Highly dispersed cobalt-based catalyst, its preparation method and application

Abstract

The application discloses a kind of high-dispersion cobalt-based catalyst and its preparation method and application, belong to cobalt-based catalyst technical field, the present application with four carboxyl phthalocyanine cobalt and nitrogen defect carbon nanotube as raw material, through molecular self-assembly in organic solvent and form pre-assembly complex, then the pre-assembly complex is programmed microwave heating, obtain the high-dispersion cobalt-based catalyst, the present application utilizes the means that specificity molecular precursor and carrier defect engineering are combined, by liquid phase pre-assembly constructs "molecular anchor-anchor position" pre-connection system, again with the principle of programmed microwave energy precise input, successfully solve the key technical problems that existing microwave method preparation cobalt-based catalyst when metal atom is easy to gather, active site structure is uncontrollable and catalytic performance is mediocre etc..

Description

Technical Field

[0001] This invention belongs to the field of cobalt-based catalyst technology, and particularly relates to a highly dispersed cobalt-based catalyst, its preparation method, and its application. Background Technology

[0002] Currently, common methods for preparing highly dispersed cobalt-based catalysts (Co-Cat) include wet impregnation-pyrolysis, chemical vapor deposition, and electrochemical displacement. In recent years, research has also begun to explore the application of microwave heating in the preparation of single-atom catalysts (SACs). For example, a paper (Single-Atom Cobalt Supported on NCNTs as Bifunctional Electrocatalysts Synthesized by Microwave-Assisted Treatment for Zn-Air Batteries, Industrial & Engineering Chemistry Research, 2023, 62(35), 13848-13854) reported that single-atom cobalt catalysts could be prepared on nitrogen-doped carbon nanotubes in just 90 seconds using microwave-assisted treatment of cobalt porphyrin and nitrogen-doped carbon nanotubes. This method aims to utilize the rapid, uniform, and energy-efficient characteristics of microwave heating to achieve the dispersion of metal atoms.

[0003] Although the microwave method described above shows some potential, it still has significant drawbacks when used to prepare high-performance, highly dispersed cobalt-based catalysts, especially for the treatment of recalcitrant antibiotic wastewater:

[0004] (1) Metal atoms are prone to agglomeration: Inorganic cobalt salts (such as cobalt nitrate) have a very fast reduction rate in a microwave field, but it is difficult to precisely control the synergy between the reduction and anchoring processes, resulting in a high probability of metal atoms migrating and agglomerating into nanoparticles and a low rate of dispersed site formation.

[0005] (2) Weak interaction between precursor and support: Simple physical mixing is insufficient to ensure strong molecular-level interaction between the metal precursor and the carbon support. During microwave rapid heating, cobalt species that are not firmly fixed will be reduced first and have high mobility, which is one of the fundamental reasons for aggregation.

[0006] (3) The active site structure is simple and unclear: When using inorganic salt precursors, the coordination environment of the cobalt active center (such as Co-N4) is highly dependent on the inherent nitrogen species on the support surface, which is difficult to precisely control and optimize, resulting in unsatisfactory catalytic activity and selectivity of the catalyst for specific pollutants (such as lomefloxacin hydrochloride).

[0007] (4) Although the method is highly universal, its performance is mediocre: Although the existing microwave preparation method is simple, it cannot solve the above key problems. The performance of the prepared catalyst is often not as good as that of the catalyst prepared by complex high-temperature pyrolysis method. Its advantage is limited to "fast" and it is difficult to achieve "high efficiency", which limits its practical application value.

[0008] The reason for these problems is that microwave heating is essentially bulk heating, which has a global effect on the activation of reactants and lacks sequential and regional control over the key step of "anchoring-reduction" of metal precursors. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention proposes a highly dispersed cobalt-based catalyst, its preparation method, and its application.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] This invention provides a method for preparing a highly dispersed cobalt-based catalyst, using cobalt tetracarboxylated phthalocyanine (CoPc-COOH) and nitrogen-deficient carbon nanotubes (ND-CNTs) as raw materials, forming a pre-assembled composite through molecular self-assembly in an organic solvent, and then subjecting the pre-assembled composite to programmed microwave heating to obtain the highly dispersed cobalt-based catalyst.

[0012] The programmed microwave heating is divided into three stages, with the power of the second stage heating being greater than that of the first stage heating, and the power of the third stage heating being greater than that of the second stage heating.

[0013] Creating a sufficient number of uniformly distributed anchoring sites on a carrier during the rapid microwave heating process has always been a challenge for those skilled in the art. To address this issue, this invention provides a cobalt organometallic precursor (tetracarboxylated cobalt phthalocyanine), whose molecular structure combines excellent microwave absorption properties with pre-defined anchoring sites. This invention creates anchoring sites rich in specific nitrogen vacancies on the surface of multi-walled carbon nanotubes through controlled oxidation and subsequent treatment. These sites exhibit strong adsorption of the tetracarboxylated cobalt phthalocyanine precursor, similar to molecular recognition. The specific precursor (tetracarboxylated cobalt phthalocyanine) is coupled to a specially treated carrier (nitrogen-deficient carbon nanotubes) via a two-step "liquid-phase pre-assembly - solid-phase microwave conversion" method. This ensures that before microwave heating, cobalt atoms are molecularly dispersed and firmly pre-anchored on the carrier surface, fundamentally preventing atomic migration and aggregation during microwave heating. This invention simulates the "annealing" effect by controlling the microwave heating mode (gradient heating and intermittent irradiation) instead of continuous heating with a single power, causing the precursor molecules to decompose in an orderly manner and promoting the precise embedding of cobalt atoms into the nitrogen defects of the carbon support, forming a uniform and abundant Co-N4-C active site. The highly dispersed cobalt-based catalyst prepared using this method exhibits significantly higher catalytic activity and stability than catalysts prepared by traditional methods when activating persulfate (PMS) to degrade antibiotics such as lomefloxacin hydrochloride. This invention utilizes a combination of specific molecular precursors and support defect engineering, constructing a "molecular anchor-anchor positioning" pre-connected system through liquid-phase pre-assembly, and then employing the principle of precise input of programmed microwave energy. This successfully solves the key technical problems existing in the preparation of cobalt-based catalysts using current microwave methods, such as easy aggregation of metal atoms, uncontrollable active site structure, and mediocre catalytic performance.

[0014] Furthermore, the preparation method of the tetracarboxylated cobalt phthalocyanine includes the following steps:

[0015] Cobalt phthalocyanine was dissolved in concentrated sulfuric acid, and fuming nitric acid was added dropwise at a temperature of 0-5°C. The reaction was then carried out under heating conditions to obtain cobalt tetranitrophthalocyanine.

