Preparation method and application of a mesoporous sulfur-doped transition metal-based persulfate activator

Abstract

The present invention relates to the field of water treatment technology and discloses a method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator, comprising the following steps: S1, adding a transition metal salt to a mesoporous molecular sieve suspension to obtain a transition metal-based persulfate activator precursor; S2, calcining the transition metal-based persulfate activator precursor to obtain a mesoporous transition metal-based persulfate activator; S3, adding the mesoporous transition metal-based persulfate activator to a sulfide solution for a solvent thermal reaction to form a mesoporous sulfur-doped transition metal-based persulfate activator. The mesoporous structure of the mesoporous sulfur-doped transition metal-based persulfate activator prepared by the present invention can greatly enhance the removal of new pollutants and SO4 •− The mass transfer efficiency within the activator increases the reaction probability between the two, thereby improving the activity of the activator; sulfur doping can increase the electron cloud density of the material, improve the performance of the transition metal from a high valence state to a low valence state, and thus enhance the stability of the activator.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, in particular to a preparation method and application of a mesoporous sulfur-doped transition metal-based persulfate activator. Background Art

[0002] In recent years, emerging pollutants such as endocrine disruptors, antibiotics, and perfluorinated compounds have attracted significant attention. Although these pollutants are present in low concentrations in the environment, their high frequency of use, long half-lives, and high bioaccumulation pose a threat to human health and ecosystems, necessitating efficient disposal. Traditional wastewater treatment technologies struggle to effectively treat these emerging pollutants, prompting the emergence of advanced oxidation technologies.

[0003] Compared with traditional advanced oxidation technologies such as Fenton oxidation and ozone oxidation, which use hydroxyl radicals (•OH) as the main active substance, the main active substance of persulfate advanced oxidation technology is sulfate radicals (SO4 •− ), higher redox potential, stronger oxidizing ability, wider selectivity, and more thorough degradation of organic pollutants; SO4 •− The longer the lifespan, the greater the chance of contact with organic pollutants, and the easier it is to react; the more diverse the activation methods, the more hydroxyl radicals (•OH) and superoxide radicals (O2 •- ), singlet oxygen ( 1 O2) and other active species, which have higher removal efficiency for organic pollutants; it is less affected by the acidity and alkalinity of the solution and has a high degradation efficiency of organic pollutants even under neutral conditions; persulfate advanced oxidation technology will be a potential alternative technology to traditional advanced oxidation technology.

[0004] Since persulfate itself has a weak oxidizing ability, it needs to be activated by an activator to produce highly oxidizing SO4 •− Transition metal-based activators are more common activators, including homogeneous transition metal-based activators and heterogeneous transition metal-based activators. Homogeneous transition metal-based activators have the advantages of low energy consumption and high activity, but their application is limited because the metals are difficult to recycle and are prone to secondary pollution. Heterogeneous transition metal-based activators have the advantages of metal recyclability and low secondary pollution, and have application potential, but their activity and stability are not high. In order to meet the actual needs of sewage treatment, the activity and stability of heterogeneous transition metal-based activators still need to be improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of a mesoporous sulfur-doped transition metal-based persulfate activator to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator comprises the following steps:

[0008] S1. Adding a transition metal salt to a mesoporous molecular sieve suspension, stirring and mixing uniformly during the addition process, and then standing to allow solid-liquid separation. After removing the supernatant, the solid is dried to obtain a transition metal-based persulfate activator precursor;

[0009] S2, calcining the transition metal-based persulfate activator precursor obtained in step S1, washing, and drying to obtain a mesoporous transition metal-based persulfate activator;

[0010] S3. Add the mesoporous transition metal-based persulfate activator obtained in step S2 to the sulfide solution, perform ultrasonic treatment, and after uniform mixing, perform solvent thermal reaction. After washing and drying, a mesoporous sulfur-doped transition metal-based persulfate activator is formed.

[0011] As a further solution of the present invention: in the step S1, the transition metal salt is one or more soluble transition metal salts, preferably, the soluble transition metal salt is a nitrate or a chloride salt, for example, the nitrate is cobalt nitrate or manganese nitrate, and the chloride is manganese dichloride.

[0012] As a further solution of the present invention: in the step S1, the mesoporous molecular sieve in the mesoporous molecular sieve suspension is SBA-15, for example, with a pore size of 6 to 11 nm and a specific surface area of 550 to 600 m 2 / g of SBA-15.

