Multi-metal phosphate solid solution catalyst as well as preparation method and application thereof

Abstract

The invention discloses a multi-metal phosphate solid solution catalyst as well as a preparation method and application thereof, and belongs to the field of environmental catalytic materials. The preparation method of the catalyst comprises the following steps: firstly, preparing a nickel-based phosphate hollow porous nano material as a carrier material, and dispersing the nickel-based phosphate hollow porous nano material in water to obtain a suspension; dissolving ferric salt, cobalt salt, manganese salt and copper salt in water to obtain a mixed salt solution; and uniformly mixing the mixed salt solution and the suspension, and carrying out ion exchange to prepare the multi-metal phosphate solid solution catalyst. According to the invention, nickel and transition metals of iron, cobalt, manganese and copper with different valence states are introduced into a catalyst system at the same time, the catalytic performance of the catalyst is significantly improved by using the synergistic promotion effect generated by multiple metals, the Fenton reaction can be effectively catalyzed, and efficient degradation of organic pollutants is realized.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalytic materials, specifically relating to a polymetallic phosphate solid solution catalyst, its preparation method, and its application. Background Technology

[0002] With the intensification of industrialization and agricultural activities, the residues and accumulation of organic pollutants, especially antibiotics and dyes, in aquatic environments have become a serious environmental problem. The excessive use and improper handling of antibiotics, as well as organic pollutants such as dyes generated during industrial production, not only threaten ecosystems but may also affect human health through the food chain. Organic pollutants have poor biodegradability, and traditional treatment methods are often insufficient to effectively remove them, leading to persistent water pollution and increased antibiotic resistance.

[0003] Regarding antibiotic pollution, tetracycline antibiotics have received particular attention due to their widespread use and difficulty in biodegradation. However, tetracycline is just one example among many organic pollutants; others such as penicillins, cephalosporins, macrolide antibiotics, and various industrial dyes also cause serious environmental pollution.

[0004] Currently, degradation technologies for these organic pollutants mainly include biodegradation, chemical degradation, and physical degradation. However, these methods generally suffer from low treatment efficiency, high cost, and secondary pollution. Furthermore, existing catalyst preparation methods are often complex, costly, and have unstable catalytic efficiency, which limits their widespread application in practice.

[0005] To address this challenge, researchers have been searching for and developing novel, highly efficient catalysts and catalytic methods to improve the degradation efficiency of organic pollutants and reduce treatment costs. Metal-based catalysts, due to their unique electronic structure and catalytic activity, have shown great application potential in the field of organic pollutant degradation. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a polymetallic phosphate solid solution catalyst, its preparation method, and its application. This invention introduces nickel and transition metals with different valence states (iron, cobalt, manganese, and copper) simultaneously into the catalyst system. Utilizing the synergistic promoting effect of the multiple metals, the catalytic performance of the catalyst is significantly improved, effectively catalyzing the Fenton reaction and achieving the degradation of organic pollutants. The main aspects of this invention include the following: The first aspect of this invention is to provide a method for preparing a polymetallic phosphate solid solution catalyst, comprising the following steps: A phosphate precursor solution and a nickel salt solution were prepared separately. The nickel salt solution was added to the phosphate precursor solution, and the reaction was carried out under stirring conditions. After low-temperature aging, nickel-based phosphate hollow porous nanomaterials were obtained. Preferably, the phosphate used to prepare the phosphate precursor solution was at least one of disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, and sodium phosphate; the nickel salt used to prepare the nickel salt solution was at least one of nickel sulfate, nickel chloride, and nickel nitrate. Iron, cobalt, manganese, and copper salts are dissolved in water to obtain a mixed salt solution; nickel-based phosphate hollow porous nanomaterials are dispersed in water to obtain a suspension; the mixed salt solution and suspension are mixed evenly, and a multi-metal phosphate solid solution catalyst is prepared by ion exchange. Preferably, the iron, cobalt, manganese, and copper salts are each independently selected from metal chlorides, nitrates, sulfates, or organometallic salts; the molar ratio of iron:cobalt:manganese:copper in the mixed salt solution is (30-45):(15-25):(10-20):(5-15).

