Preparation of a Fe3O4@CuO Magnetic Nanocatalyst and Its Application in the Directional Acidification of Humic Acid

Abstract

The present invention discloses the preparation of a Fe3O4@CuO magnetic nanocatalyst and its application in the directional acidification of humic acid. Ferric chloride hexahydrate, sodium acetate, and cetyltrimethylammonium bromide are added to an ethylene glycol solution, stirred evenly, and placed in a reaction kettle for reaction. After washing and drying, Fe3O4 nanoparticles with uniform particle size are prepared. A copper chloride solution is prepared and complexed with the Fe3O4 nanoparticles, which are then calcined in a muffle furnace and naturally cooled. Cu is loaded onto the Fe3O4 nanoparticles by the impregnation method. The generated catalyst and the reactants react at a suitable temperature using hydrogen peroxide as an oxidant to achieve the catalytic directional acidification of humic acid. The synthesis conditions of this catalyst are mild, the synthesis method is simple, and the catalytic directional acidification of humic acid only requires normal temperature and pressure, with simple conditions, significant acidification effect, long catalyst life, easy recovery and recycling, and easy realization of industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic materials, and in particular to the preparation of a Fe3O4@CuO magnetic nanocatalyst and its application in the directional acidification of humic acid. Background Art

[0002] Humic acid belongs to natural organic macromolecular compounds, mainly composed of elements such as C, H, O, N, S, etc. It has a wide range of sources and mainly exists in weathered coal, lignite, peat, water bodies, and soil. Humic acid contains abundant active groups (hydroxyl, carboxyl, carbonyl, etc.), and it often has hydrophilicity, acidity, interfacial activity, complexing ability, cation exchange ability, and adsorption and dispersion ability, etc. Therefore, humic acid plays an important role in the fields of agriculture, animal husbandry, environmental protection, industry, and medicine. Therefore, it is of research value to study the extraction and application of humic acid.

[0003] Due to its rigid macromolecular structure and limited content of active functional groups, it is necessary to carry out activation treatment on it. Currently, most methods use oxidative degradation to convert macromolecular humic acid into small-molecular humic acid and increase the content of active functional groups. The oxidants used include potassium permanganate, potassium dichromate, hydrogen peroxide, nitric acid, sulfuric acid, etc. However, after oxidation, the activation performance of humic acid is still insufficient, and the impurity content is high and it is difficult to wash clean.

[0004] Therefore, it is of great significance to prepare a catalyst that can directionally acidify humic acid, increase the content of its carboxyl functional groups, and improve its activity. Summary of the Invention

[0005] Aiming at the above existing technical deficiencies, the purpose of the present invention is to provide the preparation of a Fe3O4@CuO magnetic nanocatalyst and its application in the directional acidification of humic acid. The synthesis conditions of the catalyst are mild, the synthesis method is simple, and the catalytic directional acidification of humic acid only needs to be carried out under normal temperature and pressure, the conditions are simple, the acidification effect is remarkable, and the catalyst has a long service life, is easy to recycle, and is easy to realize industrial production.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] An object of the present invention is to provide a Fe3O4@CuO magnetic nanocatalyst, and its preparation method includes the following steps:

[0008] S1: Weigh ferric chloride hexahydrate, sodium acetate, and cetyltrimethylammonium bromide and add them to an ethylene glycol solution, and stir in an open reactor to mix evenly;

[0009] S2: Put the mixed solution in step S1 into a reaction kettle, carry out a temperature-raising reaction, and naturally cool to room temperature after the reaction;

[0010] S3: Magnetically separate the reaction product in step S2, wash it several times, and dry it to prepare Fe3O4 nanoparticles with uniform particle size.

[0011] S4: Prepare a copper chloride solution at a certain concentration so that the copper ions account for 0.2% of the Fe3O4 nanoparticles. Use the impregnation method to complex with the Fe3O4 nanoparticles generated in step S3, place it in a muffle furnace for calcination, and then cool it naturally to prepare the Fe3O4@CuO magnetic nanocatalyst.

[0012] Preferably, the molar ratio of ferric chloride hexahydrate, sodium acetate, cetyltrimethylammonium bromide to ethylene glycol is (0.5 - 1.5):(1 - 3):(1 - 3):(20 - 60).

[0013] Preferably, in step S1, at room temperature, use a rotor to mix at 200 - 1500 r / min for 1 - 5 h.

