Method for removing benzohydroxamic acid through cobalt monatomic catalyst polymerization

Abstract

The invention belongs to the field of water treatment, and discloses a method for removing benzohydroxamic acid through cobalt monatomic catalyst polymerization. The method comprises the following steps: mixing a potassium hydrogen peroxymonosulfate solution and an aqueous solution containing benzohydroxamic acid, then adding a cobalt monatomic catalyst, and carrying out a mixed reaction so as to remove benzohydroxamic acid in a polymerization manner. The cobalt monatomic catalyst has a Co-N4 atom coordination structure; and the loading capacity of the cobalt single atoms is 2%-3%. The method disclosed by the invention has the advantages of high removal rate of the benzohydroxamic acid, low consumption of the oxidant, suitability for wide pH conditions, recyclability, high removal rate after repeated use, realization of efficient removal of the benzohydroxamic acid and directional recovery of carbon resources in actual beneficiation wastewater treatment, and very high economic benefits.

Description

Technical Field

[0001] The present invention belongs to the field of water treatment, and particularly relates to a method for polymerizing and removing benzohydroxamic acid by a cobalt single-atom catalyst. Background Art

[0002] In recent years, the urgent need for efficient treatment of mine wastewater and water environmental protection has become imminent, and improving the recycling rate of wastewater is an ideal way to solve this problem. Currently, one of the main problems restricting the reuse of mine wastewater is the refractory beneficiation reagents in the residual recycled water. These reagents are difficult to be effectively degraded during the natural purification process in the tailings pond, resulting in a greater impact on the mineral flotation process in the beneficiation process. As an organic flotation reagent, benzohydroxamic acid is widely used in the flotation process of sulfide or oxidized minerals. Due to its benzene ring structure and oxime group, it has stable chemical properties and toxicity. Residual in wastewater will lead to an increase in the chemical oxygen demand of the water body, and the accumulation of nitrogen element content is also likely to cause water eutrophication, which is not conducive to the survival of aquatic plants, and ultimately destroys the water environmental quality and affects the ecological balance. Therefore, benzohydroxamic acid in the beneficiation wastewater needs to be treated urgently.

[0003] Currently, the treatment methods for beneficiation wastewater containing benzohydroxamic acid are mainly divided into three categories: flocculation precipitation method, biological method, and advanced oxidation method. The flocculation precipitation method realizes the removal of beneficiation wastewater containing benzohydroxamic acid by adding metal ions, precipitants, chelating agents, and flocculants to the wastewater. Its treatment effect is limited, the treatment time is long, the sludge settlement is slow, and dehydration is difficult. The biological method removes benzohydroxamic acid by adding microorganisms capable of decomposing benzohydroxamic acid to the beneficiation wastewater containing benzohydroxamic acid through biological decomposition. Its wastewater treatment cycle is long, the treatment conditions are relatively harsh, and it is difficult to be widely applied. The advanced oxidation method mainly relies on generating free radicals with a relatively high redox potential to attack the benzohydroxamic acid molecule, resulting in the ring opening and bond breaking of benzohydroxamic acid, and finally generating carbon dioxide and water to be removed. It has the advantages of fast decomposition speed and strong wastewater purification ability, and is a method with broad prospects for treating refractory beneficiation wastewater containing benzohydroxamic acid.

[0004] However, there are still obvious deficiencies in the current advanced oxidation method for treating beneficiation wastewater containing benzohydroxamic acid: (1) The active free radicals have low selectivity for benzohydroxamic acid, and the oxidation ability is greatly interfered by the quality conditions of the beneficiation wastewater; (2) In the existing technology, the benzohydroxamic acid in the beneficiation wastewater is generally completely decomposed to generate carbon dioxide, nitrogen oxides, and water, which is determined by the stoichiometry of chemical reactions, and its energy consumption is huge. Taking potassium monopersulfate (KHSO5·0.5KHSO4·0.5K2SO4) as an oxidant, for every 1 mol of benzohydroxamic acid (137 g) treated, 18 mol (5526 g) of potassium monopersulfate is required; (3) After benzohydroxamic acid is attacked by free radicals, it may form stronger dicarboxylic intermediates and nitrogen oxides, with the risk of secondary pollution.

