Mo, k co-doped mn02 catalyst, preparation method thereof and method for degrading pollutants by activating peroxyacetic acid

Abstract

The application provides a Mo and K co-doped MnO2 catalyst, which is obtained by doping Mo and K in alpha-MnO2 nanowires, and Mo and K are uniformly distributed on the surface and tunnel structure of the alpha-MnO2 nanowires, and the catalyst has a hydroxyl functional group. The application also provides a preparation method of the catalyst, and a method for degrading pollutants by activating peracetic acid with the catalyst, wherein peracetic acid and the catalyst are added into wastewater containing organic pollutants under stirring, and the pH value of the wastewater is controlled to be 5-9; in the wastewater treatment process, the catalyst activates the peracetic acid to generate organic free radicals and singlet oxygen to degrade the organic pollutants in the wastewater. The application can improve the ability of the MnO2-based catalyst to activate peracetic acid to generate active species to degrade organic pollutants, and solves the problems that the existing MnO2-based catalyst has low ability to activate peracetic acid and poor degradation ability for organic pollutants.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and relates to Mo and K co-doped MnO2 catalysts and their preparation methods, as well as methods for activating peracetic acid to degrade pollutants. Background Technology

[0002] Naproxen (NAP) is a typical nonsteroidal anti-inflammatory drug (NSAID) with anti-inflammatory, antipyretic, and analgesic effects. Due to its few side effects and good tolerability, it is widely used globally. With the increasing popularity of NAP, it has been frequently detected in natural water bodies in recent years. After being ingested by humans, NAP's incomplete metabolites are excreted into wastewater systems and eventually enter natural water bodies. Characterized by low concentrations, large production volumes, and significant toxicity to aquatic organisms, NAP is classified as a biohazardous drug (PhACs) and poses a potential threat to ecological safety. Therefore, targeted treatment of NAP has gradually gained attention.

[0003] Because NAP (non-phosphorus acid) in water bodies inhibits microorganisms, traditional biological treatment methods often fail to achieve the desired results. Some commonly used chemical oxidation methods often suffer from drawbacks such as low oxidant utilization efficiency, significant secondary pollution, and unsatisfactory pollutant removal. In recent years, advanced oxidation processes (AOPs) have attracted attention and are increasingly being applied to the degradation of PhACs due to their advantages, including thorough oxidation of PhACs, low oxidant consumption, high pollutant removal efficiency, and less secondary pollution.

[0004] Peracetic acid (PAA) is a novel oxidant emerging in wastewater treatment and disinfection, showing great potential in advanced oxidation processes due to its unique chemical properties and molecular structure. Compared with many traditional oxidants, PAA not only has higher oxidizing power but also produces fewer disinfection byproducts. These two characteristics make PAA a promising disinfectant and oxidant for degrading organic micropollutants in water. However, PAA is difficult to directly oxidize and degrade most pollutants. To improve the removal efficiency of PAA, activation treatment is necessary. During PAA activation, O-O bonds break, generating active species with strong oxidizing power. These active species can be used to degrade organic pollutants in water. Currently, PAA is mainly activated through energy input (e.g., ultraviolet irradiation, heating, or ultrasound) or catalysts (metal ions or heterogeneous catalysts). Among these, catalyst activation is relatively more economical and efficient, while heterogeneous catalyst activation of PAA has advantages in catalyst recovery and prevention of secondary pollution.

[0005] Transition metals are considered a viable class of catalysts due to their high abundance and low cost. MnO2, with its considerable surface reserves, low price, and non-toxic nature, along with diverse crystal structures and oxidation states, is a catalyst of great research and application value. Despite these advantages, current MnO2-based catalysts are not very effective at activating PAA (particulate organic compounds) to degrade pollutants. Therefore, it is necessary to further improve existing MnO2-based catalysts for activating PAA to generate higher oxidation-active species, in order to effectively enhance their ability to activate PAA and degrade pollutants. Summary of the Invention

[0006] To address the problem that existing MnO2-based catalysts have poor degradation capabilities for organic pollutants when activating peracetic acid (PAA), this invention improves upon existing MnO2-based catalysts used for PAA activation by providing a Mo / K co-doped MnO2 catalyst, its preparation method, and a method for activating peracetic acid to degrade pollutants based on this Mo / K co-doped MnO2 catalyst. This enhances the ability of existing MnO2-based catalysts to activate PAA and generate active species to degrade organic pollutants.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0008] A Mo / K co-doped MnO2 catalyst is obtained by doping Mo and K into α-MnO2 nanowires. Mo and K are uniformly distributed on the surface and in the tunnel structure of the α-MnO2 nanowires. The catalyst contains hydroxyl functional groups. The preparation method of the catalyst includes the following steps:

[0009] (1) Mix α-MnO2 nanowires with KOH solution thoroughly and place them in a high-pressure reactor. React at 140-160℃ for 3-6 hours. Wash the reaction product with water until the washing liquid is neutral. Dry the product to obtain K-doped MnO2.

[0010] In this step, α-MnO2 nanowires are thoroughly mixed with KOH solution at a molar ratio of K to Mn of 1:(0.115~0.144);

[0011] (2) Add the K-doped MnO2 prepared in step (1) to water, and add (NH4)6Mo7O 24 ·4H2O, stir at 35-45℃ for 10-15h, then stir at 55-65℃ for 1-3h, then stir at 75-85℃ for 1-3h, dry the resulting reaction product and calcine at 300-400℃ in air for 3-6h to obtain the Mo and K co-doped MnO2 catalyst.

[0012] In this step, (NH4)6Mo7O is controlled.24 The mass ratio of 4H2O to K-doped MnO2 is (0.03~0.04):1.

[0013] Among the above-mentioned technical solutions for Mo and K co-doped MnO2 catalysts, a feasible method for preparing α-MnO2 nanowires is as follows: KMnO4 and MnSO4·H2O are dissolved in water, and the molar ratio of KMnO4 to MnSO4·H2O is controlled at 1:(1.6~1.65). The mixture is thoroughly mixed, and the resulting mixed solution is placed in an autoclave and reacted at 150~152℃ for 12~13h. The reaction product is washed with water and dried to obtain the final product.

[0014] In the above-mentioned technical solution of Mo and K co-doped MnO2 catalyst, in order to increase the uniformity of K and Mo loading on α-MnO2 nanowires, step (1) is preferably carried out after obtaining K-doped MnO2, grinding or pulverizing the K-doped MnO2 into a uniform powder state before carrying out the reaction in step (2). Step (2) is preferably carried out after drying the obtained reaction product, grinding or pulverizing it into a uniform powder state before calcining it in an air atmosphere at 300-400℃.

[0015] The present invention, through relevant characterization experiments, confirms that the morphology of the above-mentioned Mo and K co-doped MnO2 catalyst is a bundle-like nanowire structure with a length of 1–2.5 μm and a diameter of 61–68 nm. Mo and K are uniformly dispersed on the surface and in the tunnel structure of the α-MnO2 nanowires. The doping of Mo and K causes the expansion of the tunnels in the α-MnO2 nanowires to a certain extent, but does not significantly affect the crystal phase of the α-MnO2 nanowires. At the same time, the doping of Mo and K forms hydroxyl groups on the surface of the α-MnO2 nanowires, which is beneficial to enhancing the hydrophilicity of the obtained catalyst and its dispersibility in aqueous media. In the Mo and K co-doped MnO2 catalyst, the valence state of Mn is MnO2. 2+ Mn 3+ Mn 4+ , Mo valence state is Mo 4+ Mo 6+ The price state of K is K + .

[0016] This invention also provides a method for activating peracetic acid to degrade pollutants using the above-mentioned Mo, K co-doped MnO2 catalyst, comprising the following steps:

[0017] Peracetic acid and the above-mentioned Mo, K co-doped MnO2 catalyst were added to wastewater containing organic pollutants. The wastewater was treated under stirring conditions, and the pH value of the wastewater was controlled to be 5-9. During the wastewater treatment process, the Mo, K co-doped MnO2 catalyst activated the peracetic acid to generate organic free radicals and singlet oxygen to degrade the organic pollutants in the wastewater. After the treatment of one batch of wastewater was completed, the Mo, K co-doped MnO2 catalyst was recovered for the treatment of the next batch of wastewater.

[0018] In the above-mentioned method for activating peracetic acid to degrade pollutants using a Mo and K co-doped MnO2 catalyst, the organic free radicals include CH3C(O)O· and CH3C(O)OO·.