[0016] Iron powder is mixed with the tetranitrophthalocyanine cobalt in a mixture of ethanol and hydrochloric acid, and the mixture is refluxed. After post-treatment, tetraaminophthalocyanine cobalt is obtained. In this step, iron powder is used as a reducing agent.

[0017] The tetraaminophthalocyanine cobalt was diazotized with sodium nitrite at a temperature of 0-5°C, then hydrolyzed in dilute sulfuric acid. The pH was adjusted to acidic to precipitate the product, which was then washed and dried to obtain the tetracarboxylated phthalocyanine cobalt.

[0018] Furthermore, in the preparation method of tetracarboxylated cobalt phthalocyanine, the ratio of cobalt phthalocyanine to concentrated sulfuric acid is 1.50 g: 60 mL;

[0019] The reaction was carried out under the heating conditions as follows: at 45°C for 12 hours.

[0020] The reflux reaction was carried out at a temperature of 85°C for 6 hours.

[0021] The mass ratio of the iron powder to the cobalt phthalocyanine is 5:1.5.

[0022] Further, the preparation method of the nitrogen-deficient carbon nanotubes includes the following steps: placing multi-walled carbon nanotubes in a mixed acid composed of nitric acid and sulfuric acid, and carrying out a reflux reaction under heating conditions; after cooling, filtering, washing with water until neutral, and vacuum drying to obtain carbon oxide nanotubes (CNTs) (O-CNTs); calcining the carbon oxide nanotubes under an NH3 atmosphere, naturally cooling, calcining under an inert gas atmosphere, and naturally cooling again to obtain the nitrogen-deficient carbon nanotubes.

[0023] Furthermore, in the method for preparing nitrogen-deficient carbon nanotubes, the volume ratio of nitric acid to sulfuric acid is 1:(2-3); the reflux reaction temperature is 70-80℃, and the time is 4-6h.

[0024] Furthermore, in the method for preparing nitrogen-deficient carbon nanotubes, when calcining the carbon oxide nanotubes under an NH3 atmosphere: the NH3 gas flow rate is 200 mL / min, the calcination temperature is 500℃, the holding time is 2h, and the heating rate is 5℃ / min;

[0025] When calcining under an inert gas atmosphere: the inert gas is Ar gas, the Ar gas flow rate is 200 mL / min, the calcination temperature is 800-900℃, the holding time is 1h, and the heating rate is 5℃ / min.

[0026] Further, the step of forming the pre-assembled composite by molecular self-assembly in an organic solvent is as follows: dissolving the nitrogen-deficient carbon nanotubes and the tetracarboxylated cobalt phthalocyanine in an organic solvent at a mass ratio of 1:(1.2-1.8), ultrasonically dispersing, magnetically stirring, and rotary evaporating to remove the organic solvent to obtain the pre-assembled composite.

[0027] Furthermore, the organic solvent is N,N-dimethylformamide (DMF).

[0028] Further, adjusting the pH to acidic conditions will precipitate the product by adjusting the pH to 2-3.

[0029] For example, during programmed microwave heating, the power of the first stage of heating is 300-400W, the power of the second stage of heating is 500-600W, and the power of the third stage of heating is 700-800W.

[0030] Furthermore, the specific steps of the programmed microwave heating are as follows: placing the pre-assembled composite into a microwave reactor, introducing inert gas to replace the air, and performing three-stage heating:

[0031] In the first stage, heat at 300-400W power for 5-8 minutes to raise the temperature to 250-300℃;

[0032] In the second stage, switch to 500-600W power and heat for 10-15 minutes to maintain the temperature at 350-400℃.

[0033] In the third stage, switch to 700-800W power, heat for 15-30 seconds, and the temperature will rise to 600-700℃ instantly. Then turn off the microwave on the reactor for 15-30 seconds. Repeat this on-off cycle 2-5 times.

[0034] The programmed microwave heating process is carried out entirely in an inert gas atmosphere.

[0035] The present invention also provides a highly dispersed cobalt-based catalyst prepared according to the above preparation method.

[0036] The present invention also provides the application of the above-mentioned highly dispersed cobalt-based catalyst in the treatment of recalcitrant organic wastewater by advanced oxidation treatment, wherein the recalcitrant organic wastewater by advanced oxidation treatment is selected from wastewater containing lomefloxacin hydrochloride (LOH), wastewater containing tetracycline hydrochloride, and / or wastewater containing dye-like organic matter.

[0037] For example, the dye-like organic compound is methylene blue.

[0038] Compared with the prior art, the present invention has the following advantages and technical effects:

[0039] 1. Fundamentally inhibiting the migration and aggregation of cobalt atoms: The tetracarboxylated cobalt phthalocyanine precursor (CoPc-COOH) generates strong intermolecular forces through its carboxyl functional groups with nitrogen defect sites (ND-CNTs) created on the surface of carbon nanotubes through precise pretreatment. This achieves molecular-level dispersion and firm pre-fixation of cobalt atoms during the liquid-phase self-assembly stage before microwave heating. This restricts the migration of cobalt atoms released from precursor decomposition during subsequent microwave heating to a very small area near the anchoring points, allowing them to be captured in situ and embedded into defect sites, significantly reducing the probability of long-range migration and aggregation into nanoparticles. HAADF-STEM results clearly demonstrate the perfectly high dispersion of cobalt in the final product.

[0040] 2. Precise design and construction of active site structures were achieved: "Nitrogen defects" serve as pre-set anchor points, and their electronic structure determines that highly dispersed atoms are ultimately formed. The synergistic effect of the controllable decomposition of the tetracarboxylated cobalt phthalocyanine precursor and programmed microwave heating (gradient heating and intermittent irradiation) simulates a "solid-phase annealing" environment, enabling cobalt atoms to be embedded in the target defects in an orderly and stable manner, forming Co-N4 active centers with uniform structure and optimized electronic structure.

[0041] 3. Significantly improved catalytic performance and stability: The highly dispersed cobalt-based catalyst prepared by the method of this invention has a high density of active sites, a well-defined structure, and high electron transport efficiency. In the degradation of lomefloxacin hydrochloride (LOM) by activated persulfate (PMS), this catalyst (Co-SACs / ND-CNTs, Cat-1) exhibited catalytic efficiency (removal rate ≥85% within 30 minutes) and cycling stability (efficiency still >72% after 5 cycles) far exceeding that of the comparative example. Its excellent performance stems from abundant, highly intrinsically active, highly dispersed cobalt atomic sites and stable cobalt-carbon support bonding, the latter also ensuring extremely low metal dissolution rate (≤0.023 mg / L). Attached Figure Description

[0042] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0043] Figure 1 A photograph of the highly dispersed cobalt-based catalyst prepared in Example 1;

[0044] Figure 2 The HAADF-STEM characterization results of the highly dispersed cobalt-based catalyst prepared in Example 1;

[0045] Figure 3 The mapping elemental distribution results are shown for the highly dispersed cobalt-based catalyst prepared in Example 1.

