Catalyst, preparation method and method for degrading plasticizer

Abstract

The invention provides a catalyst, a preparation method and a plasticizer degradation method, the catalyst comprises manganese dioxide, and an iron element and a nickel element which exist in a manganese dioxide lattice, and the total doping amount of the iron element and the nickel element accounts for 5-10% of the total mass. On one hand, an iron element and a nickel element enter crystal lattices of manganese dioxide at the same time, the nickel element and the iron element have a synergistic effect, the ion radius is similar to that of manganese ions, the nickel element and the iron element have complementary electronic structures, and compared with main group metal elements, the nickel element and the iron element enter the crystal lattices of manganese dioxide more easily, and crystal lattice stress is reduced; on the other hand, the iron element enables the catalyst to have magnetism, so that the catalyst is convenient to recycle.

Description

Technical Field

[0001] The present invention relates to the technical field of plasticizer degradation, and in particular to a catalyst, a preparation method and a method for degrading plasticizer. Background Art

[0002] Plasticizers (such as phthalates), widely used additives in plastic products, are prone to accumulation in the environment due to their hydrophobic and lipophilic properties. Through bioaccumulation, they can cause endocrine disruption and reproductive toxicity in humans. Currently, advanced oxidation technologies based on activated persulfates are widely used in plasticizer treatment due to their high degradation capabilities. The performance of the catalyst directly determines degradation efficiency and cost.

[0003] Manganese dioxide (MnO2), a promising heterogeneous catalyst in advanced oxidation processes, is widely used to remove pollutants from aquatic environments. However, when doped with metal elements, MnO2 cannot adapt well to the original crystal lattice, resulting in increased lattice stress and thus affecting catalytic activity. Furthermore, during the catalytic degradation of phthalates, MnO2 readily produces toxic intermediates such as monophthalate and benzoic acid. Therefore, the existing technology needs further development. Summary of the Invention

[0004] In view of the various deficiencies of the existing technology and in order to solve the above problems, a catalyst, a preparation method and a method for degrading plasticizers are proposed, and the following technical solutions are provided: A catalyst comprises manganese dioxide and iron and nickel elements present in the manganese dioxide crystal lattice, wherein the total doping amount of the iron and nickel elements accounts for 5-10% of the total molar amount.

[0005] Furthermore, the molar ratio of the iron element to the nickel element is (1-3):1.

[0006] Furthermore, the manganese dioxide is β-MnO2.

[0007] In addition, the present invention also proposes a method for preparing a catalyst, which is as follows: dissolving a manganese source, an iron source, and a nickel source in water to obtain a mixed solution, adjusting the pH value of the mixed solution to 3-5, and then performing a hydrothermal reaction to obtain a catalyst.

[0008] Furthermore, oxygen or air is introduced during the hydrothermal process.

[0009] Furthermore, after the thermal reaction, high temperature annealing is performed at 500-700° C. in an inert atmosphere.

[0010] Furthermore, the temperature of the hydrothermal reaction is 200-220° C., and the time is 16-20 hours.

[0011] Furthermore, the manganese source is manganese nitrate, manganese sulfate or potassium permanganate; the iron source is ferric nitrate or ferric chloride; and the nickel source is elemental nickel.

[0012] Furthermore, the molar ratio of iron ions in the iron source to nickel ions in the nickel source is (1-3):1.

[0013] In addition, the present invention also proposes a method for degrading plasticizers, which comprises adding a peroxide and the catalyst according to any one of claims 1 to 3 to water containing the plasticizer, and stirring to complete the degradation reaction.

[0014] Beneficial effects: 1. In the catalyst prepared by the present invention, iron and nickel elements simultaneously enter the manganese dioxide lattice. Iron and nickel have multiple oxidation states. Iron and nickel rapidly convert between different oxidation states, promoting the generation and migration of active oxygen species and increasing the acidity of the surface of the prepared catalyst, so that phthalates are completely oxidized and decomposed during advanced oxidation, avoiding the accumulation of intermediate products.

[0015] 2. The ionic radius of iron ions and nickel ions is similar to that of manganese ions. They are elements with complementary electronic structures. There is electronic interaction between iron, nickel and manganese dioxide. This synergistic effect can enable phthalate molecules to be adsorbed and activated in a specific manner on the catalyst surface, directly oxidizing them into harmless substances such as carbon dioxide and water. The iron element can also make the catalyst magnetic, facilitating its recycling and reuse. Under an external magnetic field (0.5T), more than 95% of the catalyst can be recovered within 5 minutes.

