Method for degrading organic pollutants by complexing modified birnessite to activate PAA

Abstract

The invention discloses a method for degrading organic pollutants by complexing modified birnessite to activate PAA, and relates to the technical field of sewage treatment.The method comprises the steps that firstly, potassium permanganate and a hydrochloric acid aqueous solution are prepared for use; then in the process of stirring and heating the potassium permanganate solution, dropwise adding a hydrochloric acid solution through a constant flow pump, and continuously reacting to generate a turbid liquid; standing the turbid liquid at a constant temperature, performing suction filtration, and sequentially performing water washing, alcohol washing, drying, grinding and sieving treatment to obtain birnessite powder; and finally, mixing the modified birnessite with a complexing agent solution, and modifying through a surface complexing reaction to obtain the complexing modified birnessite catalyst. According to the method for degrading the organic pollutants by activating PAA through complexing modified birnessite, the distribution of manganese active sites on the surface of birnessite and a charge transfer path are optimized through a complexing agent, efficient activation of PAA is achieved under the normal-temperature condition without external energy input, active free radicals with strong oxidizing property are generated, the organic pollutants in water are further oxidized, and the degradation efficiency of the organic pollutants is improved. The organic pollutants are degraded.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a method for activating PAA by complex-modified birnessite to degrade organic pollutants. Background Art

[0002] Environmental endocrine disruptors, namely environmental hormones, are widely distributed in the natural environment and can invade the human body or biological systems through various channels. Their toxicity can disrupt the endocrine balance and cause abnormalities in the reproductive system. Sulfonamides, especially sulfamethoxazole (SMX), are typical environmental endocrine disruptors, which are stable in the environment, hardly volatile and hardly hydrolyzed. The removal ability of traditional water treatment technologies for SMX is limited. In contrast, although adsorption and membrane methods can effectively remove SMX, their high costs limit their large-scale application. In addition, the biological treatment of SMX takes a long time and may produce toxic by-products during the treatment process. These by-products are difficult to biodegrade and will cause long-term harm to the aquatic environment.

[0003] Advanced oxidation technologies based on the generation of reactive oxygen species (ROS) have received extensive attention due to their strong oxidation ability. Among many oxidants, peracetic acid (PAA) stands out for its environmental friendliness. After activation, PAA can generate highly reactive free radicals such as acetylperoxy radicals (CH3C(O)OO•) and hydroxyl radicals (•OH). These free radicals have extremely strong oxidation ability and can efficiently degrade organic pollutants in water, including some stubborn pollutants that are difficult to be treated by traditional methods. However, most of the existing PAA activation technologies rely on transition metal ions (such as , ) or ultraviolet light. Although the transition metal ion activation method is effective, there is a problem of catalyst loss, which not only increases the treatment cost but also may cause secondary pollution to the water body. At the same time, the use of transition metal ions may also generate metal sludge, which requires additional treatment steps. The ultraviolet light activation method faces the challenge of high energy consumption. Long-term high-intensity ultraviolet light irradiation not only increases the operating cost but also may damage the equipment. In addition, the heterogeneous catalytic system has relatively weak electron transfer ability, resulting in insufficient PAA activation ability and low ROS yield, etc., and it is difficult to meet the demand for efficient degradation of organic pollutants.

[0004] Birnessite is a strong oxidant, which is widely present in the natural environment and is prone to redox reactions under natural conditions. Therefore, it can adsorb and exchange various cations and participate in the oxidation and degradation process of organic pollutants. However, the synthesis of traditional birnessite usually requires high-temperature calcination or water bath heating, and the reaction conditions are usually complex and the preparation cost is high. Moreover, when traditional birnessite activates PAA to degrade organic pollutants, there will be dissolution phenomenon, which leads to secondary pollution, reduced catalyst activity and poor reaction stability.

[0005] In addition, studies have shown that complexing agents can change the oxidation state distribution of Mn and promote the decomposition of PAA to generate free radicals. However, the complex-modified birnessite prepared by the coprecipitation method requires precise control of reaction conditions, is not suitable for large-scale preparation, and cannot timely change the type of complexing agent according to the conditions of polluted water bodies, resulting in poor flexibility.

[0006] In view of this, the present invention provides a method for activating PAA by complex-modified birnessite to degrade organic pollutants, which optimizes the distribution of manganese active sites on the surface of birnessite and the electron transfer path, and realizes the efficient activation of PAA and the rapid degradation of pollutants under normal temperature conditions without external energy input such as microwave, light, and electricity. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for activating PAA by complex-modified birnessite to degrade organic pollutants, so as to solve the deficiencies in the prior art such as poor stability, poor PAA activation effect, and easy secondary pollution of water bodies when birnessite degrades organic pollutants.

[0008] To achieve the above purpose, the present invention provides the following technical solution: A preparation method of a complex-modified birnessite catalyst, specifically including the following steps: S1. Prepare an aqueous potassium permanganate solution with a concentration of and an aqueous hydrochloric acid solution with a concentration of , and set aside; S2. Add the prepared aqueous potassium permanganate solution in S1 to a beaker, stir and heat it, and then use a constant flow pump to gradually add the prepared aqueous hydrochloric acid solution in S1 dropwise to the heated potassium permanganate solution. After the addition is completed, react for 30 - 60 min to obtain a suspension; S3. Let the suspension obtained in S2 stand in a constant temperature oven, then perform suction filtration and wash it with deionized water until the conductivity of the filtrate is less than to obtain a precipitate. Then, successively perform alcohol washing, drying, grinding, and sieving on the obtained precipitate, and finally obtain birnessite powder; S4. Add the birnessite powder obtained in S3 into a conical flask, and then add a complexing agent solution for mixing to modify the surface of birnessite through complexation reaction to obtain a complex-modified birnessite catalyst.

[0009] Further, the heating temperature in S2 is 80 - 100 °C.

[0010] Further, in S3, the suspension is left to stand in a constant temperature oven, and at this time, the temperature of the oven is set to 50 - 80 °C; the standing time is set to 10 - 18 h.

