A method for activating PMS catalytic organic pollutants by using A-site lanthanum-doped lithium cobalt oxide

Abstract

This invention discloses a method for activating PMS (persulfate monosulfate) catalysts to degrade organic pollutants using A-site lanthanum-doped lithium cobalt oxide, belonging to the field of environmental catalysis and pollutant treatment technology. This invention synthesizes an A-site lanthanum-doped lithium cobalt oxide catalyst in one step via a sol-gel method, and uses it to activate PMS to degrade pharmaceutical wastewater with carbamazepine as a model pollutant. In this invention, A-site lanthanum doping significantly enhances the activation ability for PMS, achieving the goal of highly efficient carbamazepine degradation. Simultaneously, during the catalytic degradation of carbamazepine using cobalt as the active site, the leaching of cobalt ions is extremely low after five cycles; furthermore, the catalyst material exhibits strong cycle repeatability. This invention improves the degradation rate of carbamazepine through a simple synthesis method, making it suitable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalysis and pollutant treatment technology, specifically relating to a method for activating PMS catalysis of organic pollutants using A-site lanthanum-doped lithium cobalt oxide. Background Technology

[0002] Clean water resources are crucial for human life and production activities. However, with environmental pollution from industrial production and daily life, the Earth's available water resources are struggling to cope with the rapidly growing population, prompting greater attention to water purification technologies. Advanced oxidation processes are among the most effective and promising technologies for wastewater remediation, especially for treating recalcitrant organic matter. The reactions involved in advanced oxidation technologies primarily generate reactive oxygen species with strong oxidizing capabilities, which can rapidly decompose organic matter into harmless water and carbon dioxide.

[0003] Ozone oxidation, photocatalytic oxidation, the Fenton process, and persulfate activation are several important methods in advanced oxidation processes, with catalysts being the central source of reactive oxygen species. Therefore, developing highly efficient catalysts for advanced oxidation reactions is a key step in advancing efficient catalysis.

[0004] Currently, lithium cobalt oxide has been reported as an excellent catalyst in advanced oxidation technologies, capable of activating PMS to catalyze the degradation of pollutants in water. However, during the PMS activation and degradation of pollutants, Co in lithium cobalt oxide is easily precipitated, causing a decline in the material's performance in degrading pollutants, poor stability, and environmental pollution. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a method for activating PMS (Proton Sedimentation System) to catalyze the degradation of organic pollutants using A-site lanthanum-doped lithium cobalt oxide. This invention improves not only the efficiency of PMS activation in degrading carbamazepine but also the degradation stability by modifying lithium cobalt oxide materials with A-site lanthanum doping.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for activating PMS-catalyzed organic pollutants using A-site lanthanum-doped lithium cobalt oxide, specifically comprising:

[0008] (1) Dissolve cobalt nitrate hexahydrate, lithium nitrate and lanthanum nitrate hexahydrate in water and stir until well mixed. Add ethylene glycol dropwise and continue stirring. Adjust the pH to 10. Then react at 70°C to form a sol-gel. Finally, dry, calcine and grind to obtain A-site lanthanum-doped lithium cobalt oxide.

[0009] (2) Add lanthanum-doped lithium cobalt oxide at site A to an organic wastewater solution, and add PMS at the same time. React at room temperature and under natural light to achieve the degradation of organic wastewater.

[0010] In a preferred embodiment of the present invention, the molar ratio of cobalt nitrate hexahydrate, lithium nitrate and lanthanum nitrate hexahydrate is 1:0.7:0.3.

[0011] In a preferred embodiment of the present invention, in step (2), after PMS is added, the concentration of PMS in the organic wastewater solution is 0.2 mmol / L.

[0012] In a preferred embodiment of the present invention, the molar ratio of cobalt nitrate hexahydrate to ethylene glycol is 1:0.3.

[0013] In a preferred embodiment of the present invention, the organic wastewater solution is a carbamazepine aqueous solution with a concentration of 2.5 mg / L.

[0014] In a preferred embodiment of the present invention, the mass ratio of the lanthanum-doped lithium cobalt oxide at the A site to the organic pollutants in the organic wastewater solution is 12:0.25.

