Preparation method and application of autocatalytic oxidation catalyst

Abstract

The invention relates to a preparation method and application of an autocatalytic oxidation catalyst. The invention belongs to the technical field of environmental governance. The problems of secondary pollution and high cost of byproducts caused by additional addition of a persulfate oxidizing agent in the existing chemical treatment technology are solved. The method comprises the following steps: preparing a nitrate intercalated hydrotalcite precursor material, and then stirring a solution of the nitrate intercalated hydrotalcite precursor material with sulfate powder in a nitrogen atmosphere in an anoxic manner to complete ion exchange. In the actual treatment process of wastewater containing new pollutants, the LDHs material intercalated between environment-friendly metal elements and persulfate is introduced, the efficient degradation efficiency is guaranteed, meanwhile, the generation level of SO4 < 2-> and other by-products is remarkably reduced through an electron transfer mechanism in an induction system, and the application cost is reduced. The method can be used for effectively removing trace new pollutants, natural organic matters, inorganic salts and other components in the polluted water body; and the removal rate of new pollutants in the wastewater reaches 96%-99.9%.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental governance; specifically, it relates to a preparation method and application of a self-catalytic oxidation catalyst. Background Art

[0002] New pollutants refer to a class of toxic and harmful chemical pollutants with characteristics such as biotoxicity, environmental persistence, and bioaccumulation, which are caused by human activities, currently clearly exist, but there are no laws, regulations, or standards to regulate them, and the management regulations are imperfect, posing a greater risk to human health or the ecological environment. They are usually organic pollutants, with low concentrations but widely distributed in the environment. In recent years, water pollution incidents stressed by new pollutants have occurred frequently. Due to their characteristics such as trace residues and difficulty in complete mineralization, higher requirements are put forward for existing water treatment technologies.

[0003] Currently, existing water treatment technologies have defects such as poor performance, high toxicity of by-products, and high treatment costs in dealing with new pollutants, and are very likely to cause secondary pollution, affecting the treatment effect and increasing the treatment cost. In contrast, the chemical treatment method based on advanced oxidation technology has characteristics such as a stronger redox potential (2.5 - 3.1V), higher stability, and a fast reaction cycle, and has great practical application prospects in water treatment. However, advanced oxidation technology often relies on the input of energy, making it difficult to be widely applied in centralized water treatment technologies. To overcome the key problem of the large amount of chemical reagents and energy input in traditional AOPs treatment technologies that restricts their practical application, current main research focuses on the development of highly efficient heterogeneous catalysts and their supporting processes. The catalysts introduced in the heterogeneous system can further enhance the degradation efficiency and increase the reaction active sites in the degradation system. At the same time, by regulating the structural characteristics of catalyst synthesis, different types of new pollutants can be selectively removed, which is more targeted and efficient, and is the preferred application technology for treating new pollutants in the current advanced oxidation system.

[0004] In recent years, layered double metal hydroxides (LDHs) have developed very rapidly as a new type of material and have shown excellent performance in many aspects. They are widely used in multiple fields such as adsorption materials, catalysts, photoelectrochemistry, medicine, functional materials, pesticides, and military materials. LDHs are a general term for hydrotalcite-like compounds, consisting of positively charged layered flakes and anion intercalations, and their structural formula is [M 1-x 2+ M x 3+ (OH)2] x+ (A n- ) x n·mH2O, where M 2+ is a divalent metal ion, such as Co 2+ , Zn 2+ , Cu2+ , Fe 2+ etc., M 3+ is a trivalent metal ion, such as Al 3+ , Fe 3+ , Mn 3+ and Cr 3+ etc. A n- represents the interlayer anion. The surface effect, defect effect, topological effect, confinement effect, memory effect, and size effect of its microstructure can flexibly regulate the physical and chemical properties and catalytic characteristics of LDHs. Therefore, the synthesis and application of highly efficient catalysts in the advanced oxidation system can be realized by improving the structure of LDHs.