[0019] In the above-mentioned technical solution of the method for activating peracetic acid to degrade pollutants using Mo and K co-doped MnO2 catalyst, the dosage of Mo and K co-doped MnO2 catalyst in wastewater can be adjusted according to the water quality of the wastewater. Preferably, the dosage of Mo and K co-doped MnO2 catalyst in wastewater is 0.05 to 0.15 g / L.

[0020] In the above-mentioned technical solution of the method for activating peracetic acid to degrade pollutants using Mo and K co-doped MnO2 catalyst, the dosage of peracetic acid in wastewater can be adjusted according to the water quality of the wastewater. Preferably, the dosage of peracetic acid in wastewater should be such that the concentration of peracetic acid in the wastewater is 0.3 to 0.4 mmol / L.

[0021] This invention demonstrates through experiments that, when the Mo, K co-doped MnO2 catalyst is activated to degrade naproxen wastewater using peracetic acid, recycling the Mo, K co-doped MnO2 catalyst four times maintains a naproxen removal rate of over 90%, and recycling it five times maintains a naproxen removal rate of over 86%. Therefore, in practical applications, the Mo, K co-doped MnO2 catalyst can be recycled to reduce wastewater treatment costs. The minimum recycling number is five times, and the specific number of recycling times can be determined based on the requirements for pollutant degradation rate, degradation efficiency, and cost in practical applications. Typically, the recycling number of the Mo, K co-doped MnO2 catalyst can be 5 to 10 times.

[0022] This invention experimentally confirms that low concentrations (e.g., concentrations not exceeding 0.5 mmol / L) of anions Cl⁻, H₂PO₄⁻, and HCO₃⁻, as well as humic acid (HA), in water bodies have virtually no adverse effect on the ability of Mo / K-MnO₂ to activate PAA and degrade NAP. This indicates that Mo / K-MnO₂ can resist the adverse effects of low concentrations of common water matrix on the activated PAA degradation of organic pollutants. Therefore, in the above-mentioned method for activating peracetic acid to degrade pollutants using a Mo / K co-doped MnO₂ catalyst, the wastewater containing organic pollutants also contains at least one of Cl⁻, H₂PO₄⁻, HCO₃⁻, and humic acid. Generally, the concentration of anions Cl⁻, H₂PO₄⁻, HCO₃⁻, or humic acid does not exceed 0.5 mmol / L.

[0023] In the above-mentioned technical solution of the method for activating peracetic acid to degrade pollutants using Mo and K co-doped MnO2 catalyst, the wastewater treatment time can be determined according to the specific wastewater quality (e.g., the type and concentration of organic pollutants). Generally, the treatment time is sufficient until the removal rate of organic pollutants in the wastewater reaches equilibrium. Typically, the wastewater treatment time should not exceed 60 minutes. For example, the wastewater treatment time can be controlled within 20–60 minutes, 20–40 minutes, or 20–30 minutes.

[0024] In the above-mentioned technical solution of the method for activating peracetic acid to degrade pollutants with Mo and K co-doped MnO2 catalyst, the temperature of the wastewater does not significantly affect the degradation efficiency and effect during wastewater treatment. In order to save wastewater treatment costs, wastewater treatment can usually be carried out at room temperature, for example, the temperature of the wastewater can be controlled between 5 and 35°C.

[0025] In the above-mentioned method for activating peracetic acid to degrade pollutants using a Mo and K co-doped MnO2 catalyst, the organic pollutants in the wastewater containing organic pollutants can be nonsteroidal anti-inflammatory drugs, especially naproxen.

[0026] In the above-mentioned technical solution of the method for activating peracetic acid to degrade pollutants using Mo and K co-doped MnO2 catalyst, it is best to control the stirring conditions during the wastewater treatment process to keep the Mo and K co-doped MnO2 catalyst in a fluidized state.

[0027] This invention preliminarily assesses the application prospects of Mo, K co-doped MnO2 catalysts. The method for activating peracetic acid (PAA) to degrade pollutants using the Mo, K co-doped MnO2 catalyst provided by this invention is mainly used in the advanced wastewater treatment process, belonging to advanced oxidation technology for wastewater treatment. Compared with traditional water treatment processes, advanced treatment processes remove additional pollutants, thus incurring additional financial costs and energy consumption. Compared with other advanced treatment processes, advanced oxidation technology has a significant economic advantage in terms of construction investment and operating costs due to its lower construction and installation costs, equipment replacement costs, and chemical and energy consumption. The application cost of the method for activating peracetic acid to degrade pollutants using the Mo, K co-doped MnO2 catalyst provided by this invention in water treatment mainly comes from the construction investment of the process unit and the consumption of chemical reagents. Based on the preparation process and raw material costs of the Mo, K co-doped MnO2 catalyst, the production cost of this catalyst is relatively low, approximately RMB 18.62 / 500g (data from Alibaba's official website). Furthermore, the catalyst exhibits good activation effect and stability of PAA and can be reused; therefore, the majority of the wastewater treatment cost is consumed in the process construction phase. Currently, the market price of PAA solution is around 14,000 yuan / ton (data from Alibaba's official website). Therefore, roughly estimated, for a PAA dosage of 300 μmol / L, the additional cost required to remove NAP at a concentration of 10 μmol / L from wastewater is only 1.29 yuan / ton. Combining the method of activating peracetic acid to degrade pollutants with the Mo, K co-doped MnO2 catalyst provided in this invention with other treatment processes (such as ozone combined with biological activated carbon process) can significantly reduce treatment costs while achieving similar effluent quality. Therefore, the method of activating peracetic acid to degrade pollutants with the Mo, K co-doped MnO2 catalyst provided in this invention has certain economic advantages in the advanced treatment of wastewater and is conducive to its promotion and application in engineering practice.

[0028] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects:

[0029] 1. This invention provides a Mo and K co-doped MnO2 catalyst. By co-doping MnO2 with Mo and K, the ability of existing MnO2-based catalysts to generate advanced oxidative active species when activating PAA is effectively improved, thus solving the problem of the ability of existing MnO2-based catalysts to generate active species to degrade organic pollutants when activating PAA.

[0030] 2. This invention also provides a method for degrading pollutants by activating peracetic acid with a Mo,K co-doped MnO2 catalyst. The method involves adding peracetic acid and a Mo,K co-doped MnO2 catalyst to wastewater containing organic pollutants, treating the wastewater under stirring conditions, and controlling the pH of the wastewater to be 5-9. During the wastewater treatment process, the Mo,K co-doped MnO2 catalyst activates the peracetic acid to generate organic free radicals (CH3C(O)O· and CH3C(O)OO·) and singlet oxygen, which degrade the organic pollutants in the wastewater. After treating one batch of wastewater, the Mo,K co-doped MnO2 catalyst is recovered for use in the treatment of the next batch of wastewater. This method can achieve highly efficient degradation of wastewater containing organic pollutants (e.g., naproxen), improving degradation efficiency while reducing wastewater treatment costs.

[0031] 3. Experiments have demonstrated that the Mo / K co-doped MnO2 catalyst described in this invention, when activating peracetic acid to degrade naproxen wastewater, maintains a naproxen removal rate of over 90% after four recycling cycles, and over 86% after five recycling cycles, exhibiting excellent recyclability. Furthermore, the method of this invention has a wide applicable pH range for wastewater, demonstrating excellent degradation performance for wastewater with pH values ​​from 5 to 9. Therefore, in practical applications, the Mo / K co-doped MnO2 catalyst can be recycled, and wastewater treatment can be carried out over a wide pH range, thereby saving on catalyst costs and reagent costs for adjusting the pH of the wastewater. These characteristics facilitate the widespread application of the catalyst and wastewater treatment method provided by this invention in engineering practice.

[0032] 4. This invention experimentally demonstrates that low concentrations (e.g., concentrations not exceeding 0.5 mmol / L) of anions Cl⁻, H₂PO₄⁻, and HCO₃⁻, as well as humic acid (HA), in water bodies have virtually no adverse effect on the ability of the Mo, K co-doped MnO₂ catalyst to activate PAA and degrade NAP. This indicates that the Mo, K co-doped MnO₂ catalyst can resist the adverse effects of low concentrations of common water matrix on the activation of PAA and degradation of organic pollutants. This also provides a guarantee for the application of the catalyst and wastewater treatment method described in this invention in practical scenarios. Attached Figure Description

[0033] Figure 1 Figures (a) to (d) are SEM images of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1 and Mo-MnO2 prepared in Comparative Example 1, respectively. Figure 1Figure (e) shows the XRD patterns of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1, and Mo-MnO2 prepared in Comparative Example 1. Figure 1 Figure (f) shows the FTIR spectra of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1 and Mo-MnO2 prepared in Comparative Example 1.