[0015] In a preferred embodiment of the present invention, the calcination temperature is 900°C and the time is 10 hours.

[0016] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention synthesizes an A-site lanthanum-doped lithium cobalt oxide catalyst in one step via a sol-gel method, which is then used to activate PMS to degrade pharmaceutical wastewater with carbamazepine as a model pollutant. On the one hand, A-site lanthanum doping greatly enhances the activation ability for permonosulfate (PMS), achieving the goal of efficient carbamazepine degradation. On the other hand, A-site lanthanum doping of La improves the material structure, making the chemical bonding force of Co ions in the material stronger and less prone to precipitation; moreover, the byproducts generated during the PMS catalysis of carbamazepine doping do not cause poisoning of the A-site lanthanum-doped lithium cobalt oxide catalyst, thus preventing material deactivation. Therefore, the A-site lanthanum-doped lithium cobalt oxide material exhibits strong cycle repeatability, with no significant deactivation observed after 5 cycles. In addition, the A-site lanthanum-doped lithium cobalt oxide material has higher safety, with extremely low cobalt ion leaching and minimal secondary pollution. Attached Figure Description

[0017] Figure 1 This is a SEM image of the lithium cobalt oxide prepared in Comparative Example 1 of this invention.

[0018] Figure 2 SEM image of the A-site lanthanum-doped lithium cobalt oxide prepared in the example.

[0019] Figure 3 This is a comparison of the catalytic degradation of carbamazepine by PMS activated by the A-site lanthanum-doped lithium cobalt oxide material prepared in Example 1 of the present invention and PMS alone.

[0020] Figure 4Comparison of the catalytic degradation of carbamazepine by PMS activated by the materials prepared in Examples 1-3 and Comparative Example 1 of this invention and PMS alone.

[0021] Figure 5 This is a comparison of the catalytic degradation of carbamazepine after five cycles of recycling of the A-site lanthanum-doped lithium cobalt oxide material prepared in Example 1 of this invention.

[0022] Figure 6 The amount of cobalt ions leached out after five cycles of recycling of the A-site lanthanum-doped lithium cobalt oxide material prepared in Example 1 of this invention.

[0023] Figure 7 The amount of cobalt ion leaching is represented by the proportions of lanthanum-doped lithium cobalt oxide materials prepared in Comparative Examples 1-4 of this invention.

[0024] Figure 8 The image shows a comparison of the catalytic degradation of carbamazepine by lithium cobalt oxide with different proportions of lanthanum doped at the A site prepared in Example 1 of the present invention and the lithium cobalt oxide material prepared in Comparative Example 1 under thiocyanate quenching. Detailed Implementation

[0025] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0026] Example 1

[0027] A method for preparing A-site lanthanum-doped lithium cobalt oxide material includes the following steps:

[0028] Weigh 0.9653 g of lithium nitrate, 5.8206 g of cobalt nitrate hexahydrate, and 2.5980 g of lanthanum nitrate hexahydrate, and dissolve them in 200 mL of deionized water. Add 3.39 mL of ethylene glycol to the mixed solution, mix thoroughly, adjust the pH of the solution to 10, transfer to a 70 °C water bath and stir until a sol-gel state is reached. Dry in an 80 °C oven for 12 h. Place the dried material in a box furnace and calcine at 900 °C for 10 h. After grinding, obtain A-site lanthanum-doped cobalt oxide, denoted as La0.3.

[0029] Comparative Example 1

[0030] A method for preparing lithium cobalt oxide material includes the following steps:

[0031] Weigh 1.3790 g of lithium nitrate and 5.8206 g of cobalt nitrate hexahydrate and dissolve them in 200 mL of deionized water. Add 3.39 mL of ethylene glycol to the mixed solution and mix thoroughly. Adjust the pH of the solution to 10, transfer it to a 70 °C water bath and stir until it reaches a sol-gel state. Dry it in an 80 °C oven for 12 h. Place the dried material in a box furnace and calcine it at 900 °C for 10 h. After grinding, lithium cobalt oxide is obtained, denoted as La0.

