A cobalt-based armor nanozyme and its preparation method and application

Abstract

The present invention discloses a cobalt-based armor nanozyme and its preparation method and application. The method comprises uniformly mixing a cobalt salt solution, a 2,2'-bipyridine solution, and a g-C3N4 dispersion, performing sufficient reaction followed by pretreatment to obtain a precursor, and grinding and calcining the precursor to obtain the cobalt-based armor nanozyme. The cobalt-based armor nanozyme prepared by the present invention has high catalytic activity and the stability of carbonaceous materials. While ensuring efficient catalysis, it greatly reduces secondary pollution caused by cobalt metal leaching. The cobalt-based armor nanozyme can be used to remove organic pollutants from solid pollutants such as soil and water, and can also be used for targeted enrichment of numerous organic pollutants in contaminated wastewater, thereby improving removal efficiency.

Description

Technical Field

[0001] The technical solution of the present invention belongs to the field of organic pollutant treatment, and in particular relates to a novel cobalt-based armored nanozyme and its preparation method and application. Background Art

[0002] Advanced oxidation technology (ADT) is currently the most effective treatment method for organic pesticide degradation. It primarily uses hydrogen peroxide as an oxidant, generating hydroxyl radicals through activation, which in turn degrade organic pollutants. However, in practical applications, large amounts of hydrogen peroxide are required, resulting in a low effective utilization rate. This leaves a large amount of oxidant residue in the resulting solution, requiring subsequent treatment and increasing operating costs.

[0003] In recent years, advanced oxidation processes based on peroxymonosulfides (PMS) have attracted widespread interest due to their excellent performance and adaptability for the degradation of recalcitrant organic pollutants. Among various catalysts, cobalt-based catalysts offer the best activation for PMS. However, secondary contamination caused by metal leaching or precipitation has significantly limited the widespread application of these catalysts. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a nanozyme and a preparation method thereof that have high catalytic activity while greatly reducing the secondary pollution caused by cobalt metal leaching. The nanozyme obtained by this preparation method produces a variety of highly active free radicals by efficiently activating PMS and driving the Fenton-like reaction, which can efficiently remove a variety of common organic pollutants in water bodies.

[0005] To solve the above technical problems, the present invention provides a method for preparing a cobalt-based armor nanozyme, comprising the following steps:

[0006] (1) Preparation of cobalt-based precursor:

[0007] The cobalt salt solution, 2,2'-bipyridine solution, and g-C3N4 dispersion are mixed and stirred thoroughly, the solvent is removed by vacuum rotary evaporation, and the mixture is dried at 70° C. to obtain a precursor, wherein the cobalt salt is preferably cobalt nitrate, cobalt sulfate, or cobalt chloride, and the concentration thereof in the reaction system is 1-300 mmol / L;

[0008] Preferably, the molar ratio of the cobalt salt to 2,2'-bipyridine is 1:1-1:32.

[0009] (2) Preparation of cobalt-based armor nanozymes:

[0010] After the obtained precursor was fully ground, it was calcined in a tubular furnace with a gradient temperature increase under a nitrogen atmosphere, then cooled to 500°C at a rate of 10°C / min. After natural cooling, it was taken out and washed with 3 mol / L hydrochloric acid at 80°C for 3 hours. The precipitate was collected by centrifugation and washed with deionized water until neutral. Finally, it was washed three times with anhydrous ethanol and dried in an oven at 70°C for 12 hours. The resulting product was cobalt-based armored nanozyme.

[0011] Preferably, the solvent of the cobalt salt solution in step (1) is water, N,N-dimethylformamide, methanol, ethanol, or a mixture of two or more thereof in different proportions.

[0012] Preferably, the solvent of the 2,2'-bipyridine solution in step (1) is N,N-dimethylformamide, methanol or ethanol.

[0013] Preferably, the dispersant of the g-C3N4 dispersion in step (1) is N,N-dimethylformamide, methanol or ethanol.

[0014] Preferably, the concentration of g-C3N4 in the reaction system in step (1) is 0-150 g / L.

