A mineral-based cobalt catalyst, and a preparation method and application thereof

Abstract

The application discloses a mineral-based cobalt catalyst and a preparation method and application thereof. The mineral-based cobalt catalyst is prepared by using dolomite and a cobalt salt as raw materials, using anhydrous ethanol or deionized water as a solvent, and through simple water bath and temperature control calcination methods, and has high catalytic activity and low cobalt ion leaching. The mineral-based cobalt catalyst has the characteristics of low cobalt ion leaching and high catalytic activity, and has a good application prospect in the degradation of organic pollutants by activating persulfate (PMS).

Description

Technical Field

[0001] This invention belongs to the technical field of natural mineral-based environmental catalytic materials and their preparation and application, specifically relating to a mineral-based cobalt catalyst and its preparation method and application. Background Technology

[0002] With the rapid development of industries such as pharmaceuticals, energy, and chemicals, the manufacturing and use of products may lead to the emission of various new pollutants. These pollutants have a wide range of sources, most of them are persistently toxic, and they pose hidden exposure risks and are difficult to effectively decompose and treat.

[0003] To address the problem of organic pollution in water bodies, advanced oxidation technologies such as Fenton oxidation, persulfate oxidation, electrochemical oxidation, photocatalysis, and ozone oxidation have attracted much attention. Among them, novel advanced oxidation technologies based on peroxymonosulfate (KHSO5, PMS) (SR-AOPs) exhibit a wide pH range (pH = 2–9) and stability advantages when degrading organic pollutants. Researchers have developed various cobalt-based catalysts and utilized materials such as carbon nanotubes and graphene, as well as natural minerals such as kaolin and calcite, to enhance their efficiency. Compared with other synthetic materials, natural non-metallic minerals are widely available and relatively inexpensive, showing great potential for further development and enhancement of their applications in catalytic reactions.

[0004] Therefore, in-depth exploration and full utilization of the advantages of natural non-metallic resources will become one of the key research directions in order to achieve better environmental pollution purification effects. Summary of the Invention

[0005] The present invention aims to provide a mineral-based cobalt catalyst, its preparation method and application, wherein the mineral-based cobalt catalyst has the characteristics of low cobalt ion leaching and high catalytic activity.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a mineral-based cobalt catalyst includes the following steps:

[0008] (1) Weigh out a cobalt metal salt and dissolve it in a solvent to obtain a cobalt metal salt solution;

[0009] The cobalt salt is selected from one or a mixture of two of the following: Co(NO3)2·6H2O, CoCl2·6H2O, CoSO4·7H2O, cobalt acetate, cobalt acetylacetonate, disodium ethylenediaminetetraacetate cobalt salt hydrate, cobalt oxalate, and cobalt phthalocyanine, with CoCl2·6H2O being preferred.

[0010] The solvent is selected from one or a mixture of two of anhydrous ethanol and deionized water, preferably anhydrous ethanol;

[0011] The molar volume ratio of cobalt salt to solvent is 1:70-80, mol / L; preferably 1:80, mol / L.

[0012] (2) Add natural alkaline earth metal minerals to the cobalt salt solution obtained in step (1), stir evenly, place in a water bath at 50-70℃ and stir for 6-12 hours, filter and dry to obtain solid powder;

[0013] The natural alkaline earth metal minerals are selected from one or a mixture of two of dolomite, brucite, and olivine. In this embodiment of the invention, dolomite is selected.

[0014] The mass-to-volume ratio of natural alkaline earth metal minerals to cobalt salt solution is 1:11.1–16.7, g / mL; preferably 1:16.7, g / mL.

[0015] The preferred water bath temperature is 60℃, and the stirring time is 6 hours.

[0016] The preferred drying temperature is 60–70°C;

[0017] (3) The solid powder obtained in step (2) is calcined under an air or nitrogen atmosphere. The calcination conditions are: heating rate of 2-5℃ / min, annealing at 400-500℃ for 2h, and natural cooling to room temperature to obtain the mineral-based cobalt catalyst.

[0018] Preferably, the solid powder is calcined in a covered crucible under a nitrogen atmosphere;

[0019] Preferred calcination conditions: heating rate 5℃ / min, annealing at 500℃ for 2h.

[0020] This invention relates to mineral-based cobalt catalysts prepared by the above-described method.

