Synthesis method and application of iron-aluminum co-doped catalyst

Abstract

The invention discloses a synthesis method and application of an iron-aluminum co-doped catalyst, and the synthesis method is characterized by comprising the following steps: S1, dissolving an aluminum metal salt and an iron metal salt in a beaker containing deionized water to obtain a solution A; s2, adding a phosphorus source into the solution A, and adjusting the pH to form a turbid liquid B; s3, biomass is added into the turbid liquid B to be stirred for 30 min, and a solution C is obtained; s4, adding a nitrogen source into the solution C, and drying the beaker in a water bath kettle; mixing the obtained dried product with an activating agent, and calcining under inert gas to obtain a catalyst crude product; and S5, grinding the catalyst crude product, washing with ethanol and deionized water, and carrying out vacuum drying to obtain the iron-aluminum co-doped catalyst. The preparation method is simple and low in equipment requirement. The invention discloses a novel nitrogen-doped carbon-coated zero-valent iron nanoparticle catalyst which can degrade pollutants by utilizing electron transfer of the pollutants and the catalyst under the condition of adding any oxidizing agent. Under the neutral room temperature condition, the catalyst has a very good removal effect on degradation of organic pollutants which are difficult to biodegrade, has very good stability, and is low in iron ion dissolution rate.

Description

Technical Field

[0001] The present invention belongs to the field of water treatment, and particularly relates to a synthesis method and application of an iron-aluminum co-doped catalyst. Background Art

[0002] In recent years, emerging pollutants, such as antibiotics, pharmaceuticals, personal care products, hormones, artificial sweeteners, and endocrine disrupting chemicals, have been widely detected in the wastewater of the pharmaceutical, dye, pesticide, paper-making, and plastic industries. Even in the water treated by sewage treatment plants, trace levels can reach from ng / L to μg / L. Some studies have shown that the concentrations of emerging pollutants in untreated water in the Asian region are higher than those in some countries in Europe and North America. Extensive experiments have proved that the presence of these substances will have an adverse impact on the aquatic ecosystem and human health. Taking antibiotics as an example, antibiotics are widely used in the treatment of human and animal diseases, and they persist in the environment through the vicious cycle of transformation and bioaccumulation, and are widely spread through natural water systems. Antibiotic exposure can promote the generation of bacterial drug resistance, change many basic physiological balances, and promote long-term diseases. At present, the treatment cost of advanced oxidation technology is relatively high, the biological treatment effect is not good, and it will produce drug-resistant genes and bring harm. Therefore, there is an urgent need to develop a low-energy and high-efficiency technology to treat organic pollutants in wastewater, reduce the cost of wastewater treatment, and reduce the generation of drug-resistant genes. Summary of the Invention

[0003] The purpose of the present invention is to provide a synthesis method and use of an iron-aluminum co-doped graphene wastewater self-purification catalyst. This method uses cyclodextrin as an organic ligand, ferric chloride hexahydrate as an iron source, and urea as a nitrogen source to synthesize a precursor by a copolymerization method, and synthesizes the target catalyst by pyrolysis under a nitrogen atmosphere.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] 1. A synthesis method of an iron-aluminum co-doped catalyst, comprising the following steps:

[0006] S1: Dissolve an aluminum metal salt and an iron metal salt in a beaker containing deionized water to obtain solution A;

[0007] S2: Add a phosphorus source to solution A and adjust the pH to form suspension B;

[0008] S3: Add biomass to suspension B and stir for 30 min to obtain solution C;

[0009] S4: Add a nitrogen source to solution C, place the beaker in a water bath to dry; mix the obtained dried product with an activator and calcine it under an inert gas to obtain a crude catalyst;

[0010] S5: Grind the crude catalyst product, then wash it with ethanol and deionized water, and dry it under vacuum to obtain the iron-aluminum co-doped catalyst.

[0011] Further, in step S1, the metal iron salt includes one of ferric chloride hexahydrate, ferric chloride, ferric nitrate nonahydrate, ferric acetate, ferric sulfate, and iron acetylacetonate, with a mass of 0.5 - 3 g; the metal aluminum salt includes one of aluminum chloride, aluminum nitrate, and aluminum sulfate, and the molar ratio of iron to aluminum is (1 - 6):1.

[0012] Preferably, the metal iron salt is ferric chloride hexahydrate; the metal aluminum salt is aluminum chloride.

[0013] Further, the phosphorus source in step S2 includes one of phosphate, phytic acid, and triphenylphosphine, with a mass of 0.1 - 1 g.

[0014] Preferably, the phosphate is sodium dihydrogen phosphate, sodium phosphate, etc., and phytic acid is preferred.