[0013] As a further solution of the present invention: in the S1 step, the solvent in the mesoporous molecular sieve suspension is deionized water and ethanol mixed in a volume ratio of (3 to 6): 1, for example: 37.5 mL of water is mixed with 12.5 mL of ethanol to form a solvent; 40 mL of water is mixed with 10 mL of ethanol to form a solvent; 41.5 mL of water is mixed with 8.3 mL of ethanol to form a solvent; 42.6 mL of water is mixed with 7.1 mL of ethanol to form a solvent, and the solvent must ensure that the transition metal salt is completely dissolved, and the ratio of the mesoporous molecular sieve to the solvent is 1: (50 to 200) g / mL, for example: 1 g of SBA-15 is mixed with 50 mL of solvent to form a mesoporous molecular sieve suspension; 0.75 g of SBA-15 is mixed with 50 mL of solvent to form a mesoporous molecular sieve suspension; 0.5 g of SBA-15 is mixed with 50 mL of solvent to form a mesoporous molecular sieve suspension; 0.25 g of SBA-15 is mixed with 50 mL of solvent to form a mesoporous molecular sieve suspension. mL of solvent is used to form a mesoporous molecular sieve suspension; and the ratio of transition metal salt to mesoporous molecular sieve is 1:(100-300) mol / g, for example: 0.01 mol of cobalt nitrate is added to a mesoporous molecular sieve suspension containing 1 g of SBA-15; 0.005 mol of cobalt nitrate is added to a mesoporous molecular sieve suspension containing 1 g of SBA-15; 0.0034 mol of cobalt nitrate is added to a mesoporous molecular sieve suspension containing 1 g of SBA-15.

[0014] As a further scheme of the present invention: in the step S1, the stirring speed is 150-600 r / min, the stirring time is 2-6 h; the standing time is 6-12 h, the drying temperature is 70-90 ° C, and the drying time is 3-6 h; for example: the stirring speed is 150 r / min, the stirring time is 6 h, the standing time is 6 h, the drying temperature is 70 ° C, and the drying time is 6 h; the stirring speed is 400 r / min, the stirring time is 4 h, the standing time is 9 h, the drying temperature is 80 ° C, and the drying time is 4.5 h; the stirring speed is 600 r / min, the stirring time is 2 h, the standing time is 12 h, the drying temperature is 90 ° C, and the drying time is 6 h.

[0015] As a further solution of the present invention: in the S2 step, the calcination temperature is 300-600 ° C, the heating rate is 2 ° C / min, and the calcination time is 4-6 h. For example: the transition metal salt is cobalt nitrate, and the transition metal-based persulfate activator precursor is calcined into cobalt oxide at a calcination temperature of 350 ° C and a calcination time of 6 h; the transition metal salt is manganese dichloride, and the transition metal-based persulfate activator precursor is calcined into manganese oxide at a calcination temperature of 400 ° C and a calcination time of 4 h.

[0016] As a further solution of the present invention: in the S2 step, the cleaning is carried out by alkali washing, water washing and alcohol washing in sequence, wherein the alkali washing is carried out with a NaOH solution, the concentration of the NaOH solution is 1 to 5 mol / L, and the volume ratio of the NaOH solution to the transition metal-based persulfate activator precursor is (6 to 11):1, for example: 20 mL of the transition metal-based persulfate activator precursor is rinsed 3 times with a 2 mol / L NaOH solution, each time using a volume of 60 mL of NaOH solution, until the SBA-15 is completely removed; the water washing is carried out with deionized water, and the washing is carried out until the pH of the liquid after washing is 7; the alcohol washing is carried out with anhydrous ethanol, and the volume ratio of anhydrous ethanol to the transition metal-based persulfate activator precursor is (2 to 3):1; and the drying temperature is 50 to 60 ° C, and the drying time is 3 to 6 h, for example: the drying temperature is 50 ° C, the drying time is 6 h; the drying temperature is 60 ° C, and the drying time is 3 h.

[0017] As a further solution of the present invention: in the step S3, the sulfide is one or more soluble sulfide salts, and preferably the soluble sulfide salt is sodium sulfide.

[0018] As a further solution of the present invention: in the S3 step, the ultrasonic time is 30 to 50 minutes, the solvent thermal reaction temperature is 80 to 100°C, and the reaction time is 20 to 27 hours. For example, sodium sulfide is selected as the sulfide, cobalt nitrate is selected as the transition metal salt, the mesoporous transition metal-based persulfate activator is thermally reacted to form sulfur-doped cobalt oxide, the solvent reaction temperature is 90°C, and the reaction time is 24 hours.