[0015] Preferably, the cobalt salt solution, 2,2'-bipyridine solution, and g-C3N4 dispersion in step (1) are mixed by first mixing the cobalt salt solution and the 2,2'-bipyridine solution and stirring for 1-10 hours, and then adding the g-C3N4 dispersion to the above mixture and continuing to stir for 1-10 hours;

[0016] Preferably, the cobalt salt solution, 2,2'-bipyridine solution, and g-C3N4 dispersion in step (1) can be mixed by first mixing the cobalt salt solution and the g-C3N4 dispersion for 1-10 hours, and then adding the 2,2'-bipyridine solution to the above mixture and continuing to stir for 1-10 hours.

[0017] Preferably, the rotary evaporation temperature in step (1) is 50-80°C, preferably 60-70°C.

[0018] Preferably, the gradient temperature increase in step (2) is 1-10°C / min, the calcination temperature is 700-1200°C, and the calcination time is 0.5-4 hours.

[0019] The cobalt-based armored nanozyme obtained by the present invention has a nanosheet or nanotube morphology, the diameter of the carbon layer-embedded cobalt nanoclusters is 1-50nm, the number of carbon layers is 1-15 layers, and the mass fraction of the cobalt element is 10%-40%.

[0020] The present invention provides an application of the cobalt-based armor nanozyme obtained by the above technical solution in the remediation of organic pollutants.

[0021] Preferably, the concentration of the cobalt-based armor nanozyme for removing organic pollutants in water is 1-300 mg / L, more preferably 5-50 mg / L.

[0022] Preferably, the organic pollutants include: acetamiprid, isoprocarb, thiamethoxam, atrazine, simazine, cyanazine, simetryn, propazine, prometryn, mesotrione, nicosulfuron, bensulfuron-methyl, ametryn, diuron, glyphosate, metalaxyl, paclobutrazol, carbendazim, tebuconazole, ciprofloxacin, norfloxacin, tetracycline hydrochloride, sulfadiazine, ibuprofen, phenol, bisphenol A, and guaiacol.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention uses a relatively small number of raw materials, and a simple pretreatment and calcination process allows the production of highly active and stable nanozymes. Compared with other methods, the present method offers advantages such as simplicity, mild reaction conditions, ease of operation, and cleanliness, making it suitable for large-scale production and readily applicable to industrial applications.

[0025] The cobalt-based armored nanozyme provided by the present invention has both the efficient catalytic activity of cobalt metal and the stability of carbonaceous materials. While ensuring efficient catalytic activity, it greatly reduces the secondary pollution caused by cobalt metal leaching. It can effectively degrade a variety of organic pollutants and has broad application prospects in the degradation of environmental pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a transmission electron microscope image of the prepared cobalt-based armor nanozyme.

[0027] Figure 2 This is the degradation effect of cobalt-based armor nanozyme on PMS activation on imidacloprid at different concentrations.

[0028] Figure 3 Cobalt-based armored nanozymes are repeatedly used to activate PMS to degrade imidacloprid.

[0029] Figure 4 The changes in the degradation efficiency of cobalt-based armored nanozymes during the continuous flow degradation of imidacloprid by repeatedly using activated PMS.

[0030] Figure 5 Comparison of the degradation effects of cobalt-based armored nanozymes on 27 organic pollutants by activating PMS. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail through the following preferred embodiments, which are only used to specifically illustrate the present invention but not to limit the present invention. In particular, the preparation method and application of cobalt-based armor nanozymes are only illustrative and not limiting of this patent. The specific implementation methods are as follows: Example

[0032] 0.5 mmol Co(NO₃)₂·6H₂O (0.147 g) was dissolved in 5 mL of deionized water (Solution A), 2.5 g of 2,2'-bipyridine was dissolved in 10 mL of N,N-dimethylformamide (Solution B), and 2 g of g-C₃N₄ was dispersed in 15 mL of N,N-dimethylformamide (Solution C). Solution A was first added dropwise to Solution B under magnetic stirring and stirring was continued for 1 hour. Then, Solution C was added to the mixture and stirring was continued for 2 hours. Finally, the solvent was removed by vacuum rotary evaporation at 70°C and the mixture was dried in a 70°C oven for 12 hours to obtain the precursor.

