A synergistic catalyst for phase separation in advanced oxidation and a method of preparing the same

Abstract

The application discloses a phase separation synergistic catalyst for advanced oxidation and a preparation method thereof, and the catalyst is prepared by using MnOOH prepared by hydrothermal potassium permanganate as a precursor, and then adopting a method of wrapping MnOOH with dopamine hydrochloride to load cobalt, and the catalyst is calcined in an inert atmosphere to obtain a bimetallic catalyst with metal Co loaded on the surface of MnOOH in the form of an element, which has a good ability of activating persulfate. ‑1 Under the conditions that the concentration of an oxidant is 0.2 g / L and the catalyst dosage is 0.1 g / L, the complete degradation of bisphenol A with a concentration of 20 ppm can be basically realized within 13 min, the reaction rate constant reaches 0.463 min ‑1 , and the MnCo bimetallic catalyst has a good magnetic recovery effect and can be recycled. The application provides an effective integrated high-efficiency catalyst for advanced oxidation of environmental pollutants, and is expected to play a key role in environmental governance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water treatment material preparation, and particularly relates to a phase separation synergistic catalyst for advanced oxidation and a preparation method thereof BACKGROUND

[0002] Bisphenol A (BPA) is a widely used phenolic compound, which is usually used for the synthesis of polycarbonate, epoxy resin, etc. It is often used to manufacture various daily consumer goods, including water pipes, food and beverage packaging, and electronic equipment, etc., but BPA is stable in nature and is difficult to degrade in the natural environment, and has significant lipophilicity and is easy to accumulate in the body, which has estrogenic effects on higher organisms, seriously affecting the normal endocrine function of organisms and human bodies, and thus has obvious harm to humans and the environment. Therefore, a green and efficient phenolic treatment technology is urgently needed to remove residual phenolic pollutants in the environment.

[0003] Generally speaking, the final rule of catalytic methods is to rapidly decompose pollutants in wastewater into carbon dioxide and water or small molecular organic matter through chemical reactions such as oxidation technology under the action of efficient catalysts, especially catalysts involving heterogeneous materials. It is worth noting that advanced oxidation processes (AOPs) are widely studied and developed because they can handle high-concentration wastewater from industry and life. AOPs involving persulfate (PMS) based on controllable hydroxyl radicals (·OH), sulfate radicals (SO4 ·- ), even peroxide (O2 · ) and singlet oxygen ( 1 O2) have very high oxidation capacity and great superiority compared to traditional treatment processes.

[0004] Compared with photocatalysts or carbon-based catalysts, transition metal oxide-based catalysts have attracted more and more attention due to their low cost, good long-term stability, and the ability to effectively activate PMS in a wide pH range. Co, Fe, Cu, Mn and Ni transition metal catalysts have been widely concerned in the activation of persulfate due to their flexible valence state, controllable composition and low cost. Among them, Co-based materials have many advantages in AOPs due to their adjustable redox potential, rich surface active sites, and obvious surface oxygen vacancies that can activate PMS. However, single metal ions have the disadvantages of serious leaching, low reuse efficiency, secondary pollution, etc., which increase the cost. In order to solve this problem, people have proposed methods such as morphology adjustment, atomic doping, alloying and hybridization with other materials. SUMMARY

[0005] The application provides a phase separation synergistic catalyst for advanced oxidation and a preparation method thereof, and provides an efficient and recyclable catalyst, improves the removal rate of refractory phenolic macromolecular organic pollutants such as BPA, reduces the use of oxidants, and has good universality for various pollutants.

[0006] The application provides a phase separation synergistic catalyst for advanced oxidation, and the catalyst is a MnO@Co / C-X bimetallic catalyst, and X=500 / 600 / 700.

[0007] Preferably, the precursor MnOOH has a diameter of 150 nm, and the Co element loaded on the MnOOH has a diameter of 100 nm.

[0008] The application provides a preparation method of the phase separation synergistic catalyst for advanced oxidation, and the method comprises the following steps:

[0009] S1, dissolving potassium permanganate in a water / ethanol mixed solvent, stirring at room temperature until the potassium permanganate is completely dissolved, then performing hydrothermal treatment, collecting the precipitate, centrifuging, washing and drying to obtain a MnOOH precursor;

[0010] S2, dissolving trimethylol aminomethane in an aqueous HCl solution to obtain a buffer solution;

[0011] S3, dissolving the MnOOH obtained in S1 in the buffer solution and uniformly stirring by ultrasonic stirring; after adjusting the pH value, adding dopamine hydrochloride, stirring until the dopamine hydrochloride is dissolved, and then adding cobalt acetate tetrahydrate, and stirring at room temperature to prepare a polydopamine-coated bimetallic catalyst;

[0012] S4, placing the obtained catalyst in a nitrogen atmosphere and performing calcination by heating.