[0005] In view of this, there is an urgent need for a method for treating the ore dressing wastewater of benzohydroxamic acid with high selectivity, low consumption of oxidant, and not mainly using active free radicals as the oxidation method to solve the above deficiencies. Summary of the Invention

[0006] In order to overcome the above-mentioned disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide an application of a cobalt single-atom catalyst in the polymerization for removing benzohydroxamic acid.

[0007] Another object of the present invention is to provide a method for polymerizing and removing benzohydroxamic acid by using a cobalt single-atom catalyst.

[0008] The object of the present invention is achieved by the following solutions:

[0009] An application of a cobalt single-atom catalyst in the polymerization for removing benzohydroxamic acid.

[0010] The cobalt single-atom catalyst has a Co-N4 atomic coordination structure; the loading amount of cobalt single atoms is 2% - 3%; it has the characteristics of high catalytic activity and low metal component dissolution.

[0011] The cobalt single-atom catalyst is prepared according to the following steps:

[0012] S1. In the presence of a solvent, 2-methylimidazole and zinc nitrate hexahydrate are ultrasonically dissolved to obtain a white suspension, denoted as solution A;

[0013] S2. In the presence of a solvent, cobalt nitrate hexahydrate is ultrasonically dissolved, denoted as solution B;

[0014] S3. Mix and stir solution A and solution B to undergo a complexation substitution reaction to obtain a purple suspension containing the precursor of the cobalt single-atom catalyst;

[0015] S4. Centrifuge, wash, and dry the suspension of the cobalt single-atom catalyst precursor to obtain a purple cobalt single-atom catalyst precursor;

[0016] S5. Perform high-temperature treatment on the cobalt single-atom catalyst precursor to obtain the cobalt single-atom catalyst;

[0017] The solvents selected in steps S1 and S2 are the same, and the solvent is selected from at least one of water, ethanol, and methanol, preferably methanol;

[0018] The mass ratio of 2-methylimidazole, zinc nitrate hexahydrate, and cobalt nitrate hexahydrate is: (5.5 - 6.5):(3.5 - 4.5):(0.1 - 0.5);

[0019] The volume ratio of solution A and solution B in step S3 is (100 - 200):(50 - 100);

[0020] The complex substitution reaction conditions described in step S3 are as follows: the stirring temperature is 20-60 °C, the stirring speed is 200-800 r / min, and the stirring time is 10-24 h;

[0021] The cleaning described in step S4 is preferably carried out with at least one of water, ethanol, and methanol.

[0022] The high-temperature treatment conditions described in step S5 are as follows: in an inert gas atmosphere, the temperature is 900-1100 °C, the heating rate is 2-5 °C / min, and the time is 1-3 h.

[0023] A method for polymerizing and removing benzohydroxamic acid by a cobalt single-atom catalyst includes the following steps:

[0024] Mix a potassium monopersulfate solution and an aqueous solution containing benzohydroxamic acid, and then add a cobalt single-atom catalyst. The mixed reaction can polymerize and remove benzohydroxamic acid.

[0025] Before mixing the potassium monopersulfate solution and the aqueous solution containing benzohydroxamic acid, it is preferred to adjust the two solutions to the same pH first. The range of the same pH is 3.00-11.00; the pH regulator is a sulfuric acid solution or a sodium hydroxide solution, and the concentration is 0.1-1 mol / L.

[0026] Before adding the cobalt single-atom catalyst after mixing the potassium monopersulfate solution and the aqueous solution containing benzohydroxamic acid, the concentration of the potassium monopersulfate solution in the obtained mixed solution is 0.5-6 mmol / L, and the concentration of the benzohydroxamic acid solution is 0.1-3 mmol / L.

[0027] After adding the cobalt single-atom catalyst, the concentration of the cobalt single-atom catalyst is 0.1-0.5 g / L.

[0028] Preferably, before adding the cobalt single-atom catalyst, the concentration of the potassium monopersulfate solution is 1-3 mmol / L, the concentration of the benzohydroxamic acid solution is 0.5-1.5 mmol / L, and the concentration of the cobalt single-atom catalyst is 0.3 g / L after adding the cobalt single-atom catalyst. At this time, the removal rate of benzohydroxamic acid can be >99.5%.