[0033] The precursor was fully ground and transferred to an alumina crucible, placed in a tube furnace, and slowly heated to 900°C at a heating rate of 2°C / min under nitrogen protection and maintained for 1 hour. Then, the temperature was reduced to 500°C at a cooling rate of 10°C / min. After naturally cooling to room temperature, it was taken out and washed with 3 mol / L hydrochloric acid reflux at 80°C for 3 hours. The precipitate was collected by centrifugation and washed with deionized water until neutral. Finally, it was washed with anhydrous ethanol three times and placed in a 70°C oven to dry for 12 hours. The resulting product is cobalt-based armor nanozyme, recorded as cobalt-based armor nanozyme A. Example

[0034] 0.5 mmol Co(NO₃)₂·6H₂O (0.147 g) was dissolved in 5 mL of deionized water (Solution A), 2.0 g of 2,2'-bipyridine was dissolved in 10 mL of N,N-dimethylformamide (Solution B), and 2 g of g-C₃N₄ was dispersed in 15 mL of N,N-dimethylformamide (Solution C). Solution A was first added dropwise to Solution B under magnetic stirring and stirring was continued for 1 hour. Then, Solution C was added to the mixture and stirring was continued for 2 hours. Finally, the solvent was removed by vacuum rotary evaporation at 70°C and the mixture was dried in a 70°C oven for 12 hours to obtain the precursor.

[0035] The precursor was fully ground and transferred to an alumina crucible, placed in a tubular furnace, and slowly heated to 900°C at a heating rate of 2°C / min under nitrogen protection and maintained for 1 hour. The temperature was then lowered to 500°C at a cooling rate of 10°C / min. After naturally cooling to room temperature, the product was taken out and washed with 3 mol / L hydrochloric acid at 80°C for 3 hours. The precipitate was collected by centrifugation and washed with deionized water until neutral. Finally, it was washed three times with anhydrous ethanol and dried in an oven at 70°C for 12 hours. The resulting product was cobalt-based armor nanozyme, recorded as cobalt-based armor nanozyme B. Example

[0036] 0.5 mmol Co(NO₃)₂·6H₂O (0.147 g) was dissolved in 5 mL of deionized water (Solution A), 2.5 g of 2,2'-bipyridine was dissolved in 10 mL of N,N-dimethylformamide (Solution B), and 3.6 g of g-C₃N₄ was dispersed in 15 mL of N,N-dimethylformamide (Solution C). Solution A was first added dropwise to Solution B under magnetic stirring and stirring was continued for 1 hour. Then, Solution C was added to the mixture and stirring was continued for 2 hours. Finally, the solvent was removed by vacuum rotary evaporation at 70°C and the mixture was dried in a 70°C oven for 12 hours to obtain the precursor.

[0037] The precursor was fully ground and transferred to an alumina crucible, placed in a tube furnace, and slowly heated to 900°C at a heating rate of 2°C / min under nitrogen protection and maintained for 1 hour. Then, the temperature was reduced to 500°C at a cooling rate of 10°C / min. After naturally cooling to room temperature, it was taken out and washed with 3 mol / L hydrochloric acid reflux at 80°C for 3 hours. The precipitate was collected by centrifugation and washed with deionized water until neutral. Finally, it was washed with anhydrous ethanol 3 times and placed in a 70°C oven to dry for 12 hours. The resulting product is cobalt-based armor nanozyme, recorded as cobalt-based armor nanozyme C. Example

[0038] 0.5 mmol Co(NO₃)₂·6H₂O (0.147 g) was dissolved in 5 mL of deionized water (Solution A), 2.5 g of 2,2'-bipyridine was dissolved in 10 mL of N,N-dimethylformamide (Solution B), and 3.6 g of g-C₃N₄ was dispersed in 15 mL of N,N-dimethylformamide (Solution C). Solution A was first added dropwise to Solution C under magnetic stirring and stirred for 2 hours. Then, Solution B was added to the mixture and stirred for another hour. Finally, the solvent was removed by vacuum rotary evaporation at 70°C and the mixture was dried in a 70°C oven for 12 hours to obtain the precursor.

[0039] The precursor was fully ground and transferred to an alumina crucible, placed in a tubular furnace, and slowly heated to 900°C at a heating rate of 2°C / min under nitrogen protection and maintained for 1 hour. The temperature was then lowered to 500°C at a cooling rate of 10°C / min. After naturally cooling to room temperature, the product was taken out and washed with 3 mol / L hydrochloric acid reflux at 80°C for 3 hours. The precipitate was collected by centrifugation and washed with deionized water until neutral. Finally, it was washed three times with anhydrous ethanol and dried in an oven at 70°C for 12 hours. The resulting product was cobalt-based armor nanozyme, recorded as cobalt-based armor nanozyme D.