[0046] Figure 4 The scanning electron microscope (SEM) characterization results of the highly dispersed cobalt-based catalyst prepared in Example 1;

[0047] Figure 5 Transmission electron microscopy (TEM) characterization results of the highly dispersed cobalt-based catalyst prepared in Example 1;

[0048] Figure 6 The results show the comparative effects of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 on the degradation of lomefloxacin hydrochloride by activated persulfate (PMS);

[0049] Figure 7The results show the comparison of the removal rates of lomefloxacin hydrochloride after 30 minutes of PMS degradation by the catalysts prepared in Examples 1-4 and Comparative Examples 1-4.

[0050] Figure 8 The three-dimensional fluorescence spectra of the solutions prepared by the catalysts activated by Examples 1-4 and Comparative Examples 1-4 for the degradation of lomefloxacin hydrochloride by PMS at degradation processes of 0 min, 15 min and 30 min are shown, where a is 0 min, b is 15 min and c is 30 min.

[0051] Figure 9 The results show the Co dissolution concentration after 30 minutes of PMS degradation of lomefloxacin hydrochloride by the catalysts prepared in Examples 1-4 and Comparative Examples 1-4.

[0052] Figure 10 The XRD patterns of the catalyst before and after the PMS degradation of lomefloxacin hydrochloride by the highly dispersed cobalt-based catalyst in Example 1 are shown.

[0053] Figure 11 The results show the comparison of the degradation effects of Co-SACs / ND-CNTs on lomefloxacin hydrochloride in Example 1 on different environmental substrates;

[0054] Figure 12 The results show the comparison of the degradation performance of Co-SACs / ND-CNTs for different types of organic matter in Example 1;

[0055] Figure 13 The results show the cycling performance of Co-SACs / ND-CNTs activated PMS for the degradation of lomefloxacin hydrochloride in Example 1. Detailed Implementation

[0056] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0057] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0058] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0059] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0060] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0061] The present invention provides a method for preparing a highly dispersed cobalt-based catalyst, using cobalt tetracarboxylated phthalocyanine (CoPc-COOH) and nitrogen-deficient carbon nanotubes (ND-CNTs) as raw materials, forming a pre-assembled complex through molecular self-assembly in an organic solvent, and then subjecting the pre-assembled complex to programmed microwave heating to obtain a highly dispersed cobalt-based catalyst.

[0062] Programmable microwave heating is divided into three stages. The power of the second stage heating is greater than that of the first stage heating, and the power of the third stage heating is greater than that of the second stage heating.

[0063] In an embodiment of the present invention, the preparation method of cobalt tetracarboxylated phthalocyanine includes the following steps:

[0064] Cobalt phthalocyanine was dissolved in concentrated sulfuric acid, and fuming nitric acid was added dropwise at a temperature of 0-5°C. The reaction was then carried out under heating conditions to obtain cobalt tetranitrophthalocyanine.

[0065] Iron powder and tetranitrocobalt phthalocyanine were mixed in a mixture of ethanol and hydrochloric acid, refluxed, and then post-treated to obtain tetraaminocobalt phthalocyanine.

[0066] Tetraaminocobalt phthalocyanine was diazotized with sodium nitrite at 0-5°C, followed by hydrolysis in dilute sulfuric acid. The pH was adjusted to 2-3 to precipitate the product, which was then washed and dried to obtain tetracarboxylated cobalt phthalocyanine. This invention efficiently introduces four carboxyl groups onto the cobalt phthalocyanine ring through a three-step reaction involving nitration, reduction, and diazotization-hydrolysis, thus obtaining tetracarboxylated cobalt phthalocyanine.

[0067] In an embodiment of the present invention, in the preparation method of tetracarboxylated cobalt phthalocyanine, the ratio of cobalt phthalocyanine to concentrated sulfuric acid is 1.50 g: 60 mL; the reaction is carried out under the following heating conditions: at 45°C for 12 hours; the reflux reaction temperature is 85°C for 6 hours; and the mass ratio of iron powder to cobalt phthalocyanine is 5:1.5.

[0068] For example, in the preparation of CoPc-COOH, the concentration of concentrated sulfuric acid is 98 wt% and the concentration of dilute sulfuric acid is 2 mol / L.

[0069] For example, in the preparation of CoPc-COOH, the concentration of hydrochloric acid in the ethanol / hydrochloric acid mixture is 37 wt%, and the volume ratio of ethanol to hydrochloric acid is 2:1.

[0070] In an embodiment of the present invention, the post-treatment process for obtaining tetraaminophthalocyanine cobalt during the preparation of CoPc-COOH is as follows: after the reaction is completed, the mixture is cooled and filtered while hot to remove excess iron powder and the generated iron salt precipitate; then, the filtrate is poured into an ice-water mixture and stirred while pouring to precipitate tetraaminophthalocyanine cobalt; then, the solid product is collected by vacuum filtration and washed with deionized water and cold ethanol in sequence until the washing solution is neutral and colorless, and finally vacuum dried.

[0071] This invention involves a three-step reaction process—nitration, reduction, and diazotization hydrolysis—in the preparation of tetracarboxylated cobalt phthalocyanine. First, cobalt phthalocyanine is nitrated in concentrated sulfuric acid at 0-5°C to introduce a nitro group. Second, the nitro group is reduced to an amino group under acidic conditions using a reducing agent. Finally, the amino group is converted to a carboxyl group via nitrite diazotization and acidic hydrolysis at 0-6°C. Unlike existing direct carboxylation methods, this invention uses the amino group as a key intermediate, achieving efficient and specific introduction of the carboxyl group through a diazotization hydrolysis pathway.

[0072] In an embodiment of the present invention, the method for preparing nitrogen-deficient carbon nanotubes includes the following steps: placing multi-walled carbon nanotubes in a mixed acid composed of nitric acid and sulfuric acid, and performing a reflux reaction under heating conditions; after cooling, filtering, washing with water until neutral, and vacuum drying to obtain carbon oxide nanotubes (CNTs) (O-CNTs); calcining the carbon oxide nanotubes in an NH3 (ammonia) atmosphere, naturally cooling, calcining in an inert gas atmosphere, and naturally cooling again to obtain nitrogen-deficient carbon nanotubes.

[0073] In an embodiment of the present invention, in the method for preparing nitrogen-deficient carbon nanotubes, the volume ratio of nitric acid to sulfuric acid is 1:(2-3), the concentration of nitric acid is 68wt%, and the concentration of sulfuric acid is 98wt%; the reflux reaction temperature is 70-80℃, and the time is 4-6h.