[0021] This invention also relates to the application of the mineral-based cobalt catalyst in the activated persulfate (PMS) degradation of organic pollutants;

[0022] The catalytic degradation function of the mineral-based cobalt catalyst of the present invention is accomplished by activating persulfate. Therefore, those skilled in the art can anticipate that any organic pollutant that can be degraded using PMS is within the scope of protection of the present invention. Specific organic pollutants include, for example, one or more of metronidazole, 5-fluorouracil, norfloxacin, tetracycline, and ciprofloxacin. In one embodiment of the present invention, the organic pollutant is metronidazole.

[0023] The specific application methods are as follows:

[0024] A mineral-based cobalt catalyst was dispersed in an aqueous solution of organic pollutants, and persulfate was added for stirring and degradation.

[0025] In the aqueous solution of organic pollutants, the concentration of organic pollutants is 5–50 mg / L, preferably 20 mg / L;

[0026] Persulfate is selected from potassium peroxymonosulfate and potassium persulfate;

[0027] The mass-to-volume ratio of the mineral-based cobalt catalyst to the aqueous solution of organic pollutants is 0.2–2:1, g / L; preferably 0.5:1, g / L.

[0028] The mass-to-volume ratio of persulfate to the aqueous solution of organic pollutants is 0.25–2:1, g / L; preferably 0.5:1, g / L.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. The mineral-based cobalt catalyst prepared by this invention uses natural minerals as a support to load amorphous cobalt catalyst, which can disperse cobalt, prevent cobalt particle agglomeration, increase active sites, and improve the atomic utilization rate and catalytic activity of cobalt.

[0031] 2. The mineral-based cobalt catalyst prepared by this invention uses soluble inorganic cobalt salt as a precursor, does not require additional organic cobalt ligands (or complexing agents), and is prepared by a simple impregnation and calcination method, without generating wastewater or waste liquid during the process.

[0032] 3. The mineral-based cobalt catalyst prepared by this invention uses dolomite as a support, which can enhance the activation effect of cobalt catalyst on PMS, and at the same time effectively control the leaching of Co ions (<1mg / L), meeting the limit specified in the "Integrated Wastewater Discharge Standard" (GB8978-1996). It also helps to reduce the production cost of the catalyst, has green and environmentally friendly characteristics, and is conducive to large-scale application.

[0033] 4. By controlling the temperature during calcination, this invention can significantly improve the stability of cobalt in mineral-based cobalt catalysts and reduce the leaching of Co ions during the catalytic process.

[0034] 5. Compared with traditional cobalt catalyst preparation methods (such as element doping, porous carbon-supported cobalt, and cobalt-phenanthroline ligand-regulated loading), the mineral-based cobalt catalyst prepared by this invention has the advantages of high catalytic activity and low environmental risk.

[0035] 6. The cobalt catalyst supported on the surface of dolomite in this invention has an amorphous structure, which can increase the catalytic active sites. By utilizing the synergistic effect of the dolomite's own catalytic PMS activity, it exhibits excellent degradation and removal efficiency for organic pollutants.

[0036] 7. The mineral-based cobalt catalyst prepared by this invention has the advantage of high catalytic efficiency compared with other transition metal catalysts prepared based on dolomite (such as copper catalysts based on dolomite). Attached Figure Description

[0037] Figure 1 The composite material Co@B prepared in Example 1, the composite material Co@BL prepared in Comparative Example 10, and the XRD pattern of dolomite.

[0038] Figure 2 Local energy dispersive X-ray spectra of the composite material Co@BKS prepared in Example 2; wherein, (a) is a local electron image of Co@BKS; (b) is a C element mapping; (c) is a Ca element mapping; (d) is a Mg element mapping; (e) is an O element mapping; and (f) is a Co element mapping. Detailed Implementation

[0039] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0040] In the following embodiments,

[0041] CoCl2·6H2O is from Aladdin Biochemical Technology Co., Ltd.; CuCl2 is from Aladdin Biochemical Technology Co., Ltd.; Al(NO3)3·9H2O is from Aladdin Biochemical Technology Co., Ltd.; Dolomite powder is from Guzhang County Shanlin Shiyu Mineral Products Co., Ltd.; Calcium carbonate powder is from Aladdin Biochemical Technology Co., Ltd.; Magnesite powder is from Guzhang County Shanlin Shiyu Mineral Products Co., Ltd.

