Graphite carbon and monatomic manganese co-modified carbon nitride catalyst and application thereof

Abstract

The invention discloses a graphite carbon and monatomic manganese co-modified carbon nitride catalyst, which is prepared by taking 5-amino-1H-tetrazole, manganese chloride and glucose as precursors and synchronously anchoring manganese monatomic and graphite carbon in C3N5 through a thermal polymerization method. Wherein the introduction of manganese single atoms provides a large number of ozone adsorption and activation sites, the existence of graphite carbon enhances the electron transfer ability of a reaction system, and the synergistic effect of manganese single atoms and graphite carbon accelerates the chain reaction process of converting ozone into active oxygen species, so that the catalyst shows excellent performance in ozonization of organic pollutants. Through detection, the degradation rate of the obtained catalyst to phenol within 30 min reaches 98%, the mineralization rate of the catalyst to phenol within 60 min reaches 96.9%, the activity loss is only 4.4% after 5 cycles, the loss of metal manganese ions is low (less than 0.04 mg / L), and the catalyst has the advantages of simple preparation and low raw material cost, and is suitable for efficient deep treatment of complex organic wastewater.

Description

Technical Field

[0001] This invention belongs to the field of advanced oxidation water treatment technology, specifically relating to a carbon nitride catalyst co-modified with graphite carbon and single-atom manganese. By simultaneously introducing manganese single-atom active centers and graphite carbon, this catalyst can significantly improve ozone activation efficiency, and thus can be used for the efficient degradation of water-soluble organic pollutants in wastewater. Background Technology

[0002] Currently, industrial wastewater contains some persistent organic pollutants (such as phenol and bisphenol A), and traditional wastewater treatment technologies such as physical adsorption, flocculation, and biochemical methods are difficult to achieve deep mineralization of these organic pollutants. In recent years, researchers have proposed using advanced oxidation technologies to treat pollutants in water. Among these, ozone catalytic oxidation technology has become a research hotspot due to its advantages such as rapid reaction and no secondary pollution. However, its core bottleneck lies in the poor selectivity of direct oxidation of ozone molecules (O3). It is necessary to use highly efficient catalysts to activate ozone to generate reactive species such as hydroxyl radicals (·OH) and superoxide radicals (·O2⁻) to mineralize organic pollutants.

[0003] Currently, catalysts used for ozone activation are mainly divided into two categories: transition metal-based catalysts and non-metallic catalysts. While transition metal (such as Co, Fe, Mn, etc.)-based catalysts possess high catalytic activity, they pose a risk of metal ion dissolution in practical applications, potentially leading to secondary pollution, and exhibit poor long-term operational stability. Non-metallic catalysts, such as graphitic carbon nitride (g-C3N4), while exhibiting good chemical stability and environmental friendliness, have limited electron conductivity, resulting in low catalytic efficiency. On the other hand, traditional single-atom catalysts, although theoretically possessing the highest atom utilization rate, are prone to metal atom migration and aggregation during preparation and reaction, leading to a reduction in active sites and a decline in catalytic performance. Therefore, developing a novel, highly efficient, and stable single-atom-based heterogeneous catalyst is of great significance for promoting the practical application of ozone catalytic oxidation technology. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon nitride catalyst co-modified with graphite carbon and single-atom manganese catalyst. It is simple to synthesize and easy to operate, and exhibits good catalytic activity in catalyzing the mineralization of organic pollutants by ozone, and has good application prospects.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A carbon nitride catalyst co-modified with graphite carbon and single-atom manganese is obtained by thermal polymerization of 5-amino-1H-tetrazole, manganese chloride and glucose to obtain a C3N5 catalyst co-modified with graphite carbon and manganese. The introduced graphite carbon increases the conductivity of the catalyst, while manganese is dispersed in the C3N5 framework in the form of single atoms and serves as an active site for activating ozone to degrade organic pollutants.

[0006] Furthermore, the preparation of the carbon nitride catalyst co-modified with graphite carbon and single-atom manganese includes the following steps: 1) Dissolve 5-amino-1H-tetrazole and manganese chloride in water, stir and evaporate to dryness, then add glucose and grind evenly to obtain a solid mixture; 2) The resulting solid mixture was calcined in a muffle furnace to obtain a black solid powder; 3) The obtained black solid powder was dispersed in sulfuric acid solution and stirred for 10-15 h. After washing and drying, the C3N5 catalyst co-modified with graphite carbon and single-atom manganese was obtained.