[0074] In an embodiment of the present invention, in the method for preparing nitrogen-deficient carbon nanotubes, when calcining carbon oxide nanotubes under an NH3 atmosphere: the NH3 gas flow rate is 200 mL / min, the calcination temperature is 500℃, the holding time is 2h, and the heating rate is 5℃ / min.

[0075] When calcining under an inert gas atmosphere: the inert gas is Ar gas, the Ar gas flow rate is 200 mL / min, the calcination temperature is 800-900℃, the holding time is 1h, and the heating rate is 5℃ / min.

[0076] This invention uses a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid to oxidize the raw carbon nanotubes, introducing oxygen-containing functional groups such as carboxyl groups. After cleaning and drying, a first-stage heat treatment is performed under an ammonia atmosphere, causing the oxygen-containing functional groups to react with ammonia to generate nitrogen-containing functional groups. Subsequently, a second-stage heat treatment at a higher temperature is performed under an inert atmosphere (such as Ar), creating precise nitrogen defects in the carbon framework by evaporating unstable nitrogen species at high temperature. This step is crucial for creating specific anchoring sites.

[0077] In an embodiment of the present invention, the step of forming a pre-assembled composite by molecular self-assembly in an organic solvent is as follows: nitrogen-deficient carbon nanotubes and tetracarboxylated cobalt phthalocyanine are dissolved in an organic solvent at a mass ratio of 1:(1.2-1.8), ultrasonically dispersed, magnetically stirred, and the organic solvent is removed by rotary evaporation to obtain the pre-assembled composite.

[0078] For example, when forming a pre-assembled complex by molecular self-assembly in an organic solvent, the ultrasonic dispersion time is 1 hour, the magnetic stirring time is 12 hours, and the rotary evaporation temperature is 60°C.

[0079] In the embodiments of the present invention, the organic solvent is N,N-dimethylformamide (DMF).

[0080] This invention involves mixing nitrogen-deficient carbon nanotubes (CNTs) and cobalt tetracarboxylated phthalocyanine (CTC) in a specific organic solvent (such as DMF) via ultrasonication and stirring. Utilizing hydrogen bonds, π-π stacking, and electrostatic interactions between the carboxyl groups of the CoPc-COOH molecules and the lone pairs of electrons or residual functional groups at the defects of ND-CNTs, molecular-level self-assembly occurs, forming a stable pre-assembled composite. The solvent is then removed by rotary evaporation to obtain a dry solid powder. This step ensures the molecular-level dispersion and pre-fixation of cobalt atoms.

[0081] In an embodiment of the present invention, during programmed microwave heating, the power of the first stage of heating is 300-400W, the power of the second stage of heating is 500-600W, and the power of the third stage of heating is 700-800W.

[0082] In an embodiment of the present invention, the specific steps of programmed microwave heating are as follows: placing the pre-assembled composite into a microwave reactor, introducing inert gas to replace the air, and performing three-stage heating:

[0083] In the first stage, heat at 300-400W power for 5-8 minutes to raise the temperature to 250-300℃;

[0084] In the second stage, switch to 500-600W power and heat for 10-15 minutes to maintain the temperature at 350-400℃.

[0085] In the third stage, switch to 700-800W power, heat for 15-30 seconds, and the temperature will rise to 600-700℃ instantly. Then turn off the microwave reactor for 15-30 seconds. Repeat this on-off cycle 2-5 times.

[0086] The programmed microwave heating process is carried out entirely in an inert gas atmosphere.

[0087] Under an inert atmosphere (such as Ar), this invention employs a programmed gradient microwave heating mode to irradiate the pre-assembled composite. This mode includes a slow heating phase starting at low power, a medium-power holding phase, and a short-duration high-power rapid excitation phase, and can incorporate intermittent irradiation (on-off cycling). This unique microwave energy input method aims to precisely control the decomposition of precursor molecules, the release of cobalt atoms, and their migration and anchoring to defect sites, ultimately forming a highly dispersed cobalt-based catalyst (Co-SACs / ND-CNT).

[0088] An embodiment of the present invention also provides a highly dispersed cobalt-based catalyst prepared according to the above preparation method.

[0089] The embodiments of the present invention also provide the application of the above-mentioned highly dispersed cobalt-based catalyst in the treatment of recalcitrant organic wastewater by advanced oxidation treatment. The recalcitrant organic wastewater by advanced oxidation treatment is selected from wastewater containing lomefloxacin hydrochloride (LOH), wastewater containing tetracycline hydrochloride, and / or wastewater containing dye-like organic compounds.

[0090] For example, a dye-type organic compound is methylene blue.

[0091] For example, the synthesis process of tetracarboxylated cobalt phthalocyanine (CoPc-COOH) is as follows: First, cobalt phthalocyanine is dissolved in concentrated sulfuric acid, and fuming nitric acid is added dropwise at 0-5°C. Then, the reaction is carried out at 45°C for 12 hours to obtain tetranitrocobalt phthalocyanine. Next, the product is mixed with 5.0 g of iron powder in an ethanol / hydrochloric acid mixture and refluxed at 85°C for 6 hours. After post-treatment, tetraaminocobalt phthalocyanine is obtained. Finally, the obtained tetraaminocobalt phthalocyanine is diazotized with sodium nitrite at 0-5°C, and then hydrolyzed in dilute sulfuric acid at 60°C for 4 hours. The pH is adjusted to 2-3 to precipitate the product. After washing and drying, the target product tetracarboxylated cobalt phthalocyanine is obtained with a yield of approximately 78%.

[0092] This invention uses cobalt tetracarboxylated phthalocyanine as a precursor; carbon nanotubes are sequentially subjected to mixed acid oxidation, ammonia treatment and heat treatment to prepare a nitrogen-deficient carrier; a liquid-phase self-assembly pre-anchoring step is performed before microwave heating; and a programmed gradient microwave heating mode is used for the final conversion.

[0093] This invention utilizes a combination of specific molecular precursors and carrier defect engineering to construct a "molecular anchor-anchor positioning" pre-connection system through liquid-phase pre-assembly. Furthermore, it employs the principle of precise input of programmed microwave energy to successfully solve the problems of easy agglomeration of metal atoms, uncontrollable active site structure, and mediocre catalytic performance that exist in existing microwave methods for preparing cobalt-based catalysts.

[0094] Compared with patent CN118304931A, the differences are as follows: Regarding the carrier, this invention uses nitrogen-deficient carbon nanotubes obtained through a "mixed acid-ammoniation-annealing" pretreatment process, instead of hollow tubular carbon nitride; regarding the precursor, this invention innovatively uses structurally designable tetracarboxylated cobalt phthalocyanine molecules, instead of inorganic cobalt acetate; regarding the core process, this invention uniquely employs a "liquid-phase pre-assembly + programmed microwave conversion" route, precisely constructing Co-N4 active sites through gradient heating and intermittent irradiation, replacing the traditional "hydrothermal-calcination" method. This gives it significant advantages in inhibiting cobalt atom aggregation, reducing metal leaching (≤0.023 mg / L), and improving the degradation efficiency of specific pollutants such as lomefloxacin hydrochloride.