[0011] Further, in S4, the complexing agent is ethylenediaminetetraacetic acid or diethylenetriaminepentaacetic acid; the molar ratio of birnessite powder to the complexing agent in S4 is 1-6:1.

[0012] The present invention also discloses a complex-modified birnessite catalyst, which is prepared by a preparation method of a complex-modified birnessite catalyst.

[0013] The present invention also discloses a method for activating PAA by complex-modified birnessite to degrade organic pollutants, which specifically includes the following steps: A1. Add the complex-modified birnessite catalyst and peracetic acid to the polluted water body containing organic pollutants to obtain a mixed water body; A2. Adjust the pH of the mixed water body with an acid or a base, and carry out a degradation reaction under normal temperature and pressure to obtain a degraded reaction solution.

[0014] Further, the concentration of the complex-modified birnessite catalyst in the A1 mixed water body is 0.025 g / L - 0.1 g / L; the organic pollutant is a sulfonamide drug.

[0015] Further, the concentration of peracetic acid in the A1 mixed water body is 0.5 mM - 5 mM.

[0016] Further, the A2 degradation reaction is carried out under the condition of pH 3 - 9.

[0017] Compared with the prior art, the method for activating PAA by complex-modified birnessite to degrade organic pollutants provided by the present invention has the following beneficial effects: 1. The complex-modified birnessite catalyst provided by the present invention has a simple preparation method, does not require high-temperature calcination, has a short catalytic time, and has a high degradation effect on organic pollutants; the degradation rate of sulfamethoxazole can reach more than 94% within 2 h, and it has great application prospects in degrading organic pollutants in water bodies.

[0018] 2. The complex-modified birnessite catalyst provided by the present invention optimizes the distribution of manganese active sites on the surface of birnessite and the charge transfer path through the complexing action of EDTA, and can realize the efficient activation of PAA under normal temperature conditions without external energy input, generate strongly oxidizing active free radicals, further oxidize organic pollutants in water, degrade organic pollutants, and improve the water quality environment.

[0019] 3. The complex-modified birnessite catalyst provided by the present invention is easy to recycle and reuse, can be reused multiple times, is an environment-friendly material, has no secondary pollution, and is suitable for fields such as sewage treatment and environmental remediation. Description of the Drawings

[0020] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0021] Figure 1 SEM image of the birnessite powder catalyst provided by the embodiment of the present invention; Figure 2 XRD patterns of the birnessite powder catalyst provided by the embodiment of the present invention before and after the reaction. Detailed implementation manners

[0022] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the following will further introduce the present invention in detail in conjunction with the drawings.

[0023] A preparation method of a complex modified birnessite catalyst specifically includes the following steps: S1. Prepare an aqueous potassium permanganate solution with a concentration of and an aqueous hydrochloric acid solution with a concentration of for standby; Specifically, prepare 300 mL of an aqueous potassium permanganate solution with a concentration of and 45 mL of an aqueous hydrochloric acid solution with a concentration of for standby.

[0024] S2. Add the aqueous potassium permanganate solution prepared in S1 to a beaker, stir and heat it, and then use a constant flow pump to gradually dropwise add the aqueous hydrochloric acid solution prepared in S1 into the heated potassium permanganate solution. After the dropping is completed, react for 30 - 60 min to obtain a suspension; Specifically, add the aqueous potassium permanganate solution prepared in S1 to a beaker, stir and heat it to 100 °C, and then use a constant flow pump to gradually dropwise add the aqueous hydrochloric acid solution prepared in S1 into the heated potassium permanganate solution at a rate of . After the dropping is completed, react for 30 min to obtain a suspension.

[0025] S3. Let the suspension obtained in S2 stand in a constant temperature oven, then perform suction filtration and wash it with deionized water until the conductivity of the filtrate is less than to obtain a precipitate. Then, sequentially perform alcohol washing, drying, grinding, and sieving on the obtained precipitate, and finally obtain birnessite powder; Specifically, let the suspension obtained in S2 stand in a 60 °C constant temperature oven, then perform suction filtration and wash it with deionized water until the conductivity of the filtrate is less than , a precipitate is obtained, and then the obtained precipitate is successively subjected to alcohol washing, drying, grinding, and sieving treatments, and finally birnessite powder is obtained.

[0026] S4. Add the birnessite powder obtained in S3 into a conical flask, and then add a complexing agent solution for mixing. The surface of the birnessite is modified through a complexation reaction to obtain a complexation-modified birnessite catalyst; the complexing agent is ethylenediaminetetraacetic acid or diethylenetriaminepentaacetic acid; the molar ratio of the birnessite powder to the complexing agent is 1-6:1.

[0027] The present invention also discloses a complexation-modified birnessite catalyst.

[0028] The present invention also discloses a method for activating PAA by a complexation-modified birnessite catalyst to degrade organic pollutants, which specifically includes the following steps: A1. Add a complexation-modified birnessite catalyst and peracetic acid into a polluted water body containing organic pollutants to obtain a mixed water body; the concentration of the complexation-modified birnessite catalyst is 0.025 g / L - 0.1 g / L; the organic pollutant is sulfamethoxazole (SMX) or sulfadiazine (SD) in sulfonamide drugs; the concentration of peracetic acid in the A1 mixed water body is 0.5 mM - 5 mM; A2. Adjust the pH of the mixed water body with an acid or a base, and carry out a degradation reaction under normal temperature and pressure to obtain a degraded reaction solution; the degradation reaction is carried out under the condition that the pH is 3 - 9.

[0029] The specific implementation method is as follows. First, add a complexation-modified birnessite catalyst with a concentration of 0.025 g / L - 0.1 g / L and peracetic acid with a concentration of 0.5 mM - 5 mM into a polluted water body containing sulfamethoxazole (SMX) to obtain a mixed water body; then adjust the pH of the mixed water body with an acid or a base, and carry out a degradation reaction under normal temperature and pressure to obtain a degraded reaction solution; finally, measure the content of sulfamethoxazole (SMX) in the degraded reaction solution by liquid chromatography to obtain the degradation efficiency of SMX in the polluted water body. The acid is at least one of hydrochloric acid, nitric acid, and sulfuric acid; the base is sodium hydroxide or potassium hydroxide.