[0014] Preferably, the reaction kettle in step S2 is a hydrothermal kettle, the reaction temperature is 160 - 220 °C, the reaction time is 20 - 30 h, and Fe3O4 is synthesized by a one-pot hydrothermal method.

[0015] Preferably, the washing solution in step S3 is deionized water and ethanol, the magnetic separation is by magnet separation method, the drying is by vacuum drying oven drying method, the drying temperature is 40 - 70 °C, and the drying time is 6 - 24 h.

[0016] Preferably, the metal loading rate of the impregnation method in step S4 is 0.15 - 0.3%, the calcination temperature of the muffle furnace is 400 °C, the calcination time is 3 - 6 h, and the programmed heating rate is 6 - 10 °C / min.

[0017] Another object of the present invention is to provide the application of the Fe3O4@CuO magnetic nanocatalyst in the directional acidification of humic acid. The above Fe3O4@CuO magnetic nanomaterial has the activities of peroxidase-like, catalase-like, superoxide dismutase-like and phenol oxidase-like, and can be used to prepare peroxidase-like, catalase-like, superoxide dismutase-like or phenol oxidase-like catalysts. Its catalytic directional acidification of humic acid includes the following steps:

[0018] S5: Weigh humic acid and dissolve it in ultrapure water, add the catalyst, where the mass ratio of ultrapure water, humic acid to the catalyst is 100:5:1, stir and react at room temperature for 4 - 8 h. An oxidant needs to be added during the reaction, and the mass ratio of the added oxidant to humic acid is 1:1, and the addition rate is 1 - 2 mL / h.

[0019] S6: Finally, centrifuge to separate the product, put it in an oven to dry the catalyst and the product, and then use a magnet to separate the product and the catalyst.

[0020] Preferably, the centrifugation conditions in step S6 are 5000 - 7000 rad / min, the centrifugation time is 15 - 30 min, the oven temperature is 40 - 70 °C, and the drying time is 4 - 8 h.

[0021] Preferably, the finally recovered catalyst repeats steps S5 and S6 to catalyze the directional acidification reaction of humic acid.

[0022] Preferably, the oxidant in step S6 is a 30% hydrogen peroxide solution

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. The method for synthesizing the catalyst of the present invention synthesizes Fe3O4 nanoparticles by a one-pot hydrothermal method, and then loads Cu onto the Fe3O4 nanoparticles by an impregnation method. The synthesis conditions are mild, the synthesis method is simple, and the cost is low. There is no need to use complex and expensive instruments and drugs;

[0025] 2. The catalyst of the present invention has the activities of peroxidase-like, catalase-like, superoxide dismutase-like and phenolic oxidase-like. Using it to catalyze humic acid, the catalytic conditions are simple, only at normal temperature and pressure, and the catalyst has magnetism, so it is easy to recycle and is easy to realize industrial production;

[0026] 3. The catalyst synthesized by the present invention makes humic acid undergo directional acidification during catalysis, and the acidification effect is remarkable. The carboxylic acid content increases from the original 2.453% to 6.975%. The catalyst can weaken the hydrogen bond energy connecting hydroxyl groups, reduce the reaction activation energy, and break the hydrogen bond with less energy. The catalyst breaks the carbonyl bond, free olefin bond and oxygen-containing double bond of hydrocarbons in humic acid, generating alcohols and phenolic compounds, so as to improve the activity of humic acid. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is the scanning electron microscope image of the Fe3O4@CuO magnetic nanocatalyst in one of the embodiments of the present invention;

[0029] Figure 2 It is the transmission electron microscope image of the Fe3O4@CuO catalyst in one of the embodiments of the present invention;

[0030] Figure 3 Full-spectrum analysis map of the Fe3O4@CuO catalyst in one embodiment of the present invention;

[0031] Figure 4 X-ray diffraction pattern of the Fe3O4@CuO catalyst in one embodiment of the present invention;

[0032] Figure 5 Comparison chart of the Fe3O4@CuO catalyst in one embodiment of the present invention catalyzing humic acid at different times;

[0033] Figure 6 Liquid-phase spectrum of the Fe3O4@CuO catalyst in one embodiment of the present invention catalyzing specific reactants;

[0034] Figure 7 Element determination map of the Fe3O4@CuO catalyst in one embodiment of the present invention; Detailed implementation manners

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] Example 1

[0037] a. Preparation of Fe3O4 nanoparticles. 2.7 g of FeCl3·6H2O, 7.2 g of sodium acetate, and 2.0 g of cetyltrimethylammonium bromide were successively added to a conical flask containing 0.1 L of ethylene glycol, and the mixture was stirred evenly under continuous stirring. The solution was transferred to a 100 mL hydrothermal autoclave, then sealed, and kept at 200 °C for 12 h. After cooling down, the product was separated by a magnet, washed several times with distilled water and absolute ethanol, and then dried in a vacuum oven at 50 °C for 12 h.