[0034] Figure 2 This is the XPS spectrum of Mo / K-MnO2 prepared in Example 1.

[0035] Figure 3 Figure (a) is a TEM image of Mo / K-MnO2 prepared in Example 1. Figure 3 Figure (b) is an HRTEM image of Mo / K-MnO2 prepared in Example 1. Figure 3 Figure (c) shows the Raman spectra of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1, and Mo-MnO2 prepared in Comparative Example 1. Figure 3 Figure (d) is the TG curve of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1 and Mo-MnO2 prepared in Comparative Example 1.

[0036] Figure 4 These are Tafel diagrams of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1 and Mo-MnO2 prepared in Comparative Example 1.

[0037] Figure 5 Figure (a) shows the change of C / CO with treatment time during the degradation of NAP in Example 3. Figure 5 Figure (b) shows the change of C / CO with treatment time when different pollutants were degraded in Example 4.

[0038] Figure 6 The results show the effects of different reaction conditions on the degradation of NAP. Figure (a) shows the effects of different Mo / K-MnO2 dosages, Figure (b) shows the effects of different PAA dosages, Figure (c) shows the effects of different NAP concentrations, Figure (d) shows the effects of different degradation temperatures, and Figure (e) shows the effects of simulated wastewater with different pH values.

[0039] Figure 7 These are the test results on the effect of the coexistence of different types of anions on the degradation effect.

[0040] Figure 8 These are test results of the degradation effect on actual wastewater containing NAP.

[0041] Figure 9 These are the results of the recycling performance test of Mo / K-MnO2.

[0042] Figure 10 These are the XRD patterns of Mo / K-MnO2 before and after use.

[0043] Figure 11 Figure (a) shows the effect of different quenchers on NAP degradation in the Mo / K-MnO2 / PAA system. Figure 11 Figure (b) shows the degradation of NB and p-CBA, which act as ·OH probes, in the Mo / K-MnO2 / PAA system. Figure 11 Figure (c) is an indication 1 Degradation of O2-generated probe DPA in the Mo / K-MnO2 / PAA system Figure 11 Figure (d) shows the experiment of premixing oxidant and catalyst. Figure 11 (e) is the high performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (HPLC-quadrupole-MS / MS) spectrum of CH3COO·-TEMPO.

[0044] Figure 12 The effects of different quenchers on the activation of PAA and degradation of NAP by MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1 and Mo-MnO2 prepared in Comparative Example 1 are investigated. Detailed Implementation

[0045] The following examples further illustrate the Mo, K co-doped MnO2 catalyst and its preparation method provided by the present invention, as well as the method for activating peracetic acid to degrade pollutants using the Mo, K co-doped MnO2 catalyst. It should be noted that the following examples are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above description are still within the scope of protection of the present invention.

[0046] In the following examples, the peracetic acid (PAA) used was analytical grade PAA.

[0047] Example 1

[0048] In this embodiment, the Mo / K co-doped MnO2 catalyst is prepared by the following steps:

[0049] (1) Dissolve KMnO4 and MnSO4·H2O in deionized water, stir thoroughly to mix evenly, pour the resulting mixed solution into a polytetrafluoroethylene-lined autoclave, react at 150℃ for 12h, wash the resulting reaction product with deionized water, centrifuge, and then dry in air at 80℃ for 10h. Grind the dried product to obtain α-MnO2. In this step, the molar ratio of KMnO4 to MnSO4·H2O is controlled to be 1:1.63.

[0050] (2) Take the α-MnO2 prepared in step (1) and mix it with 1 mol / L KOH solution. Sonicate for 20 min to mix evenly. Then transfer it to a high pressure vessel with a polytetrafluoroethylene liner and react at 150℃ for 4 h. Wash the obtained product repeatedly with deionized water and centrifuge until the washing liquid is neutral. Then dry it in an air atmosphere at 80℃. Grind the dried product to obtain powdered K-doped MnO2, which is denoted as K-MnO2.

[0051] In this step, the α-MnO2 prepared in step (1) is mixed with a 1 mol / L KOH solution at a molar ratio of K to Mn of 1:0.144.

[0052] (3) Take the K-MnO2 prepared in step (2) and add it to deionized water, then add (NH4)6Mo7O 24 ·4H2O, stir at 40℃ for 14h, then stir at 60℃ for 2h, then stir at 80℃ for 2h, dry the resulting reaction product at 110℃ for 5h, grind the dried product into powder, put it in a crucible, calcine at 400℃ for 4h in air atmosphere, grind the resulting product to obtain powdered Mo, K co-doped MnO2 catalyst, denoted as Mo / K-MnO2.

[0053] In this step, K-MnO2 is added to deionized water at a mass ratio of 1:150, and the (NH4)6Mo7O is controlled. 24 The mass ratio of 4H2O to K-MnO2 is 0.0382:1.

[0054] Comparative Example 1

[0055] In this comparative example, the preparation of the Mo-doped MnO2 catalyst (Mo-MnO2) follows these steps:

[0056] (1) Follow the same steps as in Example 1 (1).

[0057] (2) Take the α-MnO2 prepared in step (1) and add it to deionized water, then add (NH4)6Mo7O 24 ·4H2O, stir at 40℃ for 14h, then stir at 60℃ for 2h, then stir at 80℃ for 2h, dry the resulting reaction product at 110℃ for 5h, grind the dried product into powder, put it in a crucible, calcine at 400℃ for 4h in air atmosphere, grind the resulting product to obtain powdered Mo-doped MnO2 catalyst, denoted as Mo-MnO2.

[0058] In this step, MnO2 is added to deionized water at a mass ratio of 1:150, and the (NH4)6Mo7O is controlled. 24 The mass ratio of 4H2O to MnO2 is 0.0382:1.

[0059] Example 2

[0060] In this embodiment, the MnO2 (i.e., α-MnO2), K-MnO2, Mo / K-MnO2 prepared in Example 1 and the Mo-MnO2 prepared in Comparative Example 1 were characterized.

[0061] The sample was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and thermogravimetric analysis (TG).

[0062] Figure 1 Figures (a) to (d) are SEM images of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1 and Mo-MnO2 prepared in Comparative Example 1. Figure 1 Figure (e) shows the XRD patterns of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1, and Mo-MnO2 prepared in Comparative Example 1. Figure 1 Figure (f) shows the FTIR spectra of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1 and Mo-MnO2 prepared in Comparative Example 1. Figure 2 This is the XPS spectrum of Mo / K-MnO2 prepared in Example 1. Figure 3 Figure (a) is a TEM image of Mo / K-MnO2 prepared in Example 1. Figure 3 Figure (b) is an HRTEM image of Mo / K-MnO2 prepared in Example 1. Figure 3 Figure (c) shows the Raman spectra of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1, and Mo-MnO2 prepared in Comparative Example 1. Figure 3 Figure (d) is the TG curve of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1 and Mo-MnO2 prepared in Comparative Example 1. Figure 4 These are Tafel diagrams of MnO2, K-MnO2, Mo / K-MnO2 prepared in Example 1 and Mo-MnO2 prepared in Comparative Example 1.

[0063] SEM results of MnO2 and K-MnO2 showed that MnO2 had a typical nanowire morphology with a smooth surface and no agglomeration. After doping with K, and after doping with both K and Mo, the morphology of K-MnO2 and Mo / K-MnO2 remained nanowire-like, but the originally dispersed nanowires became aligned along the diameter and formed a bundle structure. Figure 1 and Figure 3 The SEM and TEM images show that Mo / K-MnO2 has a length of 1–2.5 μm and a diameter of 61–68 nm, arranged along the diameter direction to form a bundle structure with clear lattice fringes and good crystallinity. Combined with the HRTEM images of MnO2, K-MnO2, and Mo / K-MnO2, it can be seen that K-MnO2 formed after K doping generates oxygen vacancies (OV), leading to lattice distortion and loss, resulting in blurred lattice fringes in some areas. According to crystal plane theory, the relationship between the 2θ degree, corresponding crystal plane, and interplanar spacing in XRD can be analyzed. The interplanar spacing of nanowire-shaped MnO2 is 0.491 nm, corresponding to the (200) crystal plane of PDF#44-0141. After K doping, the interplanar spacing increases from 0.491 nm to 0.498 nm. After K and Mo doping, the interplanar spacing of the formed Mo / K-MnO2 further increases from 0.498 nm to 0.527 nm. This indicates that the co-doping of Mo and K causes tunnel expansion in MnO2, allowing Mo and K to successfully enter the tunnel structure and be fully dispersed, which may lead to changes in the catalyst's performance.

