Cobaltosic oxide / activated aluminum oxide composite material as well as preparation method and application thereof

Abstract

The invention discloses a cobaltosic oxide / activated aluminum oxide composite material as well as a preparation method and application thereof. The method comprises the following steps: dissolving tannic acid and cobalt salt in water, then adding activated aluminum oxide powder, and roasting the dried solid in an air atmosphere at 300-600 DEG C to obtain the cobaltosic oxide / activated aluminum oxide nano-catalyst with high catalytic activity. The cobaltosic oxide / activated aluminum oxide composite material has ultra-small and high-dispersion cobaltosic oxide, the degradation efficiency of activated persulfate on rhodamine B can reach 99% within 10 min, and the cobaltosic oxide / activated aluminum oxide composite material has wide application prospects in degradation of organic pollutants.

Description

Technical Field

[0001] The invention belongs to the field of water treatment materials and relates to a cobalt tetroxide / activated alumina composite material and a preparation method and application thereof. Background Art

[0002] Advanced oxidation technology utilizes highly oxidative reactive oxygen species, including hydroxyl radicals (·OH), sulfate radicals (SO4 ·- ), singlet oxygen ( 1 O2), etc., can convert refractory toxic organic pollutants into low-toxic or non-toxic products, and has potential in treating organic pollutants. Persulfate (PS) advanced oxidation technology has a wide pH adaptability range, SO4 ·- It is favored for its high oxidation potential and strong selectivity. Advanced oxidation technology based on sulfate free radicals has good application prospects.

[0003] Due to Co 2+ / monopersulfate (PMS) system has excellent degradation efficiency for pollutants. Co-based oxides are considered to be one of the best catalysts for catalyzing PMS. The development of highly active Co-based oxide / PMS system has become a research hotspot in the environmental field. However, heterogeneous catalytic persulfate degradation of pollutants has problems such as difficulty in achieving both catalyst activity and stability, and difficulty in large-scale preparation and recycling of catalysts, which hinders its further practical application. Therefore, it is necessary to improve the activity and stability of Co-based oxides. The design strategy to improve the activity of the catalyst is, on the one hand, to regulate the composition of the catalyst and improve the intrinsic activity of the catalyst, and on the other hand, to increase the specific surface area of ​​the catalyst and increase the number of active sites.

[0004] By loading the active components on a carrier (metal oxide, carbon material, metal organic framework, etc.), reducing the particle size of the active components, not only can the number of active sites of the catalyst be increased, but also the agglomeration of the active components can be avoided. Document 1 is based on a cobalt-based metal organic framework precursor, and a well-dispersed cobalt tetraoxide / carbon composite material is prepared by etching the metal organic framework using tannic acid (J. Colloid Interface Sci. 2021, 600, 58-71.). However, carbon-based materials have poor stability in the air, and Co-based catalysts can only be prepared by low-temperature heat treatment or solvent heat, which results in higher metal ion leaching of such catalysts during degradation. Summary of the invention

[0005] The purpose of the present invention is to provide a cobalt oxide / activated alumina composite material and a preparation method and application thereof. The catalyst has good catalytic activity in the application of activating persulfate to degrade organic matter.

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

[0007] The preparation method of the cobalt oxide / activated alumina composite material is to prepare a highly dispersed cobalt oxide / activated alumina (Co3O4 / Al2O3) composite material by complexing tannic acid with cobalt ions, dispersing them on the surface of activated alumina, and performing heat treatment. The specific steps are as follows:

[0008] Dissolve tannic acid and cobalt salt in water, then add activated alumina powder, stir and ultrasonicate until evenly dispersed, dry, place the obtained solid in a tube furnace, and calcine it at 300-600°C in an air atmosphere for 0.5-5h to obtain a cobalt oxide / activated alumina composite material.

[0009] Preferably, the mass ratio of tannic acid to cobalt salt is 1:1.83-3.66.

[0010] Preferably, the stirring and ultrasonic oscillation time is 2-10 min.

[0011] Preferably, the drying temperature is 75-105°C and the drying time is 12±2h.

[0012] Preferably, the cobalt salt is selected from cobalt nitrate, cobalt acetate, cobalt chloride, cobalt sulfate and the like.

[0013] Preferably, the mass ratio of cobalt salt to aluminum oxide is 0.183:0.5 to 0.366:0.8.

[0014] Preferably, the calcination temperature is 350-500° C. and the calcination time is 3 hours.

[0015] Preferably, in the cobalt tetroxide / activated alumina composite material, the mass percentage of cobalt tetroxide is ≤50%.

[0016] The invention provides a cobaltous oxide / activated alumina composite material prepared by the preparation method.

[0017] Furthermore, the present invention provides the use of the above-mentioned cobalt trioxide / activated alumina composite material in activating persulfate to degrade organic pollutants.

[0018] Specifically, the organic pollutants are rhodamine B, phenol, antibiotics, etc.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The present invention uses activated alumina as a carrier, utilizes tannic acid to complex with cobalt ions, thereby increasing the dispersion of cobalt ions on the activated alumina, and controls the amount of cobalt tetroxide loaded by controlling the amount of cobalt nitrate added;

[0021] (2) The cobalt tetroxide / activated alumina composite material prepared by the present invention has ultra-small, highly dispersed cobalt tetroxide and high catalytic activity. Under the conditions of a rhodamine B concentration of 10 ppm, an oxidant (monopersulfate) concentration of 100 ppm, a temperature of 25° C., and a catalyst dosage of 100 mg / L, the pollutant degradation efficiency reaches 99% within 10 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the transmission electron microscope image of Co3O4 / Al2O3 prepared in Example 1.

