A magnetic cobalt-aluminum layered double hydroxide composite catalyst, a preparation method thereof and application thereof in degrading pesticides
By preparing a magnetic cobalt-aluminum layered double hydroxide composite catalyst Fe3O4@Co5Al-LDH, the problems of catalyst recovery difficulty and structural instability were solved, achieving efficient and stable pesticide degradation, which is suitable for complex water treatment.
Patent Information
- Application Number
- CN202610200736.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-11
- Publication Date
- 2026-05-29
Smart Images
Figure CN122098575A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of environmental catalytic materials and water treatment technology, specifically relating to a magnetic cobalt-aluminum layered double hydroxide composite catalyst, its preparation method, and its application in pesticide degradation. Background Technology
[0002] With the widespread use of pesticides in modern agricultural production, their residues enter the aquatic environment through runoff and infiltration, posing a serious threat to ecosystems and human health. Taking three existing pesticides as examples: atrazine (ATZ) has been classified as a Group 3 carcinogen by the International Agency for Research on Cancer (IARC) of the World Health Organization and is significantly toxic to aquatic organisms; flutriafol (EPO) degrades slowly in the environment and has endocrine-disrupting effects; and metalaxyl (MET) has the potential to interfere with the growth and reproduction of aquatic organisms such as fish. Therefore, developing efficient, safe, and economical pesticide residue degradation technologies is of urgent practical significance.
[0003] Currently, technologies for degrading pesticide residues in water mainly include adsorption, biodegradation, membrane separation, photocatalysis, electrochemistry, and advanced oxidation processes (AOPs). Among these, adsorption only transfers pollutants from the water to the adsorbent without actually degrading them, easily causing secondary pollution. Furthermore, adsorbent regeneration is difficult, resulting in high operating costs. Biodegradation has a long degradation cycle, poor tolerance to high concentrations or toxic pesticides, and is greatly affected by environmental conditions (temperature, pH, microbial species), exhibiting poor stability. Membrane separation suffers from membrane fouling and clogging, requiring frequent cleaning or replacement, increasing investment and operating costs, and only achieves phase separation without degrading pollutants. Photocatalysis relies on ultraviolet or visible light sources, resulting in high energy consumption, easy catalyst deactivation, high photogenerated electron-hole recombination rates, and low quantum efficiency. Electrochemical methods use expensive electrode materials, consume a lot of energy, and are prone to generating byproducts or electrode contamination, limiting their large-scale application. Advanced oxidation processes (AOPs) have attracted widespread attention due to their high efficiency and environmental friendliness. Advanced oxidation processes (AOPs) mainly include the traditional Fenton process and persulfate activation technology. The traditional Fenton process requires acidic conditions (pH≈3), produces iron sludge that is difficult to treat, and the catalyst is difficult to recover, easily causing secondary pollution. Persulfate activation technology utilizes various activation methods, such as heat, light, and transition metals. Commonly used activators include transition metal ions (Fe2+). 2+ Co 2+ Mn 2+ (etc.) or their oxides can generate strong oxidizing free radicals (such as hydroxyl radical •OH, sulfate radical SO4•). - This process completely mineralizes organic pollutants into CO2 and H2O or transforms them into low-toxicity intermediates.
[0004] Commonly used persulfate activators are mainly transition metals and their oxides, including homogeneous transition metal activation systems, heterogeneous transition metal activation systems, and layered double hydroxides (LDHs). Among these, homogeneous transition metal activation systems directly use Fe... 2+ Co 2+ Metal ions are used as catalysts. For example, Co... 2+ Activated permonosulfate (PMS) degrades organic pollutants at a rapid rate. However, this system suffers from several significant drawbacks: 1) metal ions are difficult to recover from the reaction system, leading to catalyst loss and high operating costs; 2) residual metal ions (especially biotoxic cobalt ions) can cause serious secondary pollution; and 3) the reaction is typically pH-sensitive (e.g., the classic Fenton system requires acidic conditions), limiting its application in real-world water bodies. To overcome the shortcomings of homogeneous transition metal activation systems, researchers have developed heterogeneous transition metal activation systems, represented by transition metal oxides or supported materials. Among these, cobalt-based catalysts have attracted considerable attention due to their excellent activation performance for permonosulfate. However, traditional cobalt-based heterogeneous catalysts (such as Co3O4, Co supported on A2O3, etc.) still face the following challenges: 1) Difficulty in separation and recovery: Nano or micron-sized catalyst powders are difficult to separate effectively in water by sedimentation and are easily lost with the effluent, causing not only catalyst loss but also potential environmental risks; 2) Metal leaching: During the catalytic process, the active component cobalt ions may leach from the support, leading to a decrease in catalytic activity and secondary pollution; 3) Poor cycle stability: Due to agglomeration, active sites being covered by intermediate products, or structural collapse, the reusability of catalysts is often unsatisfactory. Layered double hydroxides are a class of two-dimensional materials composed of divalent and trivalent metal hydroxide layers and interlayer anions. They have tunable chemical composition, large specific surface area, and abundant active sites, but are non-magnetic and difficult to separate from water, limiting their practical application; when layered double hydroxides are used directly, recovery is difficult, easily causing catalyst loss and secondary pollution; some layered double hydroxides are structurally unstable during the reaction, and metal ions are easily dissolved.
[0005] To facilitate catalyst recovery, the introduction of magnetic components (such as Fe3O4) to construct magnetically separable and recoverable catalysts is a current research trend. However, existing magnetic composite material designs often face problems such as weak bonding between the magnetic core and the catalyst shell, reduced active sites due to shell coverage, and severe interference from coexisting ions in complex water bodies, affecting their overall performance.
[0006] Therefore, developing a highly efficient, easily recyclable, and reusable heterogeneous catalyst for activating persulfate degradation of pesticides is of great significance and application value. Summary of the Invention
[0007] To address the problems existing in the prior art, this invention provides a magnetic cobalt-aluminum layered double hydroxide composite catalyst, its preparation method, and its application in pesticide degradation.
[0008] The magnetic cobalt-aluminum layered double hydroxide composite catalyst provided by this invention has the characteristics of high catalytic activity, easy magnetic separation and recovery, and reusability. It is suitable for activating persulfate to efficiently degrade pesticide residues in water.
[0009] The technical solution adopted by this invention to solve the technical problem is as follows: This invention provides a magnetic cobalt-aluminum layered double hydroxide composite catalyst, which is composed of Fe3O4 superparamagnetic nanoparticles and Co5Al layered double hydroxide.
[0010] This invention provides a method for preparing a magnetic cobalt-aluminum layered double hydroxide composite catalyst, which specifically includes the following steps: 1) Synthesis of Fe3O4 superparamagnetic nanoparticles; 2) Add aluminum nitrate and cobalt nitrate to deionized water, then add ammonium fluoride, urea and Fe3O4 magnetic nanoparticles and disperse them by ultrasonication; 3) Transfer the resulting mixed solution into a reaction vessel and hydrothermally react at 100℃-110℃ for 5-6 hours; 4) After the hydrothermal reaction is completed, the catalyst is cooled, washed and dried to obtain a magnetic cobalt-aluminum layered double hydroxide composite catalyst.