[0015] Further, the biomass in step S3 includes one of chitosan, cyclodextrin, and corncob, with a mass of 0.5 - 3 g.

[0016] Preferably, the biomass is preferably cyclodextrin.

[0017] Further, the nitrogen in step S4 includes one of urea, melamine, dicyandiamide, etc., with a mass of 1 - 16 g; the activator includes one of zinc chloride, sodium bicarbonate, and potassium hydroxide.

[0018] Preferably, the nitrogen is preferably urea, and the activator is preferably potassium hydroxide.

[0019] Further, in step S5, the uniformly ground solid product is calcined under the protection of an inert gas, which is nitrogen in a tubular furnace. The calcination temperature is 700 - 1000 °C, the calcination time is 1 - 5 h, and the heating rate of calcination is 5 °C / min. After natural cooling, the catalyst is obtained.

[0020] Preferably, the calcination temperature is 800 °C and the calcination time is 2 h.

[0021] Further, in step S5, the washing process is carried out with one of deionized water and absolute ethanol; the drying temperature is 30 - 60 °C, and the drying time is 6 - 24 h.

[0022] Preferably, the number of washing times is three, and the drying time is 24 h.

[0023] The Fe0-FexOy(Al)@NC self-degrading catalyst prepared by the method according to any one of claims 1 - 7.

[0024] Application of Fe0-FexOy(Al)@NC self-degrading catalyst in degrading organic pollutants in water as described in claim 8.

[0025] Further, the organic pollutants include one or more of BPA, 2,4-DCP, CIP, SMZ, and TC.

[0026] Beneficial effects

[0027] (1) In the experimental system, the catalyst of the present invention has a good removal efficiency for organic pollution in water without the need for external experimental conditions such as hydrogen peroxide and light.

[0028] (2) The catalyst of the present invention has a good removal effect on the degradation of recalcitrant organic pollutants under neutral room temperature conditions.

[0029] (3) The catalyst of the present invention does not produce solid foreign matters such as iron mud during the reaction process, and no foreign matter removal device is required.

[0030] (4) The present invention has good stability during the process of removing organic pollutants and low metal ion dissolution.

[0031] (5) The catalyst of the present invention is a solid catalyst, which is convenient for separation from water and convenient for recycling. Description of the drawings

[0032] Figure 1 、 2 SEM image of Fe 0 -Fe x O y (Al)@NC prepared in the example;

[0033] Figure 3 XRD spectrum of Fe 0 -Fe x O y (Al)@NC prepared in the example;

[0034] Figure 4 Degradation curve graphs of Fe 0 -Fe x O y (Al)@NC for CIP, TC, CIP, SMZ, LEV, SMX, and BPA, 2,4-DCP;

[0035] Figure 5 Prepared in the example Figure 4 For Fe 0 -Fe x O y (Al)@NC, Fe 0 -Fex O y Degradation curves of @NC, (Al)@NC, and NC for CIP;

[0036] Figure 6 Fe prepared in Example 1 0 -Fe x O y Repeated experiment activity evaluation diagram of (Al)@NC;

[0037] Figure 7 Fe prepared in the example 0 -Fe x O y Repeated experiment activity evaluation diagram of (Al)@NC loaded on zeolite in a continuous flow device with a residence time of 1 hour and continuous operation for 15 days;

[0038] Figure 8 Fe prepared in the example 0 -Fe x O y Repeated experiment activity evaluation diagram of (Al)@NC loaded on zeolite in a continuous flow device when the residence time was changed to 2 h on the 16th day and continuous operation for 15 days. Detailed implementation manners

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. 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.

[0040] Example: Preparation, characterization, and application experiments of an iron-aluminum co-doped graphene-like wastewater self-purification catalyst.

[0041] I. Preparation

[0042] In this example, two materials will be prepared, including the Fe of the present invention 0 -Fe x O y (Al)@NC, Fe 0 -Fe x O y @NC, as well as Al@NC and the substrate material NC.

[0043] Prepare Fe according to the following steps 0 -Fe x O y (Al)@NC

[0044] (1) 1 g of ferric chloride hexahydrate and 0.23317 g of aluminum chloride hexahydrate were dissolved in a beaker containing deionized water to obtain solution A;

[0045] (2) 0.5 g of phytic acid was added to solution A, and the pH was adjusted to 7 to form suspension B;

[0046] (3) 2 g of cyclodextrin was added to suspension B and stirred for 30 min;

[0047] (4) After adding 8 g of urea to the above solution, the beaker was placed in a water bath for drying;

[0048] (5) The obtained dried product was mixed with 1 g of potassium hydroxide and calcined in a tubular furnace under the protection of nitrogen: the calcination temperature was 800 °C, the calcination time was 2 h, the heating rate of calcination was 5 °C / min, and the catalyst was obtained after natural cooling;

[0049] (6) The self-purifying catalyst after natural cooling was washed 2 - 3 times with deionized water and ethanol, and then placed in a vacuum oven at 60 °C for drying.