[0013] Preferably, the concentration of potassium permanganate in S1 is 7-7.5 g / L, and the volume ratio of water to ethanol is 2-5%.

[0014] Preferably, the hydrothermal temperature in S1 is 140-145 DEG C, and the hydrothermal time is 12-13 h.

[0015] Preferably, the concentration of trimethylol aminomethane in S2 is 50-55 mMol / L, and the concentration of HCl is 2-2.5 Mol / L.

[0016] Preferably, the concentration of MnOOH in S3 is 7.1-7.6 g / L, the concentration of dopamine hydrochloride is 7.1-7.6 g / L, and the concentration of cobalt acetate tetrahydrate is 1-1.5 mMol / L.

[0017] Preferably, the pH value is adjusted to 7-9 in S3, and the stirring time is 12-13 h.

[0018] Preferably, the heating rate in S4 is 3-5 DEG C / min, the calcination time is 3-4 h, and the carbonization temperature is 500-700 DEG C.

[0019] Preferably, the MnOOH nanorods in S1 are synthesized by a hydrothermal method.

[0020] Beneficial effects: The synergistic catalyst for phase separation of advanced oxidation provided by the application retains the nanorod structure of the MnOOH precursor and changes the catalytic activity by calcination. The results show that the catalyst formed after calcination exhibits obvious Mn 3+ and elemental Co, and exhibits high catalytic activity for activated persulfate. When the catalyst usage is 5 mg and the PMS usage is 10 mg, the complete degradation of 20 ppm BPA can be achieved within 13 min, and the reaction rate constant reaches 0.463. The one-dimensional catalyst is beneficial to electron migration and is easy to recycle and use repeatedly. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a transmission electron microscope image of the nanorods of MnO@Co / C-600 obtained in Example 2;

[0022] Figure 2 is an element mapping image of the nanorods of MnO@Co / C-600 obtained in Example 2;

[0023] Figure 3 is a scanning electron microscope image of MnO@Co / C-500 and MnO@Co / C-700 obtained in Examples 3 and 4;

[0024] Figure 4 is an X-ray diffraction spectrum of a series of MnCo samples obtained in Examples 1-7;

[0025] Figure 5 is an N2 adsorption / desorption isotherm of a series of comparative MnCo samples obtained in Examples 1-7;

[0026] Figure 6 is an N2 adsorption / desorption isotherm of a series of MnO@Co / C-X series samples obtained in Examples 1-7;

[0027] Figure 7 is a degradation curve of BPA by a series of MnCo samples obtained in Examples 1-3, and the experimental conditions are: [BPA] = 20 mg / L, [PMS] = 0.2 g / L, and [catalyst] = 0.1 g / L;

[0028] Figure 8Degradation curve of BPA by the MnCo sample obtained in Example 1 under different PMS dosages, experimental conditions: [BPA] = 20 mg / L, [MnO@Co / C-600] = 0.1 g / L;

[0029] Figure 9 Degradation curve of BPA by the MnCo sample obtained in Example 1 under different MnO@Co / C-600 dosages, experimental conditions: [BPA] = 20 mg / L, [PMS] = 0.2 g / L;

[0030] Figure 10 Degradation curve of BPA by the MnCo sample obtained in Example 1 under different BPA concentrations, experimental conditions: [PMS] = 0.2 g / L, [MnO@Co / C-600] = 0.1 g / L;

[0031] Figure 11 Degradation curve of different pollutants by the MnCo sample obtained in Example 2, experimental conditions: [PMS] = 0.2 g / L, [MnO@Co / C-600] = 0.1 g / L, [pollutant] = 20 mg / L. DETAILED DESCRIPTION

[0032] The following examples further illustrate the content of the present application, but should not be understood as limiting the present application. Modifications and replacements to the method, steps or conditions of the present application, without departing from the spirit and essence of the present application, all belong to the scope of the present application. If not specifically indicated, the technical means used in the examples are conventional means known to those skilled in the art.