[0005] In the prior art, different types of catalysts can all achieve efficient removal of new pollutants. However, the highly efficient catalytic oxidation of most catalysts often requires the introduction of transition metal elements (Fe, Co, etc.). The high energy relying on the change of metal valence states is to achieve a strong activation effect on persulfate. However, there is a great risk of metal leaching during the reaction, resulting in the problem of secondary pollution of water bodies. At the same time, both the catalyst and the persulfate oxidant are in a separate dosing mode. While being costly, due to the potential SO4 2- and other by-products after the application reaction of persulfate in the system, the high residual concentration of inorganic anions is also one of the potential pollution risks in water treatment. As a type of catalyst with multi-metal regulation sites and an adjustable intercalated structure, LDHs can, while ensuring high catalytic efficiency, save costs and effectively avoid the problem of secondary pollution risks brought by heavy metal leaching and reaction by-products through the regulation of the catalyst synthesis path. Summary of the Invention

[0006] The object of the present invention is to solve the problems of secondary pollution of by-products and high costs caused by the additional dosing of persulfate oxidant in the existing chemical treatment technology, and to provide a preparation method and application of a self-catalytic oxidation catalyst.

[0007] A preparation method of a self-catalytic oxidation catalyst is realized according to the following steps:

[0008] 1. Dissolve zinc nitrate and aluminum nitrate in deionized water to obtain a mixed solution, then add an alkali solution to adjust the pH value to 10-12, mix well by magnetic stirring, and then carry out hydrothermal coprecipitation. After completion, wash the product to neutrality, and obtain a nitrate-intercalated hydrotalcite precursor material after centrifugation and drying.

[0009] 2. Add the above nitrate-intercalated hydrotalcite precursor material to distilled water to obtain a mixed solution, then place it in a nitrogen atmosphere, and then add sulfate powder to the mixed solution for anaerobic stirring. Then, centrifuge and retain the precipitate, wash it to neutrality, and obtain a self-catalytic oxidation catalyst after freeze-drying, thus completing the preparation method.

[0010] Further, the molar ratio of zinc nitrate to aluminum nitrate in the mixed solution described in Step 1 is 3:1; the concentration of zinc nitrate is 75 mmol / L, and the concentration of aluminum nitrate is 25 mmol / L.

[0011] Further, the alkali solution described in Step 1 is sodium hydroxide solution or potassium hydroxide solution.

[0012] Further, for the hydrothermal co-precipitation in Step 1: the preset temperature in the water bath is 70 °C, and the time is 24 h.

[0013] Further, for the washing in Step 1: wash with absolute ethanol and deionized water successively for 2 - 3 times.

[0014] Further, for the centrifugation and drying in Step 1: centrifuge at a speed of 5000 - 7000 r / min for 10 - 12 min, and dry at 60 - 70 °C for 8 - 10 h.

[0015] Further, the feeding ratio of the nitrate intercalated hydrotalcite precursor material to distilled water in Step 2 is (1 - 2) g : (100 - 200) ml.

[0016] Further, for the sulfate powder in Step 2: the concentration of the sulfate powder after being added to the mixed solution is 0.1 - 20 mM.

[0017] Further, the time for the anoxic stirring in Step 2 is 30 - 60 min.

[0018] Further, for the washing in Step 2: wash with deionized water for 2 - 3 times.

[0019] Further, for the freeze-drying in Step 2: the preset cold trap temperature is -60 °C, and the time is 24 - 48 h.

[0020] The application of the above self-catalytic oxidation catalyst is used to treat wastewater containing new pollutants; specifically: add the preparation method of the self-catalytic oxidation catalyst to the wastewater containing new pollutants, and after stirring for 30 - 60 min, the treatment is completed.

[0021] Further, the concentration of the preparation method of the self-catalytic oxidation catalyst in the wastewater after being added is 0.1 - 0.5 g / L; the new pollutant in the wastewater containing new pollutants is sulfamethoxazole.

[0022] The beneficial effects of the present invention:

[0023] The present invention is a method of embedding persulfate oxidant into the interlayer space of zinc-aluminum hydrotalcite through hydrothermal coprecipitation, ion exchange, etc., and a self-catalytic oxidation material with a higher redox potential and without additional addition of oxidant is prepared. This material is directly added to the polluted water body, and the efficient degradation of pollutants is achieved through the electron transfer coupling mechanism between the material and the pollutants, and the by-products after the reaction are confined in the interlayer space of zinc-aluminum hydrotalcite. The present invention is used to effectively reduce the residual of emerging pollutants, the water pollution problems of inorganic anions with strong electronegativity and natural organic matter in the environment.