[0030] Comparative Example 1: Using the single birnessite powder material as a catalyst, the removal effect of the single birnessite powder activating peracetic acid on SMX was tested through the change of the SMX peak area in liquid chromatography. The specific steps are as follows: (1) Preparation of the birnessite catalyst: Stir and heat 300 mL of a potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of a hydrochloric acid solution with a concentration of at Add the potassium permanganate solution drop by drop at a certain rate. After the addition is complete, continue the reaction for 30 min to obtain a suspension. Subsequently, place the obtained suspension in a constant-temperature oven at 60 °C and let it stand for 12 h. Then, perform suction filtration and wash it with deionized water until the conductivity of the filtrate is less than , to obtain a precipitate. Wash the precipitate 3 times with ethanol, dry it in a blast drying oven, grind it after drying, and pass it through a 100-mesh sieve to obtain birnessite powder; (2)Prepare 20 mg / L SMX solution and 50 mM peracetic acid solution for standby; (3)Use a conical flask as the reactor. Add 10 mL of 20 mg / L SMX solution, 1 mL of 50 mM peracetic acid solution, and deionized water to the reactor in sequence, keeping the volume of the solution in the reactor at 20 mL. At the same time, add 1 mg of birnessite powder catalyst. The concentration of SMX in the pharmaceutical wastewater is relatively high, and the wastewater is usually acidic due to the use of acidic solvents in the production process. Therefore, adjust the initial pH of the solution in the reactor to 3.

[0031] For comparison, take two other groups of reactors. In one group of reactors, do not add the birnessite powder catalyst, and in the other group, do not add the peracetic acid solution. Place each conical flask in a shaker at 150 rpm and carry out the reaction at room temperature, and perform fixed-point sampling analysis.

[0032] In the above three different reaction systems, the removal rates of SMX are shown in the following table: Table 1: Removal rates of SMX under different reaction systems

[0033] It can be seen from Table 1 that when adding the birnessite catalyst or peracetic acid alone, the degradation rate of SMX is relatively low (less than 5%); while when adding the birnessite catalyst and peracetic acid simultaneously, the degradation efficiency of SMX is significantly improved. After 1440 min, the degradation efficiency of SMX reaches 94.0%, indicating that peracetic acid has a good removal effect on SMX under the catalytic activation of birnessite.

[0034] Characterize the prepared birnessite powder catalyst by scanning electron microscopy (SEM), as Figure 1 shown. The catalyst as a whole presents a nano-flower-like spherical aggregate. It can be seen that the catalyst aggregate has a typical nano-layered structure, which is composed of manganese oxide octahedral layers and interlayer domains. In the manganese oxide octahedral layer, manganese ions form an octahedral coordination structure with oxygen ions, and these octahedrons are connected to each other by sharing edges or corners to form a two-dimensional layered structure; water molecules and cations can be accommodated in the interlayer domain, and the existence of these interlayer substances has an important influence on the structure and properties of birnessite.

[0035] Characterize the birnessite powder catalyst before and after the reaction with SMX by X-ray diffraction (XRD), asFigure 2 As shown, it can be seen that the peak positions of this catalyst are in good agreement with those of the PDF card JCPDS No. 00-013-0105, indicating that the crystal structure of this catalyst is consistent with the crystal structure of the substance corresponding to JCPDS No. 00-013-0105, suggesting that the prepared catalyst is birnessite with a specific crystal structure.

[0036] By comparing the XRD patterns before the reaction (black curve) and after the reaction (red curve), it can be found that the peak positions basically remain unchanged. This means that during the SMX reaction process, the crystal structure of the birnessite powder catalyst remains relatively stable, without obvious phase changes or major alterations in the crystal structure, indicating that this catalyst has stability, which helps to maintain the active sites of the catalyst and can be reused in cycles.

[0037] Comparative Example 2: Using the birnessite powder obtained in Comparative Example 1 as the catalyst, the removal effect of birnessite powder catalyst-activated peracetic acid on SMX was studied by the change in the peak area of SMX in liquid chromatography under different catalyst dosages (0.5 mg, 1 mg, 2 mg).

[0038] (1) Preparation of birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of hydrochloric acid solution with a concentration of dropwise into the potassium permanganate solution at a rate of . After the addition is complete, continue the reaction for 30 min to obtain a suspension; then place the obtained suspension in a constant temperature oven at 60 °C and let it stand for 12 h, then perform suction filtration and wash it with deionized water until the conductivity of the filtrate is less than to obtain a precipitate; wash the precipitate 3 times with ethanol and then dry it in a forced-air oven. After drying, grind it and pass it through a 100-mesh sieve to obtain birnessite powder; (2) Prepare 20 mg / L SMX solution and 50 mM peracetic acid solution for standby; (3) Use conical flasks as reactors. Add 10 mL of 20 mg / L SMX solution, 1 mL of 50 mM peracetic acid solution, and deionized water to each reactor in turn, keeping the volume of the solution in the reactor at 20 mL. At the same time, add 0.5 mg, 1 mg, 2 mg of birnessite powder catalyst to each reactor, so that the concentrations of birnessite powder catalyst in each reactor are 0.025 g / L, 0.05 g / L, 0.1 g / L respectively, and adjust the initial pH of the solution to 3. Place each conical flask in a shaker at 150 rpm and carry out the reaction at room temperature, and perform fixed-point sampling analysis.

[0039] Under the above three different catalyst dosages, the removal rates of SMX are shown in the following table: Table 2: Removal Rates of SMX under Different Catalyst Dosages

[0040] As can be seen from Table 2: At 1440 min, when the concentrations of birnessite powder catalyst in the reaction system are 0.025 mg / L, 0.05 mg / L, and 0.1 mg / L respectively, the degradation efficiencies of SMX are 68.8%, 94.1%, and 73.3% respectively. Thus, it can be seen that as the catalyst dosage increases from 0.5 mg to 2 mg, the degradation efficiency of SMX at 1440 min shows a trend of first increasing and then decreasing. Among them, when the dosage of birnessite is 1 mg, the degradation effect is the best, up to 94.1%.