[0029] The reaction mentioned above refers to a room-temperature stirring reaction. The stirring rate is 200-600 r / min, and the time is 10-30 min. After the reaction, the system is separated to obtain a solid phase. The polymerization product solution is obtained by extraction with an organic solvent, and the solid-phase polymerization product can be recovered by solvent evaporation. The organic solvent is one of tetrahydrofuran, toluene, or methanol, preferably tetrahydrofuran.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] The method disclosed by the present invention has a high removal rate of benzohydroxamic acid, low consumption of oxidant, is applicable to a wide pH range, can be recycled, and can still maintain a high removal rate after multiple uses. It can achieve the efficient removal of benzohydroxamic acid and the directional recovery of carbon resources in the actual beneficiation wastewater treatment, and has very high economic benefits. Description of the Drawings

[0032] Figure 1 For Figure 1 It is the molecular weight detection graph of the polymerization product after the reaction in Example 3 of the present invention.

[0033] Figure 2 It is the aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) photograph of the cobalt single-atom catalyst prepared in Example 1 of the present invention.

[0034] Figure 3 It is the surface scanning distribution graph of the cobalt single-atom catalyst prepared in Example 1 of the present invention.

[0035] Figure 4 It is the Co K-edge EXAFS Fourier transform spectrum graph of the cobalt single-atom catalyst prepared in Example 1 of the present invention.

[0036] Figure 5 It is the effect graph of the removal of benzohydroxamic acid at different potassium monopersulfate concentrations in Examples 2, 4 to 7.

[0037] Figure 6 It is the effect graph of the removal of benzohydroxamic acid under different pH conditions in Examples 2, 8 to 11.

[0038] Figure 7 It is the effect graph of the removal of benzohydroxamic acid in the repeated experiments of Examples 12 to 16.

[0039] Figure 8 It is the effect graph of the removal of benzohydroxamic acid in Examples 2, Test Examples 1 to 2. Detailed Embodiments

[0040] The present invention will be further described in detail below with reference to the embodiments and the drawings, but the embodiments of the present invention are not limited thereto. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0041] The reagents used in the embodiments can be conventionally purchased from the market without special instructions.

[0042] Example 1

[0043] 1) Ultrasonically dissolve 5.994 g of 2-methylimidazole and 4.044 g of zinc nitrate hexahydrate in 150 mL of methanol for 25 min to obtain a white suspension, denoted as Solution A.

[0044] 2) Ultrasonically dissolve 0.132 g of cobalt nitrate hexahydrate in 50 mL of methanol for 15 min, denoted as Solution B.

[0045] 3) Mix Solution A and Solution B, stir at room temperature at a stirring speed of 600 r / min for 18 h to undergo a complex substitution reaction, obtaining a purple suspension containing the cobalt single-atom catalyst precursor.

[0046] 4) Centrifuge the cobalt single-atom catalyst precursor at 7000 r / min for 6 min, wash the cobalt single-atom catalyst precursor with methanol, and dry the cobalt single-atom catalyst precursor at 60 °C for 4 h.

[0047] 5) Under argon protection, heat the cobalt single-atom catalyst precursor to 900 °C at a rate of 5 °C / min, hold for 2 h and then cool naturally to obtain the cobalt single-atom catalyst with a loading of 2.5 wt%.

[0048] The aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of the obtained cobalt single-atom catalyst is as Figure 2 shown, proving that cobalt exists in the form of single atoms.

[0049] The elemental mapping image of the obtained cobalt single-atom catalyst is as Figure 3 shown, proving that cobalt elements are evenly distributed in the catalyst material. After testing, the specific surface area of the catalyst is 280 m 2 / g, and the pore volume is 0.13 cm 3 / g.

[0050] The Co K-edge Fourier transform spectrum of the obtained cobalt single-atom catalyst is as Figure 4 shown, proving that cobalt has a Co-N4 coordination structure.

[0051] Example 2

[0052] 1) Use a sodium hydroxide reagent (1 mol / L) to adjust the pH of a potassium monopersulfate solution with a concentration of 2 mmol / L to 7.00, denoted as Solution a; adjust the pH of a benzohydroxamic acid solution with a concentration of 1 mmol / L to 7.00, denoted as Solution b.

