Hollow tubular CN-CoS catalyst rich in sulfur vacancies as well as preparation method and application of hollow tubular CN-CoS catalyst

Abstract

The invention discloses a preparation method of a hollow tubular CN-CoS catalyst rich in sulfur vacancies, which specifically comprises the following steps: mixing melamine, boric acid and water, stirring and uniformly mixing to obtain a mixed solution I, carrying out hydrothermal reaction, solid-liquid separation and solid washing and drying on the mixed solution I, and then calcining in a nitrogen atmosphere at 450-650 DEG C to obtain hollow tubular nitrogen carbide; and mixing the hollow tubular nitrogen carbide, thiourea, cobalt chloride and water, uniformly stirring to obtain a mixed solution II, carrying out hydrothermal reaction on the mixed solution II, carrying out solid-liquid separation, and washing and drying the solid to obtain the hollow tubular CN-CoS catalyst rich in sulfur vacancies. The hollow tubular CN-CoS catalyst prepared by the method has the advantages of high specific surface area, multiple reaction active sites, good catalytic performance, high metal atom utilization rate, stable structure and the like, can be used for activating persulfate to degrade antibionts, has a good effect, and has good application value and application prospect; the catalyst has a great application prospect in the field of environmental catalysis.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation and environmental catalysis, and particularly relates to a preparation method and application of a hollow tubular CN-CoS catalyst rich in sulfur vacancies. Background Art

[0002] Today, Fenton-type catalysts based on permonosulfate (PMS) play an important role in the purification of organic pollutants. Specifically, PMS can be activated to produce a large number of free radicals with strong oxidizing ability, such as hydroxyl radicals (•OH) and sulfate radicals (SO 4 •− )wait( E 0 (•OH / OH − ) = 1.9−2.7 V vs NHE, E 0 (SO 4 •− / SO 4 2− ) = 2.6−3.1 V vs NHE). In addition, PMS can also be activated into non-radical pathways, such as singlet oxygen ( 1 O 2 ), high-valent metal-oxygen (HV-Me) and direct electron transfer. In addition to activating PMS by heat, ultrasound, photocatalysis and other techniques, transition metal materials have been widely studied in the context of activating PMS. Transition metals have mild activation reaction conditions and high activation efficiency. Cobalt (Co) is a metal with a large redox potential (Co 3+ / Co 2+ = 1.82V) and excellent activation effect of transition metals, has been widely studied. 2+ It is not easy to recycle and causes pollution. At present, inorganic heterogeneous catalysts such as cobalt oxides, cobalt sulfides and cobalt-carbon composites have received extensive attention in the field of PMS activation. Among them, metal sulfides have the advantages of strong conductivity and high cost performance. In addition, compared with metal oxides, strongly reducing sulfur species (S 2– and S 2 2– ) have been shown to promote metal redox cycles, thereby improving catalytic activity. However, due to their tendency to aggregate under weak van der Waals forces, the number and utilization of exposed active sites need to be further improved. In addition, their weak adsorption capacity for pollutants, severe metal ion leaching, poor stability, and limited catalytic performance have greatly hindered their application.

[0003] It is generally believed that improving the ability of cobalt sulfide to activate PMS through structural engineering and defect engineering is an effective means. Sulfur vacancies (Sv) in metal sulfides have been successfully used to adjust the electron distribution, thereby exposing more metal active sites and increasing the adsorption energy between PMS and metal sulfides. In recent years, graphitic carbon nitride has been considered as one of the ideal carrier materials. Graphitic carbon nitride has attracted extensive attention due to its excellent chemical and thermal stability, non-toxicity, low cost and simple preparation. However, the existing carbon nitride materials have low specific surface area, few activation sites and low catalytic efficiency. Therefore, how to overcome the shortcomings of the above-mentioned prior art and develop and prepare simple hollow tubular carbonized nitrogen anchored CoS catalysts for persulfate activation under lightless conditions has a good development prospect. Obtaining a hollow tubular CN-CoS catalyst rich in sulfur vacancies with high catalytic activity, good stability and high specific area is of great significance for the efficient use of persulfate to degrade antibiotics in water. Summary of the invention

