Preparation of cobalt-based catalytic material for efficiently activating persulfate to degrade antibiotics

Abstract

The invention discloses a cobalt-based catalytic material for efficiently activating persulfate to degrade antibiotics and a preparation method of the cobalt-based catalytic material. The catalytic material is prepared by taking an H-Beta zeolite molecular sieve as a carrier, loading cobalt ions on the molecular sieve through an impregnation method and then carrying out high-temperature roasting treatment. The preparation method comprises the following steps: preparing a cobalt acetate tetrahydrate solution, adding an H-Beta zeolite molecular sieve into the solution to carry out ion exchange, and then carrying out drying and high-temperature roasting. The prepared catalytic material has highly dispersed cobalt active sites and excellent structural stability and catalytic activity. Compared with the prior art, the catalyst provided by the invention has the advantages of simple preparation process, lower cost, high catalytic efficiency, good stability, low cobalt ion dissolution rate, easiness in recovery and reuse and the like, and has a good practical application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental catalytic material preparation, and particularly relates to a preparation method of a cobalt-based catalytic material for activating persulfate to degrade antibiotics. BACKGROUND

[0002] In recent years, antibiotics have become a new type of environmental pollutant due to their extensive use in medical and livestock breeding industries. Due to their poor biodegradability, they are difficult to be removed by traditional wastewater treatment processes, leading to their continuous accumulation in the water environment, which not only threatens the ecological system, but also induces the generation of drug-resistant bacteria, endangering human health. Therefore, it is urgent to develop efficient and economical antibiotic wastewater treatment technologies.

[0003] Persulfate advanced oxidation technology has attracted widespread attention in the treatment of refractory organic pollutants due to its strong oxidation ability and wide application range. The efficient activation of persulfate is the core of this technology, and catalytic materials are the key to achieving efficient activation of persulfate. Cobalt-based materials, as efficient catalysts for activating persulfate, have the advantages of high catalytic activity and mild reaction conditions, but existing cobalt-based catalysts still have defects such as easy agglomeration of active sites, low cobalt utilization rate, insufficient stability, and easy agglomeration during high-temperature calcination, which limit their practical application. Beta zeolite has a regular pore structure and abundant surface hydroxyl groups, which can be used as an ideal carrier to improve the dispersion and anti-loss of metal active components.

[0004] The present application constructs highly dispersed and stable cobalt active centers on Beta zeolite by optimizing ion exchange conditions and calcination process, significantly improving the catalytic degradation efficiency of antibiotics. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a cobalt-based catalytic material for efficiently activating persulfate to degrade antibiotics and a preparation method thereof. The present application aims to solve the problems of existing catalysts for activating persulfate, especially the secondary pollution problem of cobalt-based catalysts and the complexity of preparing some catalysts and the poor stability problem. The present application optimizes ion exchange conditions and heat treatment parameters to make cobalt ions highly dispersed in the pores of Beta zeolite, improving the efficiency and cyclic stability of activated persulfate for degrading antibiotics. The present application provides a cobalt-based heterogeneous catalytic material that is efficient, stable, easy to prepare and recover, and a preparation method thereof.

[0006] The technical solution of the present application is described as follows.

[0007] The present application provides a preparation method of a cobalt-based catalytic material for efficiently activating persulfate to degrade antibiotics, and the specific steps are as follows: Step S1: solution preparation

[0008] Take 1.267 g of cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O) and dissolve it in 100 mL of deionized water. Stir for 30 minutes until the cobalt acetate tetrahydrate is completely dissolved to obtain a cobalt acetate solution;

[0009] Step S2: ion exchange

[0010] Take 10 g of H-Beta zeolite molecular sieve and add it to the above-obtained cobalt acetate solution. Place the mixed system in an oil bath at 30°C and stir vigorously with an electric stirrer for 5 hours to mix the molecular sieve and cobalt ions uniformly. Then increase the temperature of the oil bath to 80°C and keep the stirring speed unchanged. Continue stirring for 6 hours to strengthen the interaction between the two and complete the ion exchange.

[0011] Step S3: drying treatment

[0012] Filter the mixed solution after ion exchange in the above step to obtain a solid product. Dry the obtained solid product at 105°C for 12 hours to remove physically adsorbed water.

[0013] Step S4: calcination and activation

[0014] Place the dried solid product in a muffle furnace and program the temperature increase at a rate of 5°C / min from room temperature to 550°C. Keep the temperature at 550°C for 5 hours for calcination. After calcination, naturally cool to room temperature to obtain the cobalt-based catalytic material.

[0015] In the present application, in step S1, the purity of the cobalt acetate tetrahydrate is ≥99%.

[0016] In the present application, in step S2, the 30°C stirring stage is used to achieve the initial loading of cobalt ions and the dispersion on the surface of the molecular sieve. The 80°C stirring stage is used to promote the deep exchange of cobalt ions into the channels of the molecular sieve.

[0017] In the present application, in step S2, the stirring speed of the vigorous stirring is 400-600 r / min.