[0095] Compared with patent CN119481106A, the differences are as follows: In terms of application, this invention focuses on the catalytic degradation of organic pollutants (such as antibiotics) in water using persulfate, while this patent is used for electrocatalytic oxygen reduction reaction (ORR). Regarding catalyst design, this invention uses tetracarboxylated cobalt phthalocyanine molecules as a precursor to construct Co-N4 sites on nitrogen-deficient carbon nanotubes via a microwave-assisted method; this patent uses ZIF derivatives and molten sodium chloride, which are then pyrolyzed at high temperature to form a nitrogen-chlorine co-doped Co-N4Cl asymmetric structure. Furthermore, the preparation method of this invention features low-temperature, rapid, and energy-saving microwave processing, significantly different from the high-temperature pyrolysis route of this patent, reflecting completely different technical routes and application orientations.

[0096] Compared with patent CN120132909A, the differences are as follows: In terms of preparation method, this invention adopts a "carrier pretreatment-liquid phase preassembly-programmed microwave conversion" process, the core of which lies in the molecular-level pre-anchoring of tetracarboxylated cobalt phthalocyanine with nitrogen-deficient carbon nanotubes; while the patent adopts a one-step co-precipitation method, directly reacting CoCl2, NH2CN, and NaOH to generate a five-coordinate structure of CoN4(NCN) with cyanamide axial coordination. In terms of structure-activity relationship of active sites, this invention precisely constructs planar Co-N4 sites to optimize electronic structure through carrier defects and precursor design; while the patent breaks planar symmetry by introducing axial NCN2- ligands to form asymmetric five-coordinates, aiming to promote the generation of high-valence cobalt oxide species (Co(IV)=O). In addition, the microwave process of this invention and the room temperature precipitation method of the patent also show a stark contrast in reaction conditions and energy consumption.

[0097] Compared with patent CN116288487A, the differences are as follows: In terms of application, this invention focuses on activating persulfate to degrade organic pollutants in water, belonging to advanced oxidation technology; while this patent is used for electrocatalytic two-electron oxygen reduction reaction (2e... - ORR (Organic Reduction) for efficient synthesis of hydrogen peroxide (H2O2). In catalyst design, this invention uses cobalt tetracarboxylated phthalocyanine (CoPc-COOH) as a molecular precursor, constructing Co-N4 active centers on nitrogen-deficient carbon nanotubes (ND-CNTs) through liquid-phase pre-assembly and programmed microwave conversion; the patent uses cobalt chloride and perfluorooctane as cobalt and fluorine sources, respectively, to directly achieve cobalt and fluorine dual single-atom co-doping (Co-F-CNTs) on carbon nanotubes through one-step microwave irradiation, with the active site being Co-F. x Coordination structure. Furthermore, the microwave process of this invention aims to precisely construct single-atom sites and suppress aggregation, while the microwave treatment in this patent is mainly used to achieve the instantaneous generation of CoF2 and subsequent acid leaching to form single atoms. The two differ significantly in their target products (degrading pollutants and producing H2O2) and active site regulation strategies.

[0098] Compared with patent CN116809072A, the differences are as follows: In terms of application target, this invention focuses on activating persulfate to degrade organic pollutants such as antibiotics in water, belonging to the field of environmental catalysis; while this patent is used for the synthesis of azobenzene via hydrogen transfer coupling reaction of nitroaromatics, belonging to the field of organic synthesis. Regarding catalyst support and structure, this invention uses nitrogen-deficient carbon nanotubes (ND-CNTs) as a support, constructing Co-N4 active centers through pre-assembly of tetracarboxylated cobalt phthalocyanine molecules and programmed microwave conversion; this patent uses nano-networked niobium pentoxide (Nb2O5) as a support, loading cobalt single atoms onto the oxide surface through impregnation and short-time microwave treatment to form a Co / Nb2O5 structure. In terms of preparation process, the core of this invention lies in molecular-level pre-anchoring and programmed microwave energy input to precisely construct active sites; this patent relies on the special morphology of the Nb2O5 nanonetwork to provide highly dispersed sites and uses second-level short-time microwaves to achieve rapid fixation of cobalt atoms. The two are completely different in their strategies for constructing the substrate, target product, and active sites in the catalytic reaction.

[0099] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0100] All raw materials used in the embodiments of this invention were purchased commercially. As an example, multi-walled carbon nanotubes were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., model XFM13, with a length of 10-20 nm; cobalt phthalocyanine (CoPc) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity >97%.

[0101] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0102] The technical solution of the present invention will be further illustrated by the following embodiments.

[0103] Example 1

[0104] A method for preparing a highly dispersed cobalt-based catalyst, comprising the following steps:

[0105] 1. Preparation of nitrogen-deficient carbon nanotubes (ND-CNTs): 1 g of multi-walled carbon nanotubes (MWCNTs) were placed in 250 mL of mixed acid (HNO3 (68 wt%): H2SO4 (98 wt%) = 1:3 (v / v)) and refluxed at 80 °C for 4 h; after cooling, the mixture was filtered, washed with water until neutral, and vacuum dried at 80 °C for 12 h to obtain carbon oxide nanotubes (O-CNTs); 0.5 g of O-CNTs were placed in a tube furnace and heated to 500 °C at a rate of 5 °C / min under an NH3 atmosphere of 200 mL / min, and held for 2 h; after natural cooling, the temperature was switched to Ar gas (200 mL / min) and then heated to 900 °C at a rate of 5 °C / min, and held for 1 h; after natural cooling, ND-CNTs were obtained.

[0106] 2. Synthesis of tetracarboxylated cobalt phthalocyanine (CoPc-COOH): First, 1.50 g of cobalt phthalocyanine (CoPc) was dissolved in 60 mL of concentrated sulfuric acid (98 wt%), and fuming nitric acid was added dropwise at 0 °C. The mixture was then reacted at 45 °C for 12 hours to obtain tetranitrocobalt phthalocyanine. Next, this product was reacted with 5.0 g of iron powder in an ethanol / hydrochloric acid mixture (volume ratio 2:1) under reflux at 85 °C for 6 hours. After post-treatment, tetraaminocobalt phthalocyanine was obtained. The specific post-treatment process was as follows: After the reaction, the mixture was cooled and filtered while hot to remove excess iron powder and the generated iron salt precipitate. Then, the filtrate was poured into an ice-water mixture while stirring to precipitate tetraaminocobalt phthalocyanine. The solid product was then collected by vacuum filtration and washed successively with deionized water and cold ethanol until the washing solution was neutral and colorless. Finally, it was vacuum dried. Finally, the obtained tetraaminophthalocyanine cobalt was diazotized with sodium nitrite at 0°C. The specific diazotization process was as follows: tetraaminophthalocyanine cobalt was dispersed in an ice-water mixture and maintained at a low temperature of 0-5°C. The mixture was stirred vigorously at 600 rpm, and an excess (1.5 equivalents) of sodium nitrite (NaNO2) aqueous solution was added dropwise. After the addition was completed, the reaction was continued at this low temperature for 40 minutes until the diazonium salt was completely formed (the endpoint could be detected using starch-potassium iodide test paper). Then, it was hydrolyzed in dilute sulfuric acid (concentration of 2 mol / L) at 60°C for 4 hours. The pH was adjusted to 2 to precipitate the product. After washing and drying, the target product tetracarboxylated phthalocyanine cobalt (CoPc-COOH) was obtained, with a yield of approximately 78%.