[0007] A second aspect of this invention is to provide a polymetallic phosphate solid solution catalyst prepared by the method described in the first aspect above. The total metal loading in the polymetallic phosphate solid solution catalyst is 8-12 wt%. Insufficient metal loading results in insufficient active site density, while excessive metal loading may damage the original structure of the support, leading to a decrease in the effective specific surface area. This catalyst, by simultaneously introducing nickel and transition metals iron, cobalt, manganese, and copper into the catalyst system, utilizes the synergistic promoting effect of nickel and the transition metals iron, cobalt, manganese, and copper to significantly improve the catalytic performance of the catalyst, effectively catalyzing the Fenton reaction and achieving the degradation of organic pollutants.

[0008] A third aspect of the present invention is to provide the application of the polymetallic phosphate solid solution catalyst as described above in the degradation of organic pollutants in water, comprising the following steps: adding the polymetallic phosphate solid solution catalyst and an oxidant to a water body containing organic pollutants, and degrading the organic pollutants through a Fenton reaction. As a preferred embodiment, the oxidant is persulfate; the pollutants include antibiotics and dyes. Further, the antibiotics are tetracycline antibiotics, penicillin antibiotics, cephalosporin antibiotics, or macrolide antibiotics.

[0009] The present invention has the following beneficial effects: The introduction of multiple metals into the catalyst prepared in this invention helps to improve its activity and stability. Specifically, the introduction of iron / cobalt metals is beneficial to the generation of dominant free radicals, and cobalt can maintain high activity under alkaline conditions (Co... 2 + / Co 3+ (Low valence state transition energy barrier) overcomes the pH limitation of iron-based catalysts; manganese provides Mn2+ / Mn 3+ / Mn 4+ Multiple valence states promote the continuous generation of free radicals; due to Cu + / Cu 2+ The high reduction potential of the redox couple allows copper to accelerate the reduction of Fe. 3+ →Fe 2+ Reduction step. Furthermore, the solid solution catalyst prepared in this invention uses nickel-based phosphate as the support material, which combines high stability (acid and alkali resistance) with tunable magnetism (easy recovery), solving the problem of separating nanocatalysts. Integrating the cascade function of quaternary metals within the nickel-based phosphate support overcomes the bottleneck of traditional catalysts' difficulty in simultaneously achieving "activity-stability-applicability".

[0010] The raw materials used in this invention are inexpensive and readily available, the operation method is simple, and the synthesis is convenient. The prepared polymetallic phosphate solid solution catalyst can be applied to heterogeneous Fenton oxidation reactions to efficiently degrade organic pollutants. Because the catalyst is simple to prepare, easy to industrialize, and has high efficiency in pollutant degradation, it has extremely high application value in the treatment of organic pollutant wastewater and has a very good application prospect. Attached Figure Description

[0011] Figure 1 SEM image of the iron-cobalt-nickel-manganese-copper multimetallic phosphate solid solution catalyst prepared in Example 1; Figure 2 The FT-IR spectrum of the iron-cobalt-nickel-manganese-copper polymetallic phosphate solid solution catalyst prepared in Example 1 is shown below. Figure 3 XRD diffraction patterns of nickel-based phosphate hollow porous nanomaterials prepared in Example 1 and Comparative Example 1; Figure 4 The images show the effect of catalysts prepared in different embodiments and comparative examples on the degradation of tetracycline. Detailed Implementation

[0012] The present invention will be further described below with reference to specific embodiments, but the essence of the present invention is not limited to the embodiments described below. Unless otherwise specified, the methods described are conventional methods, and the materials described are available from publicly available commercial sources unless otherwise specified. Those skilled in the art should know that any simple modifications or substitutions based on the essence of the present invention fall within the scope of protection claimed by the present invention.