[0018] In the present application, in step S3, the drying process is carried out in a vacuum drying box.

[0019] In the present application, in step S4, the calcination process is carried out in an air atmosphere.

[0020] In the present application, H-Beta zeolite molecular sieve is used as the carrier, cobalt ions are loaded on the molecular sieve by ion exchange method, and then high-temperature calcination treatment is carried out. Compared with the prior art, the present application has the following beneficial effects:

[0021] (1) The application adopts the impregnation method to load cobalt ions on H-Beta zeolite molecular sieves, and combines the subsequent calcination process, so that the cobalt species is uniformly dispersed on the surface of the carrier, the number of active sites of the catalytic material is increased, the ability of activating persulfate is enhanced, and the antibiotic can be quickly and efficiently degraded.

[0022] (2) Good stability, after high-temperature calcination treatment, the cobalt-based catalytic material has good thermal stability and chemical stability, the carrier effect of the Beta zeolite molecular sieve effectively slows down the dissolution of cobalt ions, improves the stability and repeated use performance of the catalytic material, reduces the risk of secondary pollution, and still maintains high catalytic activity in the process of multiple cycles, and has a long service life.

[0023] (3) The preparation process is simple and easy to operate, the reaction conditions are mild, and the environment is friendly; without complex equipment and expensive raw materials, it has good economic efficiency, and is conducive to large-scale industrialized production.

[0024] (4) The prepared cobalt-based catalytic material has excellent activation performance on persulfate, can be widely applied to the treatment of various antibiotic-polluted water bodies, and has good environmental and economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiments will be briefly introduced below, and it should be understood that the following drawings only show some embodiments of the application, and should not be regarded as a limitation on the scope. For ordinary skilled persons in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Figure 1 The X-ray photoelectron spectroscopy analysis diagram of the material of the application. It is determined that cobalt is successfully loaded in the molecular sieve structure.

[0027] Figure 2 The scanning electron microscope diagram of the material prepared in Example 1, which shows that the material has a rich pore structure.

[0028] Figure 3 The cycle test diagram of Example 2.

[0029] Figure 4 The cobalt ion dissolution concentration monitoring diagram in Example 2.

[0030] Figure 5 The CTC degradation kinetics curve diagram of the catalyst under different dosages in Example 3.

[0031] Figure 6 The electrochemical impedance spectrum of the material prepared in Example 1, which shows that the prepared material has stronger electron transfer capacity compared with the original molecular sieve carrier. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by a person of ordinary skill in the art without creative work under the premise that the embodiments are described are within the scope of protection of the present application. The specific conditions are not specified in the embodiments, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be obtained by market purchase.

[0033] Embodiment 1:

[0034] Step one: 1.267g Co(CH3COO)2·4H2O was weighed and added to 100mL deionized water, and stirred until completely dissolved.

[0035] Step two: 10.0g H-Beta zeolite molecular sieve was added to the solution, and stirred at 500rpm in a 30℃ oil bath for 5h; then the temperature was raised to 80℃, and the same stirring intensity was maintained to continue the reaction for 6h. The low-temperature stage of this process prevents the collapse of the zeolite structure and ensures uniform initial loading; the high-temperature stage utilizes the kinetic advantage to improve the exchange capacity.

[0036] Step three: dried in a 105℃ vacuum drying oven for 12h to remove physically adsorbed water.

[0037] Step four: the dried sample was placed in a muffle furnace, and heated at a rate of 5℃ / min from room temperature to 550℃ under an air atmosphere for 5h, and then ground and sieved after natural cooling to obtain the target product.

[0038] Embodiment 2:

[0039] To evaluate the cyclic stability of the catalyst, a systematic cyclic degradation experiment was carried out at room temperature of 25°C. The catalyst prepared in Example 1 was used in the experiment. The reaction system was configured as 100 mL of an aqueous solution of chlortetracycline hydrochloride (CTC) with a concentration of 20 mg / L, which simulates the antibiotic pollution level in typical pharmaceutical wastewater. At the beginning of the reaction, the catalyst dosage of the system was set to 0.05 g / L, and the persulfate (PMS) dosage was 0.5 mM, wherein the dosage of PMS was optimized to ensure that the oxidant was always in excess in the reaction system. To maintain the uniformity of the reaction system and promote the mass transfer efficiency, a magnetic stirrer was used for continuous stirring at a constant speed of 300 rpm, which was verified in the previous stage to effectively prevent the catalyst from depositing while avoiding the stripping of active components. Each degradation reaction lasted for 20 minutes. After each reaction was terminated, solid-liquid separation was achieved by high-speed centrifugation, and the collected catalyst was washed with 50 mL of deionized water three times in sequence to remove the intermediate products and residual oxidants adsorbed on the surface, followed by heat treatment in a vacuum drying oven at 105°C for 12 hours to completely remove the physically adsorbed water and restore the active sites on the catalyst surface. The entire cyclic experiment was repeated 5 times, each time strictly maintaining the same reaction conditions and operation process.

