Preparation method of carbon cloth-deposited manganese-cobalt oxide for rapid decomposition of leaked gaseous benzene

Abstract

The present invention relates to the photocatalytic treatment of leaked toxic and volatile gaseous benzene. A new petal-shaped cobalt-manganese oxide composite material is grown on carbon cloth by a simple electrodeposition method, and the catalytic oxidative decomposition of gaseous benzene is studied under visible light irradiation. The results show that the composite material exhibits excellent photodecomposition ability and high mineralization rate for gaseous benzene under the drive of sunlight. The decomposition rate of 1000 ppm of benzene is 98.45%, and the mineralization rate is 99.5%. Moreover, after 60 cycles (30 hours) at room temperature, the decomposition rate does not decrease, and it has strong stability. At the same time, the catalytic material has a good removal effect on gaseous benzene of different concentrations from 600 ppm to 7500 ppm. The material prepared by the present invention has the advantages of being environmentally friendly, non-toxic, harmless, and low-priced. It has a fast degradation rate for gaseous benzene, good activity, good stability in use, and is easy to implement for emergency treatment of gaseous benzene in the event of industrial production emissions or leakage.

Description

Technical Field

[0001] The present invention uses different voltages to uniformly deposit manganese-cobalt oxide on carbon cloth to prepare a carbon cloth-deposited composite material. This composite material can be used to purify benzene in the atmosphere and to deal with benzene leaks. The invention belongs to the technical field of material preparation and photocatalytic toxic gas pollution control. Background Art

[0002] Benzene, a chemical raw material, is widely used in construction, decorative materials, paints, and petrochemical plants, making it an essential component of human life. When inhaled, benzene gaseous substances cannot be metabolized normally, leading to poisoning, shock, and even death. This not only affects human health but also pollutes the environment.

[0003] Up to now, the treatment scheme for gaseous benzene is generally high-temperature catalytic decomposition. However, due to its high temperature, slow reaction speed, easy generation of secondary pollutants, and generally low treatment concentration, it cannot cope with the dangerous situation of industrial production or leakage of high-concentration gaseous benzene. The present invention adopts photocatalytic technology, which can completely convert gaseous benzene into carbon dioxide and water under the condition of continuous energy provided by sunlight, without generating secondary pollutants, and has the characteristics of extremely high efficiency. The present invention uses carbon cloth as a flexible substrate and deposits MnO on the surface of the carbon cloth by step-by-step electrodeposition. x A carbon cloth-deposited manganese-cobalt oxide composite material (MnO2 and Mn5O8) and Co3O4 was successfully prepared. This composite material can rapidly and efficiently degrade gaseous benzene under sunlight. The carbon cloth in this composite material, as an excellent conductor, also efficiently transfers electrons, improving light utilization. The MnO2 and Mn5O8 content can be controlled by adjusting the deposition voltage. The prepared material possesses a rich manganese valence structure and surface defects, which significantly promote the oxidation of gaseous benzene. The addition of Co3O4 also significantly enhances the catalyst's recycling capacity, allowing it to rapidly decompose both low-concentration gaseous benzene volatilizing in the atmosphere and high-concentration gaseous benzene from industrial production or leaks. This invention is one of the most promising photocatalysts for decomposing gaseous benzene, offering advantages such as cost-effectiveness, environmental friendliness, and low cost, potentially enabling rapid purification of gaseous benzene from industrial production or leaked waste gases. Summary of the Invention

[0004] The present invention aims to prepare a carbon cloth-deposited manganese-cobalt oxide composite photocatalytic material for rapid purification of low, medium, and high concentration gaseous benzene. The specific technical scheme of the preparation method is as follows:

[0005] Step 1: Ammoniated carbon cloth (ACC) treatment

[0006] Commercially available carbon cloth was cut into appropriate sizes and ultrasonically cleaned in analytically pure anhydrous acetone, analytically pure anhydrous ethanol, and deionized water to remove surface impurities. The cleaned carbon cloth was then soaked in 30% ammonia for 24 hours, rinsed, and dried to obtain ACC. The selected carbon cloth had a thickness of 300–500 μm and could be cut to any desired size. The ultrasonication time in acetone, ethanol, and water was 20 minutes per sample.

[0007] Step 2: MnO x Preparation of (abbreviated as Mn@ACC-X)

[0008] 0.63 g of manganese nitrate tetrahydrate and 0.62 g of manganese acetate tetrahydrate were fully dissolved in 50 mL of aqueous solution. A three-electrode system was used to deposit the samples at 1.1 V, 1.3 V, 1.5 V, and 1.7 V at room temperature for 3000 s. The samples were then washed, dried, and calcined. The temperature was increased to 400 °C at a rate of 2 °C / min and kept constant for 120 min in air atmosphere to obtain Mn@ACC-1.1, Mn@ACC-1.3, Mn@ACC-1.5, and Mn@ACC-1.7.