[0013] Example 1 A method for preparing an iron-cobalt-nickel-manganese-copper polymetallic phosphate solid solution catalyst includes the following steps: Step 1: Dissolve 21.6 mg potassium dihydrogen phosphate, 163 mg dipotassium hydrogen phosphate, 711 mg sodium chloride and 18 mg potassium chloride in 90 mL of aqueous solution to prepare a phosphate precursor solution; dissolve 315.4 mg nickel phosphate hexahydrate in 4 mL of ultrapure water to prepare a nickel salt solution with a concentration of 0.3 mol / L. Step 2: Add the nickel sulfate solution dropwise to the phosphate precursor solution and stir thoroughly to ensure that the nickel ions and phosphate ions are fully mixed; Step 3: Cool the reaction system to -4°C in a refrigerator and age it at low temperature for 12 hours to promote the formation of nickel-based phosphate hollow porous nanostructures; Step 4: Centrifuge to collect the precipitate, wash the precipitate with ultrapure water to remove unreacted raw materials and by-products, and dry it under vacuum at 70°C to obtain nickel-based phosphate hollow porous nanomaterials; Step 5: Add 100 mg of washed and dried nickel-based phosphate hollow porous nanoparticles to 80 mL of ultrapure water to obtain a suspension; add 27.8 mg of ferric sulfate heptahydrate, 28.1 mg of cobalt sulfate heptahydrate, 24.1 mg of manganese sulfate monohydrate, and 24.95 mg of copper sulfate pentahydrate to 20 mL of ultrapure water to obtain a mixed salt solution; add the mixed salt solution to the suspension and stir thoroughly for 12 hours to prepare a polymetallic phosphate solid solution catalyst via ion exchange. Step 6: Centrifuge to collect the precipitate, wash the precipitate with ultrapure water to remove unreacted raw materials, and dry it under vacuum at 70°C to obtain a polymetallic phosphate solid solution catalyst material. Figure 1 The images shown are SEM images and mapping diagrams of the iron-cobalt-nickel-manganese-copper multimetallic phosphate solid solution catalyst prepared in Example 1. Image A is the SEM image, and image B is the mapping diagram. Figure 1 As can be seen, the iron-cobalt-nickel-manganese-copper polymetallic phosphate solid solution catalyst is a flocculent and plate-like mixture. Compared with the nickel-based phosphate hollow porous nanomaterial support, the product structure has changed significantly. This is because of the introduction of Fe. 3+ Co 2+ Mn 2+ Cu 2+ Multiple high-valence metal ions undergo ion exchange to form a quaternary solid solution system. This multi-metal synergistic effect breaks the single-metal doping mode. Co 2+ Mn 2+ The radii of divalent ions are significantly larger than those of Ni. 2+This leads to lattice expansion along the c-axis, forcing the system to release strain energy through two-dimensional epitaxial growth. Therefore, the final product exhibits a flocculent, sheet-like structure where residual hollow spherical fragments coexist with newly formed nanosheets. This invention, through lattice engineering induced by multi-metal synergistic doping, overcomes the dependence of traditional single / bimetallic doping on the spherical structure of the support, achieving a controllable transition from a thermodynamically stable state to a kinetically metastable state. This morphology reconstruction is essentially a reselection of the path to minimize crystal growth free energy, rather than a simple physical fragmentation process. This discovery provides a new design concept for developing high-performance catalysts—by artificially introducing a non-equilibrium stress field, the surface and interface properties of the material can be directionally controlled.

[0014] Figure 2 The image shows the FT-IR spectrum of the iron-cobalt-nickel-manganese-copper polymetallic phosphate solid solution catalyst prepared in Example 1. The FT-IR spectrum demonstrates the basic framework structure of the iron-cobalt-nickel-manganese-copper polymetallic phosphate solid solution catalyst of this invention.

[0015] Figure 3 The XRD diffraction patterns are shown for the iron-cobalt-nickel-manganese-copper polymetallic phosphate solid solution catalyst prepared in Example 1 and the nickel-based phosphate catalyst prepared in Comparative Example 1. The XRD diffraction patterns demonstrate that the iron-cobalt-nickel-manganese-copper polymetallic phosphate catalyst of this invention maintains a consistent crystal phase structure with the precursor nickel-based phosphate; therefore, this catalyst is a solid solution catalyst. This may be because metal ions enter the interstitial spaces or occupy specific positions without changing the overall structure, potentially leading to an unchanged main phase. Another possibility is that the formed solid solution belongs to the same space group, with only slight adjustments to the cell parameters, which is difficult to detect in conventional XRD.