[0050] Comparative Example 1

[0051] Fe 0 -Fe x O y @NC

[0052] (1) 1 g of ferric chloride hexahydrate was dissolved in a beaker containing deionized water to obtain solution A;

[0053] (2) 0.5 g of phytic acid was added to solution A, and the pH was adjusted to 7 to form suspension B;

[0054] (3) 2 g of cyclodextrin was added to suspension B and stirred for 30 min;

[0055] (4) After adding 8 g of urea to the above solution, the beaker was placed in a water bath for drying;

[0056] (5) The obtained dried product was mixed with 1 g of potassium hydroxide and calcined in a tubular furnace under the protection of nitrogen: the calcination temperature was 800 °C, the calcination time was 2 h, the heating rate of calcination was 5 °C / min, and the catalyst was obtained after natural cooling;

[0057] (6) The self-purifying catalyst after natural cooling was washed 2 - 3 times with deionized water and ethanol, and then placed in a vacuum oven at 60 °C for drying.

[0058] Comparative Example 2

[0059] (Al)@NC was prepared according to the following steps

[0060] (1) 0.23317 g of aluminum chloride hexahydrate was dissolved in a beaker containing deionized water to obtain solution A;

[0061] (2) 0.5 g of phytic acid was added to solution A, and the pH was adjusted to 7 to form suspension B;

[0062] (3) 2 g of cyclodextrin was added to suspension B and stirred for 30 min;

[0063] (4) After adding 8 g of urea to the above solution, the beaker was placed in a water bath for drying;

[0064] (5) The obtained dried product was mixed with 1 g of potassium hydroxide and calcined in a tubular furnace under the protection of nitrogen: the calcination temperature was 800 °C, the calcination time was 2 h, the heating rate of calcination was 5 °C / min, and the catalyst was obtained after natural cooling.

[0065] (6) The self-purifying catalyst after natural cooling was washed 2 - 3 times with deionized water and ethanol, and then dried in a vacuum oven at 60 °C.

[0066] Comparative Example 3

[0067] NC was prepared according to the following steps

[0068] (1) 0.5 g of phytic acid was added to solution A, and the pH was adjusted to 7 to form suspension B;

[0069] (2) 2 g of cyclodextrin was added to suspension B and stirred for 30 min;

[0070] (3) After adding 8 g of urea to the above solution, the beaker was placed in a water bath for drying;

[0071] (4) The obtained dried product was mixed with 1 g of potassium hydroxide and calcined in a tubular furnace under the protection of nitrogen: the calcination temperature was 800 °C, the calcination time was 2 h, the heating rate of calcination was 5 °C / min, and the catalyst was obtained after natural cooling.

[0072] (5) The self-purifying catalyst after natural cooling was washed 2 - 3 times with deionized water and ethanol, and then dried in a vacuum oven at 60 °C.

[0073] II. Characterization

[0074] Figure 1 Fe prepared in the examples 0 -Fe x O y (Al)@NC low-magnification scanning electron microscopy image (SEM). It can be seen from the figure that the catalyst has a flaky porous structure. Figure 2Fe prepared for the example 0 -Fe x O y (Al)@NC X-ray diffraction (XRD) pattern. This characterization can determine the graphitization degree and crystal structure of the biochar catalyst. It can be found from the figure that for the sample NC without Fe doping, the peak at 2θ = 24.2° corresponds to the peak of the carbon (002) crystal plane, while for Fe 0 -Fe x O y (Al)@NC, the characteristic carbon (002) peak moves to 25.8°, and the peak shape becomes sharper, indicating that the introduced Fe enters the substrate material structure and changes the catalyst surface characteristics. Comparing with the standard card, it is found that Fe 0 -Fe x O y (Al)@NC catalyst may contain substances such as Fe0 and Fe3O4.

[0075] III. Application experiment

[0076] Put 0.01 g of the above-synthesized catalyst into 50 mL of the pollutant solution, maintain the natural pH (about 6.5), keep the temperature at 35 °C, start stirring continuously, and sample and detect the concentration of the pollutant at different time points (0, 5, 15, 30, 60 min).