[0053] 2) Mix the solution a and solution b obtained in step 1) at a volume ratio of 1:1 (the concentration of potassium monopersulfate in the mixed system is 1 mmol / L; the concentration of benzohydroxamic acid is 0.5 mmol / L), add a cobalt single-atom catalyst (the catalyst concentration is 0.3 g / L), react for 15 min under the conditions of room temperature and stirring at 400 r / min, then perform solid-liquid separation. After quantitative analysis of the liquid phase, the removal rate of benzohydroxamic acid is 99.5%.

[0054] Example 3

[0055] 1) Other steps are the same as those in Example 2, except that in step 1, the concentration of the potassium monopersulfate solution becomes 6 mmol / L, and the concentration of the benzohydroxamic acid solution becomes 3 mmol / L. After the experiment, the polymeric product in the solid phase after solid-liquid separation is extracted with tetrahydrofuran, the extraction solution is evaporated to remove the solvent, and after obtaining the solid-phase polymeric product, its molecular weight is tested.

[0056] 2) After quantitative analysis of the liquid-phase product, the calculated removal rate of benzohydroxamic acid is 99.8%.

[0057] Figure 1 It is a molecular weight detection chart of the solid-phase polymeric product after the reaction. As can be seen from the figure: the mass-to-charge ratio of the solid-phase polymeric product is between 450 and 1200, which indicates that a polymerization reaction occurred during the transformation of benzohydroxamic acid, thus generating a high-molecular-weight water-insoluble polymeric product.

[0058] Example 4

[0059] Other steps are the same as those in Example 2, except that in step 1, the concentration of the potassium monopersulfate solution is 3 mmol / L (the concentration of potassium monopersulfate in the mixed system is 1.5 mmol / L). After quantitative analysis, the calculated removal rate of benzohydroxamic acid is 100%.

[0060] Example 5

[0061] Other steps are the same as those in Example 2, except that in step 1, the concentration of the potassium monopersulfate solution is 1 mmol / L (the concentration of potassium monopersulfate in the mixed system is 0.5 mmol / L). After quantitative analysis, the calculated removal rate of benzohydroxamic acid is 71.8%.

[0062] Example 6

[0063] Other steps are the same as those in Example 2, except that in step 1, the concentration of the potassium monopersulfate solution is 0.5 mmol / L (the concentration of potassium monopersulfate in the mixed system is 0.25 mmol / L). After quantitative analysis, the calculated removal rate of benzohydroxamic acid is 60%.

[0064] Example 7

[0065] Other steps are the same as those in Example 2, except that the concentration of potassium monopersulfate solution in Step 1 is 0.25 mmol / L (the concentration of potassium monopersulfate in the mixed system is 0.125 mmol / L). After quantitative analysis, the removal rate of benzohydroxamic acid is calculated to be 41.5%.

[0066] Figure 5 Figures for the removal effect of benzohydroxamic acid at different concentrations of potassium monopersulfate in Examples 2, 4 - 7. It can be seen from the figures that: with the increase in the concentration of potassium monopersulfate, both the reaction rate and the final removal rate of benzohydroxamic acid gradually increase; at low concentrations of potassium monopersulfate, due to insufficient amount of potassium monopersulfate, there is a relatively high residue of benzohydroxamic acid after it is consumed; at high concentrations of potassium monopersulfate, benzohydroxamic acid can be rapidly and completely removed.

[0067] Example 8

[0068] Other steps are the same as those in Example 2, except that the pH values of both the potassium monopersulfate solution and the benzohydroxamic acid solution are adjusted to 3.00. After quantitative analysis, the removal rate of benzohydroxamic acid is calculated to be 96.8%.

[0069] Example 9

[0070] Other steps are the same as those in Example 2, except that the pH values of both the potassium monopersulfate solution and the benzohydroxamic acid solution are adjusted to 5.00. After quantitative analysis, the removal rate of benzohydroxamic acid is calculated to be 97.8%.