[0011] As a preferred embodiment, the synthesis method of the Fe3O4 superparamagnetic nanoparticles is as follows: first, dissolve trisodium citrate dihydrate and sodium hydroxide in deionized water, then add sodium nitrate. The mass ratio of trisodium citrate dihydrate, sodium hydroxide and sodium nitrate is (1.1-2):(0.5-1.0):(14-20). Stir the resulting mixed solution continuously at 100-110℃ for 15-30 minutes until a transparent solution is formed. Add FeSO4•7H2O solution and continue stirring for 1-2 hours. After washing, dry at 60-70℃ for 6-12 hours.
[0012] In a preferred embodiment, in step 2), the molar ratio of aluminum nitrate, cobalt nitrate, ammonium fluoride and urea is (0.5-1.5):(3-7):(10-20):(20-30).
[0013] In a preferred embodiment, in step 2), the mass ratio of the Fe3O4 superparamagnetic nanoparticles to the total mass of aluminum nitrate, cobalt nitrate, ammonium fluoride, and urea is 1:(5-20).
[0014] As a preferred embodiment, in step 4), the product is dried under vacuum at 60-70°C for 5-8 hours.
[0015] This invention provides the application of a magnetic cobalt-aluminum layered double hydroxide composite catalyst in the degradation of pesticides.
[0016] As a preferred embodiment, the application of a magnetic cobalt-aluminum layered double hydroxide composite catalyst in pesticide degradation provided by the present invention specifically includes the following steps: 1) Add the catalyst to water bodies containing pesticides; 2) Add persulfate to initiate the catalytic reaction; 3) Perform the shaking reaction for 10-15 minutes at room temperature and pH = 3.0-11.0; 4) After the reaction is complete, the catalyst is separated and recovered by an external magnetic field.
[0017] In a preferred embodiment, the amount of catalyst added is 20-40 mg / L.
[0018] In a preferred embodiment, the amount of persulfate added is 0.4-5.0 mM.
[0019] The beneficial effects of this invention are: 1. The magnetic cobalt-aluminum layered double hydroxide composite catalyst provided by the present invention has superparamagnetism, can be quickly separated and recovered by an external magnetic field, and has good reusability, fundamentally solving the engineering bottleneck of difficult separation and recovery and easy loss of heterogeneous catalysts.
[0020] Specifically, addressing the problem that existing heterogeneous catalysts (such as powdered LDH or metal oxides) require complex and energy-intensive centrifugation or filtration to achieve solid-liquid separation, resulting in high operating costs and the easy loss of fine particles causing secondary pollution and catalyst loss, this invention combines catalytically active Co5Al-LDH with superparamagnetic Fe3O4 nanoparticles. The prepared catalyst, Fe3O4@Co5Al-LDH, possesses high saturation magnetization. After the reaction, complete separation of the catalyst from the reaction system can be achieved within tens of seconds using only an ordinary magnet, with a recovery rate approaching 100%. After simple washing and drying, the recovered catalyst can be reused three times, maintaining a degradation efficiency of over 92% for three pesticides. This characteristic significantly reduces operating costs and avoids resource waste and secondary environmental risks.
[0021] 2. The magnetic cobalt-aluminum layered double hydroxide composite catalyst provided by the present invention can simultaneously and efficiently degrade multiple pesticides, with a degradation efficiency of up to 100% within 15 minutes.
[0022] Specifically, addressing the issues that existing single-catalytic systems are often effective for a specific type of pesticide but experience a sharp drop in degradation efficiency for other pesticides with vastly different structures, and that homogeneous catalysts, while potentially highly efficient, are not recyclable, this invention is based on the synergistic effect of the Fe / Co bimetallic redox pair (Fe... 2+ Promote Co 3+ Reduced to highly active Co 2+ Leveraging the rich surface properties of LDH, the prepared catalyst Fe3O4@Co5Al-LDH exhibited near-synchronous high degradation efficiency for three pesticides with different properties. Under optimal conditions (catalyst 35 mg / L, PMS 0.4 mM, pH 7.0), the degradation efficiency of 30 mg / L atrazine (ATZ), metalaxyl (MET), and flutriafol (EPO) all reached 100% within 15 minutes. This demonstrates that the present invention is not a specific technology for a single organic pollutant, but rather a universal solution capable of addressing the complex pollution challenges in real-world environments.
[0023] 3. The magnetic cobalt-aluminum layered double hydroxide composite catalyst provided by the present invention has excellent chemical stability and structural stability, and can effectively inhibit the dissolution of toxic metal ions.
[0024] Specifically, addressing the issues of secondary pollution caused by the direct introduction of metal ions into existing homogeneous catalysts and the decreased activity and environmental toxicity resulting from the easy dissolution of active metals (such as Co) in some heterogeneous catalysts during the reaction, the layered crystal structure of the Fe3O4@Co5Al-LDH catalyst prepared in this invention provides a stable environment for active metals Co and Al. X-ray photoelectron spectroscopy characterization analysis confirmed that the chemical states of Co and Al species on the catalyst surface remained stable before and after the reaction. More importantly, in repeated use experiments, no precipitous drop in catalytic performance was observed; the catalytic activity remained at a high level after three cycles. This indirectly proves that the dissolution of active materials is minimal and the catalyst structure is stable. This structural stability is a key prerequisite for its practical application.
[0025] 4. The magnetic cobalt-aluminum layered double hydroxide composite catalyst provided by this invention has high catalytic activity over a wide pH range and is suitable for practical water treatment.
[0026] Specifically, addressing the issues of existing advanced oxidation processes such as the Fenton process requiring strong acidity (pH≈3) and consuming large amounts of acid-base adjusters when treating neutral or alkaline water, leading to increased costs and salinity, the catalytic system of this invention maintains high activity across a wide pH range of 3.0-11, reaching peak performance at neutral conditions of pH 7.0. This means that when treating lakes, rivers, groundwater, and even most industrial wastewater, the catalyst and persulfate can be directly added without the need for cumbersome and expensive pH pre-adjustment steps, greatly simplifying the process and reducing treatment costs and operational complexity.
[0027] 5. The catalytic system of the present invention has a clear reaction mechanism, which is dominated by the free radical pathway, ensuring the thoroughness and reliability of degradation.
[0028] Specifically, addressing the problem that many existing catalytic systems suffer from unclear mechanisms of action and unknown active substances, making process parameter optimization difficult and potentially leading to the generation of more toxic intermediates, this invention, through systematic quenching experiments and direct detection by electron paramagnetic resonance (EPR) spectroscopy, clearly confirms that sulfate radicals (SO4•) are present. - Sulfate radicals (SO4·OH) and hydroxyl radicals (•OH) are the main active substances in the degradation process. The process of pesticide degradation by PMS activated by a catalyst is mainly driven by sulfate radicals (SO4·OH). - Driven by hydroxyl radicals (•OH) and hydroxyl radicals (•OH).