[0016] Application examples The iron-cobalt-nickel-manganese-copper polymetallic phosphate solid solution catalyst obtained in this embodiment was applied to the degradation of tetracycline in water: 5 mg of the iron-cobalt-nickel-manganese-copper polymetallic phosphate solid solution catalyst prepared in Example 1 was weighed and added to 50 mL of water containing 20 mg / L tetracycline. -1 1 mM MPMS was added to the water sample, and the mixture was shaken thoroughly in a shaker at 25°C for 20 minutes. The sample was then filtered to determine the residual tetracycline content in the aqueous solution. The concentration used for detection was defined as the measurement concentration, with an initial concentration of 20 mg / L. -1 Therefore, the removal rate = measured concentration / initial concentration.

[0017] Figure 4 The figures show the degradation results of tetracycline by catalysts prepared in different embodiments and comparative examples in the presence of PMS. Figure 4 As can be seen, when the reaction time is 20 min, the catalyst prepared in Example 1 removes 98.7% of tetracycline. If only 1 mMPMS is added, without the catalyst of the present invention (marked as the blank group), the removal rate within 20 min is only 18.8%.

[0018] Comparative Example 1 Compared with Example 1, the difference in this comparative example is that only step 1 of Example 1 is performed, and the process is the same as that in Example 1; the catalyst prepared is referred to as nickel-based phosphate hollow porous nanomaterial.

[0019] The catalyst obtained in this comparative example was applied to the degradation of tetracycline in water: 5 mg of the catalyst prepared in the comparative example was weighed and added to 50 mL of water containing 20 mg / L tetracycline. -1 1 mM MPMS was added to the water sample, and the mixture was shaken thoroughly in a shaker at 25°C for 20 minutes. The sample was then filtered to determine the residual tetracycline content in the aqueous solution. Figure 4 As can be seen, when the reaction time is 20 min, the catalyst prepared in Comparative Example 1 has a tetracycline removal rate of 35.2%.

[0020] Comparative Example 2: Compared with Example 1, the difference in this example is that in step 1, 27.8 mg of ferric sulfate heptahydrate, 28.1 mg of cobalt sulfate heptahydrate, 24.1 mg of manganese sulfate monohydrate, and 24.95 mg of copper sulfate pentahydrate are replaced with 99.8 mg of copper sulfate pentahydrate. All other processes are the same as in Example 1. The catalyst prepared is denoted as copper-nickel bimetallic phosphate catalyst.

[0021] The catalyst obtained in this comparative example was applied to the degradation of tetracycline in water: 5 mg of the catalyst prepared in the comparative example was weighed and added to 50 mL of water containing 20 mg / L tetracycline. -1 1 mM MPMS was added to the water sample, and the mixture was shaken thoroughly in a shaker at 25°C for 20 minutes. The sample was then filtered to determine the residual tetracycline content in the aqueous solution. Figure 4 As can be seen, when the reaction time is 20 min, the catalyst prepared in Comparative Example 2 has a tetracycline removal rate of 74.5%.

[0022] Comparative Example 3: Compared with Example 1, the difference in this example is that in step 1, 27.8 mg of ferric sulfate heptahydrate, 28.1 mg of cobalt sulfate heptahydrate, 24.1 mg of manganese sulfate monohydrate, and 24.95 mg of copper sulfate pentahydrate are replaced with 111.2 mg of ferric sulfate heptahydrate. All other processes are the same as in Example 1. The catalyst prepared is denoted as iron-nickel bimetallic phosphate catalyst.

[0023] The catalyst obtained in this comparative example was applied to the degradation of tetracycline in water: 5 mg of the catalyst prepared in the comparative example was weighed and added to 50 mL of water containing 20 mg / L tetracycline. -1 1 mM MPMS was added to the water sample, and the mixture was shaken thoroughly in a shaker at 25°C for 20 minutes. The sample was then filtered to determine the residual tetracycline content in the aqueous solution. Figure 4 As can be seen, when the reaction time is 20 min, the catalyst prepared in Comparative Example 3 has a tetracycline removal rate of 46.2%.