[0016] 3. The present invention uses β-MnO2, which has a 1×1 tunnel structure and a compact crystal structure. The addition of appropriate amounts of nickel and iron elements into β-MnO2 can adjust the crystal structure of MnO2 and change the lattice parameters, thereby reducing the lattice stress. It has high catalytic activity in the peroxide decomposition reaction and significantly improves the reaction rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a scanning electron microscope image of the catalyst prepared in Example 1 of the present invention; Figure 2 These are the experimental results of degrading dimethyl phthalate (DMP) using the activated persulfate in Examples 1-3 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by ordinary technicians in this field without making any creative work should fall within the scope of protection of this application.

[0019] According to an embodiment of the present invention, a catalyst is provided, comprising manganese dioxide and iron and nickel elements present in the manganese dioxide lattice, wherein the total doping amount of the iron and nickel elements accounts for 5-10% of the total mass. The catalyst prepared by the present invention selects iron and nickel elements from a variety of elements, and the iron and nickel elements simultaneously enter the manganese dioxide lattice. The iron and nickel have multiple oxidation states, and the two elements work together to rapidly convert between different oxidation states. In addition, due to the presence of iron and nickel, the catalyst surface is acidic, allowing phthalates to skip the formation of harmful intermediates such as monophthalate and benzoic acid during advanced oxidation and directly undergo deep oxidation to carbon dioxide and water. The use of iron also makes the catalyst magnetic, facilitating its recycling. Under an external magnetic field (0.5 T), over 95% catalyst recovery can be achieved within 5 minutes.

[0020] The manganese dioxide is β-MnO2, which has a 1×1 tunnel structure. Iron and nickel, when incorporated into the lattice, adjust the pore structure and size of the manganese dioxide. These modified manganese dioxide pores have a specific adsorption and diffusion effect on phthalate molecules, allowing them to preferentially enter the pores, contact active sites, and be degraded.

[0021] Example 1 30 mL of manganese sulfate solution (0.4 mol / L), 1.6 mL of ferric nitrate solution (0.4 mol / L) and 0.8 mL of nickel nitrate solution (0.4 mol / L) were measured and dispersed into a polytetrafluoroethylene-lined autoclave. The pH value was adjusted to 4, and then placed in an oven at 210°C for 18 hours. Oxygen was introduced into the autoclave during the reaction. After the reaction, the reaction product was centrifuged for annealing. The annealing conditions were: heating to 600°C, maintaining in a helium atmosphere for 2 minutes, and then cooling to obtain the catalyst. The appearance structure of the catalyst is as follows: Figure 1 The total amount of doped iron and nickel elements accounts for 8% of the total molar amount, and the molar ratio of iron to nickel elements is 2:1.

[0022] Example 2 30 mL of manganese sulfate solution (0.4 mol / L), 0.75 mL of ferric nitrate solution (0.4 mol / L), and 0.75 mL of nickel nitrate solution (0.4 mol / L) were dispersed in a Teflon-lined autoclave. The pH was adjusted to 5 and the mixture was then reacted in an oven at 220°C for 16 hours. Oxygen was introduced into the autoclave during the reaction. After the reaction, the product was centrifuged and annealed. The annealing conditions were: heating to 500°C, holding in a helium atmosphere for 2 minutes, and then cooling to obtain the catalyst. The total amount of iron and nickel doping accounted for 5% of the total molar weight, with a molar ratio of 1:1.

[0023] Example 3 30 mL of manganese sulfate solution (0.4 mol / L), 2.25 mL of ferric nitrate solution (0.4 mol / L), and 0.75 mL of nickel nitrate solution (0.4 mol / L) were dispersed in a Teflon-lined autoclave. The pH was adjusted to 3 and the mixture was then placed in an oven at 200°C for 20 hours. Oxygen was introduced into the autoclave during the reaction. After the reaction, the product was centrifuged and annealed. The annealing conditions were: heating to 700°C, holding in a helium atmosphere for 2 minutes, and then cooling to obtain the catalyst. The total amount of iron and nickel doping was 10% of the total molar weight, with a molar ratio of iron to nickel of 3:1.

[0024] The magnetic properties of the catalysts prepared in Examples 1-3 were tested using a magnet, and the test results are shown in Table 1.

[0025] Table 1 Magnetic properties of catalysts in Examples 1-3 It can be seen from Table 1 that the materials obtained in Examples 1-3 are all magnetic, which is conducive to being recycled as adsorption materials using magnetism.

[0026] Application Example 1 The catalyst prepared in Example 1 was used to activate peroxymonosulfate for DMP degradation. To a 250 mL brown bottle, 4 mL of a 0.5 g / L DMP solution was added, followed by 10 mL of a 0.1 mol / L potassium peroxymonosulfate solution. Finally, 0.02 g of the catalyst was added. The brown bottle was placed on a magnetic stirrer and reacted at 500 rpm. At regular intervals, 1 mL of the solution was removed and added to a reagent bottle containing 0.1 mL of methanol for quenching. The solution was then filtered through a 0.22 μm filter membrane and the DMP concentration was determined by high-performance liquid chromatography.

