Preparation of nanowire structure Co3O4 loaded manganese-based material with controllable oxygen vacancy

Abstract

The invention aims to provide a preparation method of a Co3O4-loaded manganese-based catalyst with adjustable oxygen vacancies. The catalyst with a Co3O4 small-particle structure uniformly loaded on MnO2 nanowires is synthesized by adopting a hydrothermal method. The preparation method of the catalyst is simple, the cost is low, the ion leaching rate is low, the anti-interference capacity is higher, PMS can be activated to generate singlet oxygen (1O2) with a higher proportion due to the fact that the catalyst has rich oxygen vacancies, and therefore the purpose of degrading pollutants in the actual water environment is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of advanced oxidation technology, and particularly relates to a preparation method and application of a Co3O4-loaded manganese-based catalyst for activating a persulfate (PMS) to degrade persistent pollutants in water bodies. BACKGROUND

[0002] There are many sources of water resource pollution, among which persistent pollutants have become the focus of attention due to their characteristics of being difficult to degrade, high toxicity, easy to accumulate, etc. Agricultural chemicals are one of the main sources of persistent pollutants, and as a large agricultural country, a large amount of pesticides are used to ensure the mass production of crops, some of which will enter rivers and lakes with water circulation under natural conditions, causing serious impact on the environment. Atrazine (ATZ) as a commonly used triazine herbicide is widely used in corn and sorghum field weed control, and is difficult to degrade under natural conditions, and has the ability to migrate in the soil environment due to its water solubility. Sun et al. investigation showed that the concentration of atrazine in agricultural soil in the Yangtze River Delta region reached 113 ng·g -1 Once atrazine enters the water body, it will have a toxic effect on aquatic organisms (J. T. Sun, L. L. Pan, Yu Zhan, et al. Environ Geochem Health (2017) 39:369-378). Liu Mengxue et al. summarized the toxicity data of atrazine on the native aquatic organisms in the Yellow River Basin, and found that atrazine had toxic effects on aquatic plants, invertebrates and vertebrates. Long-term drinking of water sources containing atrazine will affect the endocrine system of the body, and even have a risk of causing cancer (Liu M S, Wang Z D, Ma Y L, et al. Asian Journal of Ecotoxicology, 2022, 17(6): 400-408 (in Chinese)). Therefore, it is necessary to use an efficient method to remove atrazine in water bodies.

[0003] Based on the current research, it can be found that transition metal-activated persulfate (PMS) has a significant effect on the removal of ATZ, especially Co-based catalysts show excellent performance. At the same time, loading Co-based catalysts on MnO2 is a good method to reduce the ion leaching of Co-based catalysts during use. During the activation of PMS, various active oxygen species are generated, which play an important role in degrading pollutants. For example, the sulfate radical (SO4 •⁻ ) and hydroxyl radical (•OH) with fast reaction rate can efficiently attack organic pollutants and promote their decomposition. In addition, singlet oxygen ( 1O2) as a non-radical species is less affected by environmental conditions (such as pH) and exhibits stable oxidative ability.

[0004] In order to make atrazine be degraded efficiently in various complex water environments, an adjustment strategy of oxygen vacancies is introduced in the preparation process of the catalyst. By reasonably regulating the number and distribution of oxygen vacancies, the proportion of O2 can be significantly increased 1 . This adjustment not only improves the adaptability of the catalyst under different pH conditions, but also enhances its tolerance to coexisting ions, thereby exhibiting more excellent degradation effect in practical application. In general, the present application uniformly loads Co3O4 small particles on MnO2 nanowires by a hydrothermal method, greatly increases the content of oxygen vacancies, and reduces the leaching of Co ions due to the interaction between metals. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a Co3O4 loaded manganese-based catalyst with adjustable oxygen vacancies. The catalyst with Co3O4 small particle structure uniformly loaded on MnO2 nanowires is synthesized by a hydrothermal method. The catalyst preparation method is simple, low in cost, low in ion leaching rate and has stronger anti-interference ability. Because it has abundant oxygen vacancies, it can activate PMS to generate a higher proportion of singlet oxygen (O2), thereby achieving the purpose of degrading pollutants in actual water environment. 1

[0006] The purpose of the present application is achieved by the following technical solutions: A preparation method of a Co3O4 loaded manganese-based catalyst with adjustable oxygen vacancies for effectively activating PMS, comprising the following steps: Preparation of MnO2: A certain amount of potassium permanganate (KMnO4) and manganese sulfate monohydrate (MnO4·H2O) (mass ratio of 5:2) are respectively dissolved in a certain amount of deionized water, stirred uniformly to form a transparent solution, and then transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle for solvothermal reaction. The hydrothermal temperature is 100-200 DEG C, and the reaction time is 10-30 h. The solid-liquid mixture after reaction is centrifuged, washed, and then dried in a vacuum drying oven to obtain MnO2 powder.

[0007] Preparation of MnO 2-x : A certain amount of MnO2 obtained in step 1) is dispersed in a certain concentration of sodium borohydride (NaBH4) solution (concentration ratio of 0-10 M) and stirred at room temperature for 5-20 h. The solid-liquid mixture after reaction is centrifuged, washed, and then dried in a vacuum drying oven to obtain MnO 2-x powder.

[0008] ​Preparation of CM: Take a certain amount of MnO obtained in step 2). 2-x The powder and a certain amount of Co(NO3)2·6H2O (molar ratio 1:1) were added to a certain amount of ethanol, stirred evenly, and then transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reactor for a solvothermal reaction at a hydrothermal temperature of 100~200℃ for 1~20 h. The resulting solid-liquid mixture was centrifuged, washed, and then dried in a vacuum drying oven to obtain CM powder.