[0029] Meanwhile, X-ray photoelectron spectroscopy characterization analysis directly revealed the Fe3O4@Co5Al-LDH surface Fe 2+ / Fe 3+ With Co 2 + / Co 3+ The redox cycle is the intrinsic mechanism of its high activity, and the mechanism by which it activates PMS is elucidated at the atomic scale. This clear understanding of the mechanism not only ensures that the target pesticide pollutants can be effectively mineralized by strong oxidizing free radicals, but also provides reliable theoretical guidance for further targeted optimization of the catalyst.
[0030] 6. The magnetic cobalt-aluminum layered double hydroxide composite catalyst provided by this invention addresses common coexisting anions in actual water bodies (such as...). , , It exhibits good tolerance and has a certain degree of anti-interference ability with strong anti-interference ability.
[0031] Specifically, this refers to the high concentration of [unspecified substance] in existing natural water bodies. , , The problem that anions quench free radicals, thus severely inhibiting the efficiency of many advanced oxidation systems, is addressed by the catalytic system of this invention at 5-10 mM. , , , , Under conditions of coexisting ions, it can still maintain a high degradation efficiency for the target pesticide. In particular, and Its presence even slightly promotes the degradation of certain pesticides, possibly due to its buffering effect maintaining a favorable pH environment for the reaction. This strong anti-interference capability significantly enhances the reliability and practicality of this invention in treating real wastewater with complex compositions. Attached Figure Description
[0032] Figure 1 Scanning electron microscope (SEM) images of Fe3O4 superparamagnetic nanoparticles and Fe3O4@Co5Al-LDH. In the image, a and c are Fe3O4 superparamagnetic nanoparticles; b and d are Fe3O4@Co5Al-LDH.
[0033] Figure 2 Transmission electron microscopy images of Fe3O4 superparamagnetic nanoparticles and Fe3O4@Co5Al-LDH. In the image, a is Fe3O4 superparamagnetic nanoparticles; b is Fe3O4@Co5Al-LDH.
[0034] Figure 3 X-ray diffraction patterns of Fe3O4 superparamagnetic nanoparticles and Fe3O4@Co5Al-LDH Figure 4 Fourier transform infrared spectra of Fe3O4 superparamagnetic nanoparticles, Co5Al-LDH, and Fe3O4@Co5Al-LDH.
[0035] Figure 5 Magnetometer images of vibrating samples of Fe3O4 superparamagnetic nanoparticles, Co5Al-LDH, and Fe3O4@Co5Al-LDH.
[0036] Figure 6 The effects of different catalyst / persulfate systems on the degradation performance of metalaxyl.
[0037] Figure 7 The effects of different catalyst / persulfate systems on the degradation performance of atrazine.
[0038] Figure 8 The effects of different catalyst / persulfate systems on the degradation performance of flutriafol.
[0039] Figure 9The effect of different solution pH values on the degradation performance of metalaxyl.
[0040] Figure 10 The effect of different solution pH values on the degradation performance of atrazine.
[0041] Figure 11 The effect of different solution pH values on the degradation performance of flutriafol.
[0042] Figure 12 The effect of different initial pesticide concentrations on the degradation performance of metalaxyl.
[0043] Figure 13 The effect of different initial pesticide concentrations on the degradation performance of atrazine.
[0044] Figure 14 The effect of different initial pesticide concentrations on the degradation performance of flutriafol.
[0045] Figure 15 To investigate the effect of different persulfate concentrations on the degradation performance of metalaxyl.
[0046] Figure 16 To investigate the effect of different persulfate concentrations on the degradation performance of atrazine.
[0047] Figure 17 To investigate the effect of different persulfate concentrations on the degradation performance of flutriafol.
[0048] Figure 18 The effect of different catalyst dosages on the degradation performance of metalaxyl.
[0049] Figure 19 The effect of different catalyst dosages on the degradation performance of atrazine.
[0050] Figure 20 The effect of different catalyst dosages on the degradation performance of flutriafol.
[0051] Figure 21 The effect of coexisting inorganic ions on the degradation performance of metalaxyl.
[0052] Figure 22 The effect of coexisting inorganic ions on the degradation performance of atrazine.
[0053] Figure 23 The effect of coexisting inorganic ions on the degradation performance of flutriafol.
[0054] Figure 24 The results are from the catalytic stability test of Fe3O4@Co5Al-LDH on metalaxyl.
[0055] Figure 25 The results are from the catalytic stability test of Fe3O4@Co5Al-LDH on atrazine.
[0056] Figure 26 The results are from the catalytic stability test of Fe3O4@Co5Al-LDH on fluroxypyr.
[0057] Figure 27 The effect of free radical quenchers on the degradation performance of metalaxyl.
[0058] Figure 28 The effect of free radical quenchers on atrazine and its degradation performance.
[0059] Figure 29 The effect of free radical quenchers on the degradation performance of flutriafol.
[0060] Figure 30 •OH, SO4• - and O2• - The electron paramagnetic resonance spectrum.
[0061] Figure 31 The electron paramagnetic resonance spectrum of ¹O₂.
[0062] Figure 32 The X-ray photoelectron spectra are the full spectra of Fe3O4@Co5Al-LDH before and after the reaction.
[0063] Figure 33 The C 1s fine scan spectra are before and after the Fe3O4@Co5Al-LDH reaction.
[0064] Figure 34 The O 1s fine scan spectra are before and after the Fe3O4@Co5Al-LDH reaction.
[0065] Figure 35 The fine scan spectra of Co 2p before and after the Fe3O4@Co5Al-LDH reaction are shown.
[0066] Figure 36 The fine scan spectra of Fe 2p before and after the Fe3O4@Co5Al-LDH reaction are shown. Detailed Implementation
[0067] In a first aspect, the present invention provides a magnetic cobalt-aluminum layered double hydroxide composite catalyst Fe3O4@Co5Al-LDH.
[0068] The present invention provides a magnetic cobalt-aluminum layered double hydroxide composite catalyst Fe3O4@Co5Al-LDH, which is composed of Fe3O4 superparamagnetic nanoparticles and Co5Al layered double hydroxide (Co5Al-LDH).
[0069] The present invention provides a magnetic cobalt-aluminum layered double hydroxide composite catalyst Fe3O4@Co5Al-LDH, which is a composite material with a core-shell structure. Fe3O4 superparamagnetic nanoparticles serve as the magnetic core, with a characteristic saturation magnetization of not less than 60 emu / g, to achieve rapid magnetic separation and recovery. Co5Al layered double hydroxide with persulfate (PMS) activation function serves as the catalytic shell, which is composed of a large number of ultrathin LDH nanosheets arranged in the same direction, exhibiting a typical bundle structure.