[0004] The invention provides a hollow tubular CN-CoS catalyst rich in sulfur vacancies, which has a high specific surface area, many reactive sites, a fast reaction rate, good stability and the ability to efficiently activate persulfate, and correspondingly provides a method for preparing the hollow tubular CN-CoS catalyst rich in sulfur vacancies, which has the advantages of simple process, convenient operation, low cost, high preparation efficiency and high yield, and also provides application of the hollow tubular CN-CoS catalyst rich in sulfur vacancies in treating antibiotic wastewater.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: 1. Mix melamine, boric acid and water, stir and mix to obtain a mixed solution I, perform a hydrothermal reaction of the mixed solution I at 160°C to 180°C for 12h to 24h, separate the solid and the liquid, wash and dry the solid, and calcine the solid at 450°C to 650°C in a nitrogen atmosphere for 1h to 5h to obtain a hollow tubular CN; The mass ratio of melamine to boric acid is 1:0.06-0.39; water or anhydrous ethanol is used for washing, and the number of washing times is 3-5 times; 2. Mix the hollow tubular CN, thiourea, cobalt chloride and water, stir and mix to obtain a mixed solution II, perform a hydrothermal reaction of the mixed solution II at 160° C. to 180° C. for 12 h to 24 h, separate the solid from the liquid, wash and dry the solid, and obtain a hollow tubular CN-CoS catalyst rich in sulfur vacancies; The mass ratio of the hollow tubular CN to thiourea is 1:2-4, the mass ratio of the hollow tubular CN to cobalt chloride is 1:0.5-2.7, and the concentration of cobalt chloride in the mixed solution II is 0.2-1 mmol / L; water or anhydrous ethanol is used for washing, and the number of washing times is 3-5 times; 3. Using the hollow tubular CN-CoS catalyst rich in sulfur vacancies to activate persulfate to degrade organic pollutants in the water body, specifically, the hollow tubular CN-CoS catalyst rich in sulfur vacancies is mixed with organic pollutant wastewater, stirred, and a persulfate solution is added to perform a catalytic degradation reaction to complete the degradation of organic pollutants in the water body.

[0006] The mass volume ratio of the hollow tubular CN-CoS catalyst rich in sulfur vacancies to the organic pollutant wastewater is 3mg-18mg:30mL; the concentration of persulfate in the reaction system is 1mmol / L-6mmol / L; the persulfate in the persulfate solution is potassium monopersulfate; the concentration of organic pollutants in the organic pollutant wastewater is 10mg / L-50mg / L; the organic pollutants in the organic pollutant wastewater are antibiotics; the antibiotics are at least one of ciprofloxacin, tetracycline and norfloxacin.