[0023] Figure 2 This is a high-resolution transmission electron microscopy image of Co3O4 / Al2O3 prepared in Example 1.

[0024] Figure 3 This is the X-ray diffraction pattern of Co3O4 / Al2O3 prepared in Example 1.

[0025] Figure 4 This is the degradation curve of Rhodamine B catalyzed by Co3O4 / Al2O3 and control samples. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0027] Example 1

[0028] (1) 0.183 g of cobalt nitrate hexahydrate and 0.1 g of tannic acid were dissolved in 10 mL of deionized water, 0.9 g of activated alumina was added, the mixture was stirred for 2 min, ultrasonicated for 5 min, and dried at 90 °C for 12 h to obtain a mixed solid.

[0029] (2) 0.5 g of the mixed solid was taken, heated to 350° C. at 3° C. / min in an air atmosphere, calcined for 3 h, and then cooled naturally to obtain a cobalt tetroxide / activated alumina composite material.

[0030] Figure 1 This is a transmission electron microscope image of Co3O4 / Al2O3, from which the morphology of the catalyst can be seen.

[0031] Figure 2 This is a high-resolution transmission electron microscope image of Co3O4 / Al2O3. The crystal lattice of cobalt tetroxide and aluminum oxide can be seen from the image. The particle size of cobalt tetroxide particles is about 5nm.

[0032] Figure 3 This is the X-ray diffraction pattern of Co3O4 / Al2O3, showing the crystal spectrum characteristics of cobalt tetroxide.

[0033] Example 2

[0034] (1) 0.366 g of cobalt nitrate hexahydrate and 0.1 g of tannic acid were dissolved in 10 mL of deionized water, 0.8 g of activated alumina was added, the mixture was stirred for 2 min, ultrasonicated for 5 min, and dried at 90 °C for 12 h to obtain a mixed solid.

[0035] (2) 0.5 g of the mixed solid was taken, heated to 350° C. at 3° C. / min in an air atmosphere, calcined for 3 h, and then cooled naturally to obtain a cobalt tetroxide / activated alumina composite material.

[0036] Example 3

[0037] (1) 0.366 g of cobalt nitrate hexahydrate and 0.1 g of tannic acid were dissolved in 10 mL of deionized water, 0.8 g of activated alumina was added, the mixture was stirred for 2 min, ultrasonicated for 5 min, and dried at 90 °C for 12 h to obtain a mixed solid.

[0038] (2) 0.5 g of the mixed solid was taken, heated to 500° C. at 3° C. / min in an air atmosphere, calcined for 3 h, and then cooled naturally to obtain a cobalt tetroxide / activated alumina composite material.

[0039] Comparative Example 1

[0040] This comparative example is basically the same as Example 1, except that tannic acid is not added to obtain a cobalt tetroxide / activated alumina comparative sample (Co3O4 / Al2O3-0).

[0041] Application Examples

[0042] Degradation experiment of Rhodamine B:

[0043] Persulfate and pH regulator were added to the Rhodamine B solution to be treated, and then the Co3O4 / Al2O3 prepared in Example 1 and the Co3O4 / Al2O3-0 catalyst prepared in Comparative Example 1 were added to start the degradation reaction. The sulfate radicals generated during the reaction oxidized Rhodamine B. After a period of reaction, Rhodamine B was oxidized and degraded. The initial concentration of the pollutant Rhodamine B was 20 mg / L, the catalyst dosage was 0.1 g / L, the persulfate dosage was 0.2 g / L, the initial pH was 8, and the reaction temperature was 25°C. The results are as follows: Figure 4 As shown in the figure, —●— represents the degradation curve of Co3O4 / Al2O3 for Rhodamine B. Under the catalytic action, the removal rate of Rhodamine B within 10 minutes reaches 99%; —◆— represents the degradation curve of Co3O4 / Al2O3-0 for Rhodamine B. The rate of catalytic degradation of Rhodamine B by the control sample Co3O4 / Al2O3-0 is significantly lower than that of Co3O4 / Al2O3, indicating that Co3O4 / Al2O3 has high catalytic activity.

Claims

1. A method for preparing a cobalt oxide / activated alumina composite material, characterized in that: The specific steps are as follows: Dissolve tannic acid and cobalt salt in water, then add activated alumina powder, stir and ultrasonicate until uniformly dispersed, dry, place the obtained solid in a tube furnace, and calcine it at 300-600°C in an air atmosphere for 0.5-5 h to obtain a cobalt tetroxide / activated alumina composite material.

2. The preparation method according to claim 1, characterized in that: The mass ratio of tannic acid to cobalt salt is 1:1.83~3.

66.

3. The preparation method according to claim 1, characterized in that The stirring and ultrasonic oscillation time is 2-10 min, the drying temperature is 75-105°C, and the drying time is 12±2h.

4. The preparation method according to claim 1, characterized in that: The cobalt salt is selected from cobalt nitrate, cobalt acetate, cobalt chloride or cobalt sulfate.

5. The preparation method according to claim 1, characterized in that: The mass ratio of cobalt salt to alumina is 0.183:0.5~0.366:0.

8.

6. The preparation method according to claim 1, characterized in that: The calcination temperature is 350~500℃ and the calcination time is 3h.

7. The preparation method according to claim 1, characterized in that: In the cobalt tetroxide / activated alumina composite material, the mass percentage of cobalt tetroxide is ≤50%.

8. The cobalt oxide / activated alumina composite material obtained according to the preparation method according to any one of claims 1 to 7.

9. Use of the cobalt oxide / activated alumina composite material according to claim 8 in activating persulfate to degrade organic pollutants.

10. The use according to claim 9, characterized in that: The organic pollutants are rhodamine B, phenol or antibiotics.

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