[0070] The present invention provides a magnetic cobalt-aluminum layered double hydroxide composite catalyst Fe3O4@Co5Al-LDH, which does not simply physically mix the magnetic component and the catalytic component, but uses a one-step solvothermal method to grow Co5Al-LDH in situ on the surface of the Fe3O4 magnetic core, forming a core-shell composite material with a strong bond and a well-defined structure. This satisfies the two contradictory requirements of high catalytic activity and convenient magnetic separation, and solves the engineering problem of the difficulty in recovering existing heterogeneous catalysts.
[0071] Secondly, the present invention provides a method for preparing a magnetic cobalt-aluminum layered double hydroxide composite catalyst.
[0072] The present invention provides a method for preparing a magnetic cobalt-aluminum layered double hydroxide composite catalyst, the specific implementation process of which is as follows: 1) Synthesis of Fe3O4 superparamagnetic nanoparticles; 2) Add aluminum nitrate and cobalt nitrate to deionized water and stir at 150-250 rpm for 5-10 minutes; then add ammonium fluoride, urea and Fe3O4 superparamagnetic nanoparticles and ultrasonically disperse for 10-15 minutes; among them, the addition of ammonium fluoride and urea is the key to inducing the directional growth of Co5Al-LDH on the surface of the magnetic core. 3) Transfer the resulting mixed solution into a reaction vessel and hydrothermally react at 100-110℃ for 5-6 hours; 4) After the hydrothermal reaction is completed, the catalyst is cooled, washed, and dried under vacuum at 60-70℃ for 6-12 hours to obtain a magnetic cobalt-aluminum layered double hydroxide composite catalyst.
[0073] Specifically, in step 1) above, the synthesis method of Fe3O4 superparamagnetic nanoparticles is as follows: First, dissolve trisodium citrate dihydrate and sodium hydroxide in deionized water, then add sodium nitrate. The mass ratio of trisodium citrate dihydrate, sodium hydroxide, and sodium nitrate is (1.1-2):(0.5-1.0):(14-20). Stir the resulting mixed solution continuously at 100-110℃ for 15-30 minutes until a transparent solution is formed. Add FeSO4•7H2O solution and continue stirring for 1-2 hours. After washing, dry at 60-70℃ for 6-12 hours.
[0074] Specifically, in step 2) above, the molar ratio of aluminum nitrate, cobalt nitrate, ammonium fluoride and urea is (0.5-1.5):(3-7):(10-20):(20-30).
[0075] Specifically, in step 2) above, the mass ratio of Fe3O4 superparamagnetic nanoparticles to the total mass of aluminum nitrate, cobalt nitrate, ammonium fluoride, and urea is 1:(5-20). In the synthesis of core-shell structured or magnetic composite materials, Fe3O4 superparamagnetic nanoparticles serve as the core, and Co5Al-LDH generated by the reaction of other reagents (aluminum nitrate, cobalt nitrate, ammonium fluoride, and urea) serves as the shell. The ratio between the two is a key parameter affecting the final composite material properties (such as magnetic strength, shell coating uniformity, specific surface area, etc.).
[0076] The present invention provides a magnetic cobalt-aluminum layered double hydroxide composite catalyst Fe3O4@Co5Al-LDH, which is prepared by a one-step solvothermal method. It can be used to activate persulfate and rapidly and synchronously degrade various pesticides with different structures (such as atrazine, metalaxyl, and flutriafol) at room temperature and pH=3.0-11.0. After the reaction, the catalyst can be rapidly and completely separated and recovered by an external magnetic field, and it has excellent reusability and stability.
[0077] Thirdly, the present invention provides an application of a magnetic cobalt-aluminum layered double hydroxide composite catalyst in the degradation of pesticides.
[0078] This invention provides a magnetic cobalt-aluminum layered double hydroxide composite catalyst that, through activation of persulfate, broadly, efficiently, and recyclably degrades organic pollutants, particularly pesticide residues, in water. The specific implementation process is as follows: 1) Add the catalyst to water bodies containing pesticides; 2) Add persulfate to initiate the catalytic reaction; 3) Perform the shaking reaction for 10-15 minutes at room temperature and pH = 3.0-11.0; 4) After the reaction is complete, the catalyst is separated and recovered by an external magnetic field.
[0079] Specifically, in step 1) above, the amount of catalyst added is preferably 20-40 mg / L; more preferably 35 mg / L.
[0080] Specifically, in step 1) above, the amount of persulfate added is preferably 0.4-5.0 mM; more preferably 4.0 mM.
[0081] Specifically, pesticides include, but are not limited to, one or more of atrazine, metalaxyl, and flutriafol.
[0082] This invention provides a magnetic cobalt-aluminum layered double hydroxide composite catalyst that achieves pesticide degradation through the activation of persulfate combined with a Fe / Co bimetallic redox synergistic mechanism. The Fe3O4 magnetic core of the catalyst contains Fe... 2+ / Fe 3+ Co with Co5Al-LDH shell 2+ / Co 3+ This constitutes a unique bimetallic redox pair synergistic system, Fe 2+ Can promote Co 3+ Reduced to highly active Co 2+ This accelerates the regeneration cycle of the active center, thereby significantly improving the activation efficiency of PMS and its broad-spectrum degradation ability against a variety of pesticides.
[0083] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0084] Example 1: Preparation of magnetic cobalt-aluminum layered double hydroxide composite catalyst 1) Synthesis of Fe3O4 superparamagnetic nanoparticles: 1.45 g of trisodium citrate dihydrate and 0.80 g of sodium hydroxide were dissolved in 95 mL of deionized water, and then 17 g of sodium nitrate was added; the above mixed solution was continuously stirred at 400 rpm for 25 minutes at 105 °C until a transparent solution was formed, and 5 mL of FeSO4·7H2O solution (2 M) was poured into the above transparent solution and stirred for 1.5 hours; the obtained black sample was washed with water and anhydrous ethanol and dried at 65 °C for 9 hours to obtain Fe3O4 superparamagnetic nanoparticles; 2) Under stirring conditions, 0.5 mmol of aluminum nitrate nonahydrate (Al(NO3)3·9H2O) and 2.5 mmol of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) were added to 70 mL of deionized water; then 8 mmol of ammonium fluoride (NH4F), 12 mmol of urea and 231.5 mg of Fe3O4 superparamagnetic nanoparticles were added to the above system and ultrasonically dispersed for 15 minutes. 3) Transfer the ultrasonically dispersed mixture to a 100mL polytetrafluoroethylene stainless steel high-pressure reactor and hydrothermally react at 105℃ for 5.5 hours; 4) After the hydrothermal reaction was completed, the product was cooled to room temperature, washed three times with deionized water and anhydrous ethanol, and then dried under vacuum at 65°C for 6.5 hours to obtain the magnetic cobalt-aluminum layered double hydroxide composite catalyst Fe3O4@Co5Al-LDH.
