prepared by the present invention has a larger specific surface area and more adjustable microporous structures than metal oxides, thereby having more adsorption sites to produce a better adsorption effect. In addition, the material can adsorb and remove fluoride ions through surface electrostatic interactions (Formulas 1-4), hydroxyl exchange (Formulas 1 and 5), and hydrogen bonds formed with surface amino groups (Formula 6). Therefore, the NH2-AC / Fe MOFs material prepared by the present invention has excellent fluoride ion adsorption performance, and does not produce any substances harmful to the human body in the process of removing fluoride ions, and is a new type of 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 - Formula 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 Formula 6

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

[0037] (3) The present application selects polyethyleneimine and ethylenediamine to modify the surface of activated carbon with amino groups, so that the product has a rougher surface and a larger specific surface area, which is beneficial 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) The NH2-AC / Fe MOFs material prepared by the present invention is added to fluoride-containing water, and the fluoride-containing water with an initial fluoride ion concentration of about 5 mg / L can be treated to reach the sanitary standard of drinking water below 1 mg / L 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the SEM morphology of the NH2-AC / Fe MOFs material prepared in Example 1. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 technicians in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0043] Example 1

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

[0045] S1. Stir 4 mL PEI and 40 mL methanol in a beaker for 1 h to obtain a mixed solution A;

[0046] S2. Add 4 g of activated carbon (AC) to the mixed solution A and stir continuously for 1 h to obtain a mixed solution B;

[0047] S3, placing the mixed solution B in a water bath, and performing a polymerization reaction at 85°C for 24 hours to functionalize the surface of the activated carbon with amino groups, filtering the obtained product, washing with pure water, and drying it to obtain an amino-functionalized activated carbon NH2-AC solid;

[0048] S4, dispersing 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 pure water, and stirring vigorously for 30 min to form a mixed solution C;

[0049] S5. Add 1 g of NH2-AC solid to the mixed solution C, stir and mix, then put it into a high-pressure reactor and react at 65°C for 6 hours. After the reaction is completed, cool it naturally; then centrifuge the product and dry it at 60°C to obtain NH2-AC / FeMOFs material.

[0050] Test example 1:

[0051] The morphology of the NH2-AC / Fe MOFs material prepared in Example 1 was characterized by scanning electron microscopy. Figure 1 As shown, it can be seen that the prepared material is an AC-loaded rod-like structure.

[0052] Test 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 the mixture was stirred for 30 minutes before sampling. The fluoride ion concentration in the water was measured and calculated using a fluoride ion electrode to be 0.402 mg / L.

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

[0055] Example 2

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

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

[0058] S2, add 8g AC to the mixed solution A, and stir the mixture continuously for 1h to obtain mixed solution B;

[0059] S3, placing the mixed solution B in a water bath, and performing a polymerization reaction at 80°C for 20 hours to functionalize the surface of the activated carbon with amino groups, filtering the obtained product, washing with pure water, and drying it to obtain NH2-AC solid;

[0060] S4, dispersing ferric chloride hexahydrate and fumaric acid in 50 mL of DMF at a molar ratio of 1:1 (ferric chloride hexahydrate 1.352 g, fumaric acid 0.580 g), and vigorously stirring for 30 min to form a mixed solution C;

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

[0062] Similar to Test Example 2, the NH2-AC / Fe MOFs material prepared in Example 2 was subjected to a fluoride removal test for fluoride-containing water. The results showed that a dosage of 0.3 g / L of NH2-AC / Fe MOFs material could reduce the initial fluoride 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 material comprises the following steps:

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

[0066] S2. Add 6 g AC to mixed solution A and stir continuously for 1 h to obtain mixed solution B;

[0067] S3, placing the mixed solution B in a water bath, and performing a polymerization reaction at 90°C for 12 hours to functionalize the surface of the activated carbon with amino groups, filtering the obtained product, washing with pure water, and drying it to obtain NH2-AC solid;

[0068] S4, dispersing 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 of solvent (a mixed solvent of 25 mL pure water and 25 mL N,N-dimethylformamide), and vigorously stirring for 30 min to obtain a mixed solution C;

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

[0070] Similar to Test Example 2, the NH2-AC / Fe MOFs material synthesized in Example 3 was subjected to a fluoride removal test for fluoride-containing water. The results showed that a dosage of 0.3 g / L of NH2-AC / Fe MOFs material could reduce the initial fluoride 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 comprises the following steps:

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

[0074] S2, add 4 g AC to mixed solution A, and stir the mixture continuously for 1 h to obtain mixed solution B;

[0075] S3, placing the obtained mixed solution B in a water bath, and performing polymerization reaction at 85°C for 24 hours to functionalize the surface of the activated carbon with amino groups, filtering the obtained product, washing with pure water, and drying to obtain NH2-AC solid;

[0076] S4, dispersing ferric nitrate nonahydrate and fumaric acid in 50 mL of pure water at a molar ratio of 1:1 (ferric nitrate nonahydrate 2.020 g, fumaric acid 0.580 g), and stirring vigorously for 30 min to obtain a mixed solution C;

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

[0078] Similar to Test Example 2, the NH2-AC / Fe MOFs synthesized in Example 4 were subjected to a fluoride removal test for fluoride-containing water. The results showed that a dosage of 0.3 g / L of NH2-AC / Fe MOFs material could reduce the initial fluoride 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 comprises the following steps:

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

[0082] S2, add 4 g AC to mixed solution A, and stir the mixture continuously for 1 h to obtain mixed solution B;

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

[0084] As in Test Example 2, the NH2-AC synthesized in Comparative Example 1 was subjected to a fluorine removal test on a fluorine-containing water sample. The results showed that an addition amount of 0.3 g / L of NH2-AC material could reduce the initial fluorine concentration of 5 mg / L to 3.137 mg / L, and its defluorination effect was significantly lower than that of the NH2-AC / Fe MOFs in the above four embodiments.