[0038] b. Preparation of Fe3O4@CuO magnetic nanomaterials. 1.2 mg of anhydrous copper chloride was dissolved in 0.3 g of water, and then 0.3 g of Fe3O4 nanoparticles was mixed with it. The container was a porcelain boat, and the loading rate was 0.2%. Then it was placed in a muffle furnace for calcination at a temperature of 400 °C for 5 h, with a programmed temperature increase of 10 °C / min.

[0039] c. Conduct the catalytic reaction for the directional acidification of humic acid. Take 500 mg of humic acid, dissolve it in 100 mL of ultrapure water, and then add the Fe3O4@CuO magnetic nanomaterial catalyst prepared in step b. The container is a 250 mL conical flask. Stir the reaction at room temperature for 6 h. Add 1 mL of hydrogen peroxide solution at the beginning of the reaction, and then add 1 mL of hydrogen peroxide solution to the reaction system every 1 h of reaction. A total of 5 mL of oxidant is added.

[0040] d. Catalyst recovery. Centrifuge and separate the product at 6000 rad / min for 20 min. Place it in an oven at 60 °C to dry the catalyst and the product for 6 h. Use a magnet to separate the product and the catalyst.

[0041] Example 2

[0042] a. Prepare Fe3O4 nanoparticles. Add 2.7 g of FeCl3·6H2O, 7.2 g of sodium acetate, and 4.95 g of cetyltrimethylammonium bromide to 0.1 L of ethylene glycol in sequence. Stir the mixture evenly under continuous stirring. Transfer the solution to a 100 mL hydrothermal autoclave, then seal it, and keep it at 200 °C for 12 h. Cool down, separate the product with a magnet, wash it several times with distilled water and absolute ethanol, and then dry it in a vacuum oven at 50 °C for 24 h.

[0043] b. Prepare Fe3O4@CuO magnetic nanomaterials. Take 1.2 mg of anhydrous copper chloride, dissolve it in 0.3 g of water, and then mix it with 0.3 g of Fe3O4 nanoparticles. The container is a porcelain boat, and the loading rate is 0.2%. Then place it in a muffle furnace for calcination at a temperature of 400 °C for 5 h, with a programmed temperature increase of 10 °C / min.

[0044] c. Conduct the catalytic reaction for the directional acidification of humic acid. Take 500 mg of humic acid, dissolve it in 100 mL of ultrapure water, and then add the Fe3O4@CuO magnetic nanomaterial catalyst. The container is a 250 mL conical flask. Stir the reaction at room temperature for 6 h. Add 1 mL of hydrogen peroxide solution at the beginning of the reaction, and then, add 1 mL of hydrogen peroxide solution to the reaction system every 1 h of reaction. A total of 5 mL of oxidant is added.

[0045] d. Catalyst recovery. Centrifuge and separate the product at 6000 rad / min for 20 min. Place it in an oven at 60 °C to dry the catalyst and the product for 6 h. Use a magnet to separate the product and the catalyst.

[0046] Example 3

[0047] a. Preparation of Fe3O4 nanoparticles. 2.7 g of FeCl3·6H2O, 7.2 g of sodium acetate, and 4.95 g of cetyltrimethylammonium bromide were successively added to 0.1 L of ethylene glycol, and the mixture was stirred evenly under continuous stirring. The solution was transferred to a 100 mL hydrothermal reactor, then sealed, and kept at 200 °C for 12 h. After cooling, the product was separated by a magnet, washed several times with distilled water and absolute ethanol, and then dried in a vacuum oven at 80 °C for 12 h.

[0048] b. Preparation of Fe3O4@CuO magnetic nanomaterials. 6 mg of anhydrous copper chloride was dissolved in 0.3 g of water, and then 0.3 g of Fe3O4 nanoparticles was mixed with it. The container was a porcelain boat, and the loading rate was 1%. Then it was placed in a muffle furnace for calcination at a temperature of 400 °C for 5 h, with a programmed heating rate of 10 °C / min.