[0027] Application Example 2 The catalyst prepared in Example 2 was used to activate peroxymonosulfate for DMP degradation. To a 250 mL brown bottle, 4 mL of a 0.5 g / L DMP solution was added, followed by 10 mL of a 0.1 mol / L potassium peroxymonosulfate solution. Finally, 0.02 g of the catalyst was added. The brown bottle was placed on a magnetic stirrer and reacted at 500 rpm. At regular intervals, 1 mL of the solution was removed and added to a reagent bottle containing 0.1 mL of methanol for quenching. The solution was then filtered through a 0.22 μm filter membrane and the DMP concentration was determined by high-performance liquid chromatography.

[0028] Application Example 3 The catalyst prepared in Example 3 was used to activate peroxymonosulfate for DMP degradation. To a 250 mL brown bottle, 4 mL of a 0.5 g / L DMP solution was added, followed by 10 mL of a 0.1 mol / L potassium peroxymonosulfate solution. Finally, 0.02 g of the catalyst was added. The brown bottle was placed on a magnetic stirrer and reacted at 500 rpm. At regular intervals, 1 mL of the solution was removed and added to a reagent bottle containing 0.1 mL of methanol for quenching. The solution was then filtered through a 0.22 μm filter membrane and the DMP concentration was determined by high-performance liquid chromatography.

[0029] Comparative Example 1 To a 250 mL brown bottle, add 4 mL of a 0.5 g / L DMP solution, followed by 10 mL of a 0.1 mol / L potassium permonosulfate solution, and finally 0.02 g of potassium permonosulfate. Place the brown bottle on a magnetic stirrer and react at 500 rpm. Remove 1 mL of the solution at regular intervals and add it to a reagent bottle containing 0.1 mL of methanol for quenching. The solution is then filtered through a 0.22 μm filter and the DMP concentration is determined by high-performance liquid chromatography.

[0030] Comparative Example 2 To a 250mL brown bottle, add 4mL of a 0.5g / L DMP solution, followed by 10mL of a 0.1mol / L potassium permonosulfate solution, and finally 0.02g of MnO2. Place the bottle on a magnetic stirrer at 500 rpm to react. At regular intervals, remove 1mL of the solution and add it to a reagent bottle containing 0.1mL of methanol for quenching. The solution is then filtered through a 0.22μm filter and the DMP concentration is determined by high-performance liquid chromatography.

[0031] The experimental results of the activated persulfate degradation of DMP using Examples 1-3 and Comparative Examples 1-2 are as follows: Figure 2 As shown. Figure 2It can be seen that in the system with only potassium permonosulfate, DMP is almost not degraded, and there is a certain degradation activity after adding manganese dioxide. The degradation activity of the manganese dioxide catalyst doped with iron and nickel is significantly improved, and the doping amount also has a certain effect on the degradation activity of the catalyst. With the increase of the doping amount, the degradation activity shows a trend of first increasing and then decreasing. Among them, the degradation activity of the catalyst with the total amount of iron and nickel doping accounting for 8% of the total molar amount is the highest.

[0032] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A catalyst, characterized in that The catalyst comprises manganese dioxide and iron and nickel elements present in the manganese dioxide crystal lattice, wherein the total doping amount of the iron and nickel elements accounts for 5-10% of the total molar amount.

2. The catalyst according to claim 1, characterized in that The molar ratio of the iron element to the nickel element is (1-3):

1.

3. The catalyst according to claim 1, characterized in that The manganese dioxide is β-MnO2.

4. A method for preparing a catalyst according to any one of claims 1 to 3, characterized in that: The preparation method of the catalyst is as follows: dissolving a manganese source, an iron source and a nickel source in water to obtain a mixed solution, adjusting the pH value of the mixed solution to 3-5, and then performing a hydrothermal reaction to obtain the catalyst.

5. The method for preparing a catalyst according to claim 4, characterized in that: Oxygen or air is introduced during the hydrothermal process.

6. The method for preparing a catalyst according to claim 4, characterized in that: After the hydrothermal reaction, high temperature annealing is performed at 500-700° C. in an inert atmosphere.

7. The method for preparing a catalyst according to claim 4, characterized in that: The temperature of the hydrothermal reaction is 200-220° C., and the time is 16-20 hours.

8. The method for preparing a catalyst according to claim 4, characterized in that: The manganese source is manganese nitrate, manganese sulfate or potassium permanganate; the iron source is ferric nitrate or ferric chloride; and the nickel source is nickel element.

9. The method for preparing a catalyst according to claim 8, characterized in that: The molar ratio of iron ions in the iron source to nickel ions in the nickel source is (1-3):

1.

10. A method for degrading plasticizers, characterized in that: Add peroxide and the catalyst according to any one of claims 1 to 3 to water containing the plasticizer, and stir to complete the degradation reaction.

Images