[0009] The applications of the catalysts mentioned above in activating PMS to degrade persistent pollutants include the following aspects: Performance test of PMS activation for degradation of persistent pollutants: A certain amount of the above-prepared CM catalyst was dispersed in ATZ solution, a certain amount of PMS was added, and a certain amount of sample was taken out at regular intervals. The sample was immediately filtered with a syringe with a filter tip. A certain amount of filtrate was added to a certain amount of methanol to quench the reaction, and then the concentration was measured by high performance liquid chromatography.

[0010] The above method utilizes a two-step solvothermal approach to prepare a Co3O4-supported manganese-based catalyst with adjustable oxygen vacancies. Because Co3O4 is supported on MnO2, the leaching of Co ions is reduced to some extent. Furthermore, the abundant oxygen vacancies in the catalyst can significantly increase the generation of singlet oxygen during PMS activation, thus significantly enhancing the catalyst's resistance to environmental interference.

[0011] Compared with the prior art, the beneficial effects of the present invention are: The present invention provides a Co3O4-supported manganese-based catalyst with tunable oxygen vacancies, synthesized using a hydrothermal method. Oxygen vacancies are generated on a nanowire-like MnO2 substrate through sodium borohydride reduction, while simultaneously loading small Co3O4 particles onto it. This strategy increases the singlet oxygen content during PMS activation, enhancing the catalyst's resistance to environmental disturbances.

[0012] 2. The Co3O4-supported manganese-based catalyst with adjustable oxygen vacancies prepared in this invention possesses cobalt-manganese bimetallic active sites, significantly reducing the amount of catalyst required. Furthermore, due to the abundance of oxygen vacancies in the material, the generation of singlet oxygen is facilitated, resulting in excellent resistance to ion interference during the degradation process. Attached Figure Description Figure 1 SEM images of CM-X (X = 0 and 0.05) samples prepared according to the present invention. Figure 2 XRD pattern of the CM-0.05 sample prepared in this invention. Figure 3 Performance of the prepared catalyst in degrading ATZ with PMS, influence of coexisting anions and leaching concentration of Mn and Co after reaction: (a) ATZ degradation curve, (b) influence of coexisting anions, (c) leaching concentration of metal ions. Figure 4 MnO2, MnO 2-x O1S fine spectrum of CM-0.05: (a) MnO2, (b) MnO 2-x -0.05, (c) CM-0.05. Figure 5 Singlet oxygen capture experiment of CM-0 and CM-0.05 prepared by the present application: (a) CM-0, (b) CM-0.05.

Claims

1. A preparation of a controllable oxygen vacancy nanowire structure Co304 supported manganese-based material, characterized in that, The preparation method comprises the following steps: Synthesis of Co3O4 / MnO nanowires by two-step solvothermal method 2-x :1). Synthesis of MnO2, two manganese sources were dissolved in deionized water respectively, after complete dissolution, the two were mixed and stirred uniformly, then put into the reaction kettle, after high temperature hydrothermal reaction for a certain time, the obtained solid-liquid mixture was washed, dried and then obtained nanowire-like MnO2.2). Synthesis of MnO 2-x , nanowire-like MnO2 was dispersed into a solution with a certain concentration of reducing agent, the solution was stirred for a certain time and then centrifuged, washed and dried to obtain nanowire-like MnO 2-x with a certain oxygen vacancy.3). Synthesis of Co3O4 / MnO 2-x , MnO 2-x and cobalt source were put into ethanol at the same time, after stirring uniformly, they were put into the reaction kettle for solvothermal reaction. The obtained solid-liquid mixture was washed, dried to obtain Co3O4 / MnO 2-x powder, marked as CM.

2. A controllable oxygen vacancy nanowire structure Co304 supported manganese-based material preparation and application according to claim 1, characterized in that, In step 1), the cobalt and manganese sources are soluble potassium permanganate and manganese sulfate monohydrate respectively, the reducing agent in step 2) is sodium borohydride, and the cobalt source in step 3) is soluble cobalt nitrate hexahydrate.

3. A process for the preparation of controllable oxygen vacancy nanowire structured Co304 supported manganese based material as claimed in claim 1, wherein the process comprises of the steps of: In step 1) a certain mass ratio of manganese source, in step 2) a certain concentration of sodium borohydride, in step 3) a certain molar ratio of MnO 2-x and cobalt source.

4. A process for the preparation of controllable oxygen vacancy nanowire structured Co304 supported manganese based material as claimed in claim 1, wherein the process comprises of the steps of: In step 1), the temperature of the solvothermal heating of the manganese source is 100-200 DEG C, and the reaction time is 10-30 h; in step 2), the concentration of sodium borohydride is 0-10 M, and the reaction time at room temperature is 5-20 h; in step 3), the temperature of the solvothermal heating is 100-200 DEG C, and the reaction time is 1-20 h.

5. The preparation of a controllable oxygen vacancy nanowire structure Co3O4 loaded manganese-based material according to claims 1-4, which uniformly loads Co3O4 small particles on the MnO2 nanowire, which is conducive to the formation of abundant oxygen vacancy structures, promotes the generation of most of the active oxygen species as singlet oxygen in the PMS activation process, and enhances the ion interference resistance of the catalyst.

6. The preparation of a manganese-based material supported on Co3O4 with controllable oxygen vacancies in nanowire structure as described in claim 1, characterized in that... The specific application method is that the Co3O4 loaded manganese-based catalyst is applied to activate PMS to degrade persistent pollutants in water.

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