[0019] A method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator and its application in the degradation of pollutants by persulfate advanced oxidation technology, wherein the specific surface area of the activator is 30 to 45 m 2 / g, pore size is 10-20 nm, for example: specific surface area is 35.4 m 2 / g, and the pore diameters are 12 nm and 15.8 nm.

[0020] Mesoporous sulfur-doped transition metal-based persulfate activators are highly reductive due to their strong S 2- The doping of high-valent metal ions can quickly achieve the reduction of high-valent metal ions (such as Co 3+ Reduction to Co 2+ ), thereby continuously and efficiently activating persulfate to degrade organic pollutants in water.

[0021] Mesoporous sulfur-doped transition metal-based persulfate activators have the advantage of highly efficient persulfate activation. They can not only effectively reduce the dosage of persulfate and activator, but also have a high degradation efficiency of organic pollutants. For example, 0.5 mmol / L persulfate and 0.05 g / L activator can degrade 10 mmol / L of atrazine by 100% within 8 minutes.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The mesoporous structure of the mesoporous sulfur-doped transition metal-based persulfate activator prepared by the present invention can greatly enhance the new pollutants and SO4 •− The mass transfer efficiency within the activator increases the reaction probability between the two, thereby improving the activity of the activator; sulfur doping can increase the electron cloud density of the material, improve the performance of the transition metal from a high valence state to a low valence state, and thus enhance the stability of the activator. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the X-ray diffraction pattern of mesoporous sulfur-doped cobalt oxide in Example 1;

[0025] Figure 2 This is a scanning electron microscope image of mesoporous sulfur-doped cobalt tetroxide in Example 1;

[0026] Figure 3 This is a transmission electron microscope image of mesoporous sulfur-doped cobalt tetroxide in Example 1;

[0027] Figure 4 This is a nitrogen adsorption-desorption curve of mesoporous sulfur-doped cobalt tetroxide in Example 1;

[0028] Figure 5 This is the pore size distribution diagram of mesoporous sulfur-doped cobalt tetroxide in Example 1;

[0029] Figure 6 This is a diagram showing the degradation effects of atrazine under different activators in Example 2;

[0030] Figure 7 This is a graph showing the degradation efficiency of atrazine at different sulfur doping levels in Example 2;

[0031] Figure 8 This is a graph showing the degradation efficiency of atrazine at different persulfate dosages in Example 2;

[0032] Figure 9 This is a graph showing the degradation efficiency of atrazine at different initial pH values in Example 2. DETAILED DESCRIPTION Example

[0033] In an embodiment of the present invention, a method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator is provided. The prepared mesoporous sulfur-doped transition metal-based persulfate activator is mesoporous sulfur-doped cobalt tetroxide (S-Co3O4). The preparation method comprises the following steps:

[0034] S1. Prepare 35 mL of a mixture of ethanol and deionized water in a volume ratio of 1:6; add 1.5 g of SBA-15 and 4.34 g of Co(NO3)2•6H2O to the ethanol-water mixture simultaneously, and stir continuously at room temperature for 5 h at a stirring speed of 400 r / min; let the stirred suspension stand for 10 h, remove the supernatant, and obtain a pink sludge; dry the pink sludge at 80°C for 3 h to obtain a pink powder;

[0035] S2. The pink powder was transferred to a crucible and calcined at 350°C for 6 h, and then cooled naturally to obtain a black powder. The black powder was rinsed with 100 mL of 2 mol / L NaOH three times, each time for 0.5 h, to obtain a black sludge. The black sludge was repeatedly washed with deionized water until the pH of the washing solution reached 7, and then washed with 20 mL of ethanol three times, and dried at 60°C for 1 h to obtain black cobalt tetroxide.

[0036] S3. Add 18 mg of cobalt trioxide and 37.7 mg of sodium sulfide to 25 mL of deionized water and mix them evenly with ultrasound. Transfer the mixed solution to a 50 mL high-pressure reactor for solvothermal reaction at 90 °C for 24 h. After washing and drying, mesoporous sulfur-doped cobalt trioxide is formed.