[0107] 3. Preparation of the pre-assembled complex: 100 mg of ND-CNTs and 150 mg of CoPc-COOH were dissolved in 100 mL of N,N-dimethylformamide (DMF), and the mixture was sonicated for 1 h to ensure complete dispersion. Then, the mixture was magnetically stirred for 12 h, and the DMF was removed by rotary evaporation at 60 °C to obtain a dry black solid powder, which is the pre-assembled complex (CoPc-COOH / ND-CNTs).

[0108] 4. Microwave solid-phase anchoring conversion: The above-mentioned black solid powder was placed in a quartz boat and then placed in a microwave reactor (equipped with an atmosphere control system). Ar gas (50 mL / min) was first introduced to replace the air for 30 min. Then, the microwave program was set as follows: In the first stage, the power was 400W for 5 min to raise the temperature to 300℃; in the second stage, the power was switched to 600W and the power was 600W for 10 min (the temperature was maintained at 400℃); in the third stage, the power was switched to 800W and the power was 80W for 30 s (the temperature instantly rose to 700℃). Then, the microwave reactor was turned off for 30 s. This on-off cycle was repeated 3 times. The microwave process was carried out under an Ar atmosphere. After the reaction was completed, the mixture was allowed to cool naturally to obtain a highly dispersed cobalt-based catalyst, denoted as Cat-1 (Co-SACs / ND-CNTs, with a theoretical Co loading of 1.5 wt%).

[0109] A physical image of the highly dispersed cobalt-based catalyst prepared in this embodiment is shown below. Figure 1 As shown, it is a black powder; the HAADF-STEM characterization results of the highly dispersed cobalt-based catalyst prepared in this embodiment are as follows. Figure 2 As shown, the results indicate that the distribution of each element is relatively uniform; the mapping diagram of the highly dispersed cobalt-based catalyst prepared in this embodiment is shown in the figure. Figure 3 As shown in the mapping diagram, C, N, O, and Co are relatively uniformly distributed on the carbon nanotube matrix, especially Co, which is very uniformly distributed with no obvious agglomeration. The scanning electron microscopy (SEM) characterization results of the highly dispersed cobalt-based catalyst prepared in this embodiment are as follows: Figure 4 As shown, the transmission electron microscopy (TEM) characterization results are as follows: Figure 5 As shown, no obvious particle aggregation phenomenon was observed.

[0110] Example 2 (Changing the heat treatment temperature and microwave program of ND-CNTs)

[0111] 1. Preparation of ND-CNTs: Take 1g of MWCNTs and place them in 250mL of mixed acid (HNO3:H2SO4 = 1:3 (v / v)), reflux at 80℃ for 4h; after cooling, filter, wash with water until neutral, and vacuum dry at 80℃ for 12h to obtain O-CNTs; take 0.5g of O-CNTs and place them in a tube furnace, under an NH3 atmosphere of 200 mL / min, raise the temperature to 500℃ at 5℃ / min, and hold for 2h; after natural cooling, switch to Ar gas (200 mL / min), raise the temperature to 800℃ at 5℃ / min, and hold for 1h; after natural cooling, obtain ND-CNTs;

[0112] 2. Synthesis of CoPc-COOH: Same as in Example 1;

[0113] 3. Preparation of pre-assembled complex: 100 mg ND-CNTs and 120 mg CoPc-COOH were dissolved in 100 mL DMF, sonicated for 1 h, magnetically stirred for 12 h, and DMF was removed by rotary evaporation at 60 °C to obtain a dry black solid powder (CoPc-COOH / ND-CNTs).

[0114] 4. Microwave solid-phase anchoring conversion: The above-mentioned black solid powder was placed in a microwave reactor (equipped with an atmosphere control system). Under Ar gas protection, the microwave program was set as follows: First stage, heating at 300W power for 8 minutes (temperature rises to 250℃); Second stage, switching to 500W power, reactor for 15 minutes (temperature maintained at 350℃); Third stage, switching to 700W power, heating for 20 seconds (temperature instantaneously rises to 600℃), then the microwave reactor was turned off for 20 seconds. This on-off cycle was repeated twice. After the reaction was completed, the catalyst was naturally cooled to obtain the catalyst, denoted as Cat-2 (theoretical Co loading is 1.2 wt%).

[0115] Example 3 (Changing mixed acid oxidation conditions and pre-assembly solvent)

[0116] 1. Preparation of ND-CNTs: Take 1g of MWCNTs and place them in 250mL of mixed acid (HNO3:H2SO4 = 1:2 (v / v)) and reflux at 70℃ for 6h; after cooling, filter, wash with water until neutral, and vacuum dry at 80℃ for 12h to obtain O-CNTs; the subsequent ammoniation and heat treatment steps are the same as in Example 1 to obtain ND-CNTs;

[0117] 2. Synthesis of CoPc-COOH: Same as in Example 1;

[0118] 3. Preparation of pre-assembled complex: 100 mg ND-CNTs and 150 mg CoPc-COOH were dissolved in 100 mL N-methylpyrrolidone (NMP), sonicated for 1 h, magnetically stirred for 12 h, and NMP was removed by rotary evaporation at 60 °C to obtain a dry solid powder (CoPc-COOH / ND-CNTs).

[0119] 4. Microwave solid-phase anchoring conversion: The microwave procedure was the same as in Example 1, and the resulting catalyst was designated Cat-3 (theoretical Co loading was 1.5 wt%).

[0120] Example 4 (Adjusting the precursor ratio and microwave intermittent cycling)

[0121] 1. Preparation of ND-CNTs: Same as in Example 1;

[0122] 2. Synthesis of CoPc-COOH: Same as in Example 1;

[0123] 3. Preparation of pre-assembled complex: 100 mg ND-CNTs and 180 mg CoPc-COOH (to increase the amount of precursor) were dissolved in 100 mL DMF, sonicated for 1 h, magnetically stirred for 12 h, and DMF was removed by rotary evaporation at 60 °C to obtain dry solid powder (CoPc-COOH / ND-CNTs).