[0041] Comparative Example 3: Using the birnessite powder obtained in Comparative Example 1 as the catalyst, the removal effect of birnessite powder catalyst activating peracetic acid on SMX under different peracetic acid dosages (0.2 mL, 0.4 mL, 1 mL, 2 mL) was studied by the change of SMX peak area in liquid chromatography.

[0042] (1) Preparation of birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of hydrochloric acid solution with a concentration of dropwise into the potassium permanganate solution at a rate of . After the addition is complete, continue the reaction for 30 min to obtain a suspension; then place the obtained suspension in a constant temperature oven at 60 °C and let it stand for 12 h, then perform suction filtration and wash it with deionized water until the conductivity of the filtrate is less than to obtain a precipitate; wash the precipitate 3 times with ethanol and dry it in a blast drying oven, then grind it and pass it through a 100-mesh sieve to obtain birnessite powder; (2) Prepare 20 mg / L SMX solution and 50 mM peracetic acid solution for standby; (3) Use a conical flask as the reactor, sequentially add 10 mL of 20 mg / L SMX solution and deionized water to each reactor. At the same time, add 0.2 mL, 0.4 mL, 1 mL, and 2 mL of 50 mM peracetic acid solution to each reactor respectively, so that the concentrations of peracetic acid solution in each reactor are 0.5 mM, 1 mM, 2.5 mM, and 5 mM respectively. Keep the volume of the solution in the reactor at 20 mL, then add 1 mg of birnessite powder catalyst, and adjust the initial pH of the solution to 3. Place each conical flask in a shaker at 150 rpm and carry out the reaction at room temperature, and perform fixed-point sampling analysis.

[0043] The removal rates of SMX at different peracetic acid dosages are shown in the following table: Table 3: Removal rates of SMX at different peracetic acid concentrations

[0044] As can be seen from Table 3: At 1440 min, when 0.2 mL, 0.4 mL, 1 mL, and 2.0 mL of peracetic acid were added, the corresponding degradation efficiencies of SMX were 10.4%, 55.0%, 94.3%, and 84.2% respectively. It can be seen that as the peracetic acid addition amount increased from 0.2 mL to 2.0 mL, the overall degradation efficiency of SMX showed an upward trend. Among them, when the peracetic acid dosage was 1.0 mL, the degradation efficiency of SMX was the highest.

[0045] Comparative Example 4: Using the birnessite powder obtained in Comparative Example 1 as a catalyst, the effect of the activation of peracetic acid by the birnessite powder catalyst on the degradation of SMX was studied by the change in the peak area of SMX in liquid chromatography at different initial solution pH values (pH = 3, pH = 5, pH = 7, pH = 9).

[0046] (1) Preparation of the birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of hydrochloric acid solution with a concentration of dropwise into the potassium permanganate solution at a rate of . After the addition is complete, continue the reaction for 30 min to obtain a suspension; then place the obtained suspension in a constant temperature oven at 60 °C and let it stand for 12 h, then perform suction filtration and wash with deionized water until the conductivity of the filtrate is less than to obtain a precipitate; wash the precipitate 3 times with ethanol and then dry it in a blast drying oven, grind it after drying and pass it through a 100-mesh sieve to obtain birnessite powder; (2) Prepare 20 mg / L SMX solution and 50 mM peracetic acid solution for standby; (3) Use conical flasks as reactors. Add 10 mL of 20 mg / L SMX solution, 1 mL of 50 mM peracetic acid solution, and deionized water to each reactor in sequence, keep the volume of the solution in the reactor at 20 mL, and at the same time add 1 mg of birnessite powder catalyst to each reactor, and adjust the initial solution pH to 3, 5, 7, and 9 respectively. Place each conical flask in a shaker at 150 rpm and carry out the reaction at room temperature, and perform fixed-point sampling analysis.

[0047] The removal rates of SMX under different initial pH conditions are shown in the following table: Table 4: Removal rates of SMX at different initial solution pH values

[0048] As can be seen from Table 4: At 1440 min, when the initial pH of the solution was 3, 5, 7, and 9, the degradation efficiencies of SMX were 91.1%, 70.2%, 46.7%, and 25.7%, respectively. As the initial pH of the solution increased from 3 to 9, the degradation efficiency of SMX showed a downward trend, decreasing from 94.1% to 25.7%. Therefore, the catalytic effect of birnessite powder catalyst was better under acidic conditions, and the degradation efficiency of SMX was the highest when pH = 3.

[0049] Example 1: A method for complex-modified birnessite to activate PAA for degrading organic pollutants: Using EDTA complex-modified birnessite as a catalyst, the removal effect of EDTA complex-modified birnessite catalyst activating peracetic acid on SMX was tested by the change of SMX peak area in liquid chromatography under different catalyst dosages (0.5 mg, 1 mg, 2 mg). The specific steps are as follows: (1) Preparation of EDTA complex-modified birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of hydrochloric acid solution with a concentration of dropwise into the potassium permanganate solution at a rate of . After the addition is completed, continue the reaction for 30 min to obtain a suspension; then place the obtained suspension in a 60 °C constant temperature oven and let it stand for 12 h, then perform suction filtration and wash it with deionized water until the conductivity of the filtrate is less than to obtain a precipitate; wash the precipitate 3 times with ethanol and dry it in a blast drying oven. After drying, grind it and pass it through a 100-mesh sieve to obtain birnessite powder; respectively mix 0.5 mg, 1 mg, and 2 mg of birnessite powder with 2 mL of 1.8 mM EDTA, and modify the surface of the birnessite powder through complexation reaction to obtain three kinds of EDTA complex-modified birnessite catalysts with molar ratios of 1.5:1, 3:1, and 6:1; (2) Prepare 20 mg / L SMX solution and 50 mM peracetic acid solution for standby; (3) Use a conical flask as a reactor, sequentially add 10 mL of 20 mg / L SMX solution, 1.0 mL of 50 mM peracetic acid solution, and deionized water to each reactor. At the same time, add the above three kinds of EDTA complex-modified birnessite catalysts to each reactor respectively, keep the volume of the solution in the reactor at 20 mL, and adjust the initial pH of the solution to 3. Place the conical flask in a 150 rpm shaker and react at room temperature, and perform fixed-point sampling analysis.