[0085] Comparative Example 2

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

[0087] S1, dispersing 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 solvent (mixed with 25 mL pure water and 25 mL N,N-dimethylformamide), and vigorously stirring for 30 min to obtain a mixed solution C;

[0088] S2. Add 1 g AC solid to the mixed solution C and stir for 2 h, then put it into a high-pressure reactor and react at 65 °C for 6 h. After the reaction is completed, cool it 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 fluorine removal test for fluorine-containing water. The results showed that an addition amount of 0.3 g / L of AC / Fe MOFs material could reduce the initial fluorine concentration of 5 mg / L to 2.516 mg / L, and the fluorine removal effect was lower than that of the NH2-AC / Fe MOFs prepared in Example 4 above.

[0090] Comparative Example 3

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

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

[0093] S2, dispersing 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 solvent (mixed with 25 mL pure water and 25 mL N,N-dimethylformamide), and vigorously stirring for 30 min to obtain a mixed solution C;

[0094] S3. Add 1 g of A-NH2-AC solid to the mixed solution C and stir for 2 h. Then put it into a high-pressure reactor and react at 65°C for 6 h. After the reaction, cool it naturally. Then, centrifuge the product, wash it with deionized water, and dry it at 80°C 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 fluorine removal test for fluorine-containing water. The results showed that when the dosage of AC / Fe MOFs material was 0.3 g / L, the initial fluorine concentration of 5 mg / L was reduced to 1.823 mg / L.

[0096] The fluorine removal effect is low. This is because in Comparative Example 3, activated carbon modified with ammonia (A-NH2-AC) is combined with an iron metal organic framework material, and 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 fluorine ions is poor.

[0097] Comparative Example 4

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

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

[0100] S2, add 4 g AC to mixed solution A, and stir the mixture continuously for 1 h to obtain mixed solution B;

[0101] S3, placing the mixed solution B in a water bath, performing polymerization reaction at 85°C for 24 hours, filtering the obtained product, washing with pure water, and drying to obtain NH2-AC solid;

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

[0103] S5, weigh 0.132 g VC and add it into 30 mL ultrapure water to form a mixture D;

[0104] S6, adding mixed solution D to mixed solution C and stirring for 20 min to form mixed solution E;

[0105] S7. Disperse 1 g of NH2-AC solid in 30 mL of deionized water to form a mixed solution F. Then add the mixed solution F to the mixed solution E and ultrasonicate for 30 min. Transfer to a reactor and react at 150°C for 5 h. Centrifuge the cooled mixture, wash with deionized water and ethanol, and dry at 60°C for 24 h to obtain NH2-AC / Fe3O4 solid.

[0106] Similar to Test Example 2, a fluorine removal test of fluorine-containing water was carried out on NH2-AC / Fe3O4 synthesized in Comparative Example 4. The results showed that the addition amount of 0.3 g / L of NH2-AC / Fe3O4 material could reduce the initial fluorine concentration of 5 mg / L to 2.461 mg / L.

[0107] The low fluorine removal effect is because the NH2-AC / Fe MOFs material prepared in Example 4 contains a metal organic framework (MOFs) material, which has a larger specific surface area and more adjustable microporous structure than the metal oxide in Comparative Example 4, thereby having more adsorption sites to produce 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 modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing NH2-AC / Fe MOFs material, characterized in that: The following steps are involved: S1, adding an amino-containing organic compound to an alcohol solution and stirring to obtain a mixed solution A; S2, adding activated carbon to the mixed solution A, and continuously stirring to obtain a mixed solution B; S3, subjecting the mixed solution B to a water bath reaction to amino functionalization of the surface of the activated carbon to obtain amino functionalized activated carbon NH2-AC; S4, dispersing the iron salt and fumaric acid in a solvent, and stirring to form a mixed solution C; S5. Add NH2-AC to the mixed solution C, stir and mix, and then heat to react to obtain NH2-AC / Fe-MOFs material.

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

3. The preparation method according to claim 1, characterized in that: The volume ratio of the amino-containing organic matter to the activated carbon in the mixed solution B is 1:1-2.

4. The preparation method according to claim 1, characterized in that: The temperature of the water bath reaction is 80-90° C. and the reaction time is 12-24 hours.

5. 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.

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

1.

7. The preparation method according to claim 1, characterized in that: The heating reaction temperature is 65-85°C and the time is 6-12h; The volume ratio of the added mass of the NH2-AC to the mixed solution C is 10-20 g / L.

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

9. NH2-AC / Fe MOFs material prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the NH2-AC / Fe MOFs material as claimed in claim 9 in removing fluoride ions from water.

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