[0124] 4. Microwave solid-phase anchoring conversion: The powder was placed in a microwave reactor and, under Ar gas protection, the microwave program was set as follows: First stage, heating at 400W power for 5 min (temperature rises to 300℃); Second stage, switching to 600W power and heating for 10 min (temperature maintained at 400℃); Third stage, switching to 800W power and heating for 15 s (temperature instantaneously rises to 700℃), followed by turning off the microwave reactor for 15 s. This on-off cycle was repeated 5 times. After the reaction was completed, the mixture was allowed to cool naturally to obtain the catalyst, denoted as Cat-4 (theoretical Co loading is 1.8 wt%).

[0125] Comparative Example 1

[0126] Same as Example 1, except that no pre-assembly step is performed, that is: the nitrogen-deficient carbon nanotubes in step 1 of Example 1 are directly processed into step 4 to obtain catalyst Ref-1.

[0127] Comparative Example 2

[0128] Same as Example 1, except that tetracarboxylated cobalt phthalocyanine in step 3 is replaced with an equimolar amount of cobalt nitrate to obtain catalyst Ref-2 (Co loading is 1.5 wt%).

[0129] Comparative Example 3

[0130] Using CoPc-COOH prepared in Example 1 and pristine multi-walled carbon nanotubes (without ND treatment), catalyst Ref-3 was obtained by pre-assembly and microwave processing according to Example 1.

[0131] Comparative Example 4 (using commercial cobalt phthalocyanine (CoPc) instead of tetracarboxylic cobalt phthalocyanine)

[0132] 1. Preparation of ND-CNTs: Same as in Example 1;

[0133] 2. Preparation of pre-assembled complex: 100 mg ND-CNTs and 150 mg CoPc (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) were dissolved in 100 mL DMF, sonicated for 1 h, magnetically stirred for 12 h, and DMF was removed by rotary evaporation at 60 °C to obtain dry solid powder (CoPc / ND-CNTs).

[0134] 3. Microwave solid-phase anchoring conversion: The microwave procedure was the same as in Example 1, and the catalyst was obtained, denoted as Ref-4 (theoretical Co loading was 1.5 wt%).

[0135] Application Example 1: Degradation of Lomefloxacin Hydrochloride (LOH) by Activated Persulfate

[0136] Taking the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 as examples, experiments were conducted on the degradation of lomefloxacin hydrochloride by activated persulfate. The specific process was as follows: 0.02g of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were mixed with 0.015g of persulfate (PMS) and degraded in 100ml of LOH solution with an initial concentration of 20 mg / L (the aqueous matrix was pure water). After 30 minutes, the corresponding absorbance was measured at a wavelength of 280nm in a UV-Vis spectrophotometer and the removal rate was calculated.

[0137] The catalysts prepared in Examples 1-4 and Comparative Examples 1-4 showed improved performance in activating PMS to degrade lomefloxacin hydrochloride. Figure 6 and Figure 7 As shown, the removal rates of lomefloxacin hydrochloride after 30 minutes of PMS degradation by the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were 85.0%, 83.6%, 80.3%, 76.7%, 63.7%, 48.4%, 36.6%, and 67.3%, respectively. The catalysts prepared in Examples 1-4 all exhibited relatively fast antibiotic degradation rates, with the catalyst prepared in Example 1 showing the best degradation effect.

[0138] In addition, the three-dimensional fluorescence spectra of the solutions of lomefloxacin hydrochloride activated by the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were tested at degradation times of 0 min, 15 min, and 30 min. The results are as follows: Figure 8 As shown in the figure, the results indicate that a strong fluorescence peak (excitation wavelength E) is observed in the fluorescence spectrum of the solution at 0 min. x = 277 nm, emission wavelength E m =412 nm). After 30 minutes of catalytic degradation, only a few weak fluorescence peaks remained in the fluorescence spectrum, indicating that most of the lomefloxacin hydrochloride in the solution had been removed, and the catalyst showed good catalytic degradation performance.

[0139] Application Example 2: Evaluation of Co dissolution concentration after 30 minutes of PMS activation and lomefloxacin hydrochloride degradation using catalysts prepared in Examples 1-4 and Comparative Examples 1-4.

[0140] The water sample that had undergone degradation in 30 minutes, as described in Example 1, was analyzed by ICP-MS to determine the concentration of dissolved Co in the solution. The results are as follows: Figure 9As shown, the concentrations of Co in the solution after 30 minutes of PMS degradation of lomefloxacin hydrochloride by the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were 0.022 mg / L, 0.028 mg / L, 0.027 mg / L, 0.024 mg / L, 0.204 mg / L, 0.185 mg / L, 0.087 mg / L, and 0.075 mg / L, respectively. This indicates that the Co dissolution concentration in the solution after 30 minutes of PMS degradation of lomefloxacin hydrochloride by the catalysts prepared in Examples 1-4 were all low, with Example 1 having the lowest Co dissolution concentration. This also shows that the preparation method proposed in this invention can firmly embed Co into the CNT matrix, avoiding the shedding of a large amount of Co.

[0141] The XRD patterns of the catalyst before and after the activation of PMS by the highly dispersed cobalt-based catalyst in Example 1 for the degradation of lomefloxacin hydrochloride are shown below. Figure 10 As shown, the position and intensity of the highly dispersed cobalt-based catalyst peak in Example 1 did not change significantly before and after the degradation reaction, indicating that the highly dispersed cobalt-based catalyst prepared by the method of the present invention has excellent structural stability.

[0142] Application Example 3: Evaluation of the effect of different environmental substrates on the degradation of lomefloxacin hydrochloride by highly dispersed cobalt-based catalysts

[0143] Taking the highly dispersed cobalt-based catalyst prepared in Example 1 as an example, the effect of different environmental substrates on the degradation of lomefloxacin hydrochloride by the highly dispersed cobalt-based catalyst was tested. The experimental process was the same as in Application Example 1, except that the water substrate in Application Example 1 was pure water, while in this application example, tap water, river water and seawater were used instead.

[0144] The effects of different environmental substrates on the degradation of lomefloxacin hydrochloride by the highly dispersed cobalt-based catalyst in Example 1 are as follows: Figure 11 As shown, the highly dispersed cobalt-based catalyst prepared in Example 1 exhibits good degradation effects on lomefloxacin hydrochloride in pure water, tap water, river water, and seawater substrates, indicating that the highly dispersed cobalt-based catalyst prepared by the method of the present invention has excellent environmental adaptability.