[0007] Compared with the prior art, the present invention has the following advantages: (1) The present invention aims to solve the problems existing in the preparation methods of existing carbonized nitrogen-cobalt sulfide catalysts, such as complex preparation process and high cost, as well as the problems existing in the prepared catalysts, such as low specific surface area, few reactive sites, easy metal agglomeration, low catalytic activity, and poor cycle stability. The present invention proposes a preparation method of a hollow tubular CN-CoS catalyst rich in sulfur vacancies. The method adopts a hydrothermal and calcination method to prepare a hollow tubular CN-CoS catalyst rich in sulfur vacancies with excellent performance. Specifically, melamine, boric acid and water are mixed to form a mixture. Solution I, and the mixed solution I is subjected to a hydrothermal reaction. During the hydrothermal reaction, the formation process of carbon nitride is affected by acidic self-assembly, which is conducive to the formation of tubular morphology, which can not only increase the specific surface area of ​​the carbon nitride catalyst, but also provide more sites for anchoring CoS. Finally, after calcining and stabilizing the hollow tubular CN structure rich in sulfur vacancies, the hollow tubular CN, thiourea, cobalt chloride, and water are mixed to obtain a mixed solution II, hydrothermal reaction, solid-liquid separation, solid washing and drying, and then a hollow tubular CN-CoS catalyst rich in sulfur vacancies is prepared. Compared with the existing conventional preparation method, in the method of the present invention, the self-assembly of melamine under acidic conditions is used, which is more conducive to the formation of a tubular structure, and the subsequent CoS aggregates on the surface, which is conducive to improving the dispersibility and utilization rate of CoS in the catalyst, and can significantly improve the catalytic efficiency of the catalyst. Therefore, the preparation method of the present invention can prepare a hollow tubular CN-CoS catalyst rich in sulfur vacancies with high CoS loading and high utilization rate, good CoS dispersibility, and high catalytic activity. Compared with conventional CN-anchored CoS catalysts, the hollow tubular CN-CoS catalyst rich in sulfur vacancies prepared by the present invention also has a higher specific surface area and more reactive sites, and thus can exhibit better catalytic performance. The hollow tubular CN-CoS catalyst rich in sulfur vacancies prepared by the preparation method of the present invention has the advantages of high specific surface area, many reactive sites, good catalytic performance, high metal atom utilization rate, etc., can be widely used to activate persulfate to degrade organic pollutants (such as antibiotics), and can achieve good degradation effects, and has good application value and application prospects; at the same time, the preparation method of the present invention also has simple process, convenient operation, easy availability of raw materials, low cost, easy to achieve industrial production, and has great application prospects, especially in the field of environmental catalysis; (2) The hollow tubular CN-CoS catalyst rich in sulfur vacancies prepared by the present invention comprises tubular carbon nitride, CoS is embedded on the tube wall and in the internal pore structure of the tubular carbon nitride, and the hollow tubular CN-CoS catalyst rich in sulfur vacancies is doped with boron. By embedding CoS in the tube wall of the tubular carbon nitride and in the internal filling network structure at the same time, the tubular carbon nitride with a large specific surface area is conducive to inhibiting the agglomeration of CoS; (3) The present invention utilizes a hollow tubular CN-CoS catalyst rich in sulfur vacancies to activate persulfate to degrade antibiotics in water. By mixing the hollow tubular CN-CoS catalyst rich in sulfur vacancies with antibiotic wastewater, stirring, and adding persulfate, effective degradation of organic pollutants can be achieved. The process has the advantages of simple process, convenient operation, low cost, high treatment efficiency, good degradation effect, etc., and has good degradation effects on various organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 The SEM images are of the hollow tubular carbonized nitrogen (Figure A) of Example 1, the hollow tubular CN-CoS catalyst rich in sulfur vacancies (Figure C), and the CoS catalyst prepared in Comparative Example 1 (Figure B); Figure 2 XRD patterns of the hollow tubular carbonized nitrogen B-CN of Example 1, the hollow tubular CN-CoS catalyst rich in sulfur vacancies, and the CoS catalyst prepared in Comparative Example 1; Figure 3 is the EPR spectrum of the hollow tubular CN-CoS catalyst rich in sulfur vacancies in Example 1; Figure 4 is the SEM image of the layered CN-CoS catalyst; Figure 5 The time-degradation efficiency diagram of the degradation of tetracycline hydrochloride by persulfate activation of hollow tubular CN-CoS catalyst rich in sulfur vacancies, CoS catalyst, hollow tubular carbonized nitrogen, and layered CN-CoS catalyst; Figure 6 The degradation rate constant fitting diagram of tetracycline hydrochloride degradation by persulfate activated by hollow tubular CN-CoS catalyst rich in sulfur vacancies, CoS catalyst, hollow tubular nitrogen carbide, and layered CN-CoS catalyst; Figure 7 The degradation efficiency of tetracycline hydrochloride by persulfate activation over hollow tubular CN-CoS catalyst rich in sulfur vacancies is plotted against the number of cycles; Figure 8 Time-degradation efficiency diagram of persulfate activation for degradation of tetracycline hydrochloride (TC), oxytetracycline (OTC), chlortetracycline (CTC), and ciprofloxacin (CIP) over hollow tubular CN-CoS catalysts rich in sulfur vacancies. DETAILED DESCRIPTION