[0024] The present invention regulates the structural characteristics of LDHs materials, and introduces persulfate into the middle interlayer of LDHs materials through hydrothermal coprecipitation and ion exchange and other effects to form a catalyst without additional addition of oxidant and with self-catalytic oxidation. In the actual treatment process of wastewater containing emerging pollutants, by introducing environmentally friendly metal elements and LDHs materials with persulfate intercalation, while ensuring high degradation efficiency, the electron transfer mechanism in the system is induced, and the generation level of by-products such as SO4 2- is significantly reduced, and the application cost is reduced. The present invention can be used to effectively remove trace emerging pollutants, natural organic matter and inorganic salts and other components in polluted water bodies; the removal rate of emerging pollutants (sulfonamide antibiotics) in wastewater reaches 96% - 99.9%.

[0025] The present invention is suitable for preparing a self-catalytic oxidation catalyst based on persulfate intercalation modification and used for treating wastewater containing emerging pollutants. Description of the Drawings

[0026] Figure 1 It is the TEM material characterization diagram of ZnAl-LDH and ZnAl-PDS-LDH in the examples;

[0027] Figure 2 It is the XRD material characterization diagram of ZnAl-LDH and ZnAl-PDS-LDH in the examples;

[0028] Figure 3 It is the cyclic voltammetry test curve diagram of ZnAl-LDH and ZnAl-PDS-LDH in the examples;

[0029] Figure 4 It is the effect comparison diagram of the degradation of SMX by ZnAl-LDH and ZnAl-PDS-LDH in the examples;

[0030] Figure 5 It is the SMX degradation effect diagram after adding 4 different probe substances to the ZnAl-PDS-LDH system in the examples;

[0031] Figure 6Capture result diagrams based on two scavengers, DMPO and TEMP, in the examples;

[0032] Figure 7 Open circuit potential test result diagrams based on two different systems, ZnAl-LDH and ZnAl-PDS-LDH, in the examples;

[0033] Figure 8 Chronoamperometry test result diagrams based on two different systems, ZnAl-LDH and ZnAl-PDS-LDH, in the examples;

[0034] Figure 9 Raman material characterization diagrams of ZnAl-PDS-LDH materials before and after the reaction in the examples;

[0035] Figure 10 PDS residue level test diagrams based on two different systems, ZnAl-LDH and ZnAl-PDS-LDH, at different reaction time points in the examples;

[0036] Figure 11 Sulfate ion residue concentration result diagrams of the ZnAl-PDS-LDH system at different reaction time points in the examples. Detailed implementation manners

[0037] The technical solution of the present invention is not limited to the following listed specific implementation manners, and also includes any combination between the specific implementation manners.

[0038] Specific implementation manner one: A preparation method of a self-catalytic oxidation catalyst according to this implementation manner is achieved by the following steps:

[0039] 1. Dissolve zinc nitrate and aluminum nitrate in deionized water to obtain a mixed solution, then add an alkali solution to adjust the pH value to 10 - 12, magnetically stir and mix evenly, then carry out hydrothermal co-precipitation. After completion, wash the product to neutrality, and obtain a nitrate-intercalated hydrotalcite precursor material through centrifugation and drying;

[0040] 2. Add the above nitrate-intercalated hydrotalcite precursor material to distilled water to obtain a mixed solution, then place it in a nitrogen atmosphere, and then add sulfate powder to the mixed solution for anaerobic stirring. Then, centrifuge and retain the precipitate, and wash it to neutrality. After freeze-drying, obtain a self-catalytic oxidation catalyst, that is, complete the preparation method.

[0041] The anaerobic stirring in step two of this implementation manner is to carry out an ion exchange reaction to displace the nitrate ions.

[0042] A self-catalytic oxidation catalyst prepared by this implementation manner is a self-catalytic oxidation catalyst based on persulfate intercalation modification.

[0043] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that in the mixed solution in Step 1, the molar ratio of zinc nitrate to aluminum nitrate is 3:1; the concentration of zinc nitrate is 75 mmol / L, and the concentration of aluminum nitrate is 25 mmol / L. Other steps and parameters are the same as those in Specific Embodiment 1.