[0145] Application Example 4: Comparison of the degradation performance of highly dispersed cobalt-based catalysts on different types of organic matter

[0146] Taking the highly dispersed cobalt-based catalyst prepared in Example 1 as an example, its degradation performance on different types of organic matter was tested. The specific process was as follows: The highly dispersed cobalt-based catalyst prepared in Example 1 was used to degrade different pollutants (tetracycline hydrochloride, methylene blue) under the same conditions as the degradation of lomefloxacin hydrochloride. That is, 0.02g of highly dispersed cobalt-based catalyst was used to activate 0.015g of permonosulfate (PMS) to degrade 100ml of lomefloxacin hydrochloride solution (water matrix is ​​pure water), tetracycline hydrochloride solution (water matrix is ​​pure water), and methylene blue solution (water matrix is ​​pure water) with an initial concentration of 20 mg / L. After 30 minutes, the absorbance values ​​were measured at wavelengths of 280nm (suitable for lomefloxacin hydrochloride), 355nm (suitable for tetracycline hydrochloride), and 664nm (suitable for methylene blue) in a UV-Vis spectrophotometer, and the removal rate was calculated.

[0147] The results of the highly dispersed cobalt-based catalyst prepared in Example 1 degrading different pollutants (lomefloxacin hydrochloride, tetracycline hydrochloride, and methylene blue) are as follows: Figure 12 As shown, the highly dispersed cobalt-based catalyst prepared in Example 1 has good removal effects on lomefloxacin hydrochloride, tetracycline hydrochloride, and dye organics (methylene blue), indicating that the highly dispersed cobalt-based catalyst prepared by the method of the present invention has good universality in organic matter removal.

[0148] Application Example 5: Evaluation of the Cyclic Performance of PMS Activated by Highly Dispersed Cobalt-Based Catalyst for Lomefloxacin Hydrochloride Degradation

[0149] Taking the highly dispersed cobalt-based catalyst prepared in Example 1 as an example, the cyclic performance of activated PMS in degrading lomefloxacin hydrochloride was tested. The specific process was as follows: 10 portions of 0.02g of the highly dispersed cobalt-based catalyst prepared in Example 1 were taken and subjected to the same experiment as in Example 1 in degrading lomefloxacin hydrochloride, which was recorded as one reaction. After filtration, washing, and drying, the above operation was repeated for 10 portions of the catalyst, which was recorded as two reactions. The same experiment was performed 5 times in total, which was recorded as 5 cycles.

[0150] Results of the cycling performance of PMS activated by highly dispersed cobalt-based catalyst for the degradation of lomefloxacin hydrochloride are as follows: Figure 13 As shown, after 5 cycles, the highly dispersed cobalt-based catalyst prepared in Example 1 still achieved a removal rate of 72% for lomefloxacin hydrochloride at 30 minutes, which was only 15.3% lower than the 85% achieved in the first cycle. This indicates that the highly dispersed cobalt-based catalyst prepared by the method of the present invention has good cycle stability.

[0151] In summary, this invention combines the "rapid" advantage of microwave method with the "controllable" advantage of precision synthesis to successfully prepare a high-performance, highly dispersed cobalt-based catalyst, effectively solving the core pain points of the prior art, and providing a stable and efficient catalyst preparation method for advanced oxidation treatment of recalcitrant organic wastewater.

[0152] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a highly dispersed cobalt-based catalyst, characterized in that, Using cobalt tetracarboxylated phthalocyanine and nitrogen-deficient carbon nanotubes as raw materials, a pre-assembled composite is formed in an organic solvent through molecular self-assembly. Then, the pre-assembled composite is subjected to programmed microwave heating to obtain the highly dispersed cobalt-based catalyst. The programmed microwave heating is divided into three stages, with the power of the second stage heating being greater than that of the first stage heating, and the power of the third stage heating being greater than that of the second stage heating. The specific steps of the programmed microwave heating are as follows: the pre-assembled composite is placed in a microwave reactor, inert gas is introduced to replace the air, and heating is carried out in three stages: In the first stage, heat at 300-400W power for 5-8 minutes to raise the temperature to 250-300℃; In the second stage, switch to 500-600W power and heat for 10-15 minutes to maintain the temperature at 350-400℃. In the third stage, switch to 700-800W power, heat for 15-30 seconds, and the temperature will rise to 600-700℃ instantly. Then turn off the microwave reactor for 15-30 seconds. Repeat this on-off cycle 2-5 times. The programmed microwave heating process is carried out entirely in an inert gas atmosphere.

2. The method for preparing the highly dispersed cobalt-based catalyst according to claim 1, characterized in that, The method for preparing the nitrogen-deficient carbon nanotubes includes the following steps: placing multi-walled carbon nanotubes in a mixed acid composed of nitric acid and sulfuric acid, and carrying out a reflux reaction under heating conditions; after cooling, filtering, washing with water until neutral, and vacuum drying to obtain carbon oxide nanotubes; calcining the carbon oxide nanotubes under an NH3 atmosphere, naturally cooling, calcining under an inert gas atmosphere, and naturally cooling again to obtain the nitrogen-deficient carbon nanotubes.

3. The method for preparing the highly dispersed cobalt-based catalyst according to claim 2, characterized in that, The volume ratio of nitric acid to sulfuric acid is 1:(2-3). And / or, the reflux reaction is carried out at a temperature of 70-80°C for 4-6 hours.

4. The method for preparing the highly dispersed cobalt-based catalyst according to claim 2, characterized in that, When the carbon oxide nanotubes were calcined in an NH3 atmosphere: the NH3 gas flow rate was 200 mL / min, the calcination temperature was 500℃, the holding time was 2h, and the heating rate was 5℃ / min. And / or, when calcining is carried out in an inert gas atmosphere: the inert gas flow rate is 200 mL / min, the calcination temperature is 800-900℃, the holding time is 1h, and the heating rate is 5℃ / min.

5. The method for preparing the highly dispersed cobalt-based catalyst according to claim 1, characterized in that, The step of forming a pre-assembled composite by molecular self-assembly in an organic solvent is as follows: the nitrogen-deficient carbon nanotubes and the tetracarboxylated cobalt phthalocyanine are dissolved in an organic solvent at a mass ratio of 1:(1.2-1.8), ultrasonically dispersed, magnetically stirred, and the organic solvent is removed by rotary evaporation to obtain the pre-assembled composite.

6. A highly dispersed cobalt-based catalyst, characterized in that, It is prepared according to any one of claims 1-5.

7. The application of the highly dispersed cobalt-based catalyst as described in claim 6 in the treatment of recalcitrant organic wastewater using advanced oxidation processes, characterized in that... The advanced oxidation treatment of recalcitrant organic wastewater is selected from wastewater containing lomefloxacin hydrochloride, wastewater containing tetracycline hydrochloride, and / or wastewater containing dye-like organic compounds.

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