[0009] The content of the present invention is further explained by the following examples, but these examples do not limit the protection scope of the present invention. The methods in the embodiments are conventional methods unless otherwise specified, and the reagents used are conventional reagents sold on the market unless otherwise specified; Example 1: Preparation of hollow tubular CN-CoS catalyst rich in sulfur vacancies 1. Take 2g of melamine and 0.385g of boric acid, dissolve them in 70mL of deionized water, and stir them at a constant speed for 3h at 25℃ to obtain a uniform mixed solution I; transfer the mixed solution I to a 100mL autoclave, keep it at 180℃ for 12h, and filter it after natural cooling. After the solid is rinsed with water 5 times, it is dried at 60℃ for 4h to obtain a supramolecular precursor; put the supramolecular precursor solid into a crucible, wrap the crucible with tin foil, place it in a tubular furnace under nitrogen protection, heat it to 550℃ at a heating rate of 2.5℃ / min, and keep it at 550℃ for 4h. After natural cooling, take it out to obtain a light yellow powder sample, that is, a hollow tubular carbonized nitrogen (B-CN); the SEM image of the hollow tubular CN is shown in Figure 1 A. From the figure, it can be seen that CN is a hollow tubular structure. Its XRD pattern is shown in Figure 2 ,From the figure, we can see that the diffraction peaks of the (100) and (200) crystal planes of the hollow tubular CN are 13.5° and 27.3°, indicating that the hollow tubular graphite phase carbonized nitrogen was successfully prepared; 2. 0.1 g of hollow tubular carbonized nitrogen, 0.325 g of thiourea, 0.1575 g of cobalt chloride, and 80 mL of deionized water were mixed and stirred at a constant speed for 6 h at 25 ° C to obtain a mixed solution II. The mixed solution II was subjected to a hydrothermal reaction at 180 ° C for 16 h. After natural cooling, it was filtered. The solid was rinsed with water 5 times and vacuum dried at 80 ° C for 6 h to obtain a hollow tubular CN-CoS catalyst rich in sulfur vacancies; the SEM image of CN-CoS is shown in Figure 1 C. It can be seen from the figure that CoS is distributed on the inner and outer walls of the hollow tubular CN. Its XRD pattern is shown in Figure 2 From the figure, it can be seen that the characteristic peaks of carbonized nitrogen in the graphite phase are clearly retained, and the CoS (PDF#75-0605) card peak appears after CoS doping, indicating the successful preparation of hollow tubular CN-CoS rich in sulfur vacancies; its EPR diagram is shown in Figure 3 ,It can be seen from the figure that the hollow tubular CN-CoS has a sharper peak pair at g = 2.005 than CoS, indicating that the hollow tubular CN-CoS is rich in more sulfur vacancies; Comparative Example 1: Preparation of CoS catalyst 0.325 g thiourea, 0.1575 g cobalt chloride and 80 mL deionized water were mixed and stirred at a constant speed for 6 h at 25 °C to obtain a mixed solution II. The mixed solution II was subjected to a hydrothermal reaction at 180 °C for 16 h. After natural cooling, it was filtered. The solid was rinsed with water 5 times and vacuum dried at 80 °C for 6 h to obtain a CoS catalyst. The SEM image of the catalyst CoS is shown in FIG. Figure 1 B. From the figure, it can be seen that the CoS catalyst is in agglomerated form; Comparative Example 2: The hollow tubular carbonized nitrogen prepared in step 1 is used as the catalyst of Comparative Example 2; Comparative Example 3: Preparation of layered CN-CoS catalyst 2 g of melamine was dissolved in 70 mL of deionized water, and stirred at a constant speed for 3 h at 25 ° C to obtain a uniform mixed solution; the mixed solution was transferred to a 100 mL autoclave and kept at 180 ° C for 12 h. After natural cooling, it was rinsed with water 5 times and filtered. The solid was dried at 60 ° C for 4 h to obtain a supramolecular precursor. The supramolecular precursor solid was placed in a crucible, the crucible was wrapped with tin foil, and placed in a tubular furnace under nitrogen protection, and heated to 550 ° C at a heating rate of 2.5 ° C / min, and The mixture was kept at 550°C for 4 h, and after being cooled naturally, it was taken out to obtain a yellow powder sample, which was layered carbonized nitrogen. 0.1 g of layered carbonized nitrogen, 0.325 g of thiourea, 0.1575 g of cobalt chloride and 80 mL of deionized water were mixed and stirred at 25°C for 6 h to obtain a mixed solution II. The mixed solution II was subjected to hydrothermal reaction at 180°C for 16 h, and after being cooled naturally, it was filtered. The solid was rinsed with water 5 times and then vacuum dried at 80°C for 6 h to obtain a layered CN-CoS catalyst ( Figure 4 ).

[0010] Example 2: Application of catalysts from Example 1 and Comparative Examples 1-3 in treating antibiotic wastewater The hollow tubular CN-CoS catalyst rich in sulfur vacancies in Example 1, the CoS catalyst in Comparative Example 1, the hollow tubular carbonized nitrogen in Comparative Example 2, and the layered CN-CoS catalyst in Comparative Example 3 were weighed, 6 mg each, and placed in 30 mL of a 50 mg / L tetracycline hydrochloride solution, and then 27.3 mg of potassium hydrogen sulfate was added to the tetracycline hydrochloride solution to start the catalytic degradation reaction. During the persulfate activation reaction, 3 mL of the tetracycline hydrochloride solution was taken at 1 min, 3 min, 5 min, 7 min, and 9 min, respectively, and the absorbance value of tetracycline hydrochloride in the solution was measured by a spectrophotometer, and the degradation efficiency of the tetracycline hydrochloride solution by different catalysts under different time conditions was calculated.

[0011] Results Figure 5 As can be seen from the figure, the hollow tubular CN-CoS catalyst rich in sulfur vacancies exhibits the best catalytic activity, degrading 80.0% of tetracycline hydrochloride in 5 minutes and 100% in 9 minutes, indicating that the hollow tubular CN-CoS catalyst rich in sulfur vacancies has the ability to efficiently activate PMS and produce a large amount of active oxygen.