[0032] Comparative Example 2

[0033] The only difference between the preparation method of the A-site lanthanum-doped lithium cobalt oxide material described in this comparative example and Example 1 is that the mass of lithium nitrate is 0.6895 g and the mass of lanthanum nitrate hexahydrate is 4.3301 g, denoted as La0.5.

[0034] Comparative Example 3

[0035] The only difference between the preparation method of the A-site lanthanum-doped lithium cobalt oxide material described in this comparative example and Example 1 is that the mass of lithium nitrate is 1.1032 g and the mass of lanthanum nitrate hexahydrate is 1.7320 g, denoted as La0.8.

[0036] Comparative Example 4

[0037] The only difference between the preparation method of the A-site lanthanum-doped lithium cobalt oxide material described in this comparative example and Example 1 is that the mass of lithium nitrate is 0 g and the mass of lanthanum nitrate hexahydrate is 8.6602 g, denoted as La1.

[0038] Example of effect 1

[0039] Test samples: Materials prepared in Example 1 and Comparative Examples 1-4.

[0040] A method for activating PMS to catalyze organic pollutants using A-site lanthanum-doped lithium cobalt oxide specifically includes: adding 0.012 g of test sample and 0.2 mmol / L PMS to 100 mL of 2.5 mg / L carbamazepine solution, reacting at room temperature and under natural light for 10 min, taking samples every 1 min, and determining the residual concentration of carbamazepine by liquid chromatography, with C / C0 representing the degradation rate of carbamazepine.

[0041] In contrast, the method of using PMS alone to catalyze organic pollutants specifically includes: adding 0.2 mmol / L PMS to 100 mL of a 2.5 mg / L carbamazepine solution, reacting for 10 min at room temperature and under natural light, taking samples every 1 min, and determining the residual concentration of carbamazepine by liquid chromatography, with C / C0 representing the degradation rate of carbamazepine.

[0042] Depend on Figure 3 It can be seen that the A-site lanthanum-doped lithium cobalt oxide material prepared in Example 1 activated PMS with a 100% degradation rate of carbamazepine, which is significantly different from the degradation rate of pollutants by PMS alone (around 20%). Therefore, A-site lanthanum-doped lithium cobalt oxide La0.3 can effectively activate PMS, while PMS alone has a limited effect on the degradation of carbamazepine, highlighting the ability of A-site lanthanum-doped lithium cobalt oxide material to activate PMS.

[0043] Depend on Figure 4 It can be seen that the A-site lanthanum-doped lithium cobalt oxide La0.3 prepared in Example 1 achieved a 100% degradation rate of carbamazepine in about 5 minutes. However, the degradation rates of carbamazepine were not significant in Comparative Examples 1, 2-3 (A-site lanthanum-doped lithium cobalt oxide La0.5 and La0.8), and 4 (comparative Example 4 (lanthanum cobalt oxide La1), especially in the A-site lanthanum-doped lithium cobalt oxide La0.8 and the undoped lithium cobalt oxide materials.

[0044] This invention also explored the effect of different doping sites on its performance in activating PMS catalytic removal of carbamazepine. Compared with A-site lanthanum-doped lithium cobalt oxide, undoped lithium cobalt oxide or B-site-doped lithium cobalt oxide showed weaker PMS catalytic removal capabilities for carbamazepine. Figure 8 The active site data show that after thiocyanate quenching of the Co sites in the materials prepared in Example 1 and Comparative Example 1, the degradation rate of carbamazepine decreased to 13.74% and 16.29%, respectively, indicating that the lanthanum-doped lithium cobalt oxide material at the A site enhances the activity of the Co sites and is more conducive to the activation of PMS.

[0045] Example 2

[0046] Test samples: Materials prepared in Example 1 and Comparative Examples 1-4.

[0047] The five-cycle catalytic degradation of carbamazepine involved the following steps: 0.012 g of test sample was added to 100 mL of a 2.5 mg / L carbamazepine solution, along with 0.2 mmol / L PMS. The mixture was reacted for 10 min at room temperature and under natural light, with samples taken every 1 min. The residual concentration of carbamazepine was determined by liquid chromatography, and the degradation rate was expressed as C / C0. The reaction solution was immediately filtered through a 0.45 μm filter membrane. The filter material was washed multiple times with deionized water and dried at 80 °C. The dried material was then used to activate PMS for carbamazepine degradation. This process was repeated five times.