[0033] The principle of the preparation process of the MnO@Co / C-600 catalyst prepared based on MnOOH in the present application is that: the process first uses the MnOOH nanorod synthesized by the hydrothermal method as a precursor. The nanorod obtained in this step has a good morphology, and the diameter size is about 150 nm. Then dopamine and a metal Co source are loaded by a one-step method. Then the obtained material is centrifuged, washed and dried, and the purpose of this step is to remove residual water and other inorganic ions. Then high-temperature carbonization is carried out in a tube furnace, and the purpose of this step is to remove the excess organic skeleton and leave a stable metal existing carbon layer.

[0034] Example 1:

[0035] (1) 0.25 g of potassium permanganate was dissolved in 36.0 ml of a mixed water / ethanol solvent with a volume ratio of 2%, and stirred at room temperature for 10 min until the potassium permanganate was completely dissolved. It was transferred to a stainless steel hydrothermal kettle with a polytetrafluoroethylene lining, and hydrothermal treatment was carried out at 140℃ for 12 h. Centrifugation, washing of the precipitate, and drying were carried out, and it was labeled as MnOOH, and the X-ray diffraction spectrum was as follows:Figure 4 as shown in FIG. 2, and the N2adsorption / desorption isotherm is as shown in FIG. 3. Figure 5 as shown in FIG. 4.

[0036] Example 2:

[0037] (1) 0.26 g of potassium permanganate was dissolved in 36.0 ml of a mixed water / ethanol solvent with a volume ratio of 3%, and stirred at room temperature for 10 min until the potassium permanganate was completely dissolved. It was transferred to a stainless steel hydrothermal kettle with a polytetrafluoroethylene liner, and hydrothermal treatment was carried out at 142°C for 12.5 h. After centrifugation, the precipitate was washed and dried, and was marked as MnOOH.

[0038] (2) 6.057 g of tris-hydroxymethyl aminomethane was dissolved in 12 ml of 2 mol / L aqueous HCl solution, and diluted to 1000 ml to obtain a buffer solution with a concentration of 50 mMol / L.

[0039] (3) 0.5 g of MnOOH nanorods was dissolved in 70 ml of the buffer solution, and ultrasonic dispersion was carried out until uniform. Subsequently, the pH value was adjusted to 7, and then 0.5 g of dopamine hydrochloride was added, and stirred until dissolved. Finally, 1 mmol of cobalt acetate tetrahydrate was added to obtain a black solution, which was stirred at 25°C for 12 h. After centrifugation, the precipitate was washed and dried, and was marked as MnOOH@Co / PDA.

[0040] (4) The obtained nanorods were calcined at 600°C under a nitrogen atmosphere at a rate of 3°C / min for 3 h to obtain the MnO@Co / C-600 catalyst. The basic morphology of the catalyst is as shown in FIG. 5, the element mapping is as shown in FIG. 6, the X-ray diffraction spectrum is as shown in FIG. 7, and the N2adsorption / desorption isotherm is as shown in FIG. 8. Figure 1 Figure 2 Figure 4 Figure 6 The degradation characteristics are characterized in that the removal rate of BPA is 98% within 13 min, and the removal rate is 0.463 min -1 as shown in FIG. 9. Figure 7

[0041] (5) A series of variable control experiments were carried out on the obtained MnO@Co / C-600 catalyst, as shown in FIG. 10, and an extended experiment on different pollutants was carried out on the MnO@Co / C-600, and the results are as shown in FIG. 11. Figures 8-10 Figure 11

[0042] Example 3:

[0043] ​​​​​​(1) 0.27 g KMnO4 was dissolved in 36.0 ml mixed water / ethanol solvent with volume ratio of 5%, stirred at room temperature for 10 min until KMnO4 was completely dissolved. It was transferred into a stainless steel hydrothermal kettle with a polytetrafluoroethylene liner, and hydrothermal at 145 °C for 13 h. The precipitate was centrifuged, washed, and dried, and was marked as MnOOH.

[0044] (2) 6.663 g Tris was dissolved in 12 ml 2.2 mol / L HCl aqueous solution, and diluted to 1000 ml to obtain a buffer solution with a concentration of 50 mMoL / L.

[0045] (3) 0.52 g MnOOH nanorods were dissolved in 70 ml buffer solution and ultrasonically dispersed. Then, the pH value was adjusted to 8.5, 0.52 g dopamine hydrochloride was added, stirred until dissolved, and finally 1.3 mmol cobalt acetate tetrahydrate was added to obtain a black solution. The solution was stirred at 25 °C for 12.5 h, centrifuged, washed, and dried, and was marked as MnOOH@Co / PDA.