[0037] like Figure 1 As shown in the X-ray diffraction (XRD) diagram of mesoporous sulfur-doped cobalt oxide, it can be concluded that the prepared mesoporous sulfur-doped cobalt oxide material has high crystallinity and high purity;

[0038] like Figure 2 As shown in the scanning electron microscope (SEM) image of mesoporous sulfur-doped cobalt tetroxide, it can be concluded that the prepared mesoporous sulfur-doped cobalt tetroxide material has high dispersion;

[0039] like Figure 3 As shown in the transmission electron microscope (TEM) image of mesoporous sulfur-doped cobalt tetroxide, it can be concluded that the prepared mesoporous sulfur-doped cobalt tetroxide material has orderly microscopic pores;

[0040] like Figure 4 As shown in the nitrogen adsorption-desorption curve of mesoporous sulfur-doped cobalt tetroxide, it can be concluded that the structure of the prepared mesoporous sulfur-doped cobalt tetroxide material is mesoporous and the specific surface area is 35.4 m 2 / g;

[0041] like Figure 5 As shown in the pore size distribution diagram of mesoporous sulfur-doped cobalt tetroxide, it can be concluded that the average pore size of the prepared mesoporous sulfur-doped cobalt tetroxide material is 15.8 nm. Example

[0042] In an embodiment of the present invention, an activator prepared by a method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator is used in the process of degrading pollutants using persulfate advanced oxidation technology. The sulfur-doped cobalt tetroxide prepared in Example 1 is used as an activator to activate persulfate to degrade atrazine.

[0043] 1. The comparative analysis of the degradation effects of atrazine by mesoporous sulfur-doped cobalt tetroxide and mesoporous non-sulfur-doped cobalt tetroxide activated persulfate is as follows:

[0044] Potassium persulfate and an activator (mesoporous sulfur-doped cobalt oxide (S-Co3O4) was added to one solution and mesoporous non-sulfur-doped cobalt oxide (Co3O4) was added to the other solution) were added to two 10 mmol / L atrazine solutions, respectively. The dosage of potassium persulfate was 0.5 mmol / L, and the dosages of S-Co3O4 and Co3O4 were both 0.05 g / L. Stirring was continued at room temperature. Samples of the two solutions were taken at appropriate times to determine the atrazine concentration.

[0045] like Figure 6 As shown in the degradation effect diagram of two activators (S-Co3O4 and Co3O4), it can be concluded that: S-Co3O4 activated potassium persulfate can completely degrade atrazine within 8 minutes; while Co3O4 activated potassium persulfate, the atrazine removal rate reached 93% after 90 minutes.

[0046] It can be seen that mesoporous sulfur-doped cobalt tetroxide can significantly improve the degradation efficiency of atrazine.

[0047] 2. The effect of sulfur doping amount on the degradation of atrazine by mesoporous sulfur-doped cobalt tetroxide-activated persulfate is analyzed as follows:

[0048] To a 10 mmol / L atrazine solution, 0.05 g / L cobalt oxide with different sulfur doping amounts (the mass ratio of sodium sulfide to cobalt oxide was 10%, 30%, 60%, and 120%, abbreviated as 1S-Co3O4, 3S-Co3O4, 6S-Co3O4, and 12S-Co3O4, respectively) and 0.5 mmol / L potassium persulfate were added. The solution was stirred continuously at room temperature, and samples were taken at appropriate times to determine the atrazine concentration.

[0049] like Figure 7As shown in the degradation effect diagram of four mesoporous sulfur-doped cobalt tetroxides with different sulfur doping amounts (S-Co3O4, 3S-Co3O4, 6S-Co3O4 and 12S-Co3O4), it can be concluded that the removal rates of atrazine degradation by activated persulfate of S-Co3O4, 3S-Co3O4, 6S-Co3O4 and 12S-Co3O4 are 55.3%, 100%, 32.4% and 37.3%, respectively.

[0050] It can be seen from this that 3S-Co3O4 activated persulfate has the best effect on degrading atrazine, that is, the optimal sulfur doping amount is 30%.

[0051] 3. The effect of persulfate (PMS) dosage on the degradation of atrazine by sulfur-doped cobalt tetroxide-activated persulfate is analyzed as follows:

[0052] 3S-Co3O4 material was added to a 10 mmol / L atrazine solution. The dosage of 3S-Co3O4 was 0.05 g / L, and the dosages of potassium persulfate were 0.1, 0.5, 1.5, and 2.0 mmol / L, respectively. Stirring was continued at room temperature, and samples were taken at appropriate times to determine the atrazine concentration.