[0042] Example 1

[0043] (1) Take 0.238g (0.001mol) CoCl2·6H2O and dissolve it in 80mL of anhydrous ethanol to obtain mixed solution A.

[0044] (2) Add 4.8g of dolomite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0045] (3) Place powder B in a covered crucible and incubate it in nitrogen at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@B.

[0046] Example 2

[0047] (1) Take 0.238g (0.001mol) CoCl2·6H2O and dissolve it in 80mL of deionized water to obtain mixed solution A.

[0048] (2) Add 4.8g of dolomite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0049] (3) Place powder B in a covered crucible and incubate it in air at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@BKS.

[0050] Example 3

[0051] (1) Take 0.476g (0.002mol) CoCl2·6H2O and dissolve it in 80mL of deionized water to obtain mixed solution A.

[0052] (2) Add 4.8g of dolomite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0053] (3) Place powder B in a covered crucible and incubate it in air at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 h, followed by natural cooling to room temperature, yielded 2Co@BKS.

[0054] Example 4

[0055] (1) Take 0.238g (0.001mol) CoCl2·6H2O and dissolve it in 80mL of anhydrous ethanol to obtain mixed solution A.

[0056] (2) Add 4.8g of dolomite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0057] (3) Place powder B in a covered crucible and incubate it in nitrogen at 400℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@400B.

[0058] Comparative Example 1

[0059] (1) Take 0.238g (0.001mol) CoCl2·6H2O and dissolve it in 80mL of anhydrous ethanol to obtain mixed solution A.

[0060] (2) Add 4.8g of dolomite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 1h, filter, and dry at 60℃ to obtain powder B.

[0061] (3) Place powder B in a covered crucible and incubate it in nitrogen at 500℃ and 5℃·min. -1Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@B. 1h .

[0062] Comparative Example 2

[0063] (1) Take 0.238g (0.001mol) CoCl2·6H2O and 0.96g o-phenanthroline, dissolve them in 80mL of anhydrous ethanol to obtain mixed solution A. After stirring thoroughly, place it in a constant temperature water bath at 60℃ for 6h. After filtration, dry at 60℃ to obtain powder B.

[0064] (2) Place powder B in a covered crucible and incubate it in nitrogen at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@L.

[0065] Comparative Example 3

[0066] (1) Take 0.238g (0.001mol) CoCl2·6H2O and dissolve it in 80mL of anhydrous ethanol to obtain mixed solution A.

[0067] (2) Add 4.8g of calcium carbonate powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0068] (3) Place powder B in a covered crucible and incubate it in nitrogen at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@CaCO3.

[0069] Comparative Example 4

[0070] (1) Take 0.238g (0.001mol) CoCl2·6H2O and dissolve it in 80mL of anhydrous ethanol to obtain mixed solution A.

[0071] (2) Add 4.8g of dolomite powder to mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B. This comparative example directly uses powder B for subsequent degradation experiments and is named B.

[0072] Comparative Example 5

[0073] (1) Place dolomite powder in a covered crucible and heat it in nitrogen at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields 500B.

[0074] Comparative Example 6

[0075] (1) Take 0.134g (0.001mol) CuCl2 and dissolve it in 80mL of anhydrous ethanol to obtain mixed solution A.

[0076] (2) Add 4.8g of dolomite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0077] (3) Place powder B in a covered crucible and incubate it in nitrogen at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Cu@B.

[0078] Comparative Example 7

[0079] (1) Take 0.238g (0.001mol) CoCl2·6H2O and dissolve it in 80mL of anhydrous ethanol to obtain mixed solution A.

[0080] (2) Add 4.8g of dolomite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0081] (3) Place powder B in a covered crucible and incubate it in nitrogen at 800℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@800B.

[0082] Comparative Example 8

[0083] (1) Take 0.238g (0.001mol) CoCl2·6H2O and 0.375g (0.001mol) Al(NO3)3·9H2O, dissolve them in 80mL of anhydrous ethanol to obtain mixed solution A.

[0084] (2) Add 4.8g of dolomite powder (Guzhang County Shanlin Stone Mineral Products Co., Ltd.) to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6 hours, filter, and dry at 60℃ to obtain powder B.