[0085] The scanning electron microscope image of the synthesized Fe3O4 superparamagnetic nanoparticles in this embodiment is as follows: Figure 1 As shown in a and c. Figure 1 Figure a shows monodisperse spherical particles with rough surfaces and clear outlines. Figure 1 Image c shows the aggregated state of Fe3O4 superparamagnetic nanoparticles. Each particle maintains a near-spherical shape and a rough surface, with the particles tightly stacked and exhibiting a porous structure. This indicates the successful synthesis of Fe3O4 superparamagnetic nanoparticles with a near-spherical shape and a rough surface structure. The particles are uniform in size, but exhibit agglomeration characteristics.
[0086] The scanning electron microscope image of Fe3O4@Co5Al-LDH obtained in this embodiment is as follows: Figure 1 As shown in b and d. Figure 1 As shown in Figure b, a single Fe3O4@Co5Al-LDH particle has a spherical core with Fe3O4 superparamagnetic nanoparticles, and its surface area is significantly larger than that of a typical Fe3O4@Co5Al-LDH particle. Figure 1 The Fe3O4 superparamagnetic nanoparticles shown in Figure a are more porous, exhibiting outward-protruding lamellar structures, and their overall size is slightly larger than that of pure Fe3O4 superparamagnetic nanoparticles. Figure 1 As shown in Figure d, the structure of Fe3O4@Co5Al-LDH particle agglomerates is... Figure 1 The structure shown in Figure c is more complex, with clearly visible lamellar structures on the surface of each Fe3O4@Co5Al-LDH particle. These lamellar structures intertwine, giving the Fe3O4@Co5Al-LDH particle aggregates a greater sense of layering and fluffiness. This indicates the successful preparation of a magnetic cobalt-aluminum layered double hydroxide composite catalyst. Co5Al-LDH was successfully coated onto the surface of Fe3O4 superparamagnetic nanoparticles in a lamellar structure, forming a core-shell composite structure. While the composite Fe3O4 superparamagnetic nanoparticles still exhibit agglomeration, the spatial structure and morphology of the Fe3O4@Co5Al-LDH particle aggregates are significantly different from those of pure Fe3O4 superparamagnetic nanoparticle aggregates due to the presence of the lamellar structure.
[0087] Transmission electron microscope images of the Fe3O4 superparamagnetic nanoparticles and Fe3O4@Co5Al-LDH obtained in this embodiment are as follows: Figure 2As shown in a and b, the Fe3O4 superparamagnetic nanoparticles are spherical / near-spherical with relatively rounded outlines. Some particles exhibit slight irregularities, and clear single-particle boundaries are visible. Their size is approximately 50-100 nm, showing good uniformity. The Fe3O4@Co5Al-LDH exhibits a distinct core-shell composite structure, with Fe3O4 superparamagnetic nanoparticles as the core and Co5Al-LDH sheet-like structures coating the surface. The overall size of Fe3O4@Co5Al-LDH is larger than that of pure Fe3O4 superparamagnetic nanoparticles, and the aggregation phenomenon is more pronounced. This indicates the successful synthesis of Fe3O4 superparamagnetic nanoparticles with uniform size and regular morphology, possessing the typical TEM characteristics of magnetic metal oxide nanoparticles. Simultaneously, the growth and coating of Co5Al-LDH on the surface of Fe3O4 superparamagnetic nanoparticles was achieved, forming a well-defined core-shell composite structure. The core-shell composite structure fully preserves the core structure of Fe3O4 superparamagnetic nanoparticles, while also endowing the material with the unique layered and lamellar morphology of LDH, proving the successful composite of Fe3O4 superparamagnetic nanoparticles and Co5Al-LDH.
[0088] The X-ray diffraction patterns of the Fe3O4 superparamagnetic nanoparticles and Fe3O4@Co5Al-LDH obtained in this embodiment are as follows: Figure 3 As shown, the Fe3O4 superparamagnetic nanoparticles exhibited distinct characteristic diffraction peaks at 2θ = 30.1°, 35.5°, 43.2°, 53.5°, 57.1° and 62.6°, which correspond to the (220), (311), (400), (422), (511) and (440) crystal planes of the Fe3O4 superparamagnetic nanoparticles, respectively. The Fe3O4@Co5Al-LDH composite exhibits characteristic diffraction peaks from the Fe3O4 superparamagnetic nanoparticles (such as diffraction peaks from the (220), (311), and (400) crystal planes) after being combined with Co5Al-LDH. This indicates that the crystal structure of the Fe3O4 superparamagnetic nanoparticles was not destroyed during the preparation of Fe3O4@Co5Al-LDH, and its original structure was maintained. Furthermore, characteristic diffraction peaks of Co5Al-LDH appeared at 2θ = 11.7°, 23.6°, 34.7°, 39.3°, and 46.9°, corresponding to the (003), (006), (012), (015), and (018) crystal planes of Co5Al-LDH, which are basically consistent with the characteristic peak positions in the standard CoAl-LDH spectrum. This demonstrates the successful preparation of Fe3O4@Co5Al-LDH.
[0089] The Fourier transform infrared spectra of the Fe3O4 superparamagnetic nanoparticles, Co5Al-LDH, and Fe3O4@Co5Al-LDH obtained in this embodiment are as follows: Figure 4As shown: Fe3O4 superparamagnetic nanoparticles at 581 cm⁻¹ -1 The adsorption peak at 3440 cm⁻¹ is attributed to the Fe-O-Fe vibration, a characteristic peak of Fe₃O₄ superparamagnetic nanoparticles; -1 A broad and strong absorption peak appears at 1639 cm⁻¹, which belongs to the OH stretching vibration peak of surface adsorbed water; -1 The absorption peak at 3440 cm⁻¹ corresponds to the HOH bending vibration peak of adsorbed water. Co₅Al-LDH shows an absorption peak at 3440 cm⁻¹. -1 The broad peak at 1600 cm⁻¹ represents the OH stretching vibration peak of interlayer water and hydroxyl groups; -1 The peak of the HOH bending vibration of interlayer water is located at 1393 cm⁻¹. -1 The strong absorption peak at that point corresponds to the LDH interlayer. The stretching vibration peak; 833cm -1 591cm -1 The absorption peak at 591 cm⁻¹ belongs to the stretching vibration peak of the metal-oxygen bond (Co-O, Al-O), which is a typical characteristic of LDH materials. Fe₃O₄@Co₅Al-LDH exhibits both the characteristic absorption peaks of Fe₃O₄ superparamagnetic nanoparticles and Co₅Al-LDH: retaining the characteristic absorption peak of Fe₃O₄ superparamagnetic nanoparticles at 591 cm⁻¹. -1 The characteristic peaks of the Fe-O bond at this location also show that Co5Al-LDH occurs at 1649 cm⁻¹. -1 (Water bending vibration), 1393cm -1 ( Characteristic absorption peaks of stretching vibrations and metal-oxygen bonds; compared with the single material, the positions of some characteristic peaks are slightly shifted after composite formation (e.g., 1649 cm⁻¹). -1 Comparison with 1600cm -1 1639cm -1 Furthermore, the peak intensity also changed. This indicates that Fe3O4@Co5Al-LDH was successfully prepared, and the composite material simultaneously possesses the characteristic absorption peaks of both Fe3O4 superparamagnetic nanoparticles and Co5Al-LDH. The shift and intensity changes of the peaks indicate an interaction between the two materials, proving that Co5Al-LDH was successfully coated on the surface of Fe3O4 superparamagnetic nanoparticles, forming a core-shell composite structure.