[0049] c. Conduct the humic acid directional acidification catalysis reaction. 500 mg of humic acid was dissolved in 100 mL of ultrapure water, and then the Fe3O4@CuO magnetic nanomaterial catalyst was added. The container was a 250 mL conical flask, and the reaction was stirred at room temperature for 3 h. 3 mL of hydrogen peroxide solution was added at the beginning of the reaction, and then 1 mL of hydrogen peroxide solution was added to the reaction system every 1 h, with a total of 5 mL of oxidant added.

[0050] d. Catalyst recovery. Finally, the product was separated by centrifugation at 6000 rad / min for 20 min, and the catalyst and product were dried in an oven at 60 °C for 6 h. A magnet was used to separate the product and the catalyst.

[0051] Example 4

[0052] a. Preparation of Fe3O4 nanoparticles. 2.7 g of FeCl3·6H2O, 7.2 g of sodium acetate, and 4.95 g of cetyltrimethylammonium bromide were successively added to 0.1 L of ethylene glycol, and the mixture was stirred evenly under continuous stirring. The solution was transferred to a 100 mL hydrothermal reactor, then sealed, and kept at 200 °C for 12 h. After cooling, the product was separated by a magnet, washed several times with distilled water and absolute ethanol, and then dried in a vacuum oven at 50 °C for 12 h.

[0053] b. Preparation of Fe3O4@CuO magnetic nanomaterials. 6 mg of anhydrous copper chloride was dissolved in 0.3 g of water, and then 0.3 g of Fe3O4 nanoparticles was mixed with it. The container was a porcelain boat, and the loading rate was 1%. Then it was placed in a muffle furnace for calcination at a temperature of 400 °C for 5 h, with a programmed heating rate of 10 °C / min.

[0054] c. Conduct the catalytic reaction for the directional acidification of humic acid. Take 500 mg of humic acid, dissolve it in 100 mL of ultrapure water, and then add the Fe3O4@CuO magnetic nanomaterial catalyst. The container is a 250 mL conical flask, and the reaction is stirred at room temperature for 6 h. Add 1 mL of hydrogen peroxide solution at the beginning of the reaction, and then add 1 mL of hydrogen peroxide solution to the reaction system every 1 h. A total of 5 mL of oxidant is added.

[0055] d. Catalyst recovery. Finally, centrifuge and separate the product at 6000 rad / min for 20 min, put it in an oven at 120 °C to dry the catalyst and the product for 6 h, and use a magnet to separate the product and the catalyst.

[0056] Example 5

[0057] a. Prepare Fe3O4 nanoparticles. Add 2.7 g of FeCl3·6H2O, 7.2 g of sodium acetate, and 4.95 g of cetyltrimethylammonium bromide to 0.1 L of ethylene glycol in sequence, and stir the mixture evenly under continuous stirring. Transfer the solution to a 100 mL hydrothermal autoclave, then seal it, and keep it at 200 °C for 12 h. Cool down, separate the product with a magnet, wash it several times with distilled water and absolute ethanol, and then dry it in a vacuum oven at 50 °C for 12 h.

[0058] b. Prepare Fe3O4@CuO magnetic nanomaterials. Take 6 mg of anhydrous copper chloride, dissolve it in 0.3 g of water, and then mix it with 0.3 g of Fe3O4 nanoparticles. The container is a porcelain boat, and the loading rate is 1%. Then place it in a muffle furnace for calcination at a temperature of 400 °C for 5 h, with a programmed temperature increase of 10 °C / min.

[0059] c. Conduct the catalytic reaction for the directional acidification of humic acid. Take 500 mg of humic acid, dissolve it in 100 mL of ultrapure water, and then add the Fe3O4@CuO magnetic nanomaterial catalyst. The container is a 250 mL conical flask, and the reaction is stirred at 50 °C for 6 h. Add 1 mL of hydrogen peroxide solution at the beginning of the reaction, and then add 1 mL of hydrogen peroxide solution to the reaction system every 1 h. A total of 5 mL of oxidant is added.

[0060] d. Catalyst recovery. Finally, centrifuge and separate the product at 6000 rad / min for 20 min, then put it in an oven at 60 °C to dry the catalyst and the product for 6 h, and use a magnet to separate the product and the catalyst.