[0085] (3) Place powder B in a covered crucible and incubate it in nitrogen at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields CoAl@B.

[0086] Comparative Example 9

[0087] (1) Take 0.238g (0.001mol) CoCl2·6H2O and dissolve it in 80mL of anhydrous ethanol to obtain mixed solution A.

[0088] (2) Add 7.2g of dolomite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0089] (3) Place powder B in a covered crucible and incubate it in nitrogen at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@B. 7.2 .

[0090] Comparative Example 10

[0091] (1) Take 0.238g (0.001mol) CoCl2·6H2O and 0.96g o-phenanthroline, dissolve them in 80mL of anhydrous ethanol to obtain mixed solution A.

[0092] (2) Add 4.8g of dolomite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0093] (3) Place powder B in a covered crucible and incubate it in nitrogen at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@BL.

[0094] Comparative Example 11

[0095] (1) Take 0.238g (0.001mol) CoCl2·6H2O and dissolve it in 80mL of anhydrous ethanol to obtain mixed solution A.

[0096] (2) Add 4.8g of magnesite powder to the mixed solution A, stir thoroughly, place in a constant temperature water bath at 60℃ for 6h, filter, and dry at 60℃ to obtain powder B.

[0097] (3) Place powder B in a covered crucible and incubate it in nitrogen at 500℃ and 5℃·min. -1 Annealing at a heating rate of 2 hours, followed by natural cooling to room temperature, yields Co@LM.

[0098] Application Comparison Experiment

[0099] 1. Organic matter catalytic degradation test: A 20 mg / L metronidazole solution was prepared to simulate organic pollutants. 0.025 g of samples from Examples 1-4 and Comparative Examples 1-11 were placed in 50 mL of metronidazole solution, and 0.025 g of potassium persulfate (PMS) was added. After reacting for 5 min, a small amount of solution was taken for solid-liquid separation. The absorbance of residual metronidazole in the solution was measured using a UV spectrophotometer. The degradation rate of metronidazole by the samples was calculated, as shown in Table 1.

[0100] 2. Co ion leaching test: After stirring the reaction for another 30 minutes, take the filtered degradation reaction solution and test the Co ion leaching concentration, as shown in Table 2.

[0101] Table 1 Sample Degradation Rate Data

[0102]

[0103] Table 2. Co leaching data of samples

[0104]

[0105]

[0106] 1. As can be seen from Examples 1-4 in Table 1, the dolomite-based catalyst prepared in this invention can achieve efficient degradation of the target organic matter within only 5 minutes.

[0107] 2. As can be seen from Examples 1-4 in Table 2, the Co ion leaching level in the dolomite-based catalyst is within the limit specified in GB8978-1996 (<1 mg / L).

[0108] 3. The comparison between Example 1 and Comparative Example 1 in Table 1 shows that reducing the water bath time (1h) will reduce the catalytic performance of the dolomite-based catalyst.

[0109] 4. The comparison between Example 1 and Comparative Example 4 in Table 1 shows that dolomite alone has a low efficiency in degrading organic pollutants.

[0110] 5. The comparison between Example 1 and Comparative Example 5 in Table 1 shows that the efficiency of calcined dolomite at 500℃ in degrading organic pollutants is relatively low.

[0111] 6. The comparison between Example 1 and Comparative Example 6 in Table 1 shows that the Co-based dolomite catalyst has significantly better catalytic performance than the Cu-based dolomite catalyst.

[0112] 7. The comparison between Example 1 and Comparative Example 8 in Table 1 shows that the Co-based dolomite catalyst has significantly better catalytic performance than the CoAl-based dolomite catalyst.

[0113] 8. The comparison between Example 1 and Comparative Example 3 in Table 1 shows that using calcium carbonate as a support will reduce the catalytic performance of the cobalt catalyst.

[0114] 9. The comparison between Example 1 and Comparative Example 11 in Table 1 shows that using magnesite as a support will reduce the catalytic performance of the cobalt catalyst.

[0115] 10. The comparison between Example 1 and Comparative Example 2 in Table 1 shows that replacing dolomite with the organic compound o-phenanthroline reduces the catalytic performance of the cobalt catalyst.

[0116] 11. As can be seen from the comparison between Example 1 and Comparative Example 10 in Table 1, the addition of the organic compound o-phenanthroline reduces the catalytic performance of the cobalt catalyst.