[0044] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 is that in Step 1, the alkali solution is sodium hydroxide solution or potassium hydroxide solution. Other steps and parameters are the same as those in Specific Embodiment 1.

[0045] Specific Embodiment 4: The difference between this embodiment and Specific Embodiment 1 is that in Step 1, for the hydrothermal co-precipitation: the preset temperature in the water bath is 70 °C and the time is 24 h. Other steps and parameters are the same as those in Specific Embodiment 1.

[0046] Specific Embodiment 5: The difference between this embodiment and Specific Embodiment 1 is that in Step 1, for the washing: it is washed 2 - 3 times successively with absolute ethanol and deionized water. Other steps and parameters are the same as those in Specific Embodiment 1.

[0047] Specific Embodiment 6: The difference between this embodiment and Specific Embodiment 1 is that in Step 1, for the centrifugation and drying: it is centrifuged at a speed of 5000 - 7000 r / min for 10 - 12 min and dried at 60 - 70 °C for 8 - 10 h. Other steps and parameters are the same as those in Specific Embodiment 1.

[0048] Specific Embodiment 7: The difference between this embodiment and Specific Embodiment 1 is that in Step 2, the dosing ratio of the nitrate-intercalated hydrotalcite precursor material to distilled water is (1 - 2) g : (100 - 200) ml. Other steps and parameters are the same as those in Specific Embodiment 1.

[0049] Specific Embodiment 8: The difference between this embodiment and Specific Embodiment 1 is that in Step 2, for the sulfate powder: after the sulfate powder is added to the mixed solution, the concentration is 0.1 - 20 mM. Other steps and parameters are the same as those in Specific Embodiment 1.

[0050] Specific Embodiment 9: The difference between this embodiment and Specific Embodiment 1 is that in Step 2, the time for the anoxic stirring is 30 - 60 min. Other steps and parameters are the same as those in Specific Embodiment 1.

[0051] Specific Embodiment 10: The difference between this embodiment and Specific Embodiment 1 is that in Step 2, for the washing: it is washed 2 - 3 times with deionized water. Other steps and parameters are the same as those in Specific Embodiment 1.

[0052] Embodiment XI: The difference between this embodiment and Embodiment I is that in step two, for freeze-drying, the preset cold trap temperature is -60°C and the time is 24 - 48 h. Other steps and parameters are the same as those in Embodiment I.

[0053] Embodiment XII: An application of a self-catalytic oxidation catalyst in this embodiment is for treating wastewater containing new pollutants; specifically: adding the self-catalytic oxidation catalyst to the wastewater containing new pollutants, and after stirring for 30 - 60 min, the treatment is completed.

[0054] Embodiment XIII: The difference between this embodiment and Embodiment XII is that the concentration of the self-catalytic oxidation catalyst in the wastewater after addition is 0.1 - 0.5 g / L; the new pollutant in the wastewater containing new pollutants is sulfamethoxazole. Other steps and parameters are the same as those in Embodiment XII.

[0055] The beneficial effects of the present invention are verified through the following examples:

[0056] Example:

[0057] A preparation method of a self-catalytic oxidation catalyst is realized according to the following steps:

[0058] I. Dissolve zinc nitrate and aluminum nitrate in deionized water to obtain a mixed solution, then add an alkali solution to adjust the pH value to 10 - 12, magnetically stir and mix evenly, then carry out hydrothermal co-precipitation. After completion, wash the product to neutrality, and after centrifugation and drying, obtain a nitrate-intercalated hydrotalcite precursor material, denoted as ZnAl-LDH;

[0059] II. Add the above-mentioned nitrate-intercalated hydrotalcite precursor material to distilled water to obtain a mixed solution, then place it in a nitrogen atmosphere, and then add sulfate powder to the mixed solution for anoxic stirring, then centrifuge and retain the precipitate, and then wash it to neutrality. After freeze-drying, obtain a self-catalytic oxidation catalyst, denoted as ZnAl-PDS-LDH, and thus complete the preparation method.

[0060] In step I of this example, the dosage of zinc nitrate is 75 mM (2.2312 g); the dosage of aluminum nitrate is 25 mM (0.9378 g); the concentration of zinc nitrate is 75 mmol / L, and the concentration of aluminum nitrate is 25 mmol / L.