[0009] Step 3: Preparation of manganese cobalt oxide composite photocatalytic material (abbreviated as Mn / Co@ACC)

[0010] 0.73 g of cobalt nitrate hexahydrate and 0.63 g of cobalt acetate tetrahydrate were fully dissolved in 50 mL of aqueous solution. Using a three-electrode system, Mn@ACC-1.5 in step 2 was further deposited with Co3O4 for 800 s. The product was washed, dried, and calcined. The temperature was increased to 400 °C at a heating rate of 2 °C / min and kept constant for 120 min in the air atmosphere to obtain Mn / Co@ACC.

[0011] Application of the catalyst material prepared in the present invention in the decomposition of gaseous benzene:

[0012] The prepared Mn / Co@ACC was placed in a square closed reactor equipped with an air circulation device and purged with nitrogen to exhaust the carbon dioxide in the reactor. Gaseous benzene was transferred into the reactor by air bubbling, and the concentration was controlled by adjusting the airflow. A 300 W xenon lamp was used as the light source. The changes in the benzene concentration in the reaction gas were detected by a gas infrared detector and gas chromatography, and the decomposition activity and mineralization rate of gaseous benzene at different concentrations were determined.

[0013] The beneficial effects of the present invention are:

[0014] 1. This invention combines carbon cloth with manganese-cobalt oxide for the first time. The electrodeposition method used effectively adheres the sample to the surface of the carbon cloth, preventing it from falling off and causing particle contamination. Furthermore, the carbon cloth can be adapted to various shapes and sizes during use.

[0015] 2. The uniqueness of this invention is that the ratio between oxides can be adjusted by changing the voltage, and the photocatalytic activity can be further controlled. MnO is prepared by deposition method. x (MnO2 and Mn5O8) heterogeneous structure, simple and convenient preparation, low price, suitable for large-scale industrial production. x The advantages of rich valence structure and surface defects enhance the oxidizability of the material, making it have good application prospects in purifying gaseous benzene;

[0016] 3. The present invention uses distributed deposition to further deposit MnO on Co3O4 x On the surface, the synergistic effect of CoMn effectively inhibits the generation of CO and effectively resists the photocorrosion of the material;

[0017] 4. The present invention has a rapid response capability to low, medium and high concentrations of gaseous benzene. It can not only remove low concentrations of gaseous benzene in the atmosphere, but also provide a possibility for emergency treatment of gaseous benzene leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The XRD patterns of the prepared Mn@ACC-X and Mn / Co@ACC materials at different deposition voltages are shown. When different deposition voltages are used, the crystal phases of the synthesized manganese oxides differ, showing a transition from MnO2 to Mn5O8. When the electrolyte solution contains only cobalt salts, pure Co3O4 is obtained. Meanwhile, the corresponding Mn / Co@ACC exhibits peaks of both manganese and cobalt oxides.

[0019] Figure 2 Scanning electron micrographs of the prepared samples (from ad) are Mn@ACC-1.1, Mn@ACC-1.3, Mn@ACC-1.5, Mn@ACC-1.7, Mn / Co@ACC, and Co@ACC. SEM results show that as the deposition voltage increases, the particles gradually assemble into irregular, wrinkled nanosheets. The spacing between the wrinkled nanosheets increases with the deposition voltage, resulting in a rough surface. After composite formation, the Mn / Co@ACC nanosheets transform into a fully open, dispersed, petal-like structure.

[0020] Figure 3This is the in situ diffuse reflectance Fourier transform infrared spectrum of Mn / Co@ACC. Before the experiment, the sample was treated in a benzene atmosphere balanced with 20% oxygen and 80% nitrogen. Six stable benzene adsorption bands were detected during the dark reaction at room temperature. 1037, 1485 cm -1 The absorption bands at 1814 and 1957 cm are the C–H plane bending vibration and C–C skeleton stretching vibration of the aromatic ring. -1 and 3045, 3087 cm -1 The bands at 1645 and 1697 cm-1 can be attributed to the combined bands of C–H bending vibration and C–H stretching mode, respectively. As the irradiation time increases, the adsorption of gaseous benzene on the catalyst surface gradually weakens, and some new infrared spectra appear. For example, the bands at 1645 and 1697 cm-1 -1 The absorption band at 1506 cm-1 is probably due to the C=O stretching vibration of quinone or other ketone species. -1 1560 cm -1 The band at 1457 cm is attributed to the stretching vibration of COOH on the acetate surface. -1 The band at 3600–3750 cm is attributed to maleate species. In addition, the absorption band of free water is at 3600–3750 cm -1 It is clearly visible everywhere;

[0021] Figure 4 Figure 2 shows the benzene oxidation study of the prepared catalyst under sunlight irradiation. Figure a shows the performance of 1000 ppm gaseous benzene oxidation removal, Figure b shows the generation and mineralization rate of the benzene oxidation product CO2, and Figure c shows the production of byproduct CO. For Mn@ACC, the benzene removal effect shows a normal distribution with the change of deposition voltage. The performance is optimal when the voltage is 1.5 V. When the reaction reaches a steady state, Mn@ACC almost completely mineralizes the gaseous benzene. However, it is worth noting that a small amount of byproduct CO is adsorbed on the catalyst surface and reaches a peak of approximately 44.66 ppm at the 6th minute of the oxidation process, which is higher than the national CO safety and health standard (34.37 ppm, 25 °C). In contrast, the Mn / Co@ACC composite material not only increases the degradation rate and mineralization rate of gaseous benzene (99.5%), but most importantly, it also greatly reduces the generation of byproduct CO (15.77 ppm).