[0064] Depend on Figure 1 As shown in Figure (e), the XRD patterns reveal that the diffraction peaks of MnO2, K-MnO2, Mo-MnO2, and Mo / K-MnO2 are aligned with those of the tetragonal α-MnO2 (PDF#44-0141), exhibiting characteristic diffraction peaks at 2θ = 12.784°, 18.107°, 28.841°, and 37.522°, corresponding to the (110), (200), (301), and (211) crystal planes, respectively. The typical characteristic peaks of α-MnO2 in MnO2, K-MnO2, Mo-MnO2, and Mo / K-MnO2 indicate that doping with K and Mo did not significantly affect the crystal phase of MnO2. Mo and K are highly dispersed on MnO2 and do not form oxides of Mo or K. Meanwhile, with the doping of K and Mo, all diffraction peaks gradually shift to lower angles, and the trend of the diffraction peaks on the (200) crystal plane is clearer, further illustrating the tunneling expansion. Furthermore, no other impurity peaks were observed in the XRD patterns of MnO2, K-MnO2, Mo / K-MnO2, and Mo-MnO2; the peaks were sharp, indicating that the prepared MnO2, K-MnO2, Mo / K-MnO2, and Mo-MnO2 have good crystallinity and high purity.

[0065] Depend on Figure 1 As shown in Figure (f), the FTIR spectrum reveals that the synthesized Mo / K-MnO2 contains functional groups including hydroxyl groups and metal-oxygen adducts. Mo and K doping creates hydroxyl groups on the surface of MnO2, which enhances its hydrophilicity and dispersibility. Furthermore, Mo and K doping also strengthens the stretching vibrations of Mn-O. Since the peak positions of the Raman spectrum of MnO2 are mainly determined by the [MnO6] octahedral structure, further Raman spectroscopy is used to better understand the crystal structure of MnO2 in K-MnO2, Mo-MnO2, and Mo / K-MnO2 to gain a clearer understanding of their structural composition.

[0066] Depend on Figure 3 As shown in Figure (c), the Raman spectrum at 182 cm⁻¹ is... -1 The peak observed can be attributed to external vibrations caused by the translational motion of the [MnO6] octahedron, and is located at 386 cm⁻¹. -1 The Raman spectral peak at 570 cm⁻¹ corresponds to the bending vibration of the Mn-O bond. -1 638cm -1 The Raman spectral peaks appearing at this point can be attributed to vibrations within the [MnO6] octahedron, with the peak at 570 cm⁻¹ being the most significant. -1 The Raman spectral peak at 638 cm⁻¹ corresponds to the displacement vibrations of Mn and O atoms along the octahedral double chain direction, while the peak at 638 cm⁻¹ corresponds to the displacement vibrations of Mn and O atoms along the octahedral double chain direction. -1 The Raman spectral peak appearing at 574 cm⁻¹ is attributed to the vibration of the Mn-O bond perpendicular to the [MnO₆] octahedral double chain direction. -1 and 631cm -1 The Raman spectral peaks correspond to the well-developed one-dimensional tunnel-like (2×2) tetragonal structure of α-MnO2. Simultaneously, Mn-O is present in Mo / K-MnO2, but Mo=O and O-Mo-O are absent, indicating the absence of detectable free molybdenum oxide (MoO3), consistent with the results of XRD and EDS. Mo doping enhances the bending vibrations of the Mn-O bonds, altering the chemical environment and reducing properties within the α-MnO2 tunnel structure, indicating that Mo has fully penetrated the tunnels.

[0067] Depend on Figure 2 The XPS results shown indicate that Mn2p 3 / 2 The peaks with binding energies at 640.84–641.15 eV, 642.13–642.38 eV, and 643.13–643.86 eV are attributed to Mn, respectively. 2+ Mn 3+ and Mn 4+In O1s, the binding energies at 529.69–529.97 eV and 531.13–531.43 eV are attributed to lattice oxygen and vacancy oxygen, respectively. K doping increases the content of oxygen vacancies and low-valence manganese. In Mo-containing MnO2, the binding energies in Mo3d at 232.13–232.18 eV and 235.36–235.4 eV are attributed to Mo, respectively. 4+ and Mo 6+ .

[0068] Inductively coupled plasma atomic emission spectrometry (ICP) analysis revealed the following: In the K-MnO2 prepared in Example 1, the K content was 6.37% and the Mn content was 57.3%; in the Mo-MnO2 prepared in Comparative Example 1, the Mo content was 1.86% and the Mn content was 56.9%; and in the Mo / K-MnO2 prepared in Example 1, the K content was 6.12%, the Mo content was 1.66%, and the Mn content was 56.5%.

[0069] Depend on Figure 3 The thermogravimetric analysis results shown in Figure (d) indicate that K-MnO2 exhibits the least weight loss, suggesting that K doping enhances the thermal stability of MnO2. Oxygen vacancies (OVs) are easily filled by O2 at high temperatures, so lower mass loss corresponds to higher OV content. Combined with the fact that K-MnO2 has the least weight loss, this further demonstrates that K doping increases the OV content in the material. Figure 4 As shown in the Tafel diagram, K doping enhances the electron transport capability of the material.

[0070] Example 3

[0071] In this embodiment, the ability of MnO2 (i.e., α-MnO2), K-MnO2, Mo-MnO2, and Mo / K-MnO2 prepared in Example 1 and Comparative Example 1 to activate PAA and degrade the pollutant naproxen (NAP) was investigated.

[0072] (1) NAP was prepared into a solution with a concentration of 10 μmol / L using deionized water as simulated wastewater.

[0073] (2) Add PAA and catalyst to simulated wastewater, treat simulated wastewater under stirring conditions at 25±1℃, control the pH value of simulated wastewater to 6.3, the amount of PAA added should be such that the concentration of PAA in simulated wastewater is 0.3mmol / L, the amount of catalyst added in simulated wastewater is 0.1g / L, and the treatment time of simulated wastewater is controlled to be 20min.

[0074] In this step, a total of 4 sets of experiments were conducted, and the catalysts used in each set of experiments were MnO2, K-MnO2, Mo-MnO2 and Mo / K-MnO2, respectively.

[0075] During the simulated wastewater treatment process, the concentration C of NAP was measured every 1–5 minutes. The method for determining the NAP concentration was as follows: the sampled solution was filtered through a filter membrane, sodium thiosulfate was added to terminate the reaction, and the NAP concentration was determined by high-performance liquid chromatography (HPLC). The initial concentration of NAP was recorded as C0, and the change of C / C0 with treatment time was calculated. The results are as follows. Figure 5 As shown in Figure (a).

[0076] Depend on Figure 5 As shown in Figure (a), compared with MnO2, K-MnO2 and Mo-MnO2, the ability of Mo / K-MnO2 to activate PAA and degrade NAP was significantly improved. When the treatment time was 20 min, the degradation rate of NAP could reach 97.71%, and the corresponding reaction rate constant Kobs was 0.187.

[0077] Example 4

[0078] In this embodiment, the ability of the Mo / K-MnO2-activated PAA prepared in Example 1 to degrade different organic pollutants was investigated.

[0079] (1) Bisphenol A (BPA), sulfamethoxazole (SMX), atrazine (ATZ), BA (benzoic acid), and naproxen (NAP) were prepared into 10 μmol / L solutions using deionized water as simulated wastewater.

[0080] (2) Peracetic acid and Mo / K-MnO2 prepared in Example 1 were added to each simulated wastewater respectively. The simulated wastewater was treated under stirring conditions at 25±1℃. The pH value of each simulated wastewater was controlled to be 6.3. The amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3mmol / L and the amount of Mo / K-MnO2 added to the simulated wastewater is 0.1g / L. The treatment time of the simulated wastewater was controlled to be 20min.