[0061] In step I of this example, the alkali solution is sodium hydroxide solution.

[0062] In step I of this example, for the hydrothermal co-precipitation: the preset temperature in the water bath is 70°C and the time is 24 h.

[0063] In step I of this example, for the washing: wash 3 times successively with absolute ethanol and deionized water.

[0064] The centrifugation and drying in step 1 of this embodiment are as follows: centrifugation at a speed of 6000 r / min for 10 min and drying at 70° C. for 8 h.

[0065] In step 2 of this embodiment, the dosages of the nitrate-intercalated hydrotalcite precursor material and distilled water are 1 g and 100 ml, respectively.

[0066] The sulfate powder in step 2 of this embodiment: the concentration of the sulfate powder after being added to the mixed solution is 2 mM.

[0067] The anoxic stirring time in step 2 of this embodiment is 30 minutes.

[0068] Washing in step 2 of this embodiment: wash 3 times with deionized water.

[0069] The freeze drying in step 2 of this embodiment is as follows: the preset cold trap temperature is -60°C and the time is 24 hours.

[0070] The transmission electron microscopy (TEM) results of the ZnAl-LDH and the final product ZnAl-PDS-LDH obtained in this example are as follows: Figure 1 As shown in the figure, it can be seen that there are significant differences in the morphology and structure between the ZnAl-LDH precursor material and the ZnAl-PDS-LDH autocatalytic oxidation material. The ZnAl-LDH precursor material is composed of countless hexagonal sheet structures, while the ZnAl-PDS-LDH autocatalytic oxidation material is closer to an amorphous form than the precursor material.

[0071] The X-ray diffraction analysis (XRD) results of the ZnAl-LDH and the final product ZnAl-PDS-LDH obtained in this example are as follows: Figure 2 As shown in the figure, it can be seen that the lattice structure of the ZnAl-LDH precursor is close to that of Zn6Al2O9, with characteristic crystal plane structures of (111), (110), and (210). After the introduction of PDS by ion exchange, a characteristic crystal plane (003) appears at 19.13°, which belongs to [ZnxAlx(OH)3].(SO4) x (H2O)2], indicating that PDS was successfully introduced into the intermediate intercalation layer of the zinc-aluminum hydrotalcite material by the method in this embodiment. In addition, cyclic voltammetry tests were performed on ZnAl-LDH and ZnAl-PDS-LDH, and the results were as follows. Figure 3 As shown, the oxidation peak position of ZnAl-PDS-LDH appears at 0.46~0.64V, while that of the precursor material ZnAl-LDH is at 0.18~0.38V, indicating that the introduction of PDS significantly improves the redox potential of the material itself.

[0072] In this example, the degradation performance tests were carried out on the obtained ZnAl-LDH and the final product ZnAl-PDS-LDH respectively:

[0073] 0.1 g / L of ZnAl-LDH material was added to 100 ml of wastewater containing 20 μM of sulfamethoxazole (SMX). Subsequently, 2 mM PDS solution was added, and samples were taken at 8 main reaction time points of 0, 5, 10, 20, 30, 40, 50, and 60 min, and the sampling volume was 1 ml. The samples were added to 1 ml of 10 mM sodium thiosulfate solution to terminate the reaction. After mixing, the samples were filtered through a 0.22 μm filter membrane, and finally the filtered samples (denoted as ZnAl-LDH+PDS+SMX) were sent to an Agilent high-performance liquid chromatography for pollutant concentration detection.

[0074] 0.1 g / L of ZnAl-PDS-LDH material was directly added to 100 ml of wastewater containing 20 μM of sulfamethoxazole (SMX), and samples were taken at 8 main reaction time points of 0, 5, 10, 20, 30, 40, 50, and 60 min, and the sampling volume was 1 ml. The samples were added to 1 ml of 10 mM sodium thiosulfate solution to terminate the reaction. After mixing, the samples were filtered through a 0.22 μm filter membrane, and finally the filtered samples (denoted as ZnAl-PDS-LDH+SMX) were sent to an Agilent high-performance liquid chromatography for pollutant concentration detection. The detection method for SMX was that acetonitrile (A) and 0.1% formic acid (B) were used as the mobile phase, the mobile phase ratio was set as A:B = 40:60, the detection wavelength was 270 nm, and the chromatographic column was tested using a Waters C18 liquid chromatography column.