[0061] Analysis of the experimental results of the present invention:

[0062] As Figures 1 to 7As shown, the catalysts synthesized in Examples 1 to 5 have a simple synthesis process and low cost; the catalytic conditions for catalyzing humic acid are simple and only need to be carried out at normal temperature and pressure, which can make it increase acidity directionally. The present invention uses the Bohem titration method to measure its acid-increasing effect, and the result shows that the carboxylic acid content increases from the original 2.453% to 6.975%. The catalyst can weaken the hydrogen bond energy connecting hydroxyl groups, reduce the reaction activation energy, and break the hydrogen bond with less energy. The catalyst breaks the carbonyl bond, free olefin bond and oxygen-containing double bond of hydrocarbon compounds in humic acid to generate alcohols and phenolic compounds, so as to improve the activity of humic acid and make it play a better role in the fields of agriculture, industry, medicine, etc.

[0063] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. Application of a Fe3O4@CuO magnetic nanocatalyst in the aspect of directional acidification of humic acid, characterized in that, The preparation method of the catalyst includes the following steps: S1: Weigh ferric chloride hexahydrate, sodium acetate, and cetyltrimethylammonium bromide, add them to an ethylene glycol solution, and stir in an open reactor for uniform mixing. S2: Put the mixed solution in step S1 into a reaction kettle, carry out a temperature-raising reaction, and naturally cool to room temperature after the reaction. S3: Magnetically separate the reaction product in step S2, wash it several times, and dry it to prepare Fe3O4 nanoparticles with uniform particle size. S4: Prepare a copper chloride solution according to a certain concentration, use the impregnation method to complex the metal with the Fe3O4 nanoparticles generated in step S3. The metal loading rate of the impregnation method is 0.15 - 0.3%, place it in a muffle furnace for calcination, and then naturally cool to prepare the Fe3O4@CuO magnetic nanocatalyst. The method for the catalyst to catalyze the directional acidification of humic acid includes the following steps: S5: Weigh humic acid and dissolve it in ultrapure water, add the catalyst. The mass ratio of ultrapure water, humic acid, and the catalyst is 100:5:

1. Stir and react at room temperature for 4 - 8 h. An oxidant needs to be added during the reaction. The mass ratio of the added oxidant to humic acid is 1:1, and the addition rate is 1 - 2 mL / h. S6: Finally, centrifuge to separate the product, dry the catalyst and the product, and then use a magnet to separate the product and the catalyst.

2. Application of a Fe3O4@CuO magnetic nanocatalyst in the aspect of directed acidification of humic acid as described in claim 1, characterized in that, The molar ratio of ferric chloride hexahydrate, sodium acetate, cetyltrimethylammonium bromide to ethylene glycol is (0.5 - 1.5):(1 - 3):(1 - 3):(20 - 60).

3. Application of a Fe3O4@CuO magnetic nanocatalyst in the aspect of directed acidification of humic acid as described in claim 1, characterized in that, In step S1, mix at room temperature with a rotor at 200 - 1500 r / min and stir for 1 - 5 h.

4. Use of a Fe3O4@CuO magnetic nanocatalyst as described in claim 1 in the aspect of directional acidification of humic acid, characterized in that, The reaction kettle in step S2 is a hydrothermal kettle. The reaction temperature is 160 - 220 °C, and the reaction time is 20 - 30 h. Fe3O4 is synthesized by a one-pot hydrothermal method.

5. Application of a Fe3O4@CuO magnetic nanocatalyst in the aspect of directional acidification of humic acid as described in claim 1, characterized in that, In step S3, the washing solution is deionized water and ethanol. The magnetic separation is by the magnet separation method. The drying is by vacuum drying oven drying method. The drying temperature is 40 - 70 °C, and the drying time is 6 - 24 h.

6. The application of a Fe3O4@CuO magnetic nanocatalyst in the aspect of directional acidification of humic acid as described in claim 1, wherein In step S4, the calcination temperature in the muffle furnace is 400 °C, the calcination time is 3 - 6 h, and the programmed heating rate is 6 - 10 °C / min.

7. Use of a Fe3O4@CuO magnetic nanocatalyst as described in claim 1 in the aspect of directional acidification of humic acid, characterized in that The centrifugation conditions in step S6 are 5000 - 7000 rad / min, the centrifugation time is 15 - 30 min, the oven temperature is 40 - 70 °C, and the drying time is 4 - 8 h.

8. The application of a Fe3O4@CuO magnetic nanocatalyst in the aspect of directional acidification of humic acid as described in claim 1, characterized in that, The finally recovered catalyst repeats steps S5 and S6 to catalyze the directional acidification reaction of humic acid.

9. Use of a Fe3O4@CuO magnetic nanocatalyst as described in claim 1 in the aspect of directed acidification of humic acid, characterized in that, The oxidant in step S5 is a 30% hydrogen peroxide solution.

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