[0012] The degradation rate constant fitting results are shown in Figure 6 From the figure, it can be seen that the rate of degradation of tetracycline hydrochloride by the hollow tubular CN-CoS catalyst rich in sulfur vacancies is several times or even dozens of times higher, which more intuitively illustrates the excellent performance of the hollow tubular CN-CoS catalyst rich in sulfur vacancies.

[0013] Example 3: Stability experiment of hollow tubular CN-CoS rich in sulfur vacancies 1. 6 mg of the hollow tubular CN-CoS catalyst prepared in Example 1 was placed in 30 mL of a 50 mg / L tetracycline hydrochloride solution, and then 27.6 mg of PMS was added to perform a catalytic degradation reaction for 9 min, and the degradation of organic pollutants in the water was completed by activating persulfate, completing one cycle; 2. The reaction system in step 1 was filtered to obtain a hollow tubular CN-CoS catalyst rich in sulfur vacancies, which was filtered and washed five times with deionized water, dried at 60° C. for 4 h, and then repeatedly used for the degradation of tetracycline hydrochloride for a total of ten cycles; The degradation results of tetracycline hydrochloride solution by the catalyst at different cycle times are shown in Figure 7 ,It can be seen from the figure that the hollow tubular CN-CoS catalyst rich in sulfur vacancies can still degrade 92.0% of tetracycline hydrochloride after 10 cycles of use, indicating that the hollow tubular CN-CoS catalyst rich in sulfur vacancies is highly stable and has strong activation performance.

[0014] Example 4: Experimental study on degradation of different antibiotics by hollow tubular CN-CoS catalysts rich in sulfur vacancies 6 mg of the hollow tubular CN-CoS catalyst of Example 1 was weighed and placed in 30 mL of 50 mg / L tetracycline hydrochloride (TC), oxytetracycline (OTC), chlortetracycline (CTC) solutions and 30 mL of 20 mg / L ciprofloxacin (CIP) solutions, respectively. Then, 27.6 mg of potassium hydrogen sulfate was added to the solutions for catalytic degradation reaction. During the persulfate activation reaction, 3 mL of tetracycline hydrochloride, chlortetracycline, oxytetracycline and ciprofloxacin solutions were taken at 1 min, 3 min, 5 min, 7 min and 9 min, respectively. The absorbance values ​​in the solutions were measured with a spectrophotometer, and the degradation efficiencies of tetracycline hydrochloride, chlortetracycline, oxytetracycline and ciprofloxacin solutions under different time conditions were calculated.

[0015] The degradation results of tetracycline hydrochloride, chlortetracycline, oxytetracycline and ciprofloxacin solutions over the hollow tubular CN-CoS catalyst rich in sulfur vacancies are shown in Figure 8 From the figure, it can be seen that the hollow tubular CN-CoS catalyst rich in sulfur vacancies can efficiently degrade a variety of antibiotics within 9 minutes, indicating its universal applicability.

[0016] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a hollow tubular CN-CoS catalyst rich in sulfur vacancies, characterized in that: Melamine, boric acid and water are mixed and stirred to obtain a mixed solution I. The mixed solution I is subjected to a hydrothermal reaction at 160°C to 180°C for 12h to 24h, the solid-liquid is separated, the solid is washed and dried, and then calcined at 450°C to 650°C in a nitrogen atmosphere to obtain a hollow tubular nitrogen carbide. The hollow tubular nitrogen carbide, thiourea, cobalt chloride and water are mixed and stirred to obtain a mixed solution II. The mixed solution II is subjected to a hydrothermal reaction at 160°C to 180°C for 12h to 24h, the solid-liquid is separated, and the solid is washed and dried to obtain a hollow tubular CN-CoS catalyst rich in sulfur vacancies.

2. The preparation method according to claim 1, characterized in that: The mass ratio of melamine to boric acid is 1:0.06-0.39, the mass ratio of hollow tubular nitrogen carbonization to thiourea is 1:2-4, and the mass ratio of hollow tubular nitrogen carbonization to cobalt chloride is 1:0.5-2.

7.

3. The preparation method according to claim 1, characterized in that: The concentration of cobalt chloride in mixed solution II is 0.2-1 mmol / L.

4. A hollow tubular CN-CoS catalyst rich in sulfur vacancies prepared by the preparation method according to any one of claims 1 to 2.

5. Use of the hollow tubular CN-CoS catalyst rich in sulfur vacancies as claimed in claim 3 in treating antibiotic wastewater.

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