[0075] The results are as Figure 4 shown. In the ZnAl-LDH system set in the degradation performance test, the precursor material could only degrade 11.88% of the pollutants within 60 min, indicating that the precursor material did not have catalytic activity. However, in the ZnAl-PDS-LDH system set in the degradation performance test, 95.91% of SMX was degraded. According to the errors of multiple performance tests, the ZnAl-PDS-LDH material could achieve a degradation level of 96% - 99.9% of SMX in the degradation system. At the same time, combined with the results of cyclic voltammetry tests, it can be seen that the ZnAl-PDS-LDH material itself had a strong catalytic oxidation effect in the degradation system.

[0076] The mechanism of the obtained ZnAl-LDH and the final product ZnAl-PDS-LDH in this example was explored:

[0077] ① Free radical and non-free radical probe experiments: Methanol is a probe compound for sulfate radicals and hydroxyl radicals. tert-Butanol is a probe compound for hydroxyl radicals. L-Histidine is a probe compound for singlet oxygen. Prepare methanol, tert-butanol, and L-histidine solutions with a concentration of 5 mM each. Prepare 4 100-ml wastewater samples containing 20 μM sulfamethoxazole, add the above 4 probe reagents respectively, and then add 0.1 g / L of ZnAl-PDS-LDH material to start the detection. Sampling is carried out at 8 main reaction time points, namely 0, 5, 10, 20, 30, 40, 50, and 60 min, and the sampling volume is 1 ml. Add the sample to 1 ml of 10 mM sodium thiosulfate solution to terminate the reaction. After mixing, filter it through a 0.22-μm filter membrane and finally send it to an Agilent high-performance liquid chromatography for detecting the pollutant concentration.

[0078] ② Free radical and non-free radical capture experiments: Detect whether there are reactive species such as sulfate radicals, hydroxyl radicals, superoxide anion radicals, and singlet oxygen in the reaction system through capture experiments. In this example, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) is used as a spin trap for sulfate radicals, hydroxyl radicals, and superoxide anion radicals, and 2,2,6,6-tetramethylpiperidine (TEMP) is used as a spin trap for singlet oxygen. Among them, the concentration of DMPO is 20 μM, and the concentration of TEMP is 50 μM. Take 5 ml of samples from the ZnAl-LDH and ZnAl-PDS-LDH systems set in the degradation performance test respectively, mix them well with DMPO and TEMP traps, and finally send them to an electron paramagnetic resonance spectrometer for testing.

[0079] The degradation effect of the above probe experiments is as Figure 5 shown, and the results of the capture experiment are as Figure 6 shown. The results together confirm that there are no obvious free radical reactive species in the ZnAl-PDS-LDH system set in the degradation performance test. As Figure 5 shown, after adding 4 different probes, the degradation of SMX is inhibited by the quencher, but the inhibition degree is relatively weak. At the same time, Figure 6 the capture results of free radicals and singlet oxygen show that the characteristic peak of DMPO-OH can be captured in the ZnAl-PDS-LDH system set in the degradation performance test. However, in the system based on ZnAl-PDS-LDH, the characteristic peak of DMPO-OH disappears, indicating that there are no obvious capturable reactive species in the system. The results of TEMP also exclude 1The role of O2 is that the characteristic triplet peaks of TEMPO disappear significantly in the degradation system based on ZnAl-PDS-LDH, proving that there are no typical reactive species such as sulfate radicals, hydroxyl radicals, superoxide anions, and singlet oxygen in the ZnAl-PDS-LDH system set in the degradation performance test, further confirming that the pollutant is degraded by the autocatalytic oxidation of ZnAl-PDS-LDH.