[0046] (4) The obtained nanorods were calcined at 500 °C under a nitrogen atmosphere at a rate of 4 °C / min for 3.5 h to obtain MnO@Co / C-500 catalyst. The basic morphology of the catalyst is shown in Figure 3 , the X-ray diffraction spectrum is shown in Figure 4 , and the N2 adsorption / desorption isotherm is shown in Figure 6 .

[0047] Example 4:

[0048] (1) 0.25 g KMnO4 was dissolved in 36.0 ml mixed water / ethanol solvent with volume ratio of 2%, stirred at room temperature for 10 min until KMnO4 was completely dissolved. It was transferred into a stainless steel hydrothermal kettle with a polytetrafluoroethylene liner, and hydrothermal at 140 °C for 12 h. The precipitate was centrifuged, washed, and dried, and was marked as MnOOH.

[0049] (2) 6.057 g Tris was dissolved in 12 ml 2.5 mol / L HCl aqueous solution, and diluted to 1000 ml to obtain a buffer solution with a concentration of 50 mMoL / L.

[0050] (3) 0.53 g MnOOH nanorods were dissolved in 70 ml buffer solution and ultrasonically dispersed. Then, the pH value was adjusted to 9, 0.53 g dopamine hydrochloride was added, stirred until dissolved, and finally 1.5 mmol cobalt acetate tetrahydrate was added to obtain a black solution. The solution was stirred at 25 °C for 13 h, centrifuged, washed, and dried, and was marked as MnOOH@Co / PDA.

[0051] (4) The obtained nanorods were calcined at 700°C for 4h under nitrogen atmosphere at a rate of 5°C / min to obtain MnO@Co / C-700 catalyst. The basic morphology of the catalyst is shown in FIG. 1, the X-ray diffraction spectrum is shown in FIG. 2, and the N2 adsorption / desorption isotherm is shown in FIG. 3. Figure 3 Figure 4 Figure 6

[0052] Example 5:

[0053] (1) 0.25g of potassium permanganate was dissolved in 36.0ml of a mixed water / ethanol solvent with a volume ratio of 2%, and stirred at room temperature for 10min until the potassium permanganate was completely dissolved. It was transferred to a stainless steel hydrothermal kettle with a polytetrafluoroethylene liner, and hydrothermal treatment was carried out at 140°C for 12h. After centrifugation, the precipitate was washed and dried, and labeled as MnOOH.

[0054] (2) The obtained MnOOH nanorods were calcined at 600°C for 3h under nitrogen atmosphere at a rate of 5°C / min to obtain Mn2O3-600 catalyst. The X-ray diffraction spectrum is shown in FIG. 4, and the N2 adsorption / desorption isotherm is shown in FIG. 5. Figure 4 Figure 5

[0055] Example 6:

[0056] (1) 0.25g of potassium permanganate was dissolved in 36.0ml of a mixed water / ethanol solvent with a volume ratio of 2%, and stirred at room temperature for 10min until the potassium permanganate was completely dissolved. It was transferred to a stainless steel hydrothermal kettle with a polytetrafluoroethylene liner, and hydrothermal treatment was carried out at 140°C for 12h. After centrifugation, the precipitate was washed and dried, and labeled as MnOOH.

[0057] (2) 6.057g of tris-hydroxymethyl aminomethane was dissolved in 12ml of 2mol / L HCl aqueous solution, and diluted to 1000ml to obtain a buffer solution with a concentration of 50mMol / L.

[0058] (3) 0.5g of MnOOH nanorods were dissolved in 70ml of the buffer solution and ultrasonically dispersed. Subsequently, the pH value was adjusted to 8.5, and 0.5g of dopamine hydrochloride was added, stirred until dissolved, and stirred at 25°C for 12h. After centrifugation, the precipitate was washed and dried, and labeled as MnOOH / PDA.

[0059] (4) The obtained nanorods were calcined at 600°C for 3h under nitrogen atmosphere at a rate of 5°C / min to obtain Mn3O4 / C-600 catalyst. The X-ray diffraction spectrum is shown in FIG. 6, and the N2 adsorption / desorption isotherm is shown in FIG. 7. Figure 4 Figure 5

[0060] Example 7: ​​​​​​​

[0061] (1) 0.25 g KMn04was dissolved in 36.0 ml of 2% mixed water / ethanol solvent by volume, stirred at room temperature for 10 min until KMn04was completely dissolved. It was transferred to a stainless steel hydrothermal kettle with a polytetrafluoroethylene liner, hydrothermally treated at 140 °C for 12 h, centrifuged, washed the precipitate, dried, and labeled as MnOOH.