[0090] The magnetometer images of the vibrating samples of Fe3O4 superparamagnetic nanoparticles and Fe3O4@Co5Al-LDH obtained in this embodiment are as follows: Figure 5As shown, both the Fe3O4 superparamagnetic nanoparticles and Fe3O4@Co5Al-LDH exhibit S-shaped hysteresis loops with no significant remanence or coercivity, typical characteristics of superparamagnetic materials. The saturation magnetizations of the Fe3O4 superparamagnetic nanoparticles and Fe3O4@Co5Al-LDH are 68.0 emu / g and 64.0 emu / g, respectively. Compared to the Fe3O4 superparamagnetic nanoparticles, the magnetic intensity of Fe3O4@Co5Al-LDH is slightly lower, but its magnetization curves demonstrate sufficient superparamagnetism to meet the requirements for rapid magnetic separation between the solid material and the liquid matrix. This indicates that Co5Al-LDH was successfully coated on the surface of the Fe3O4 superparamagnetic nanoparticles, forming a core-shell composite structure.
[0091] Example 2: Experiment on the degradation of pesticides by catalyst The catalytic experiment was conducted in an Erlenmeyer flask. 35 mg of catalyst was added to 20-25 mL of a mixture containing the target pesticides (atrazine, metalaxyl, and flutriafol, all at 30 mg / L), followed by the addition of 4.0 mM persulfate to initiate the catalytic reaction. The reaction was carried out under shaking conditions at room temperature and neutral pH. After ultrasonic dispersion, the Erlenmeyer flask was placed on a constant-temperature shaker and reacted at 220 rpm for 15 minutes. 500 μL of the reaction solution was drawn off, and 500 μL of methanol was added. The reaction was terminated by mixing. The mixture was then transferred to a sample vial through a 0.22 μm filter membrane, and the pesticide residue concentration was measured. The results showed that the degradation efficiency of all three pesticides reached 100% within 15 minutes.
[0092] This embodiment addresses the coexistence of multiple pesticides in actual water bodies, verifying the broad-spectrum and high-efficiency nature of the catalyst for the treatment of complex pollution. Specifically, it demonstrates the simultaneous and efficient degradation capability of different types of pesticides, such as triazine (atrazine), amide (metalaxyl), and triazole (fluticasone), overcoming the limitation of most studies that only target single pollutants.
[0093] To investigate the adsorption and degradation effect and mechanism of the magnetic cobalt-aluminum layered double hydroxide composite catalyst Fe3O4@Co5Al-LDH on pesticides, the following experiments were conducted.
[0094] Experimental Example 1: Persulfate activation performance of Fe3O4@Co5Al-LDH The degradation performance of different catalyst / persulfate systems (including Fe3O4 superparamagnetic nanoparticles alone, Fe3O4@Co5Al-LDH alone, persulfate alone, Fe3O4 superparamagnetic nanoparticles / persulfate, and Fe3O4@Co5Al-LDH / persulfate system) on atrazine, metalaxyl, and flutriafol was evaluated. The results are as follows: Figure 6-8As shown in the figure, the degradation efficiencies of atrazine, metalaxyl, and flutriafol in the Fe3O4 superparamagnetic nanoparticle system and the Fe3O4@Co5Al-LDH system alone are negligible (<15%), indicating that the Fe3O4 superparamagnetic nanoparticles and Fe3O4@Co5Al-LDH have poor adsorption and degradation capabilities for these three pesticides. Furthermore, in the persulfate system alone, the degradation efficiencies of atrazine, metalaxyl, and flutriafol within 15 minutes are 85%, 50%, and 51%, respectively, indicating that persulfate has a certain degradation capacity for these three pesticides, while the better degradation effect of atrazine may be related to its relatively simple structure. When Fe3O4 superparamagnetic nanoparticles are used as a catalyst to activate persulfate, the degradation efficiencies of atrazine and metalaxyl within 15 minutes are only 60%, and flutriafol is only 51%, indicating that the Fe3O4 superparamagnetic nanoparticles have a weak ability to activate persulfate to generate free radicals. In contrast, in the Fe3O4@Co5Al-LDH / persulfate system, the degradation efficiency of atrazine and metalaxyl reached 100% within 10 minutes, and the degradation efficiency of flutriafol reached 92% within 15 minutes. This indicates that Fe3O4@Co5Al-LDH can effectively activate persulfate, and the loading of Co5Al-LDH can enhance the catalytic performance of the material.
[0095] Experimental Example 2: Effects of different factors on the Fe3O4@Co5Al-LDH / persulfate system 1. Effect of solution pH Solution pH significantly affects the persulfate activation system because the initial pH alters the form of persulfate and pesticides, changes the surface active sites of Fe3O4@Co5Al-LDH, and leads to free radical evolution. For example... Figure 9-11 As shown, atrazine, metalaxyl, and flutriafol can all be effectively degraded at different pH values, with the best degradation effect at pH 7.0. In contrast, the degradation effect is poor at pH 9.0, possibly due to the formation of hydroxide precipitates and the presence of SO4• - It is converted into •OH, which has lower reactivity.
[0096] 2. The effect of initial pesticide concentration The effects of different initial pesticide concentrations on degradation efficiency are as follows: Figure 12-14As shown, when the initial concentration of atrazine gradually increased from 5 mg / L to 40 mg / L, the degradation efficiency slowly decreased from 100% to 95%; when the concentration increased from 40 mg / L to 50 mg / L, the degradation efficiency decreased to 89%. This may be because the number of active sites on the Fe3O4@Co5Al-LDH surface for effectively activating persulfate is limited, resulting in insufficient active substances to rapidly decompose large amounts of atrazine. Metalaxyl showed a similar trend, but at a concentration of 50 mg / L, its degradation efficiency still reached 95%. In contrast, flutriafol achieved its minimum degradation efficiency (82%) at a concentration of 40 mg / L, with no significant difference between 30 mg / L and 40 mg / L. Therefore, to save costs, a concentration of 30 mg / L for atrazine, metalaxyl, and flutriafol was ultimately chosen as the optimal experimental condition.