[0080] The obtained ZnAl-LDH and the final product ZnAl-PDS-LDH in this example were subjected to electrochemical tests:

[0081] a. Open circuit potential (OCPT) test: The open circuit potential is used to test the electrochemical performance of the electrode surface material. Prepare 20 mg of ZnAl-LDH and ZnAl-PDS-LDH, add them to a mixed solution containing 250 μL of anhydrous ethanol and 25 μL of naphthol solution, after ultrasonic treatment for 10 min, evenly drop the mixed solution onto a 1 cm × 1 cm square conductive carbon paper with a dropper, and dry for 12 h for standby. Add to the electrolytic cell, fix the conductive carbon paper with the material on the working electrode, prepare a reference electrode and an auxiliary electrode, immerse the three electrodes in a 200 ml 25 mM sodium sulfate electrolyte solution, and connect the other end to an electrochemical workstation for open circuit potential testing.

[0082] b. Chronoamperometry (I-t) test: Chronoamperometry is used to detect the current change and electron transfer in the degradation system. Prepare 20 mg of ZnAl-LDH and ZnAl-PDS-LDH, add them to a mixed solution containing 250 μL of anhydrous ethanol and 25 μL of naphthol solution, after ultrasonic treatment for 10 min, evenly drop the mixed solution onto a 1 cm × 1 cm square conductive carbon paper with a dropper, and dry for 12 h for standby. Add to the electrolytic cell, fix the conductive carbon paper with the material on the working electrode, prepare a reference electrode and an auxiliary electrode, immerse the three electrodes in a 200 ml 25 mM sodium sulfate electrolyte solution, and connect the other end to an electrochemical workstation for instantaneous current testing. Add persulfate oxidant and the pollutant sulfamethoxazole at the 100th s and the 400th s respectively, and observe the degree of current change.

[0083] The above open circuit potential test results are as Figure 7 shown, and the chronoamperometry test results are as Figure 8 shown; as can be seen from Figure 7 , after adding the pollutant to the ZnAl-PDS-LDH degradation system set in the open circuit potential test, the open circuit potential increased sharply by 0.59 V, indicating that due to the increase in its own redox potential, the ZnAl-PDS-LDH material can undergo electron transfer after contacting the pollutant to form a complex with a higher open circuit potential, thereby achieving efficient degradation of the pollutant.Figure 8 Further confirmed the potential electron transfer in this system. Compared with the ZnAl-LDH system set in the chronoamperometry test, the addition of SMX to the ZnAl-PDS-LDH system induced a strong change in chronoamperometry, confirming that ZnAl-PDS-LDH degrades pollutants through the electron transfer mechanism.

[0084] Perform Raman spectroscopy experiments on the final product ZnAl-PDS-LDH obtained in this example:

[0085] The Raman spectroscopy experiment measures the molecular structure changes of materials in the degradation system. First, extract the ZnAl-PDS-LDH material after the reaction. After the reaction of the ZnAl-PDS-LDH system set in the degradation performance test ends, use a suction filtration device to extract the ZnAl-PDS-LDH material in the system. Select a 0.22 μM hydrophilic filter membrane for suction filtration for 10 min, and then wash the residual ZnAl-PDS-LDH material on the filter membrane with ethanol and deionized water 2 - 3 times respectively, and dry it at 60 - 70 °C for 4 - 6 h to obtain the ZnAl-PDS-LDH material after the reaction of the degradation system. Send the ZnAl-PDS-LDH material after the reaction and the ZnAl-PDS-LDH material prepared in the example to the Raman spectroscopy for detection.

[0086] The above Raman spectroscopy test results are as Figure 9 shown. The characteristic peaks of the ZnAl-PDS-LDH material before the reaction at 1076 cm -1 and 836 cm -1 are respectively attributed to the S-O and S=O stretching vibrations in S2O8 2- . In the ZnAl-PDS-LDH material after the reaction, the S=O stretching vibration at 836 cm 2- in S2O8 -1 weakens, while the S-O vibration at 982 cm -1 attributed to SO4 2- strengthens. This confirms the structural change of the intercalated PDS anion during the reaction. When pollutants are added, due to electron transfer and attack, the PDS intercalated in the ZnAl-PDS-LDH material decomposes to a certain extent, leading to a change in the sulfur form in PDS.