[0062] (2) 0.5 g of MnOOH nanorods was dissolved in 70 ml of deionized water, ultrasonically dispersed uniformly, then 1 mmol of cobalt acetate tetrahydrate was added, stirred at 25 °C for 12 h, centrifuged, washed the precipitate, dried, and labeled as MnOOH / Co.

[0063] (3) The obtained nanorods were calcined at 600 °C for 3 h at a rate of 5 °C / min under a nitrogen atmosphere to produce a MnO / Co-600 catalyst, the X-ray diffraction spectrum is shown in Figure 4 , and the N2adsorption / desorption isotherm is shown in Figure 5 .

Claims

1. A synergistic catalyst for phase separation in advanced oxidation, characterized in that, The catalyst is a MnO@Co / CX bimetallic catalyst, where X = 500 / 600 / 700. The MnO@Co / C catalyst retains the nanorod structure of the MnOOH precursor. The diameter of the MnOOH precursor is 150 nm, and the diameter of the Co element supported on the MnOOH is 100 nm. Potassium permanganate is dissolved in a water / ethanol mixed solvent and stirred at room temperature until the potassium permanganate is completely dissolved. Then, hydrothermal treatment is performed, the precipitate is collected, centrifuged, washed, and dried to obtain the MnOOH precursor. Tris(hydroxymethyl)aminomethane is dissolved in an aqueous HCl solution until homogeneous to obtain a buffer solution. The obtained MnOOH is dissolved in the buffer solution and ultrasonically stirred until homogeneous. After adjusting the pH value, dopamine hydrochloride is added and stirred until dissolved. Then, cobalt acetate tetrahydrate is added and stirred at room temperature to prepare a polydopamine-coated bimetallic catalyst. The obtained catalyst is placed in a nitrogen atmosphere and calcined at elevated temperature.

2. A method for preparing a synergistic catalyst for phase separation in advanced oxidation according to claim 1, characterized in that, Includes the following steps: S1. Dissolve potassium permanganate in a water / ethanol mixture, stir at room temperature until the potassium permanganate is completely dissolved, then perform hydrothermal treatment, collect the precipitate, centrifuge, wash and dry to obtain the MnOOH precursor. S2. Dissolve tris(hydroxymethyl)aminomethane in an aqueous HCl solution until homogeneous to obtain a buffer solution; S3. Dissolve the MnOOH obtained in S1 in a buffer solution and stir ultrasonically until homogeneous; adjust the pH value and add dopamine hydrochloride, stir until dissolved, then add cobalt acetate tetrahydrate and stir at room temperature to prepare a polydopamine-coated bimetallic catalyst. S4. Place the obtained catalyst in a nitrogen atmosphere and calcine it by heating.

3. The method for preparing the synergistic catalyst for phase separation in advanced oxidation according to claim 2, characterized in that, The potassium permanganate concentration in S1 is 7 ~ 7.5 g / L, and the water / ethanol volume ratio is 2 ~ 5%.

4. The method for preparing the synergistic catalyst for phase separation in advanced oxidation according to claim 2, characterized in that, The hydrothermal temperature in S1 is 140~145 ℃, and the hydrothermal time is 12~13 h.

5. The method for preparing the synergistic catalyst for phase separation in advanced oxidation according to claim 2, characterized in that, The concentration of tris(hydroxymethyl)aminomethane in S2 is 50-55 mmol / L, and the concentration of HCl is 2-2.5 mol / L.

6. The method for preparing the synergistic catalyst for phase separation in advanced oxidation according to claim 2, characterized in that, The concentrations of MnOOH, dopamine hydrochloride, and cobalt acetate tetrahydrate in S3 were 7.1–7.6 g / L, 7.1–7.6 g / L, and 14.3–14.8 mmol / L, respectively.

7. The method for preparing the synergistic catalyst for phase separation in advanced oxidation according to claim 2, characterized in that, Adjust the pH value to 7-9 in S3 and stir for 12-13 hours.

8. The method for preparing the synergistic catalyst for phase separation in advanced oxidation according to claim 2, characterized in that, The heating rate in S4 is 3~5 ℃ / min, the calcination time is 3~4 h, and the carbonization temperature is 500~700 ℃.

9. The method for preparing the synergistic catalyst for phase separation in advanced oxidation according to claim 2, characterized in that, MnOOH nanorods were synthesized in S1 via a hydrothermal method.

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