[0040] Prepare 5 μg·mL -1The imidacloprid aqueous solution was placed in four beakers, and 2 g of the cobalt-based armor nanozymes A, B, C, and D prepared in the above examples were weighed into the above beakers respectively. After ultrasonication for 30 minutes, 12 mg of PMS (2KHSO5•KHSO4•K2SO4) was added to each beaker. The reaction was repeated three times for each cobalt-based armor nanozyme. After the reaction lasted for 30 minutes, the samples were passed through a high-performance liquid chromatography (Agilent HPLC-1260 series) to detect the residual concentration of imidacloprid in the reaction system.

[0041] The results showed that cobalt-based armor nanozyme C had the best degradation effect on imidacloprid, with a degradation efficiency of 96.8%, followed by cobalt-based armor nanozyme D with a degradation efficiency of 96.1%, cobalt-based armor nanozyme A with a degradation efficiency of 95.2%, and cobalt-based armor nanozyme B with the lowest degradation efficiency of 94.3%.

[0042] Figure 1 This is a transmission electron microscope image of the cobalt-based armor nanozyme prepared in Example 3. Example

[0043] The cobalt-based armored nanozyme C prepared in Example 3 was used as a PMS activator to measure the degradation efficiency of imidacloprid at different concentrations.

[0044] Four different concentrations of imidacloprid aqueous solutions (1.25 μg·mL -1 , 2.50 μg•mL -1 , 5.00 μg•mL -1 , 10.00 μg•mL -1 ), the experimental method and detection method are the same as in Example 4.

[0045] Figure 2 The results show that the degradation effect of cobalt-based armored nanozyme C on the activation of PMS to imidacloprid at different concentrations was significantly improved within 30 min under the reaction conditions. -1 The degradation effect of imidacloprid was the best, with a degradation rate of 98.8%. -1 , 5.00 μg•mL -1 , 10.00 μg•mL -1 The degradation rates reached 98.7%, 96.8% and 86.9% respectively. Example

[0046] The cobalt-based nanozyme C prepared in Example 3 was used as a PMS activator, and its stability was determined by recycling and reusing the nanozyme.

[0047] Prepare 2.5 μg·mL -1Imidacloprid test solution, weigh 10 mg of cobalt-based nanozyme C and disperse it in 200 mL of imidacloprid test solution, weigh 60 mg of PMS and dissolve it in the above mixture, then time the reaction and take samples at specific time intervals. The detection method is the same as Example 4. A test cycle of 30 min is completed. After the reaction is completed, the nanozyme is centrifuged and recovered, and washed with deionized water and anhydrous ethanol 3 times each. After being fully dried at 70°C, it is weighed and the next round of testing is carried out. The total volume of the reaction system is reduced according to the actual remaining weight of the nanozyme each time, and the concentration of the nanozyme is always kept at 50 μg·mL -1 , PMS concentration was 300 μg•mL -1 , imidacloprid concentration was 2.5 μg•mL -1 .

[0048] Figure 3 The stability of cobalt-based armor nanozyme C in repeatedly activating PMS to degrade imidacloprid was compared. The results showed that there was no significant difference in the degradation efficiency after 15 cycles, indicating that the cobalt-based armor nanozyme prepared by the present invention has strong stability and still has strong degradation efficiency after repeated and multiple cycles. Example

[0049] A continuous flow packed bed column reactor was prepared using the cobalt-based nanozyme C prepared in Example 3 as the reactor filler, and a continuous flow imidacloprid degradation test was carried out.

[0050] The specific operation is as follows: the column reactor is separated into three layers using a sieve plate with a pore size of 1 μm. The bottom layer is filled with 200-mesh quartz sand with a height of 1 cm. 50 mg of cobalt-based nanozyme C is added to the middle layer with a height of 2 cm. The upper layer is filled with 1 cm of 200-mesh quartz sand.