[0097] 3. Effect of persulfate concentration Generally, the concentration of persulfate plays a crucial role in the oxidation capacity of advanced oxidation processes. The effects of persulfate concentration are as follows: Figure 15-17 As shown, when the persulfate concentration increased from 1.0 mM to 4.0 mM, the degradation efficiency of atrazine, metalaxyl, and flutriafol significantly improved. This is likely because the higher persulfate concentration enhanced the utilization of the Fe3O4@Co5Al-LDH surface active sites, thereby generating active substances for degradation more quickly. However, when the persulfate concentration increased from 4.0 mM to 5.0 mM, the degradation efficiency of atrazine, metalaxyl, and flutriafol improved slowly, possibly due to the excessive SO4• - It undergoes a self-quenching reaction, and excess persulfate can also react with SO4• - The reaction produces SO5•, which has a weak oxidizing ability. - Therefore, 4.0 mM persulfate was ultimately chosen as the optimal experimental condition.
[0098] 4. Effect of catalyst dosage The amount of catalyst used is a key factor affecting the degradation performance of pesticides. For example... Figure 18-20 As shown, the degradation efficiency of atrazine, metalaxyl, and flutriafol gradually increased when the dosage of Fe3O4@Co5Al-LDH increased from 20 mg to 35 mg. This is likely because the increased dosage of Fe3O4@Co5Al-LDH led to a greater number of active sites on its surface, expanding the catalytic surface area and thus significantly improving the degradation efficiency. When the dosage of Fe3O4@Co5Al-LDH increased from 35 mg to 40 mg, the degradation efficiency of atrazine, metalaxyl, and flutriafol increased slowly. Considering both degradation efficiency and cost, 35 mg of Fe3O4@Co5Al-LDH was ultimately selected as the optimal experimental condition.
[0099] 5. The influence of coexisting inorganic ions High concentrations of anions are prevalent in natural water bodies. These anions often compete with target pesticide pollutants for reactive oxygen species (ROS) generated during the catalytic process, thus affecting the degradation efficiency of the target pesticide pollutants. Therefore, a solution containing five common anions (including...) was prepared. , , , and SO4• - Solutions with concentrations of 5.0 mM and 10.0 mM were prepared to investigate their effect on the Fe3O4@Co5Al-LDH / persulfate system. The results are as follows: Figure 21-23 As shown.
[0100] It showed inhibitory effects on all three pesticides, which is due to the interaction between persulfate and... The reaction produces active chlorine species such as hypochlorous acid (HClO) and chlorine gas (Cl2), thereby reducing the pesticide degradation efficiency, and with... The inhibitory effect becomes more pronounced with increasing concentration.
[0101] The inhibitory effect on atrazine is weak, but increases with increasing concentration. This may be due to... With SO4• - •OH reacts to generate carbonate free radicals (CO3• - CO3• - The reactivity is lower than that of SO4• - The presence of •OH and 5.0 mM leads to a decrease in degradation efficiency. It promoted the degradation of fluconazole, while 10.0 mM It exhibits an inhibitory effect on its degradation, which indicates that the dissolved It can act as a buffer in the reaction solution, helping to maintain a favorable pH environment for the degradation of fluconazole, but at higher concentrations... It may alter the reaction conditions, making them unfavorable for degradation. and It neither inhibits nor promotes the degradation of metalaxyl.
[0102] and The presence of these ions promotes the degradation of atrazine and flutriafol, possibly because these ions can convert the solution into an alkaline buffer solution, and a weakly alkaline environment is conducive to the degradation of atrazine and flutriafol. HPO4 2- It has no inhibitory or promoting effect on the degradation of metalaxyl.
[0103] SO4 2-It showed an inhibitory effect on all three pesticides, and the addition of SO4 2- The slight inhibition observed later may be due to SO4 2- Simultaneously generating active substances and SO4• - It has an inhibitory effect on the chain reaction, possibly because it can reduce SO4• - SO4 2- The redox potential of persulfate decreases, leading to a decrease in its activation efficiency.
[0104] Experimental Example 3: Stability Study of Catalysts Catalyst stability and reusability are important evaluation indicators affecting their practicality. To investigate the catalytic stability of Fe3O4@Co5Al-LDH, three cyclic degradation experiments were conducted under the same experimental conditions. After each experiment, the catalyst was collected from the aqueous solution using a magnet, washed three times with methanol, and dried at 60℃ for reuse. The results are as follows: Figure 24-26 As shown, after three cycles of degradation experiments, the degradation efficiency of atrazine and metalaxyl remained at 100%, while the degradation efficiency of flutriafol was 92%. Specifically, the catalytic performance of Fe3O4@Co5Al-LDH remained relatively stable; after each cycle, metalaxyl and atrazine could still be completely degraded within 15 minutes. However, after the third cycle, the degradation efficiency of flutriafol decreased by 8%. The decrease in degradation efficiency may be due to the loss of a small amount of material during degradation and the possible adhesion of small molecule intermediates to the Fe3O4@Co5Al-LDH surface, leading to a decrease or deactivation of some active sites, hindering the reaction between Fe3O4@Co5Al-LDH and persulfate, and thus inhibiting SO4• - The formation of OH and •OH slightly reduces the degradation efficiency of flutriafol. Overall, Fe3O4@Co5Al-LDH exhibits excellent stability and reusability potential.
[0105] Experimental Example 4: Reaction Mechanism Study The type of active substances in the reaction system is crucial for exploring pesticide degradation pathways. This experimental example investigated the formation of active substances in the Fe3O4@Co5Al-LDH / persulfate system by adding an excess of free radical quencher to the reaction mixture. It is generally believed that •OH and SO4• - These are active free radicals participating in the reaction within the catalytic system. Furthermore, ¹ O2 and O2• - It may also attack organic compounds. Tert-butanol (TBA) is used as a specific scavenger of •OH, and methanol (MeOH) is used as a scavenger of both •OH and SO4•. - The specific scavengers, p-benzoquinone (p-BQ) and L-histidine (L-his), are used for quenching.¹ O2 and O2• - The concentrations of tert-butanol and methanol were both 500 mM, and the concentrations of p-benzoquinone and L-histidine were both 10 mM. The results are as follows... Figure 27-29 As shown, compared with the blank control, the addition of MeOH and TBA to the reaction system reduced the degradation rate of atrazine by 27% and 17%, respectively, proving the presence of •OH and SO4• in the reaction system. - Furthermore, these free radicals play an important role in the degradation of atrazine. In addition, the addition of L-his and p-BQ showed a weak inhibitory effect in the first 10 minutes of the reaction, indicating the possible presence of... ¹ O2 and O2• - However, their role in removing atrazine is negligible. The results for metalaxyl and flutriafol are consistent with this finding.
[0106] Furthermore, electron paramagnetic resonance (EPR) technology was used to further detect potentially active substances in the Fe3O4@Co5Al-LDH / persulfate system. The results are shown in Figure 30, where DMPO-•OH and DMPO-SO4• were detected. - The signal indicates the presence of •OH and SO4• in the reaction system. - In addition, DMPO-O2• was also detected. - This indicates that O2• - It exists within the system, but its contribution to the pesticide degradation process is not significant. Furthermore, such as... Figure 31 As shown, in TEMP capture ¹ A triplet peak was observed in the spectrum obtained from O2, which may be produced by the decomposition of persulfate in the reaction system. ¹ O2. The EPR results indirectly validated the experimental data on free radical quenching. This indicates that the degradation process of these three pesticides is controlled by a combination of free radical and non-free radical pathways.