[0077] Figure 3 Fe prepared for the example 0 -Fe x O y (Al)@NC degradation curves for BPA, 2,4-DCP, CIP, SMZ, and TC, etc.; at 60 minutes, the degradation rates of the above pollutants reached more than 90%, and the degradation rates of CIP and LEV reached more than 99%. Figure 4 For Fe 0 -Fe x O y (Al)@NC, Fe 0 -Fe x O y @NC, (Al)@NC, NC degradation curves for CIP. NC and (Al)@NC have poor degradation effects on CIP, while Fe 0 -Fe x O y @NC and Fe 0 -Fe x O y (Al)@NC degradation rate of CIP reached more than 90%, among which Fe 0 -Fe x O y(Al)@NC, that is, the self-degrading catalyst described in this article can achieve a degradation effect on CIP of more than 99%.

[0078] Figure 5 For the Fe prepared in the example 0 -Fe x O y (Al)@NC activity evaluation diagram for the recycling of CIP degradation. It can be seen from the figure that the catalyst runs continuously in multiple cycles, and its degradation activity for CIP slightly decreases and then stabilizes. After 4 cycles of use, the CIP degradation rate still remains above 90%. The above results fully demonstrate the stability advantage of Fe 0 -Fe x O y (Al)@NC over other Fenton catalysts and can be applied to the treatment of actual slightly polluted water bodies.

[0079] Figure 6 For the Fe prepared in the example 0 -Fe x O y (Al)@NC for the continuous flow device of CIP degradation, that is, the catalyst is loaded on zeolite. When the residence time is 1 h, after the continuous flow device operates continuously for 15 days, the degradation rate of 5 mg / L CIP still remains above 60%. Figure 7 On the 16th day of the example, the residence time was changed to 2 h, and the degradation rate of CIP increased from 60% to 80% and then gradually decreased to 65% and stabilized.

[0080] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made in these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing an iron-aluminum co-doped catalyst, Its characteristics include the following steps: S1: dissolving aluminum metal salt and iron metal salt in a beaker containing deionized water to obtain solution A; S2: adding a phosphorus source to solution A, adjusting the pH, and forming suspension B; S3: adding the biomass into the suspension B and stirring for 30 min to obtain solution C; S4: adding a nitrogen source to solution C, placing the beaker in a water bath to dry; mixing the obtained dry product with an activator and calcining under an inert gas to obtain a crude catalyst product; S5: Grind the crude catalyst product, wash it with ethanol and deionized water, and dry it in vacuum to obtain an iron-aluminum co-doped catalyst.

2. The method for synthesizing an iron-aluminum co-doped catalyst according to claim 1, characterized in that: In step S1, the metal iron salt includes one of ferric chloride hexahydrate, ferric chloride, ferric nitrate nonahydrate, ferric acetate, ferric sulfate and ferric acetylacetonate, with a mass of 0.5 to 3 g; the metal aluminum salt includes one of aluminum chloride, aluminum nitrate and aluminum sulfate, and the molar ratio of iron to aluminum is (1-6):

1.

3. The method for synthesizing an iron-aluminum co-doped catalyst according to claim 1, characterized in that: The phosphorus source in step S2 includes one of phosphate, phytic acid and triphenylphosphine, and has a mass of 0.1 to 1 g.

4. The method for synthesizing an iron-aluminum co-doped catalyst according to claim 1, characterized in that: The biomass in step S3 includes one of chitosan, cyclodextrin and corn cob, and has a mass of 0.5 to 3 g.

5. The method for synthesizing an iron-aluminum co-doped catalyst according to claim 1, characterized in that: The nitrogen in step S4 includes one of urea, melamine, dicyandiamide, etc., with a mass of 1 to 16 g; the activator includes one of zinc chloride, sodium bicarbonate and potassium hydroxide.

6. The method for synthesizing an iron-aluminum co-doped catalyst according to claim 1, characterized in that: In step S5, the uniformly ground solid product is calcined in a tubular furnace under the protection of an inert gas such as nitrogen, with a calcination temperature of 700 to 1000° C., a calcination time of 1 to 5 hours, and a calcination heating rate of 5° C. / min. The catalyst is obtained after natural cooling.

7. The method for synthesizing an iron-aluminum co-doped catalyst according to claim 1, characterized in that: In step S5, the washing process is carried out using one of deionized water and anhydrous ethanol; the drying temperature is 30 to 60° C., and the drying time is 6 to 24 hours.

8. A Fe prepared by the method according to any one of claims 1 to 7 0 -Fe x O y (Al)@NC self-degradation catalyst.

9. Fe as claimed in claim 8 0 -Fe x O y Application of (Al)@NC self-degradation catalyst in degradation of organic pollutants in water.

10. Fe according to claim 9 0 -Fe x O y Application of (Al)@NC self-degradation catalyst in degrading organic pollutants in water, wherein the organic pollutants include one or more of BPA, 2,4-DCP, CIP, SMZ and TC.

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