[0040] To characterize the changes in catalyst performance, the following were measured after each cycle: (1) CTC concentration change: 2 mL of the degradation solution was taken and immediately added with 1 mL of ethanol to quench the degradation reaction and prevent further degradation after sampling, which would cause deviation in concentration measurement; UV-Vis spectrophotometer was used. (2) Dissolved cobalt ion concentration in the solution: detected by inductively coupled plasma mass spectrometry (ICP-MS). During the experiment, light was avoided to prevent potential effects of light on the activation of PMS. Figure 2 The performance curve of the catalyst prepared in Example 1 for degrading antibiotics. Figure 3 The monitoring graph of cobalt ion dissolution concentration in Example 2. Figure 2 It can be seen that the degradation rate remains >85% after 5 cycles, and the degradation rate reaches 80% within the first 10 min, indicating that the catalyst can quickly activate persulfate to generate free radicals. From the Figure 3 It can be seen that the first dissolution is slightly higher than the following several times, which is 0.34 mg / L, and the cobalt ion is released due to the loose combination on the surface, and it is stable below 0.001 mg / L from the third time; overall, Co 2+ The dissolution concentration significantly decreases with the increase in the number of cycles, and the structure of the material tends to be stable after activation, which reflects good stability of the material.

[0041] Example 3:

[0042] The present example system studies the effect of different catalyst dosages prepared in Example 1 on the degradation performance of CTC. The experiment is conducted under standard conditions: 100 mL of CTC solution with a concentration of 20 mg / L is placed in a 250 mL beaker, and 0, 0.05, 0.1, 0.2, 0.5 and 1.0 g / L of catalyst is added, respectively, and mixed using a magnetic stirrer at a speed of 300 rpm. First, a 30-minute adsorption equilibrium test is conducted, and 0.5 mM PMS is added at 0 minutes to start the catalytic reaction, and the CTC content in the solution is measured at 10, 20, 30, 60 minutes, etc. 2 mL of the degradation solution is taken out and immediately added with 1 mL of ethanol to quench the degradation reaction to prevent the concentration from deviating due to continued degradation after sampling. The residual concentration of CTC in the degradation solution is measured using a UV-visible spectrophotometer. To ensure data reliability, the degradation experiment is repeated at least 3 times, and the relative standard deviation is not more than 5%. The pH is adjusted by adding 0.1 M H2SO4 or NaOH.

[0043] Figure 4 The CTC degradation kinetics curves under different catalyst dosages in the adsorption and reaction stages are shown. Within 30 minutes before the degradation reaction, it can be observed that the CTC removal rate increases significantly with the increase of catalyst dosage, and the blank control group C / C0 remains 1.0, indicating that no adsorption occurs without catalyst. After the addition of PMS, all catalyst groups show a typical three-stage degradation characteristic: rapid period, transition period and equilibrium period. The removal rate of the blank control group by direct oxidation of PMS is less than 50%, which fully illustrates the key role of the catalyst.

Claims

1. A preparation of cobalt-based catalytic material for efficient activation of persulfate salts for degradation of antibiotics, characterized in that, The specific steps are as follows: Step S1: solution preparation 1.267 g of cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O) was weighed and dissolved in 100 mL of deionized water. The solution was stirred for 30 minutes until the cobalt acetate tetrahydrate was completely dissolved, obtaining a cobalt acetate solution; Step S2: impregnation 10 g of H-Beta zeolite molecular sieve was weighed and added to the above obtained cobalt acetate solution. The mixture was placed in a 30℃ oil bath and stirred vigorously for 5 hours to mix the molecular sieve and cobalt ions uniformly. Then the temperature of the oil bath was increased to 80℃, and the stirring speed was kept constant. The mixture was stirred for another 6 hours to strengthen the interaction between the two and complete the ion exchange. Step S3: drying treatment The mixture after ion exchange in the above step was subjected to suction filtration to obtain a solid product. The obtained solid product was dried at 105℃ for 12 hours to remove the physically adsorbed water; Step S4: calcination treatment The dried solid product was placed in a muffle furnace and heated from room temperature to 550℃ at a rate of 5℃ / min. After reaching the temperature, the calcination was carried out for 5 hours. After the calcination was completed, the temperature was naturally cooled to room temperature, obtaining the cobalt-based catalytic material.

2. The method of claim 1, wherein, In step S1, the purity of the cobalt acetate tetrahydrate is ≥99%.

3. The method of claim 1, wherein, In step S2, the 30℃ stirring stage is used to achieve the initial loading and dispersion of cobalt ions on the surface of the molecular sieve, and the 80℃ stirring stage is used to promote ion exchange.

4. The method of claim 1, wherein, In step S2, the stirring speed is 400-600 r / min.

5. The method as claimed in claim 1, wherein, In step S3, the drying process is carried out in a vacuum drying box.

6. The method of claim 1, wherein, In step S4, the calcination process is carried out in an air atmosphere.

7. Use of the cobalt-based catalytic material prepared by the method of any one of claims 1-6 in the activation of persulfate for the degradation of antibiotics.

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