[0051] Test plan: Prepare 2.5 μg·mL -1 Imidacloprid solution was added to a final concentration of 300 μg·mL -1 The mixed solution was pumped into the column reactor at a flow rate of 1 mL / min using a fusion pump, and the imidacloprid residue in the effluent was detected every 12 h using the same detection method as in Example 4.

[0052] Figure 4 The degradation efficiency of cobalt-based armored nanozyme C during continuous flow degradation of imidacloprid changes. The results show that the degradation efficiency is still above 83% after 7 days of continuous reaction, which has good application prospects. Example

[0053] The cobalt-based nanozyme C prepared in Example 3 was used as a PMS activator, and acetamiprid, isoprocarb, thiamethoxam, atrazine, simazine, cyanazine, simethicone, promethazine, promethazine, mesotrione, nicosulfuron, bensulfuron-methyl, ametryn, diuron, glyphosate, metalaxyl, paclobutrazol, carbendazim, tebuconazole, ciprofloxacin, norfloxacin, tetracycline hydrochloride, sulfadiazine, ibuprofen, phenol, bisphenol A, and guaiacol were used as model pollutants to compare the degradation performance.

[0054] The concentration of cobalt-based nanozyme C used was 50 μg·mL -1 , PMS concentration 300 μg•mL -1 , the pollutant concentration of glyphosate is 100 μg•mL -1 , the rest were 2.5 μg•mL -1 After the reaction, an equal volume of methanol was added to terminate the reaction. The sample detection method was the same as in Example 4.

[0055] Figure 5 The degradation effects of cobalt-based armor nanozyme C activated PMS on 27 organic pollutants were compared. The results showed that within 5 minutes, the degradation efficiency of cobalt-based armor nanozyme activated PMS on 27 organic pollutants was above 80%, with very good broad-spectrum degradation effect.

Claims

1. A method for preparing a cobalt-based armor nanozyme, characterized in that: The cobalt salt solution, 2,2'-bipyridine solution and g-C3N4 dispersion were mixed evenly, and after sufficient reaction, vacuum rotary evaporation was performed and the precursor was dried at 70°C. After the precursor is fully ground, it is calcined in a tube furnace, cooled, washed and dried at 70°C; The cobalt salt solution is cobalt nitrate, cobalt sulfate, or cobalt chloride, and its concentration in the reaction system is 1-300 mmol / L; The molar ratio of the cobalt salt to 2,2'-bipyridine is 1:1-1:32; The concentration of the g-C3N4 dispersion in the reaction system is 66.67 g / L; Alternatively, the concentration of the g-C3N4 dispersion in the reaction system is 120 g / L; The rotary evaporation temperature is 50-80°C; The calcination method is to increase the temperature gradually from 1 to 10 ° C / min to 700 to 1200 ° C, and the calcination time is 0.5 to 4 hours; The cooling method is to gradually reduce the temperature to 500° C. at 10° C. / min and then cool naturally.

2. The method for preparing the cobalt-based armor nanozyme according to claim 1, wherein: The uniform mixing comprises mixing the cobalt salt solution and the 2,2'-bipyridine solution and stirring for 1-10 hours, then adding the g-C3N4 dispersion to the above mixture and continuing to stir for 1-10 hours; Alternatively, the cobalt salt solution and the g-C3N4 dispersion are mixed and stirred for 1-10 hours, and then the 2,2'-bipyridine solution is added to the mixture and the stirring is continued for 1-10 hours.

3. The method for preparing the cobalt-based armor nanozyme according to claim 1, wherein: The washing method comprises washing with 3 mol / L hydrochloric acid at 80° C. for 3 h, collecting the precipitate by centrifugation and washing with deionized water until neutral, and finally washing with anhydrous ethanol for 3 times.

4. A cobalt-based armor nanozyme prepared by the preparation method according to any one of claims 1 to 3.

5. The cobalt-based armor nanozyme according to claim 4, characterized in that The diameter of the carbon layer-embedded cobalt nanocluster is 1-50nm, the number of carbon layers is 1-15, the mass fraction of cobalt element is 10%-40%, and the overall shape is nanosheet or nanotube.

6. Use of the cobalt-based armored nanozyme as claimed in claim 4 or 5 in the remediation of organic pollutants.

7. The use of the cobalt-based armor nanozyme in the remediation of organic pollutants according to claim 6, characterized in that: The usage concentration is 5-50mg / L.

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