[0081] In the simulated wastewater treatment process, the concentration C of pollutants was measured every 1–5 minutes. The method for determining the pollutant concentration was as follows: the sampled solution was filtered through a filter membrane, sodium thiosulfate was added to terminate the reaction, and the pollutant concentration was determined by HPLC. The initial concentration of pollutants was recorded as C0, and the change of C / C0 over treatment time was calculated. The results are as follows: Figure 5 As shown in Figure (b).

[0082] Depend on Figure 5As shown in Figure (b), the Mo / K-MnO2-activated PAA prepared in Example 1 could not degrade ATZ and BA, but it could degrade SMX and BPA to some extent, although the degradation effect was not ideal. In contrast, the Mo / K-MnO2-activated PAA could efficiently degrade NAP. This indicates that Mo / K-MnO2 exhibits high specificity for the types of organic pollutants when activating PAA to degrade them.

[0083] Example 5

[0084] In this embodiment, the effect of Mo / K-MnO2 dosage on the degradation of NAP by PAA activated by Mo / K-MnO2 was investigated.

[0085] (1) NAP was prepared into a solution with a concentration of 10 μmol / L using deionized water as simulated wastewater.

[0086] (2) PAA and Mo / K-MnO2 prepared in Example 1 were added to the simulated wastewater. The simulated wastewater was treated under stirring conditions at 25±1℃, and the pH value of the simulated wastewater was controlled to be 6.3. The amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3 mmol / L, and the treatment time of the simulated wastewater was controlled to be 15 min. During the wastewater treatment process, the NAP concentration C was measured every 5 min. The initial concentration of NAP was recorded as C0, and C / C0 was calculated.

[0087] In this step, four sets of experiments were set up. In each set of experiments, the amount of Mo / K-MnO2 added to the simulated wastewater was 0.05, 0.1, 0.2, and 0.3 g / L. The changes in C / CO with treatment time in each set of experiments are shown below. Figure 6 As shown in Figure (a).

[0088] Depend on Figure 6 As shown in Figure (a), under the condition that other experimental conditions remain unchanged, the removal rate of NAP increases with the increase of Mo / K-MnO2 dosage. However, with the further increase of Mo / K-MnO2 dosage, the removal rate of NAP decreases. Considering both pollutant removal rate and wastewater treatment cost, a Mo / K-MnO2 dosage of about 0.1 g / L in the simulated wastewater, such as 0.05 to 0.15 g / L, is more appropriate.

[0089] Example 6

[0090] In this embodiment, the effect of PAA dosage on the degradation of NAP by Mo / K-MnO2-activated PAA was investigated.

[0091] (1) NAP was prepared into a solution with a concentration of 10 μmol / L using deionized water as simulated wastewater.

[0092] (2) PAA and Mo / K-MnO2 prepared in Example 1 were added to the simulated wastewater. The simulated wastewater was treated under stirring conditions at 25±1℃, and the pH value of the simulated wastewater was controlled at 6.3. The amount of Mo / K-MnO2 added should be such that the concentration of Mo / K-MnO2 in the simulated wastewater is 0.1 g / L. The treatment time of the simulated wastewater was controlled at 20 min. During the wastewater treatment process, the NAP concentration C was measured every 1 to 5 min. The initial concentration of NAP was recorded as C0, and C / C0 was calculated.

[0093] In this step, four experimental groups were set up. In each group, the amount of PAA added to the simulated wastewater was 0.2, 0.3, 0.4, and 0.5 mmol / L. The changes in C / CO with treatment time in each group are shown below. Figure 6 As shown in Figure (b).

[0094] Depend on Figure 6 As shown in Figure (b), under the condition that other experimental conditions remain unchanged, the removal rate of NAP increases with the increase of PAA dosage. However, with the further increase of PAA dosage, the removal rate of NAP no longer shows a significant increase. Considering both the pollutant removal rate and the wastewater treatment cost, a PAA dosage of about 0.3 mmol / L in the simulated wastewater, such as 0.3 to 0.4 mmol / L, is more appropriate.

[0095] Example 7

[0096] In this embodiment, the effect of NAP concentration on the degradation of NAP by Mo / K-MnO2-activated PAA was investigated.

[0097] (1) NAP was prepared into solutions with concentrations of 5, 10, 15 and 20 μmol / L using deionized water as simulated wastewater.

[0098] (2) PAA and Mo / K-MnO2 prepared in Example 1 were added to the simulated wastewater. The simulated wastewater was treated under stirring conditions at 25±1℃, with the pH value controlled at 6.3. The amount of Mo / K-MnO2 added should be such that the concentration of Mo / K-MnO2 in the simulated wastewater is 0.1 g / L, and the amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3 mmol / L. The treatment time of the simulated wastewater was controlled at 20 min. During the wastewater treatment process, the NAP concentration C was measured every 1 to 5 min. The initial concentration of NAP was recorded as C0, and C / C0 was calculated.

[0099] In this step, four experimental groups were set up, with NAP concentrations of 5, 10, 15, and 20 μmol / L in each group. The changes in CCO with treatment time in each group are shown below. Figure 6 As shown in Figure (c).

[0100] Depend on Figure 6 As shown in Figure (c), the reaction of Mo / K-MnO2-activated PAA to degrade NAP follows a first-order reaction. The reaction rate increases with increasing NAP concentration. However, as the NAP concentration increases to a certain level, the intermediate products generated accumulate and mask the active sites of Mo / K-MnO2, causing the reaction rate to stop increasing. Therefore, for NAP degradation, under the Mo / K-MnO2 and PAA dosage and pH conditions of this embodiment, the NAP concentration in the wastewater is preferably no more than 20 μmol / L.

[0101] Example 8

[0102] In this embodiment, the effect of degradation temperature on the degradation of NAP by Mo / K-MnO2 activated PAA was investigated.

[0103] (1) NAP was prepared into a solution with a concentration of 10 μmol / L using deionized water as simulated wastewater.

[0104] (2) PAA and Mo / K-MnO2 prepared in Example 1 were added to the simulated wastewater. The simulated wastewater was treated under stirring conditions, and the pH value of the simulated wastewater was controlled at 6.3. The amount of Mo / K-MnO2 added should be such that the concentration of Mo / K-MnO2 in the simulated wastewater is 0.1 g / L, and the amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3 mmol / L. The treatment time of the simulated wastewater was controlled at 20 min. During the wastewater treatment process, the NAP concentration C was measured every 1 to 5 min. The initial concentration of NAP was recorded as C0, and C / C0 was calculated.

[0105] In this step, a total of 4 groups of experiments were set up, and the degradation temperature in each group was controlled at 5, 15, 25, and 35℃. The changes of C / CO with treatment time in each group of experiments are as follows: Figure 6 As shown in Figure (d).

[0106] Depend on Figure 6 As shown in Figure (d), when the degradation temperature is between 5 and 35°C, it has virtually no effect on the degradation of NAP by Mo / K-MnO2 activated PAA, indicating that the method provided by this invention can efficiently degrade NAP at room temperature without requiring special temperature control of the wastewater.

[0107] Example 9

[0108] In this embodiment, the effect of wastewater pH on the degradation of NAP by Mo / K-MnO2-activated PAA was investigated.

[0109] (1) Prepare NAP solutions with a concentration of 10 μmol / L using deionized water as simulated wastewater, and adjust the pH of the simulated wastewater to 3, 5, 6.3, 7, 9 and 11 respectively.

[0110] (2) Add PAA and Mo / K-MnO2 prepared in Example 1 to each of the above simulated wastewaters with different pH values. Treat the simulated wastewater under stirring conditions at 25±1℃. The amount of Mo / K-MnO2 added should be such that the concentration of Mo / K-MnO2 in the simulated wastewater is 0.1 g / L, and the amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3 mmol / L. Control the treatment time of the simulated wastewater to 20 min.

[0111] During wastewater treatment, NAP concentration (C) is measured every 1-5 minutes. The initial NAP concentration is recorded as C0, and C / C0 is calculated. The change of C / C0 with treatment time is shown below. Figure 6 As shown in Figure (e).

[0112] Depend on Figure 6 As shown in Figure (e), Mo / K-MnO2 can efficiently activate PAA to degrade NAP under pH conditions of 5 to 9, and the pH value of the wastewater will gradually tend to neutral during the degradation of NAP.

[0113] Example 10

[0114] In this embodiment, the effects of common anions and humic acids in water on the degradation of NAP by Mo / K-MnO2-activated PAA were investigated.