[0050] The removal rates of SMX under the above three different catalyst dosages are shown in the following table: Table 5: Removal rate of SMX under different catalyst dosages

[0051] As can be seen from Table 5, the efficiency of activating peracetic acid by birnessite modified by EDTA complexation to degrade SMX has been greatly improved, and the reaction time has been shortened from 1440 min to 120 min. After 120 min of reaction, when the content of the complexation-modified birnessite catalyst in the reaction system is 0.025 g / L, 0.05 g / L, and 0.1 g / L, the corresponding degradation efficiencies of SMX are 71.7%, 94.4%, and 58.32% respectively. Thus, as the catalyst dosage increases from 0.5 mg to 2 mg, the degradation efficiency of SMX at 120 min of reaction shows a trend of first increasing and then decreasing. Considering the reaction efficiency and cost, when the dosage of birnessite is 1 mg, the catalytic effect is the best, that is, when the molar ratio of birnessite to the complexing agent EDTA is 3:1, the degradation rate of SMX is the fastest, and the reaction rate constant k obs is , which is 100 times that of k when using birnessite alone as the catalyst obs .

[0052] The complexing agent can prevent the structural collapse or dissolution of the birnessite catalyst during the reaction process and extend its service life. The complexation-modified birnessite catalyst prepared by the post-treatment method has the advantages of simple operation and flexible adjustment of the types of complexing agents compared with the coprecipitation method, and can select appropriate complexing agents according to the pollution status of organic polluted water bodies.

[0053] The reaction formula for the degradation of SMX by the complexation-modified birnessite catalyst is as follows:

[0054] As can be seen from the above reaction formula, the efficient degradation of SMX by activating PAA with the complexation-modified birnessite catalyst is achieved through a free radical pathway mainly based on acetylperoxy radicals and superoxide radicals and a non-free radical pathway mainly based on singlet oxygen.

[0055] Example 2: This example provides a technical solution on the basis of Example 1: A method for degrading organic pollutants by activating PAA with complexation-modified birnessite uses DTPA-complexed modified birnessite as a catalyst, and tests the removal effect of DTPA-complexed modified birnessite catalyst activating peracetic acid on SMX at different molar ratios of birnessite powder to DTPA (1.5:1, 3:1, 6:1) through the change of the SMX peak area in liquid chromatography. The specific steps are as follows: (1) Preparation of DTPA-complexed modified birnessite catalyst: Add 300 mL of a solution with a concentration of The potassium permanganate solution was stirred and heated to 100 °C. 45 mL of hydrochloric acid solution with a concentration of was added dropwise to the potassium permanganate solution at a rate of . After the addition was complete, the reaction continued for 30 min to obtain a suspension. Subsequently, the obtained suspension was placed in a constant-temperature oven at 60 °C and allowed to stand for 12 h, then filtered by suction and washed with deionized water until the conductivity of the filtrate was less than , to obtain a precipitate. The precipitate was washed three times with ethanol and then dried in a blast drying oven. After drying, it was ground and passed through a 100-mesh sieve to obtain birnessite powder. 0.5 mg, 1 mg, and 2 mg of birnessite powder were respectively mixed with 2 mL of 1.8 mM DTPA, such that the molar ratios of birnessite powder to DTPA were 1.5:1, 3:1, and 6:1. The surface of the birnessite powder was modified through complexation reactions to obtain three kinds of complex-modified birnessite catalysts with molar ratios of 1.5:1, 3:1, and 6:1 respectively; (2) Prepare 20 mg / L SMX solution and 50 mM peracetic acid solution for later use; (3) Using conical flasks as reactors, 10 mL of 20 mg / L SMX solution, 1.0 mL of 50 mM peracetic acid solution, and deionized water were successively added to each reactor. At the same time, the above three kinds of DTPA complex-modified birnessite catalysts were respectively added to each reactor, keeping the volume of the solution in the reactor at 20 mL and adjusting the initial pH of the solution to 3. The conical flasks were placed in a shaker at 150 rpm and the reaction was carried out at room temperature, and fixed-point sampling analysis was performed.

[0056] The removal rates of SMX under different molar ratios of DTPA complex-modified birnessite catalysts are shown in the following table: Table 6: Removal rates of SMX under different molar ratios of DTPA complex-modified birnessite

[0057] As can be seen from Table 6: At 120 min, DTPA complex-modified birnessite catalysts with different molar ratios (1.5:1, 3:1, 6:1) all had good removal effects on SMX and could completely degrade SMX in the solution. Thus, it can be seen that as the molar ratio of birnessite to DTPA increased, the degradation rate of SMX gradually decreased. Considering the reaction efficiency and cost, when the dosage of birnessite was 0.5 mg, that is, when the molar ratio of birnessite to DTPA complexing agent was 1.5:1, the catalytic effect was the best and the degradation rate of SMX was the fastest.