[0071] Example 10

[0072] Other steps are the same as those in Example 2, except that the pH values of both the potassium monopersulfate solution and the benzohydroxamic acid solution are adjusted to 9.00. After quantitative analysis, the removal rate of benzohydroxamic acid is calculated to be 99.8%.

[0073] Example 11

[0074] Other steps are the same as those in Example 2, except that the pH values of both the potassium monopersulfate solution and the benzohydroxamic acid solution are adjusted to 11.00. After quantitative analysis, the removal rate of benzohydroxamic acid is calculated to be 100%.

[0075] Figure 6 Figures for the removal effect of benzohydroxamic acid at different pH values in Examples 2, 8 - 11. It can be seen from the figures that: under different pH conditions, the removal rate of benzohydroxamic acid is greater than 96%, which proves that the cobalt single - atom catalyst of the present invention is applicable to a wide pH range.

[0076] Example 12

[0077] After following the solution of Example 2, the first repetition is carried out.

[0078] First repetition: Other steps are the same as those in Example 2, except that after washing the solid phase separated in Example 2 three times with water, it is added to the mixed solution of a and b. After quantitative analysis, the removal rate of benzohydroxamic acid is 99.7%.

[0079] Example 13

[0080] After following the solution of Example 12, the second repetition is carried out.

[0081] Second repetition: Other steps are the same as those in Example 2, except that after washing the solid phase separated in Example 12 three times with water, it is added to the mixed solution of a and b. After quantitative analysis, the removal rate of benzohydroxamic acid is 97.0%.

[0082] Example 14

[0083] After following the solution of Example 13, the third repetition is carried out.

[0084] Third repetition: Other steps are the same as those in Example 2, except that after washing the solid phase separated in Example 13 three times with water, it is added to the mixed solution of a and b. After quantitative analysis, the removal rate of benzohydroxamic acid is 93.1%.

[0085] Example 15

[0086] After following the solution of Example 14, the fourth repetition is carried out.

[0087] Fourth repetition: Other steps are the same as those in Example 2, except that after washing the solid phase separated in Example 14 three times with water, it is added to the mixed solution of a and b. After quantitative analysis, the removal rate of benzohydroxamic acid is 90.1%.

[0088] Example 16

[0089] After following the solution of Example 15, the fifth repetition is carried out.

[0090] Fifth repetition: Other steps are the same as those in Example 2, except that after washing the solid phase separated in Example 15 three times with water, it is added to the mixed solution of a and b. After quantitative analysis, the removal rate of benzohydroxamic acid is 88.0%.

[0091] Figure 7 It is the removal effect diagram of benzohydroxamic acid for the repeated experiments of Examples 12 - 16. As can be seen from the figure, the removal rate of benzohydroxamic acid in Example 16 only decreased by 11.7% compared with Example 12, which proves that the cobalt single - atom catalyst of the present invention has good repeatability and high economic benefits.

[0092] Test Example 1

[0093] Other steps are the same as those in Example 2, except that before adding the cobalt single-atom catalyst, tert-butanol (the concentration of tert-butanol in the mixed solution of a and b is 500 mmol / L) was added to the mixed solution of a and b. After quantitative analysis, the removal rate of benzohydroxamic acid was calculated to be 96.7%.

[0094] Test Example 2

[0095] Other steps are the same as those in Example 2, except that before adding the cobalt single-atom catalyst, methanol (the concentration of methanol in the mixed solution of a and b is 500 mmol / L) was added to the mixed solution of a and b. After quantitative analysis, the removal rate of benzohydroxamic acid was calculated to be 98.7%.

[0096] Figure 8 For the removal effect diagrams of benzohydroxamic acid in Example 2 (i.e., the control in Figure 8 ), Test Examples 1 to 2, it can be seen from the figures that since tert-butanol is a strong binder of hydroxyl radicals and methanol is a strong binder of hydroxyl radicals and sulfate radicals, the addition of these two substances only has a minor impact on the removal of benzohydroxamic acid (<5%), indicating that neither the common hydroxyl radicals nor sulfate radicals in the potassium monopersulfate oxidation system are the main reaction intermediate species in the reaction process of the present invention.

[0097] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. Application of a cobalt single-atom catalyst in polymerizing and removing benzohydroxamic acid.