[0115] (1) Prepare a 10 μmol / L solution of NAP with deionized water, and then add HCO3-. - Cl - H2PO4 - Add humic acid (HA) to NAP solution and HCO3 - Cl-, H2PO4 - Simulated wastewater was obtained by adding humic acid (HA) at a concentration of 0.5 mmol / L.

[0116] NAP was prepared into a 10 μmol / L solution using deionized water. This solution was used as the simulated wastewater for the control group and was denoted as Control.

[0117] (2) PAA and Mo / K-MnO2 prepared in Example 1 were added to each simulated wastewater. The simulated wastewater was treated under stirring conditions at 25±1℃, and the pH value of the simulated wastewater was controlled to be 6.3. The amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3 mmol / L, and the amount of Mo / K-MnO2 added should be 0.1 g / L. The treatment time of the simulated wastewater was controlled to be 20 min. During the wastewater treatment process, the NAP concentration C was measured every 1 to 5 min. The initial concentration of NAP was recorded as C0, and C / C0 was calculated. The change of C / C0 with treatment time is shown in the figure. Figure 7 As shown.

[0118] Depend on Figure 7 It can be seen that low concentrations (e.g., concentrations not exceeding 0.5 mmol / L) of anions Clˉ, H2PO4ˉ, HCO3ˉ, and HA in water bodies do not have an adverse effect on the ability of Mo / K-MnO2 to activate PAA and degrade NAP. This indicates that Mo / K-MnO2 can resist the adverse effects of low concentrations of common water matrix on the activation of PAA and degradation of NAP.

[0119] Example 11

[0120] In this embodiment, the ability of Mo / K-MnO2 to activate PAA to degrade NAP in actual water bodies was investigated.

[0121] (1) Using tap water, river water, and lake water as solvents, NAP was prepared into a solution with a concentration of 10 μmol / L, denoted as wastewater. The pH of the wastewater was not specifically adjusted. The pH values ​​of the three solutions were...

[0122] The value is between 5.8 and 7.5.

[0123] (2) Add PAA and Mo / K-MnO2 prepared in Example 1 to each of the above wastewaters respectively, and treat the wastewater under stirring conditions at 25±1℃. The amount of Mo / K-MnO2 added should make the concentration of Mo / K-MnO2 in the wastewater 0.1g / L, and the amount of PAA added should make the concentration of PAA in the wastewater 0.3mmol / L. Control the wastewater treatment time to 20min.

[0124] During wastewater treatment, the concentration C of NAP is measured every 1-5 minutes. The initial concentration of NAP is recorded as C0, and C / C0 is calculated. The change of C / C0 with treatment time is shown below. Figure 8 As shown.

[0125] Depend on Figure 8It can be seen that Mo / K-MnO2 has a good and high degradation capacity in the three actual water bodies mentioned above when activating PAA to degrade NAP. In contrast, lake water has a slight inhibitory effect on the degradation of NAP by Mo / K-MnO2-activated PAA, which may be due to the relatively higher anion content in lake water. However, in our experiment, we found that when the dosage of Mo / K-MnO2 remained unchanged, increasing the dosage of PAA to a concentration of 0.6 mmol / L in the wastewater resulted in a NAP degradation effect comparable to that of this embodiment (2) in degrading NAP in tap water or river water. This indicates that when anions and other water matrix in the water body have an adverse effect on the degradation of organic pollutants, increasing the dosage of PAA is one way to improve the degradation capacity of the method of the present invention for pollutants under such circumstances.

[0126] Example 12

[0127] In this embodiment, the recycling performance of Mo / K-MnO2 prepared in Example 1 was examined when PAA was activated to degrade NAP.

[0128] (1) NAP was prepared into a solution with a concentration of 10 μmol / L using deionized water as simulated wastewater.

[0129] (2) Add PAA and Mo / K-MnO2 prepared in Example 1 to the simulated wastewater, treat the simulated wastewater under stirring conditions at 25±1℃, control the pH value of the simulated wastewater to 6.3, the amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3mmol / L, the amount added in the simulated wastewater at 25±1℃ is 0.1g / L, and the treatment time of the simulated wastewater is controlled to be 40min.

[0130] (3) After each wastewater treatment is completed, the Mo / K-MnO2 in the simulated wastewater is filtered out for the next wastewater treatment. The treatment method is the same as step (2) of this embodiment. The Mo / K-MnO2 is recycled a total of 5 times.

[0131] After each wastewater treatment, samples were taken to measure the NAP concentration, and the NAP removal rate was calculated. The NAP removal rate after 5 cycles was as follows: Figure 9 As shown in the figure, the removal rates of NAP in the first to fifth cycles were 99.57%, 97.48%, 92.55%, 91.1%, and 86.11%, respectively. This indicates that when Mo / K-MnO2 prepared by the method described in this invention activates PAA to degrade NAP, Mo / K-MnO2 has excellent recycling performance. After four cycles, the removal rate of NAP can be maintained above 90%, and after five cycles, the removal rate of NAP can still be maintained above 86%.

[0132] The Mo / K-MnO2 prepared in Example 1 before use (denoted as Fresh K) was analyzed by XRD. + Mo / K-MnO2 and Mo / K-MnO2 after 5 recycling (denoted as Used K) + The structure of Mo / K-MnO2 was characterized to further evaluate its structural stability, and the results are as follows: Figure 10 As shown.

[0133] Depend on Figure 10 It can be seen that the XRD patterns of Mo / K-MnO2 before and after use match those of standard tetragonal α-MnO2 (PDF#44-0141). The characteristic diffraction peaks of Mo / K-MnO2 at 2θ = 12.784°, 18.107°, 28.841°, and 37.522° correspond to the (110), (200), (301), and (211) crystal planes of standard tetragonal α-MnO2, respectively. This indicates that the structure of Mo / K-MnO2 has good stability. Furthermore, the positions of the characteristic diffraction peaks of Mo / K-MnO2 did not change before and after use, indicating that Mo / K-MnO2 maintains structural stability during the PAA activation and NAP degradation process.

[0134] Example 13

[0135] In this embodiment, various experiments were used to investigate the types and reaction pathways of active oxide species generated by the Mo / K-MnO2 / PAA system during the degradation of NAP in wastewater.

[0136] 1. Quenching Experiment

[0137] The quenchers used include methanol (MeOH), tert-butanol (TBA), 2,4-hexadiene (2,4-HD), methyl sulfoxide (PMSO), furfuryl alcohol (FAA), and superoxide dismutase (SOD), which are used to quench free radicals, hydroxyl radicals (·OH), organic free radicals (RO·), high-valence metals, and singlet oxygen, respectively. 1 O2) and superoxide radicals (O2) ·- ).

[0138] (1) NAP was prepared into a solution with a concentration of 10 μmol / L using deionized water as simulated wastewater.

[0139] (2) Add PAA and Mo / K-MnO2 prepared in Example 1 to the simulated wastewater, treat the simulated wastewater under stirring conditions, control the pH value of the simulated wastewater to 6.3, the amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3 mmol / L, the amount of Mo / K-MnO2 added to the simulated wastewater is 100 mg / L, and the treatment time of the simulated wastewater is controlled to be 20 min.

[0140] In step (2), quenching agents of different concentrations and types are added to the simulated wastewater, as detailed below:

[0141] Blank group: No quenching agent added;

[0142] MeOH group: MeOH was added to the simulated wastewater until the concentration of MeOH was 300 mmol / L;

[0143] TBA group: TBA was added to the simulated wastewater until the concentration of TBA reached 300 mmol / L;

[0144] 2,4-HD group: 2,4-HD was added to the simulated wastewater until the concentration of 2,4-HD was 20 mmol / L;

[0145] PMSO group: PMSO was added to the simulated wastewater until the PMSO concentration was 0.1 mmol / L;

[0146] FFA group: FFA was added to the simulated wastewater until the concentration of FFA was 20 mmol / L;

[0147] SOD group: SOD was added to the simulated wastewater until the concentration of SOD was 1200 U / mL;

[0148] During the wastewater treatment process, samples were taken at 0 min, 1 min, 3 min, 5 min, 10 min, 15 min and 20 min respectively, filtered through a filter membrane, and Na2S2O3 was added to quench the reaction. The concentration of NAP was detected by HPLC and recorded as concentration C. The initial concentration of pollutants was recorded as C0, and C / C0 was calculated.