[0058] Example Three: Based on Example 1, this example provides a technical solution: a method for activating PAA by complex modified birnessite to degrade organic pollutants. Using the EDTA complex modified birnessite with a molar ratio of 3:1 obtained in Example 1 as a catalyst, the removal effect of EDTA complex modified birnessite catalyst activating peracetic acid on SMX under different peracetic acid dosages (0.2 mL, 0.4 mL, 1 mL, 2 mL) was studied by the change of SMX peak area in liquid chromatography. The specific steps are as follows: (1) Preparation of EDTA complex modified birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to gradually add 45 mL of hydrochloric acid solution with a concentration of to the potassium permanganate solution at a rate of . After the addition is complete, continue the reaction for 30 min to obtain a suspension; then place the obtained suspension in a 60 °C constant temperature oven and let it stand for 12 h, then perform suction filtration and wash it with deionized water until the conductivity of the filtrate is less than to obtain a precipitate; wash the precipitate 3 times with ethanol and then dry it in a blast drying oven. After drying, grind it and pass it through a 100-mesh sieve to obtain birnessite powder; mix 1 mg of birnessite powder with 2 mL of 1.8 mM EDTA, and modify the surface of the birnessite powder through complexation reaction to obtain an EDTA complex modified birnessite catalyst with a molar ratio of 3:1; (2) Prepare 20 mg / L SMX solution and 50 mM peracetic acid solution for standby; (3) Use conical flasks as reactors. Add 10 mL of 20 mg / L SMX solution and deionized water to each reactor in turn. At the same time, add 0.2 mL, 0.4 mL, 1 mL, 2 mL of 50 mM peracetic acid solution to each reactor respectively, so that the concentration of peracetic acid solution in each reactor is 0.5 mM, 1 mM, 2.5 mM, 5 mM. Then add the above-mentioned EDTA complex modified birnessite catalyst to each reactor respectively, keep the volume of the solution in the reactor at 20 mL, and adjust the initial pH of the solution to 3. Place each conical flask in a shaker at 150 rpm and carry out the reaction at room temperature, and perform fixed-point sampling analysis.

[0059] The removal rates of SMX under different peracetic acid dosages are shown in the following table: Table 7: Removal rates of SMX under different peracetic acid concentrations

[0060] As can be seen from Table 7: at 120 min, when 0.2 mL, 0.4 mL, 1 mL, and 2.0 mL of peracetic acid were added, the corresponding degradation efficiencies of SMX were 68.1%, 71.1%, 94.1%, and 94.3%, respectively. From the test results, as the concentration of peracetic acid increased from 0.2 mL to 2.0 mL, the overall degradation efficiency of SMX by the EDTA-complex modified birnessite catalyst showed an upward trend. Considering the reaction efficiency and cost, the addition amount of 1.0 mL of peracetic acid was the best choice.

[0061] Example 4: This example provides a technical solution based on Example 1: a method for complex-modified birnessite to activate PAA to degrade organic pollutants. Using the EDTA-complex modified birnessite with a molar ratio of 3:1 obtained in Example 1 as a catalyst, the effect of the EDTA-complex modified birnessite catalyst activating peracetic acid on the degradation of SMX under different initial solution pH values (pH = 3, pH = 5, pH = 7, pH = 9) was studied by the change in the peak area of SMX in liquid chromatography. The specific steps are as follows:

[0062] (1) Preparation of the EDTA-complex modified birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of hydrochloric acid solution with a concentration of dropwise into the potassium permanganate solution at a rate of . After the addition is complete, continue the reaction for 30 min to obtain a suspension; then place the obtained suspension in a 60 °C constant temperature oven and let it stand for 12 h, then perform suction filtration and wash with deionized water until the conductivity of the filtrate is less than to obtain a precipitate; wash the precipitate 3 times with ethanol and dry it in a forced-air oven. After drying, grind it and pass through a 100-mesh sieve to obtain birnessite powder; mix 1 mg of birnessite powder with 2 mL of 1.8 mM EDTA, and modify the surface of the birnessite powder through a complexation reaction to obtain an EDTA-complex modified birnessite catalyst with a molar ratio of 3:1; (2) Prepare 20 mg / L SMX solution and 50 mM peracetic acid solution for standby; (3) Use conical flasks as reactors. Add 10 mL of 20 mg / L SMX solution, 1 mL of 50 mM peracetic acid solution, and deionized water to each reactor in sequence. At the same time, add the above-mentioned EDTA-complex modified birnessite catalyst to each reactor, keep the volume of the solution in the reactor at 20 mL, and adjust the initial pH of the solution to 3, 5, 7, and 9 respectively. Place each conical flask in a shaker at 150 rpm and react at room temperature, and perform fixed-point sampling analysis.

[0063] The removal rates of SMX at different initial pH values of the solution are shown in the following table: Table 8: Removal rates of SMX at different initial pH values of the solution

[0064] As can be seen from Table 8: At 120 min, when the initial pH values of the solution are pH = 3, pH = 5, pH = 7, and pH = 9 respectively, the degradation efficiencies of SMX are 94.3%, 71.1%, 61.6%, and 29.1% respectively. As the initial pH of the solution increases from 3 to 9, the degradation efficiency of SMX shows a downward trend, decreasing from 94.3% to 29.1%. Thus, it can be seen that the EDTA-complexed modified birnessite catalyst has better catalytic effect under acidic conditions, and among them, pH = 3 is the optimal reaction condition.

[0065] Example Five: This example provides a technical solution based on Example One: A method for complexing and modifying birnessite to activate PAA to degrade organic pollutants. Using the EDTA-complexed modified birnessite with a molar ratio of 3:1 obtained in Example One as the catalyst, the degradation effect of the EDTA-complexed modified birnessite catalyst activating peracetic acid on SMX was studied by the change of the SMX peak area in liquid chromatography under different dosages of humic acid (HA) (0.2 mg, 2 mg, 10 mg) in the reaction system. The specific steps are as follows:

[0066] (1) Preparation of the EDTA-complexed modified birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of hydrochloric acid solution with a concentration of dropwise into the potassium permanganate solution at a rate of . After the addition is completed, continue the reaction for 30 min to obtain a suspension; then place the obtained suspension in a constant temperature oven at 60 °C and let it stand for 12 h, then perform suction filtration and wash with deionized water until the conductivity of the filtrate is less than to obtain a precipitate; wash the precipitate 3 times with ethanol and then dry it in a blast drying oven. After drying, grind it and pass through a 100-mesh sieve to obtain birnessite powder; mix 1 mg of birnessite powder with 2 mL of 1.8 mM EDTA, and modify the surface of the birnessite powder through a complexation reaction to obtain an EDTA-complexed modified birnessite catalyst with a molar ratio of 3:1; (2) Prepare 20 mg / L SMX solution and 50 mM peracetic acid solution for standby; (3) Using a conical flask as the reactor, 10 mL of 20 mg / L SMX solution, 1 mL of 50 mM peracetic acid solution, the above-mentioned EDTA-complex modified birnessite catalyst, and deionized water were successively added to each reactor, keeping the volume of the solution in the reactor at 20 mL. Meanwhile, 0 mg, 0.2 mg, 2 mg, and 10 mg of humic acid were added to each reactor respectively, and the initial pH of the solution was adjusted to 3. Each conical flask was placed in a shaker at 150 rpm and reacted at room temperature, and samples were taken at fixed points for analysis.