[0117] 12. The comparison between Example 1 and Comparative Example 9 in Table 1 shows that reducing the amount of Co will reduce the catalytic performance of the dolomite-based catalyst.

[0118] 13. The comparison between Example 1, Example 4 and Comparative Example 7 in Table 1 shows that increasing the calcination temperature (800°C) will reduce the catalytic performance of the dolomite-based catalyst.

[0119] Figure 1 The images show the XRD patterns of the composite material Co@B prepared in Example 1, the composite material Co@BL prepared in Comparative Example 10, and dolomite. From... Figure 1 It can be seen that Co@B and Co@BL almost retain the characteristic peaks of dolomite. However, no crystal signal peaks related to Co are shown in the XRD pattern, which may be due to the low doping amount of cobalt, which helps to suppress the leaching of Co ions.

[0120] Figure 2 The image shows the local energy dispersive X-ray spectroscopy (EDS) of the Co@BKS composite material prepared in Example 2, where (a) is a local electron image of Co@BKS; (b) is the C elemental mapping; (c) is the Ca elemental mapping; (d) is the Mg elemental mapping; (e) is the O elemental mapping; and (f) is the Co elemental mapping. Figure 2 It can be seen that the composition of the Co@BKS sample is consistent with that of Ca, C, Mg, O, Co and other components and is evenly distributed. The presence of Co element indicates that Co@BKS successfully captured Co ions, and there was no particle or agglomeration phenomenon, indicating that active Co is evenly distributed on the surface of dolomite.

Claims

1. Application of a mineral-based cobalt catalyst in the activation of persulfate degradation of organic pollutants; The preparation method of the mineral-based cobalt catalyst is as follows: (1) Weigh out a cobalt metal salt and dissolve it in a solvent to obtain a cobalt metal salt solution; (2) Add natural alkaline earth metal minerals to the cobalt salt solution obtained in step (1), stir evenly, place in a water bath at 50~70 ℃ and stir for 6~12h, filter and dry to obtain solid powder; The natural alkaline earth metal mineral is dolomite; (3) Under an air or nitrogen atmosphere, the solid powder obtained in step (2) is calcined. The calcination conditions are: heating rate of 2~5℃ / min, annealing at 400~500℃ for 2h, and natural cooling to room temperature to obtain the mineral-based cobalt catalyst.

2. The application as described in claim 1, characterized in that, In step (1) of the preparation method of mineral-based cobalt catalyst, the metallic cobalt salt is selected from one or a mixture of two of the following: Co(NO3)2·6H2O, CoCl2·6H2O, CoSO4·7H2O, cobalt acetate, cobalt acetylacetone, disodium ethylenediaminetetraacetate cobalt salt hydrate, cobalt oxalate, and cobalt phthalocyanine.

3. The application as described in claim 1, characterized in that, In step (1) of the preparation method of mineral-based cobalt catalyst, the solvent is selected from one or a mixture of two of anhydrous ethanol and deionized water.

4. The application as described in claim 1, characterized in that, In step (1) of the preparation method of mineral-based cobalt catalyst, the molar volume ratio of cobalt metal salt to solvent is 1:70~80, mol / L.

5. The application as described in claim 1, characterized in that, In step (2) of the preparation method of mineral-based cobalt catalyst, the mass-volume ratio of natural alkaline earth metal mineral to cobalt salt solution is 1:11.1~16.7, g / mL.

6. The application as described in claim 1, characterized in that, The organic pollutants are one or more of the following: metronidazole, 5-fluorouracil, norfloxacin, tetracycline, and ciprofloxacin.

7. The application as described in claim 1, characterized in that, The application method is as follows: A mineral-based cobalt catalyst was dispersed in an aqueous solution of organic pollutants, and persulfate was added for stirring and degradation. In aqueous solutions of organic pollutants, the concentration of organic pollutants is 5~50 mg / L; Persulfate is selected from potassium peroxymonosulfate and potassium persulfate; The mass-to-volume ratio of the mineral-based cobalt catalyst to the aqueous solution of organic pollutants is 0.2~2:1, g / L; The mass-to-volume ratio of persulfate to organic pollutant aqueous solution is 0.25~2:1, g / L.

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