[0048] according to Figure 5 It can be seen that the A-site lanthanum-doped lithium cobalt oxide material La0.3 exhibits a carbamazepine degradation rate of 88.01% after 5 cycles, which is still close to 90%, and it reaches stability after the 4th cycle. This indicates that the A-site lanthanum-doped lithium cobalt oxide material still has a high carbamazepine degradation rate after multiple cycles, verifying the stability of the material.

[0049] In the first degradation experiment, the degradation rate of carbamazepine in Comparative Examples 1-4 was significantly lower than that in Example 1, further demonstrating that A-site doping of lanthanum can improve the activity of lithium cobalt oxide.

[0050] Example 3

[0051] Test samples: Materials prepared in Example 1 and Comparative Examples 1-4.

[0052] The leaching amount of cobalt ions after five cycles of catalytic degradation of carbamazepine was determined by the following steps: 0.012 g of test sample was added to 100 mL of 2.5 mg / L carbamazepine solution, and PMS was added simultaneously at a concentration of 0.2 mmol / L. The mixture was then reacted for 10 min at room temperature under natural light. A certain volume of sample was taken, and the concentration of leached cobalt was determined using flame atomic absorption spectrometry. The reaction solution was immediately filtered through a 0.45 μm filter membrane. The material on the filter membrane was washed multiple times with deionized water and dried at 80 °C. The dried material was used to conduct experiments on the activation of PMS catalysis of carbamazepine and the concentration of leached cobalt. The above steps were repeated five times.

[0053] Figure 6 In the study, the cobalt ion leaching amount after five cycles of carbamazepine degradation catalyzed by A-site lanthanum-doped lithium cobalt oxide was less than 0.1 mg / L, far below the 1.0 mg / L limit set by the Chinese Surface Water Environmental Standard (GB3838-2002). These results demonstrate the extremely low cobalt ion leaching amount, validating the practical feasibility of using A-site lanthanum-doped lithium cobalt oxide to activate PMS for pollutant catalytic degradation.

[0054] according to Figure 7 It can be seen that among the degradation systems of Comparative Examples 1-4 and Example 1, the cobalt leaching amount in Example 1 is the lowest, while the Co leaching amount in Comparative Examples 1-4 is relatively high. Cobalt in a heterogeneous state is not conducive to the degradation of pollutants. Therefore, the stability of the lithium cobalt oxide materials in Comparative Examples 1-4 is significantly reduced, which further illustrates the stability of the A-site doped lithium cobalt oxide material in Example 1.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for catalytic degradation of organic pollutants by PMS activated with A-site lanthanum-doped lithium cobalt oxide, characterized in that, Specifically include: (1) Cobalt nitrate hexahydrate, lithium nitrate and lanthanum nitrate hexahydrate were dissolved in water at a molar ratio of 1:0.7:0.3 and stirred until well mixed. Ethylene glycol was added dropwise and stirring was continued. The pH was adjusted to 10 and then reacted at 70°C to form a sol-gel. Finally, the mixture was dried, calcined and ground to obtain A-site lanthanum-doped lithium cobalt oxide. (2) Add lanthanum-doped lithium cobalt oxide at site A to the organic wastewater solution, and add PMS at the same time. React at room temperature and under natural light to achieve the degradation of organic wastewater.

2. The method as described in claim 1, characterized in that, In step (2), after PMS is added, the concentration of PMS in the organic wastewater solution is 0.2 mmol / L.

3. The method as described in claim 1, characterized in that, The molar ratio of cobalt nitrate hexahydrate to ethylene glycol is 1:0.

3.

4. The method as described in claim 1, characterized in that, The organic wastewater solution is a carbamazepine aqueous solution with a concentration of 2.5 mg / L.

5. The method as described in claim 1, characterized in that, The mass ratio of the lanthanum-doped lithium cobalt oxide at site A to the organic pollutants in the organic wastewater solution is 12:0.

25.

6. The method as described in claim 1, characterized in that, The roasting temperature is 900℃ and the time is 10h.

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