[0067] The removal rates of SMX at the above different dosages of HA are shown in the following table: Table 9: Removal rates of SMX at different dosages of HA

[0068] It can be seen from Table 9 that as the dosage of HA increases, the removal rate of SMX slightly decreases, indicating that the presence of HA in the solution will have a certain inhibitory effect on the degradation of SMX.

[0069] Example Six: This example provides a technical solution based on Example One: A method for complex modified birnessite-activated PAA to degrade organic pollutants. Using the EDTA-complex modified birnessite with a molar ratio of 3:1 obtained in Example One as the catalyst, the degradation effect of EDTA-complex modified birnessite catalyst-activated peracetic acid on SMX at different concentrations of coexisting anions (Cl - ) (0 mmol / L, 5 mmol / L, 50 mmol / L, 100 mmol / L) in the reaction solution was studied by the change of SMX peak area in liquid chromatography. The specific steps are as follows: (1) Preparation of EDTA-complex modified birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of hydrochloric acid solution with a concentration of dropwise into the potassium permanganate solution at a rate of . After the addition is completed, continue to react for 30 min to obtain a suspension; then place the obtained suspension in a constant temperature oven at 60 °C and let it stand for 12 h, then carry out suction filtration and wash with deionized water until the conductivity of the filtrate is less than , to obtain a precipitate; wash the precipitate with ethanol 3 times and then dry it in a blast drying oven, grind it after drying and pass through a 100-mesh sieve to obtain birnessite powder; mix 1 mg of birnessite powder with 2 mL of 1.8 mM EDTA, and modify the surface of the birnessite powder through complexation reaction to obtain an EDTA-complex modified birnessite catalyst with a molar ratio of 3:1; (2) Prepare 20 mg / L SMX solution, 50 mM peracetic acid solution and 1 mol / L NaCl solution for later use; (3) Use conical flasks as reactors. Sequentially add 10 mL of 20 mg / L SMX solution, 1 mL of 50 mM peracetic acid solution, the above-mentioned EDTA-complex modified birnessite catalyst and deionized water to each reactor. At the same time, add 0 mL, 0.1 mL, 1 mL, 2 mL of 1 mol / L NaCl solution to each reactor respectively. At this time, the coexisting anions in each reactor have concentrations of 0 mmol / L, 5 mmol / L, 50 mmol / L, 100 mmol / L respectively. Keep the volume of the solution in the reactor at 20 mL and adjust the initial pH of the solution to 3. Place each conical flask in a shaker at 150 rpm and carry out the reaction at room temperature, and take samples at fixed points for analysis.

[0070] Above at different concentrations, the removal rates of SMX are shown in the following table: Table 10: Removal rates of SMX at different concentrations

[0071] It can be seen from Table 10 that: with the addition of , the removal rate of SMX by the activation of peracetic acid with the EDTA-complex modified birnessite catalyst hardly changes, indicating that the presence of in the solution has no significant effect on the degradation of SMX.

[0072] Example Seven: This example provides a technical solution on the basis of Example One: a method for degrading organic pollutants by complex modified birnessite activating PAA. Using the EDTA-complex modified birnessite with a molar ratio of 3:1 obtained in Example One as the catalyst, study the degradation effect of the activation of peracetic acid by the EDTA-complex modified birnessite catalyst on SMX in the reaction solution at different coexisting anion concentrations (0 mmol / L, 5 mmol / L, 50 mmol / L, 100 mmol / L) through the change of the SMX peak area in liquid chromatography. The specific steps are as follows: (1) Preparation of the EDTA-complex modified birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of hydrochloric acid solution with a concentration of at The potassium permanganate solution was added dropwise at a rate of, and after the addition was completed, the reaction was continued for 30 min to obtain a suspension; subsequently, the obtained suspension was placed in a constant temperature oven at 60 °C and allowed to stand for 12 h, and then suction filtration was carried out and washed with deionized water until the conductivity of the filtrate was less than , and a precipitate was obtained; the precipitate was washed 3 times with ethanol and then dried in a blast drying oven, ground after drying and passed through a 100-mesh sieve to obtain birnessite powder; 1 mg of birnessite powder was mixed with 2 mL of 1.8 mM EDTA solution, and the surface of the birnessite powder was modified by complexation reaction to obtain an EDTA complex modified birnessite catalyst with a molar ratio of 3:1; (2) Prepare 20 mg / L SMX solution, 50 mM peracetic acid solution and 1 mol / L NaHCO3 solution for standby; (3) Using a conical flask as a reactor, 10 mL of 20 mg / L SMX solution, 1 mL of 50 mM peracetic acid solution, the above-mentioned EDTA complex modified birnessite catalyst and deionized water were successively added to each reactor, and 0 mL, 0.1 mL, 1 mL, 2 mL of 1 mol / L NaHCO3 solution were respectively added to each reactor. At this time, the coexisting anions in each reactor had concentrations of 0 mmol / L, 5 mmol / L, 50 mmol / L, 100 mmol / L respectively. The volume of the solution in the reactor was kept at 20 mL, and the initial pH of the solution was adjusted to 3. Each conical flask was placed in a shaker at 150 rpm and the reaction was carried out at room temperature, and samples were taken at fixed points for analysis.

[0073] At the above different concentrations, the removal rates of SMX are shown in the following table: Table 11: Removal rates of SMX at different concentrations

[0074] As can be seen from Table 11: with the addition of , the activation of peracetic acid by the EDTA complex modified birnessite catalyst for the degradation of SMX was significantly inhibited, and the inhibitory effect of high-concentration on the degradation of SMX was more obvious.