[0053] like Figure 8 As shown in the degradation effect diagram of four different potassium persulfate dosages (0.1, 0.5, 1.5, 2.0 mmol / L), it can be concluded that when the potassium persulfate dosage is 0.1 mmol / L, 0.5 mmol / L, 1.5 mmol / L, and 2 mmol / L, the atrazine removal efficiency is 13.3%, 100%, 100%, and 100%, respectively.

[0054] It can be seen that a dosage of 0.5 mmol / L potassium persulfate can achieve 100% removal of atrazine, and the removal rate of atrazine increases with the increase of dosage.

[0055] 4. The effect of pH on the degradation of atrazine by S-Co3O4 activated persulfate is analyzed as follows:

[0056] Potassium persulfate and S-Co3O4 were added to a 10 mmol / L atrazine solution. The dosage of potassium persulfate was 0.5 mmol / L and the dosage of S-Co3O4 was 0.05 g / L. The initial pH values of the solutions were adjusted to 3, 5, 7, 9, and 11, respectively. Stirring was continued at room temperature, and samples were taken at appropriate times to determine the atrazine concentration.

[0057] like Figure 9As shown in the degradation effect diagram of atrazine solutions with four different pH values, it can be concluded that when the pH values of atrazine solution are 3, 5, 7, 9, and 11, the removal efficiency of atrazine is 8.8%, 74.6%, 87.6%, 100% and 100%, respectively.

[0058] It can be seen from this that mesoporous sulfur-doped cobalt tetroxide has a wide pH value application range as an activator.

[0059] The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator, characterized in that: The following steps are involved: S1. Adding a transition metal salt to a mesoporous molecular sieve suspension, stirring and mixing uniformly during the addition process, and then standing to allow solid-liquid separation. After removing the supernatant, the solid is dried to obtain a transition metal-based persulfate activator precursor, wherein the mesoporous molecular sieve in the mesoporous molecular sieve suspension is SBA-15; S2, calcining the transition metal-based persulfate activator precursor obtained in step S1, washing, and drying to obtain a mesoporous transition metal-based persulfate activator; S3. Add the mesoporous transition metal-based persulfate activator obtained in step S2 to the sulfide solution, perform ultrasonic treatment, and after uniform mixing, perform a solvent thermal reaction. After washing and drying, a mesoporous sulfur-doped transition metal-based persulfate activator is formed; wherein, the ultrasonic time is 30 to 50 minutes, the solvent thermal reaction temperature is 80 to 100° C., and the reaction time is 20 to 27 hours.

2. The method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator according to claim 1, characterized in that: In the step S1, the transition metal salt is one or more soluble transition metal salts.

3. The method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator according to claim 1, characterized in that: In the S1 step, the solvent in the mesoporous molecular sieve suspension is a mixture of deionized water and ethanol in a volume ratio of (3-6):1, the ratio of the mesoporous molecular sieve to the solvent is 1:(50-200) g / mL, and the ratio of the transition metal salt to the mesoporous molecular sieve is 1:(100-300) mol / g.

4. The method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator according to claim 1, characterized in that: In the step S1, the stirring speed is 150-600 r / min, the stirring time is 2-6 hours, the standing time is 6-12 hours, the drying temperature is 70-90° C., and the drying time is 3-6 hours.

5. The method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator according to claim 1, characterized in that: In the step S2, the calcination temperature is 300-600° C., the heating rate is 2° C. / min, and the calcination time is 4-6 hours.

6. The method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator according to claim 1, characterized in that: In the S2 step, the cleaning is carried out by alkali washing, water washing and alcohol washing in sequence, wherein the alkali washing is carried out with a NaOH solution, the concentration of the NaOH solution is 1 to 5 mol / L, and the volume ratio of the NaOH solution to the transition metal-based persulfate activator precursor is (6 to 11):1; the water washing is carried out with deionized water until the pH of the liquid after washing is 7; the alcohol washing is carried out with anhydrous ethanol, and the volume ratio of anhydrous ethanol to the transition metal-based persulfate activator precursor is (2 to 3):1; and the drying temperature is 50 to 60 ° C, and the drying time is 3 to 6 hours.

7. The method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator according to claim 1, characterized in that: In the step S3, the sulfide is one or more soluble sulfide salts.

8. An application of an activator prepared by the method for preparing a mesoporous sulfur-doped transition metal-based persulfate activator according to any one of claims 1 to 7 in a process of pollutant degradation using a persulfate advanced oxidation technology, characterized in that: The specific surface area of the activator is 30 to 45 m 2 / g, pore size is 10-20nm.

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