[0024] Comparative Example 4: Compared with Example 1, the difference in this example is that in step 1, 27.8 mg of ferric sulfate heptahydrate, 28.1 mg of cobalt sulfate heptahydrate, 24.1 mg of manganese sulfate monohydrate, and 24.95 mg of copper sulfate pentahydrate are replaced with 48.2 mg of manganese sulfate monohydrate. All other processes are the same as in Example 1. The catalyst prepared is denoted as manganese-nickel bimetallic phosphate catalyst.

[0025] The catalyst obtained in this comparative example was applied to the degradation of tetracycline in water: 5 mg of the catalyst prepared in the comparative example was weighed and added to 50 mL of water containing 20 mg / L tetracycline. -1 1 mM MPMS was added to the water sample, and the mixture was shaken thoroughly in a shaker at 25°C for 20 minutes. The sample was then filtered to determine the residual tetracycline content in the aqueous solution. Figure 4 As can be seen, when the reaction time is 20 min, the catalyst prepared in Comparative Example 4 has a tetracycline removal rate of 29.1%.

[0026] The experimental results from the above examples and comparative examples show that, compared with the products obtained by ion exchange of single metal salts such as manganese, iron, and copper with nickel-based phosphates, the catalysts prepared by the combined action of multiple metal ions in the examples have better catalytic performance and can significantly improve the catalytic efficiency of the catalysts.

[0027] It should be noted that in other embodiments, the objective of the present invention can be achieved when the experimental process meets the following conditions. 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 creative effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a polymetallic phosphate solid solution catalyst, characterized in that, Includes the following steps: Phosphate precursor solution and nickel salt solution were prepared separately. The nickel salt solution was added to the phosphate precursor solution and reacted under stirring conditions. After low-temperature aging, nickel-based phosphate hollow porous nanomaterials were obtained. Iron, cobalt, manganese and copper salts were dissolved in water to obtain a mixed salt solution; nickel-based phosphate hollow porous nanomaterials were dispersed in water to obtain a suspension; the mixed salt solution and suspension were mixed evenly, and a polymetallic phosphate solid solution catalyst was prepared by ion exchange.

2. The preparation method according to claim 1, characterized in that, The phosphate used to prepare the phosphate precursor solution is at least one of disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, and sodium phosphate.

3. The preparation method according to claim 1, characterized in that, The nickel salt used to prepare the nickel salt solution is at least one of nickel sulfate, nickel chloride, and nickel nitrate.

4. The preparation method according to claim 1, characterized in that, The iron salt, cobalt salt, manganese salt, and copper salt are each independently selected from the chloride, nitrate, sulfate, or organometallic salts of metals.

5. The polymetallic phosphate solid solution catalyst prepared by the preparation method according to any one of claims 1 to 4.

6. The polymetallic phosphate solid solution catalyst according to claim 5, characterized in that, The total metal loading in the polymetallic phosphate solid solution catalyst is 8-12 wt%.

7. The application of the polymetallic phosphate solid solution catalyst as described in claim 5 or 6 in the degradation of organic pollutants in water, characterized in that, The process includes the following steps: adding a polymetallic phosphate solid solution catalyst and an oxidant to a water body containing organic pollutants, and then degrading the organic pollutants through a Fenton reaction.

8. The application of the polymetallic phosphate solid solution catalyst according to claim 7 in the degradation of organic pollutants in water, characterized in that, The oxidant is persulfate.

9. The application of the polymetallic phosphate solid solution catalyst according to claim 7 in the degradation of organic pollutants in water, characterized in that, The organic pollutants include antibiotics and dyes.

10. The application of the polymetallic phosphate solid solution catalyst according to claim 9 in the degradation of organic pollutants in water, characterized in that, The antibiotics mentioned are tetracycline antibiotics, penicillin antibiotics, cephalosporin antibiotics, or macrolide antibiotics.

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