[0022] Figure 5The gaseous benzene oxidation cycle diagram of Mn@ACC-1.5 and Mn / Co@ACC. As the number of cycles increases, the benzene degradation rate of Mn@ACC decreases from 100% to 81.15%, and the mineralization efficiency decreases significantly, and the CO content increases significantly. However, the mineralization efficiency and CO yield of Mn / Co@ACC remain almost unchanged in the 60-cycle experiment, indicating that Mn / Co@ACC has better repeatability. This shows that the addition of Co3O4 can greatly improve the stability of the catalyst, enhance its resistance to light corrosion, have high recyclability, and can decompose gaseous benzene in a practical environment;

[0023] Figure 6 The figure shows the oxidation removal performance of Mn / Co@ACC catalyst for gaseous benzene at different concentrations. The figure shows that Mn / Co@ACC has a good effect on the degradation of gaseous benzene at all concentrations. As the concentration increases, the mineralization efficiency decreases. This result can be attributed to the limited conversion of high-concentration benzene, resulting in a decrease in deep oxidation capacity. DETAILED DESCRIPTION

[0024] In this example, a 2×2 cm carbon cloth was used for the experiment. First, the prepared Mn / Co@ACC sample was placed in a square, sealed glass reactor and purged with nitrogen to remove the carbon dioxide from the reactor. Next, gaseous benzene was introduced into the reactor via air bubbling (80% nitrogen and 20% oxygen). The gaseous benzene concentration was controlled by adjusting the airflow, and a 300 W xenon lamp was used to simulate the light source. Finally, a photoacoustic spectroscopic gas monitor was used to monitor the changes in various substances in the reactor every two minutes. This monitor can also simultaneously monitor the concentrations of CO2 and CO. Following these steps, the activity of the prepared catalysts was tested under the same conditions. Under full light irradiation, the Mn / Co@ACC catalyst achieved gaseous benzene conversions of 100%, 100%, 99.8%, and 98.5% at 600 ppm, 800 ppm, 4500 ppm, and 7500 ppm within 30 minutes, respectively. The mineralization rates were also 100%, 99.5%, 80.6%, and 72.3%, respectively.

Claims

1. A method for preparing a carbon cloth-deposited manganese cobalt oxide photocatalyst for rapidly decomposing leaked gaseous benzene, referred to as a method for preparing a Mn / Co@ACC composite photocatalytic material, characterized in that: It includes the following 3 steps: Step 1: Ammoniated treatment of carbon cloth, referred to as ACC preparation The carbon cloth was cut into appropriate sizes and placed in analytical pure anhydrous acetone, analytical pure anhydrous ethanol, and water for ultrasonic cleaning to clean impurities on the surface of the carbon cloth. Then, the dried carbon cloth was soaked in a 30% ammonia solution for 24 hours, washed, and dried to obtain ACC. Step 2: Preparation of manganese oxide material deposited on carbon cloth, referred to as Mn@ACC-X 0.63 g of manganese nitrate tetrahydrate and 0.62 g of manganese acetate tetrahydrate were dissolved in 50 mL of aqueous solution. Then, electrodeposition was performed using a three-electrode system at room temperature for 3000 s. The deposited sample was washed and calcined to obtain Mn@ACC-X, where X represents the deposition voltage of 1.5 V. Step 3: Preparation of manganese cobalt oxide composite photocatalytic material deposited on carbon cloth, referred to as Mn / Co@ACC composite photocatalytic material 0.73 g of cobalt nitrate hexahydrate and 0.63 g of cobalt acetate tetrahydrate were fully dissolved in 50 mL of aqueous solution and further deposited on the Mn@ACC-1.5 material in step 2 using a three-electrode system for 800 s. The deposit was washed, dried, and calcined to obtain a Mn / Co@ACC composite photocatalytic material.

2. Application of the Mn / Co@ACC composite photocatalytic material prepared by the preparation method according to claim 1 in the decomposition reaction of gaseous benzene, characterized in that: The prepared Mn / Co@ACC composite photocatalytic material was placed in a square closed reactor equipped with an air circulation device and purged with nitrogen to exhaust the carbon dioxide in the reactor; gaseous benzene was transferred into the reactor by air bubbling, and the concentration was controlled by adjusting the airflow. A 300W xenon lamp was used as the light source; a gas infrared detector and gas chromatography were used to detect changes in the benzene concentration in the reaction gas, and the decomposition activity and mineralization rate of gaseous benzene at different concentrations were determined.

3. The use according to claim 2, characterized in that The experimental conditions completely simulate the atmospheric environment.

4. The use according to claim 2, characterized in that Using the composite photocatalytic material Mn / Co@ACC, 7500ppm of gaseous benzene was decomposed into carbon dioxide and water within 30 minutes using a xenon lamp to simulate sunlight, with a decomposition rate of 98.5% and a mineralization rate of 72.3%.

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