2. A method for polymerizing and removing benzohydroxamic acid by a cobalt single-atom catalyst, characterized in that It includes the following steps: Mix a potassium monopersulfate solution and an aqueous solution containing benzohydroxamic acid, and then add a cobalt single-atom catalyst. Through mixing and reacting, benzohydroxamic acid can be polymerized and removed.

3. The method for polymerizing and removing benzohydroxamic acid with the cobalt single-atom catalyst according to claim 2, characterized in that: The cobalt single-atom catalyst has a Co-N4 atomic coordination structure; the loading amount of cobalt single atoms is 2% - 3%.

4. The method for polymerizing and removing benzohydroxamic acid with the cobalt single-atom catalyst according to claim 2, characterized in that: The cobalt single-atom catalyst is prepared according to the following steps: S1. In the presence of a solvent, 2-methylimidazole and zinc nitrate hexahydrate are ultrasonically dissolved to obtain a white suspension, denoted as solution A; S2. In the presence of a solvent, cobalt nitrate hexahydrate is ultrasonically dissolved, denoted as solution B; S3. Mix solution A and solution B and stir them. A complex substitution reaction occurs to obtain a purple suspension containing the cobalt single-atom catalyst precursor; S4. Centrifuge, wash, and dry the suspension of the cobalt single-atom catalyst precursor to obtain a purple cobalt single-atom catalyst precursor; S5. Perform high-temperature treatment on the cobalt single-atom catalyst precursor to obtain the cobalt single-atom catalyst.

5. The method for polymerizing and removing benzohydroxamic acid with the cobalt single-atom catalyst according to claim 4, characterized in that: The solvents selected in steps S1 and S2 are the same, and the solvent is selected from at least one of water, ethanol, and methanol; The mass ratio of 2-methylimidazole, zinc nitrate hexahydrate, and cobalt nitrate hexahydrate is: (5.5 - 6.5):(3.5 - 4.5):(0.1 - 0.5); The volume ratio of solution A and solution B in step S3 is (100 - 200):(50 - 100); The conditions for the complex substitution reaction in step S3 are: the stirring temperature is 20 - 60 °C, and the stirring time is 10 - 24 h.

6. The method for polymerizing and removing benzohydroxamic acid with the cobalt single-atom catalyst according to claim 4, characterized in that: The conditions for the high-temperature treatment in step S5 are: in an inert gas atmosphere, the temperature is 900 - 1100 °C, the heating rate is 2 - 5 °C / min, and the time is 1 - 3 h.

7. The method for polymerizing and removing benzohydroxamic acid with the cobalt single-atom catalyst according to claim 2, characterized in that: Before mixing the potassium monopersulfate solution and the aqueous solution containing benzohydroxamic acid, adjust the pH values of the two solutions to be the same. The range of the same pH value is 3.00 - 11.

00.

8. The method for polymerizing and removing benzohydroxamic acid with the cobalt single-atom catalyst according to claim 2, characterized in that: Before adding the cobalt single-atom catalyst after mixing the potassium monopersulfate solution and the aqueous solution containing benzohydroxamic acid, the concentration of the potassium monopersulfate solution in the resulting mixed solution is 0.5 - 6 mmol / L, and the concentration of the benzohydroxamic acid solution is 0.1 - 3 mmol / L; After adding the cobalt single-atom catalyst, the concentration of the cobalt single-atom catalyst is 0.1 - 0.5 g / L.

9. The method for polymerizing and removing benzohydroxamic acid by using a cobalt single-atom catalyst according to claim 2, characterized in that: Before mixing the potassium monopersulfate solution and the aqueous solution containing benzohydroxamic acid and before adding the cobalt single-atom catalyst, the concentration of the potassium monopersulfate solution in the obtained mixed solution is 1-3 mmol / L, and the concentration of the benzohydroxamic acid solution is 0.5-1.5 mmol / L; After adding the cobalt single-atom catalyst, the concentration of the cobalt single-atom catalyst is 0.1-0.5 g / L.

10. The method for polymerizing and removing benzohydroxamic acid by using a cobalt single-atom catalyst according to claim 2, characterized in that: The reaction refers to a stirring reaction at room temperature for 10-30 minutes.

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