[0149] The higher the degree of inhibition of pollutant (NAP) degradation after adding the appropriate quencher, the greater the impact of the free radicals quenched by the quencher on pollutant degradation, and the more likely these free radicals are to become the main free radicals in pollutant degradation. The degradation rates of NAP in the control group and other groups with added quenchers are shown below. Figure 11As shown in Figure (a), the degradation of NAP was only slightly inhibited when 300 mmol / L TBA was added, and almost all degradation was achieved. The addition of 0.1 mmol / L PMSO had little effect on NAP degradation. The addition of 1200 U / mL SOD did not inhibit NAP degradation. However, the addition of 2,4-HD, MeOH, and FFA significantly affected NAP degradation, indicating that organic free radicals (RO·) are the main reactive oxide species for pollutant degradation in this invention. 1 O2 also plays a role in the degradation of pollutants.

[0150] 2. Probe Experiment

[0151] Nitrobenzene (NB) and p-chlorobenzoic acid (p-CBA) can capture ·OH. Experiments were conducted using NB (10 μM) and p-CBA (10 μM) as probe pollutants for ·OH. HPLC was used to detect the concentration changes of nitrobenzene, p-chlorobenzoic acid, coumarin, etc., to explore the contribution of ·OH to the degradation of pollutants in the system; 9,10-diphenylanthracene (DPA) is... 1 Chemical O2-capturing reagents can be used to confirm... 1 O2 generation. Using DPA as... 1 An experiment was conducted using an O2 probe, and changes in DPA concentration were analyzed using UV full scan to investigate... 1 The contribution of O2 to the degradation of pollutants in the system.

[0152] (1) OH probe experiment

[0153] NB and p-CBA were prepared into 10 μmol / L solutions using deionized water as probes. PAA and Mo / K-MnO2 prepared in Example 1 were added to the simulated wastewater (the simulated wastewater prepared in step 1(1)). The simulated wastewater was treated under stirring conditions. The amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3 mmol / L and the amount of Mo / K-MnO2 added should be 100 mg / L. The treatment time of the simulated wastewater was controlled to be 20 min.

[0154] In the simulated wastewater treatment process, samples were taken at 0 min, 1 min, 3 min, 5 min, 10 min, 15 min, and 20 min, respectively, and filtered through a filter membrane. Na2S2O3 was added to quench the reaction. The concentrations of NB and p-CBA were detected by HPLC and denoted as concentration C. The initial concentrations of both were denoted as C0, and C / C0 was calculated. The results are as follows: Figure 11 As shown in Figure (b) of the document.

[0155] By analyzing the degradation of NB and p-CBA, it can be determined whether ·OH groups were generated in the Mo / K-MnO2 / PAA system. Figure 11 As shown in Figure (b), NB and p-CBA are adsorbed in small amounts by Mo / K-MnO2 and are basically not degraded, indicating that the activation of PAA by Mo / K-MnO2 does not produce ·OH.

[0156] (2) 1 O2 probe experiment

[0157] PAA and Mo / K-MnO2 prepared in Example 1 were added to deionized water and the simulated wastewater (the simulated wastewater prepared in step 1(1)) was treated under stirring conditions. The amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.3 mmol / L and the amount of Mo / K-MnO2 added to the simulated wastewater is 100 mg / L. The treatment time of the simulated wastewater was controlled to be 17 min.

[0158] During the simulated wastewater treatment process, samples were taken at 0 min, 2 min, 5 min, 12 min, and 17 min, with 1.6 mL of sample taken each time. The samples were mixed with 0.1 mL of DPA and 0.8 mL of anhydrous methanol, and the changes in the characteristic peak of DPA were detected at 368 nm using a UV spectrophotometer. The changes in DPA concentration were analyzed, and the results are as follows: Figure 11 As shown in Figure (c).

[0159] Depend on Figure 11 As shown in Figure (c), the characteristic peak of DPA weakens with increasing treatment time, indicating that Mo / K-MnO2 activation of PAA produces 1 O2. The characteristic peak intensity at 17 minutes of processing is greater than that at 12 minutes, because this is due to the later stage of the reaction. 1 This is caused by a decrease in the amount of O2 generated.

[0160] 3. Premixing Experiment

[0161] To investigate the contribution of direct electron transfer to pollutant degradation in the Mo / K-MnO2 / PAA system, in order to enhance the persuasiveness of the data.

[0162] PAA and Mo / K-MnO2 prepared in Example 1 were premixed in water for 10 min, 20 min, and 30 min, respectively, and then the pollutant NAP was added. Other experimental conditions were the same as above, namely: the concentration of NAP was 10 μmol / L, the concentration of PAA was 0.3 mmol / L, the amount of Mo / K-MnO2 added was 100 mg / L, the pH of the resulting mixture was 6.3, and the mixture was treated under stirring for 20 min.

[0163] During the treatment process, samples were taken at 0 min, 1 min, 3 min, 5 min, 10 min, 15 min, and 20 min, filtered through a filter membrane, and the reaction was quenched with Na2S2O3. The concentration of NAP was detected by HPLC, and the results are as follows. Figure 11 As shown in Figure (d), the degradation rate of NAP was significantly inhibited after premixing for 10, 20, and 30 min, indicating that direct electron transfer in the Mo / K-MnO2 / PAA system contributes little to the degradation of pollutants.

[0164] 4. Mass spectrometry analysis experiment

[0165] 2,2,6,6-Tetramethylpiperidine-N-oxygen radical (TEMPO) can capture RO·(CH3COO·) to generate the relatively stable CH3COO·-TEMPO. The product CH3COO·-TEMPO can be detected using high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UPLC-QTOF-MS / MS), further illustrating the formation of RO· in the system. TEMPO was added to deionized water to a concentration of 1 mmol / L. Based on this, other substances were added to form the following three experimental groups:

[0166] Blank group: The concentration of TEMPO in the solution was 1 mmol / L and the concentration of PAA was 0.3 mmol / L;

[0167] Experimental group: The concentration of TEMPO in the solution was 1 mmol / L, the concentration of PAA was 0.3 mmol / L, and 0.1 g / L of Mo / K-MnO2 prepared in Example 1 was added.

[0168] Competition group: The concentration of TEMPO in the solution was 1 mmol / L, the concentration of PAA was 0.3 mmol / L, the concentration of NAP was 10 μmol / L, and 0.1 g / L of Mo / K-MnO2 prepared in Example 1 was added.

[0169] Each group was treated with simulated wastewater at 25±1℃ for 20 min under stirring conditions. After the wastewater treatment was completed, samples were taken and analyzed using high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry. The results are as follows: Figure 11 As shown in Figure (e), after the addition of Mo / K-MnO2, CH3COO·-TEMPO with an m / z of 216.1601 was detected, indicating that organic free radicals (such as CH3COO·) were generated in the system. The intensity of the peak decreased after the addition of NAP, indicating that NAP reacted with organic free radicals (such as CH3COO·) and competed with TEMPO, further indicating that organic free radicals (such as CH3COO·) participated in the degradation reaction of NAP.

[0170] Example 14

[0171] In this embodiment, a quenching experiment was conducted to test the types of active oxide species generated when MnO2 (i.e., α-MnO2), K-MnO2, and Mo-MnO2 prepared in Example 1 and Comparative Example 1 activated PAA to degrade pollutants (e.g., NAP). The specific operation was basically the same as "1. Quenching Experiment" in Example 13, except that Mo / K-MnO2 was replaced with MnO2, K-MnO2, or Mo-MnO2, respectively. The results are as follows. Figure 12 As shown.

[0172] Depend on Figure 12 It is known that the types of active oxide species produced when MnO2, K-MnO2, Mo-MnO2 and Mo / K-MnO2 activate PAA to degrade pollutant NAP are the same. However, compared with MnO2, K-MnO2 and Mo-MnO2, the Mo / K-MnO2 prepared in this invention has a significantly stronger ability to produce active oxide species when activating PAA, thus producing a significantly better effect on degrading pollutants (e.g., NAP).

[0173] Example 15

[0174] In this embodiment, a Mo / K co-doped MnO2 catalyst was prepared, and the ability of the prepared Mo / K-MnO2 to activate PAA and degrade the pollutant NAP was investigated. The steps are as follows:

[0175] (1) The same procedure as in Example 1 was followed to prepare α-MnO2.