[0087] Perform PDS residue experiments on the ZnAl-LDH and the final product ZnAl-PDS-LDH obtained in this example:

[0088] The residual PDS concentration was tested using the iodine titration method. 5 ml of 1 M potassium iodide solution, 1 ml of 480 mM sodium bicarbonate solution, and 3 ml of deionized water were mixed and set aside. Samples were taken from the ZnAl-LDH and ZnAl-PDS-LDH systems set in the degradation performance test at eight main reaction time points, namely 0, 5, 10, 20, 30, 40, 50, and 60 min. The sample volume was 1 ml and added to the above mixed solution and stirred thoroughly. The residual PDS concentration was then detected at 352 nm using a UV spectrophotometer. In addition, the sulfate ion concentration was detected by ion chromatography.

[0089] The test results are as follows Figure 10 and 11 As shown, Figure 10 The residual PDS content in the ZnAl-LDH and ZnAl-PDS-LDH systems used in the degradation performance test was measured. In the ZnAl-LDH degradation system with direct PDS addition, the maximum residual PDS content was 118.06 μM. In contrast, the maximum residual PDS content during the reaction of the prepared autocatalytic oxidation material ZnAl-PDS-LDH was only 1.07 μM, indicating that the material exhibits very low PDS leaching during application and poses no risk of secondary pollution to the environment. Figure 11 The residual sulfate level in the ZnAl-PDS-LDH system was detected and found to be only 1.76 μM, further confirming that the material can efficiently degrade pollutants under the mechanism of electron transfer while having extremely low residual concentrations of by-products such as persulfate and sulfate. It is an efficient, green and safe self-catalytic oxidation material.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a self-catalytic oxidation catalyst, characterized in that It proceeds as follows:

1. Dissolve zinc nitrate and aluminum nitrate in deionized water to obtain a mixed solution, then add an alkali solution to adjust the pH value to 10 - 12. After magnetic stirring and mixing evenly, carry out hydrothermal co-precipitation. After completion, wash the product to neutrality, and obtain a nitrate-intercalated hydrotalcite precursor material after centrifugation and drying; 2. Add the above-mentioned nitrate-intercalated hydrotalcite precursor material to distilled water to obtain a mixed solution, then place it in a nitrogen atmosphere. Next, add sulfate powder to the mixed solution for anaerobic stirring, then centrifuge and retain the precipitate, and then wash it to neutrality. After freeze-drying, obtain a self-catalytic oxidation catalyst, thus completing the preparation method.

2. The preparation method of an autocatalytic oxidation catalyst according to claim 1, wherein In the mixed solution in step 1, the molar ratio of zinc nitrate to aluminum nitrate is 3:1; the concentration of zinc nitrate is 75 mmol / L, and the concentration of aluminum nitrate is 25 mmol / L.

3. The preparation method of an autocatalytic oxidation catalyst according to claim 1, characterized in that The alkali solution in step 1 is sodium hydroxide solution or potassium hydroxide solution.

4. The preparation method of an autocatalytic oxidation catalyst according to claim 1, characterized in that The hydrothermal co-precipitation in step 1: The preset temperature in the water bath is 70 °C, and the time is 24 h.

5. The preparation method of an autocatalytic oxidation catalyst according to claim 1, characterized in that In step 2, the dosing ratio of the nitrate-intercalated hydrotalcite precursor material to distilled water is (1 - 2) g:(100 - 200) ml.

6. The preparation method of an autocatalytic oxidation catalyst according to claim 1, wherein The sulfate powder in step 2: The concentration of the sulfate powder in the mixed solution after addition is 0.1 - 20 mM.

7. The preparation method of an autocatalytic oxidation catalyst according to claim 1, characterized in that The time of anaerobic stirring in step 2 is 30 - 60 min.

8. The preparation method of an autocatalytic oxidation catalyst according to claim 1, characterized in that The freeze-drying in step 2: The preset cold trap temperature is -60 °C, and the time is 24 - 48 h.

9. The application of an autocatalytic oxidation catalyst according to claim 1, characterized in that It is used to treat wastewater containing new pollutants; specifically: Add the self-catalytic oxidation catalyst to the wastewater containing new pollutants, and after stirring for 30 - 60 min, the treatment is completed.

10. The application of an autocatalytic oxidation catalyst according to claim 9, characterized in that The concentration of the self-catalytic oxidation catalyst in the wastewater after addition is 0.1 - 0.5 g / L; the new pollutant in the wastewater containing new pollutants is sulfamethoxazole.

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