[0075] Example Eight: This example provides a technical solution on the basis of Example One: a method for complex modified birnessite to activate PAA to degrade organic pollutants. Using the EDTA complex modified birnessite with a molar ratio of 3:1 obtained in Example One as a catalyst, the changes in the peak area of SMX in liquid chromatography were used to study different coexisting anions in the reaction solution Degradation effects of EDTA-complex modified birnessite catalyst activating peracetic acid on SMX at different concentrations (0 mmol / L, 5 mmol / L, 50 mmol / L, 100 mmol / L). The specific steps are as follows: (1) Preparation of EDTA-complex modified birnessite catalyst: Stir and heat 300 mL of potassium permanganate solution with a concentration of to 100 °C, and use a constant flow pump to add 45 mL of hydrochloric acid solution with a concentration of dropwise into the potassium permanganate solution at a rate of . After the addition is complete, continue the reaction for 30 min to obtain a suspension; then place the obtained suspension in a constant temperature oven at 60 °C and let it stand for 12 h, then perform suction filtration and wash with deionized water until the conductivity of the filtrate is less than to obtain a precipitate; wash the precipitate 3 times with ethanol and dry it in a blast drying oven, then grind and pass through a 100-mesh sieve to obtain birnessite powder; mix 1 mg of birnessite powder with 2 mL of 1.8 mM EDTA, and modify the surface of the birnessite powder through complexation reaction to obtain an EDTA-complex modified birnessite catalyst with a molar ratio of 3:1; (2) Prepare 20 mg / L SMX solution, 50 mM peracetic acid solution and 1 mol / L Na2SO4 solution for standby; (3) Use conical flasks as reactors, and sequentially add 10 mL of 20 mg / L SMX solution, 1 mL of 50 mM peracetic acid solution, the above-mentioned EDTA-complex modified birnessite catalyst and deionized water to each reactor. At the same time, add 0 mL, 0.1 mL, 1 mL, 2 mL of 1 mol / L Na2SO4 solution to each reactor respectively. At this time, the concentrations of coexisting anions in each reactor are 0 mmol / L, 5 mmol / L, 50 mmol / L, 100 mmol / L respectively. Keep the volume of the solution in the reactor at 20 mL and adjust the initial pH of the solution to 3. Place each conical flask in a shaker at 150 rpm and carry out the reaction at room temperature, and take samples at fixed points for analysis.

[0076] At the above different concentrations, the removal rates of SMX are shown in the following table: Table 12: Removal rates of SMX at different concentrations

[0077] As can be seen from Table 12: has a certain inhibitory effect on the degradation of SMX by EDTA-complex modified birnessite catalyst activating peracetic acid. When is added, the degradation rate of SMX decreases from 94.4% to 64.1%. As With the increase of ionic concentration, the inhibitory effect on SMX degradation gradually strengthens.

[0078] Only some exemplary embodiments of the present invention have been described by way of illustration above. Undoubtedly, for those of ordinary skill in the art, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the protection scope of the claims of the present invention.

Claims

1. A preparation method of a complex-modified birnessite catalyst, characterized in that, Specifically, it includes the following steps: S1. Prepare an aqueous potassium permanganate solution with a concentration of and an aqueous hydrochloric acid solution with a concentration of for standby; S2. Add the potassium permanganate aqueous solution prepared in S1 into a beaker, stir and heat it, and then use a constant flow pump to gradually add the hydrochloric acid aqueous solution prepared in S1 drop by drop into the heated potassium permanganate solution. After the addition is completed, react for 30 - 60 minutes to obtain a suspension; S3. Leave the suspension obtained in S2 standing in a constant-temperature oven, then perform suction filtration and wash it with deionized water until the conductivity of the filtrate is less than , to obtain a precipitate. Then, successively perform alcohol washing, drying, grinding, and sieving on the obtained precipitate, and finally obtain birnessite powder; S4. Add the birnessite powder obtained in S3 into a conical flask, and then add a complexing agent solution for mixing. Modify the surface of the birnessite through a complexation reaction to obtain a complexation - modified birnessite catalyst.

2. The preparation method of a complex-modified birnessite catalyst according to claim 1, characterized in that, The heating temperature in S2 is 80 - 100 °C.

3. The preparation method of a complex-modified birnessite catalyst according to claim 1, characterized in that, In S3, let the suspension stand in a constant - temperature oven, and at this time, the temperature of the oven is set to 50 - 80 °C; the standing time is set to 10 - 18 h.

4. The preparation method of a complex modified birnessite catalyst according to claim 1, characterized in that, In S4, the complexing agent is ethylenediaminetetraacetic acid or diethylenetriaminepentaacetic acid; the molar ratio of the birnessite powder to the complexing agent in S4 is 1 - 6:

1.

5. A complex-modified birnessite catalyst, characterized in that, It is prepared by the preparation method of a complexation - modified birnessite catalyst according to any one of claims 1 - 4.

6. A method for activating PAA by complex modified birnessite to degrade organic pollutants, which is characterized in that, Specifically, it includes the following steps: A1. Add a complexation - modified birnessite catalyst and peracetic acid into a polluted water body containing organic pollutants to obtain a mixed water body; A2. Adjust the pH of the mixed water body with an acid or a base, and carry out a degradation reaction under normal temperature and pressure to obtain a reacted solution after degradation.

7. A method for activating PAA by complex modified birnessite to degrade organic pollutants according to claim 6, characterized in that, In the mixed water body of A1, the concentration of the complexation - modified birnessite catalyst is 0.025 g / L - 0.1 g / L; the organic pollutant is a sulfonamide drug.

8. A method for activating PAA by complex modified birnessite to degrade organic pollutants according to claim 7, characterized in that, In the mixed water body of A1, the concentration of peracetic acid is 0.5 mM - 5 mM.

9. A method for activating PAA by complex-modified birnessite to degrade organic pollutants according to claim 8, characterized in that, The degradation reaction in A2 is carried out under the condition that the pH is 3 - 9.

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