[0176] (2) Take the α-MnO2 prepared in step (1) and mix it with 1 mol / L KOH solution. Sonicate for 20 min to mix evenly. Then transfer it to a high pressure vessel with a polytetrafluoroethylene liner and react at 140℃ for 6 h. Wash the obtained product repeatedly with deionized water and centrifuge until the washing liquid is neutral. Then dry it in an air atmosphere at 80℃. Grind the dried product to obtain powdered K-doped MnO2, which is denoted as K-MnO2.

[0177] In this step, the α-MnO2 prepared in step (1) is mixed with a 1 mol / L KOH solution at a molar ratio of K to Mn of 1:0.115.

[0178] (3) Take the K-MnO2 prepared in step (2) and add it to deionized water, then add (NH4)6Mo7O 24·4H2O, stir at 45℃ for 10h, then stir at 65℃ for 1h, then stir at 85℃ for 1h, dry the resulting reaction product at 110℃ for 5h, grind the dried product into powder, put it in a crucible, calcine at 300℃ for 6h in air atmosphere, grind the resulting product to obtain powdered Mo, K co-doped MnO2 catalyst, denoted as Mo / K-MnO2.

[0179] In this step, K-MnO2 is added to deionized water at a mass ratio of 1:150, and the (NH4)6Mo7O is controlled. 24 The mass ratio of 4H2O to K-MnO2 is 0.03:1.

[0180] The following examines the ability of the Mo / K-MnO2-activated PAA prepared in this embodiment to degrade the pollutant NAP.

[0181] NAP was prepared into a 20 μmol / L solution using deionized water to serve as simulated wastewater, and the pH of the simulated wastewater was adjusted to 5. PAA and Mo / K-MnO2 prepared in this embodiment were added to the simulated wastewater, and the wastewater was treated under stirring conditions at 25 ± 1 °C. The amount of Mo / K-MnO2 added should be such that the concentration of Mo / K-MnO2 in the simulated wastewater is 0.15 g / L, and the amount of PAA added should be such that the concentration of PAA in the simulated wastewater is 0.4 mmol / L. The treatment time of the simulated wastewater was controlled at 20 min. After the wastewater treatment was completed, the NAP concentration was measured, and the removal rate of NAP was calculated. The results showed that the removal rate of NAP was 97.2%.

[0182] Example 16

[0183] In this embodiment, a Mo / K co-doped MnO2 catalyst was prepared, and the ability of the prepared Mo / K-MnO2 to activate PAA and degrade the pollutant NAP was investigated. The steps are as follows:

[0184] (1) The same procedure as in Example 1 was followed to prepare α-MnO2.

[0185] (2) Take the α-MnO2 prepared in step (1) and mix it with 1 mol / L KOH solution. Sonicate for 20 min to mix evenly. Then transfer it to a high pressure vessel with a polytetrafluoroethylene liner and react at 160℃ for 3 h. Wash the obtained product repeatedly with deionized water and centrifuge until the washing liquid is neutral. Then dry it in an air atmosphere at 80℃. Grind the dried product to obtain powdered K-doped MnO2, which is denoted as K-MnO2.

[0186] In this step, the α-MnO2 prepared in step (1) is mixed with a 1 mol / L KOH solution at a molar ratio of K to Mn of 1:0.130.

[0187] (3) Take the K-MnO2 prepared in step (2) and add it to deionized water, then add (NH4)6Mo7O 24 ·4H2O, stir at 35℃ for 15h, then stir at 55℃ for 3h, then stir at 75℃ for 3h, dry the resulting reaction product at 110℃ for 5h, grind the dried product into powder, put it in a crucible, calcine at 400℃ for 3h in air atmosphere, grind the resulting product to obtain powdered Mo, K co-doped MnO2 catalyst, denoted as Mo / K-MnO2.

[0188] In this step, K-MnO2 is added to deionized water at a mass ratio of 1:150, and the (NH4)6Mo7O is controlled. 24 The mass ratio of 4H2O to K-MnO2 is 0.04:1.

[0189] The following examines the ability of the Mo / K-MnO2-activated PAA prepared in this embodiment to degrade the pollutant NAP.

[0190] A 10 μmol / L NAP solution was prepared using deionized water to serve as simulated wastewater, and the pH of the simulated wastewater was adjusted to 6. PAA and the Mo / K-MnO2 prepared in this embodiment were added to the simulated wastewater, and the wastewater was treated under stirring conditions at 25 ± 1 °C. The amount of Mo / K-MnO2 added should be such that its concentration in the simulated wastewater is 0.05 g / L, and the amount of PAA added should be such that its concentration is 0.35 mmol / L. The treatment time was controlled at 20 min. After the wastewater treatment was completed, samples were taken to determine the NAP concentration, and the NAP removal rate was calculated. The results showed that the NAP removal rate was 98.9%.

Claims

1. A method for activating a Mo, K co-doped MnO2 catalyst to degrade pollutants with peracetic acid, characterized in that, Includes the following steps: Peracetic acid and Mo,K co-doped MnO2 catalyst are added to wastewater containing organic pollutants. The wastewater is treated under stirring conditions, and the pH value of the wastewater is controlled at 5-9. During the wastewater treatment process, the Mo,K co-doped MnO2 catalyst activates the peracetic acid to generate organic free radicals and singlet oxygen to degrade the organic pollutants in the wastewater. After the treatment of one batch of wastewater is completed, the Mo,K co-doped MnO2 catalyst is recovered for the treatment of the next batch of wastewater. The dosage of Mo and K co-doped MnO2 catalyst in wastewater is 0.05~0.15 g / L; the dosage of peracetic acid in wastewater should be such that the concentration of peracetic acid in wastewater is 0.3~0.4 mmol / L. The Mo and K co-doped MnO2 catalyst is obtained by doping Mo and K into α-MnO2 nanowires. Mo and K are uniformly distributed on the surface and in the tunnel structure of the α-MnO2 nanowires. The catalyst contains hydroxyl functional groups and is prepared by the following method: (1) Mix α-MnO2 nanowires with KOH solution thoroughly and place them in a high-pressure reactor. React at 140~160 °C for 3~6 h. Wash the reaction product with water until the washing liquid is neutral and dry to obtain K-doped MnO2. In this step, α-MnO2 nanowires are thoroughly mixed with KOH solution at a K:Mn molar ratio of 1:(0.115~0.144). The preparation method of the α-MnO2 nanowires is as follows: KMnO4 and MnSO4·H2O are dissolved in water, and the molar ratio of KMnO4 to MnSO4·H2O is controlled at 1:(1.6~1.65). The mixture is thoroughly mixed, and the resulting mixed solution is placed in an autoclave and reacted at 150~152℃ for 12~13 h. The reaction product is washed with water and dried to obtain the final product. (2) Add the K-doped MnO2 prepared in step (1) to water, and add (NH4)6Mo7O 24 ·4H2O, stir at 35~45 ℃ for 10~15 h, then stir at 55~65 ℃ for 1~3 h, then stir at 75~85 ℃ for 1~3 h, dry the resulting reaction product and calcine at 300~400 ℃ for 3~6 h in air atmosphere to obtain Mo and K co-doped MnO2 catalyst; In this step, (NH4)6Mo7O is controlled. 24 The mass ratio of 4H2O to K-doped MnO2 is (0.03~0.04):

1.

2. The method for activating peracetic acid to degrade pollutants using a Mo, K co-doped MnO2 catalyst according to claim 1, characterized in that, Step (1) After obtaining K-doped MnO2, grind or pulverize the K-doped MnO2 into a uniform powder state before proceeding with the reaction in step (2); Step (2) After drying the obtained reaction product, grind or pulverize it into a uniform powder state before calcining it in air at 300~400 ℃.

3. The method for activating peracetic acid to degrade pollutants using a Mo, K co-doped MnO2 catalyst according to claim 1 or 2, characterized in that, The Mo and K co-doped MnO2 catalyst can be recycled at least 5 times.

4. The method for activating peracetic acid to degrade pollutants using the Mo, K co-doped MnO2 catalyst according to claim 3, characterized in that, The Mo and K co-doped MnO2 catalyst can be recycled 5 to 10 times.

5. The method for activating peracetic acid to degrade pollutants using a Mo, K co-doped MnO2 catalyst according to claim 1 or 2, characterized in that, The wastewater containing organic pollutants also contains at least one of Clˉ, H2PO4ˉ, HCO3ˉ, and humic acid.

6. The method for activating peracetic acid to degrade pollutants using a Mo, K co-doped MnO2 catalyst according to claim 1 or 2, characterized in that, The wastewater treatment time should be controlled to be 20-40 minutes.

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