[0107] To further investigate the reaction mechanism of Fe3O4@Co5Al-LDH activation of persulfate for pesticide degradation, X-ray photoelectron spectroscopy (XPS) characterization analysis was performed on Fe3O4@Co5Al-LDH before and after the reaction. By comparing the changes in surface chemical composition and elemental content of Fe3O4@Co5Al-LDH, the possible reaction mechanism can be inferred, and the results are as follows: Figure 32 As shown, two new characteristic absorption bands appeared on the Fe3O4@Co5Al-LDH surface, namely Cl 2p and F 1s, indicating that atrazine and flutriafol were adsorbed on the Fe3O4@Co5Al-LDH surface. Figure 33It can be observed that two new peaks appeared in the C 1s spectrum after the reaction, located at 292.76 and 295.52 eV, corresponding to the C-F3 peak and π-π oscillating satellite peak, respectively, indicating that metalaxyl may have been adsorbed onto the Fe3O4@Co5Al-LDH surface. Furthermore, the contents of C=C and OC=O decreased from 57.35% and 16.24% to 48.29% and 8.25%, respectively, while the CO content increased from 26.41% to 34.46%. Figure 34 As shown, lattice oxygen (O L The content of ) decreased from 58.19% to 24.52%. Conversely, the content of oxygen vacancies (O) increased. V The content of oxygen increased from 19.08% to 52.79%, indicating that oxygen atoms can indeed be removed from the crystal lattice to form O. V Adsorbed oxygen or surface adsorbed hydroxyl groups (O) O The content of [specific component] changed relatively little, decreasing from 22.72% to 22.69%. For example... Figure 35 As shown, Co before the reaction 2+ and Co 3+ The proportions were 44.43% and 55.57%, respectively. After degradation, the Co content in the Fe3O4@Co5Al-LDH system... 3+ The content of [unclear] decreased to 45.81%, while Co [unclear] 2+ The content increased to 54.19%, indicating that Co... 3+ Converted to Co 2+ .from Figure 36 It can be seen that after degradation occurs, Fe in the system 2+ The content decreased from 61.71% to 45.46%, Fe 3+ The content increased from 38.29% to 54.54%. This indicates that Fe... 2+ To Fe 3+ The conversion. Furthermore, PMS can be used for Fe... 3+ It provides electrons, thereby completing the redox cycle.
[0108] This invention, through comprehensive analysis, proposes the following reaction mechanism for the degradation of pesticides by Fe3O4@Co5Al-LDH activated persulfate at the atomic scale: The free radical pathway involves four free radicals (•OH, SO4•). - O2• - and ¹ The generation of O2. Initially, HSO5 - Fe, a divalent metal ion 2+ / Co 2+ Activation, generating SO4• - and the corresponding trivalent metal ion Fe 3+ / Co 3+Subsequently, Fe 3+ / Co 3+ HSO5 - Reduction yields SO5• - And two divalent metal ions, thus realizing a redox cycle between divalent and trivalent metal ions. Furthermore, Fe... 2+ Co 3+ Reduced to Co 2+ Thus promoting Co 2+ / Co 3+ and Fe 2+ / Fe 3+ The degradation of the target pesticide mainly relies on the reaction of •OH and SO4•. - The oxidation process.
[0109] This clear understanding of the mechanism not only ensures that the target pesticide pollutants can be effectively mineralized by strong oxidizing free radicals, but also provides reliable theoretical guidance for further targeted optimization of catalysts.
[0110] This invention discloses a magnetic cobalt-aluminum layered double hydroxide composite catalyst, its preparation method, and its application in pesticide degradation. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The product of this invention has been described through preferred embodiments, and those skilled in the art will clearly be able to modify or appropriately change and combine the product without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.
Claims
1. A magnetic cobalt-aluminum layered double hydroxide composite catalyst, characterized in that, The catalyst is composed of Fe3O4 superparamagnetic nanoparticles and Co5Al layered double hydroxide.
2. The preparation method of the magnetic cobalt-aluminum layered double hydroxide composite catalyst as described in claim 1, characterized in that, Includes the following steps: 1) Synthesis of Fe3O4 superparamagnetic nanoparticles; 2) Add aluminum nitrate and cobalt nitrate to deionized water, then add ammonium fluoride, urea and Fe3O4 magnetic nanoparticles and disperse them by ultrasonication; 3) Transfer the resulting mixed solution into a reaction vessel and hydrothermally react at 100℃-110℃ for 5-6 hours; 4) After the hydrothermal reaction is completed, the catalyst is cooled, washed and dried to obtain a magnetic cobalt-aluminum layered double hydroxide composite catalyst.
3. The method for preparing a magnetic cobalt-aluminum layered double hydroxide composite catalyst according to claim 2, characterized in that, The synthesis method of the Fe3O4 superparamagnetic nanoparticles is as follows: first, dissolve trisodium citrate dihydrate and sodium hydroxide in deionized water, then add sodium nitrate. The mass ratio of trisodium citrate dihydrate, sodium hydroxide and sodium nitrate is (1.1-2):(0.5-1.0):(14-20). Stir the resulting mixed solution continuously at 100-110℃ for 15-30 minutes until a transparent solution is formed. Add FeSO4•7H2O solution and continue stirring for 1-2 hours. After washing, dry at 60-70℃ for 6-12 hours.
4. The method for preparing a magnetic cobalt-aluminum layered double hydroxide composite catalyst according to claim 2, characterized in that, In step 2), the molar ratio of aluminum nitrate, cobalt nitrate, ammonium fluoride and urea is (0.5-1.5):(3-7):(10-20):(20-30).
5. The method for preparing a magnetic cobalt-aluminum layered double hydroxide composite catalyst according to claim 2, characterized in that, In step 2), the mass ratio of the Fe3O4 superparamagnetic nanoparticles to the total mass of aluminum nitrate, cobalt nitrate, ammonium fluoride, and urea is 1:(5-20).
6. The method for preparing a magnetic cobalt-aluminum layered double hydroxide composite catalyst according to claim 2, characterized in that, In step 4), dry under vacuum at 60-70℃ for 5-8 hours.
7. The application of the magnetic cobalt-aluminum layered double hydroxide composite catalyst as described in claim 1 in the degradation of pesticides.
8. The application according to claim 7, characterized in that, Includes the following steps: 1) Add the catalyst to the water containing pesticides; 2) Add persulfate to initiate the catalytic reaction; 3) Perform the shaking reaction for 10-15 minutes at room temperature and pH = 3.0-11.0; 4) After the reaction is complete, the catalyst is separated and recovered by an external magnetic field.
9. The application according to claim 7, characterized in that, The catalyst is added in an amount of 20-40 mg / L.
10. The application according to claim 7, characterized in that, The amount of persulfate added is 0.4-5.0 mM.