[0007] Furthermore, in step 1), the mass ratio of manganese chloride to 5-amino-1H-tetrazole is 1:100~200, and the mass ratio of glucose to 5-amino-1H-tetrazole is 1:10~100.

[0008] Furthermore, the grinding time described in step 1) is 5 to 15 minutes.

[0009] Furthermore, the calcination described in step 2) is carried out in an air atmosphere, with the temperature increased to 500-600 ℃ at a rate of 5-10 ℃ / min, and held at that temperature for 2-10 hours.

[0010] Furthermore, the concentration of the sulfuric acid solution in step 3) is 0.5~1.5 mol / L.

[0011] The carbon nitride catalyst co-modified with graphite carbon and single-atom manganese can catalyze ozone activation, thereby effectively degrading organic pollutants in water.

[0012] Furthermore, the conditions for the catalytic reaction are an ozone concentration of 5-50 mg / L and a catalyst dosage of 0.1-0.3 g / L.

[0013] Furthermore, the organic pollutants include phenol, p-nitrophenol, bisphenol A, p-chlorophenol, and oxalic acid.

[0014] Compared with the prior art, the present invention has the following advantages: (1) The present invention prepared a C3N5 catalyst co-modified with graphite carbon and single-atom manganese by one-step thermal polymerization. The synergistic effect of graphite carbon and single-atom manganese can significantly improve the mineralization rate of organic pollutants in water by ozone, and achieve a good effect of removing pollutants. Its effect is significantly better than that of pure C3N5, C3N5 modified with single-atom manganese and C3N5 modified with graphite carbon, and the metal ion leaching rate is low.

[0015] (2) The method of the present invention is simple, the raw materials are inexpensive, the reaction conditions are mild, the production cost is low, it is green and environmentally friendly, and it is suitable for large-scale production. Attached Figure Description

[0016] Figure 1 The XRD patterns are of the catalysts prepared in Examples 1-6.

[0017] Figure 2 Fourier transform infrared spectra of the catalysts prepared in Examples 1-6.

[0018] Figure 3 The image shows a spherical aberration transmission electron microscope (TEM) image of Mn-C3N5-C prepared in Example 4.

[0019] Figure 4 The diagram shows the activity of the catalysts prepared in Examples 1-6 in the reaction of activated ozone mineralization of phenol.

[0020] Figure 5 The experimental activity diagrams of the catalysts prepared in Examples 1-4 in the mineralization reaction of phenol by activated ozone cycle are shown.

[0021] Figure 6 The cyclic activity and manganese ion leaching concentration of the catalyst prepared in Example 4 in the activated ozone mineralization reaction. Figure 7 The graph shows the cyclic activity of the catalyst prepared in Example 5 in the activated ozone mineralization of phenol and the leaching concentration of manganese ions.

[0022] Figure 8 The graph shows the cyclic activity of the catalyst prepared in Example 6 in the activated ozone mineralization of phenol and the leaching concentration of manganese ions.

[0023] Figure 9 The graph shows a comparison of the activity of the catalysts prepared in Examples 1-4 in activating ozone to mineralize different pollutants. Detailed Implementation

[0024] A carbon nitride catalyst co-modified with graphitic carbon and single-atom manganese is prepared by the following steps: 1) Dissolve 5-amino-1H-tetrazole and manganese chloride in water, stir and evaporate to dryness, then add glucose and grind for 5-15 min to make it uniform, to obtain a solid mixture; wherein the mass ratio of manganese chloride to 5-amino-1H-tetrazole is 1:100-200, and the mass ratio of glucose to 5-amino-1H-tetrazole is 1:10-100. 2) The obtained solid mixture is heated to 500-600 ℃ in a muffle furnace in an air atmosphere at a rate of 5-10 ℃ / min, and calcined for 2-10 h to obtain a black solid powder. 3) The obtained black solid powder was dispersed in a 0.5~1.5 mol / L sulfuric acid solution and stirred for 10~15 h. After washing and drying, the C3N5 catalyst co-modified with graphite carbon and single-atom manganese was obtained.

[0025] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0026] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0027] Example 1: 10 g of 5-amino-1H-tetrazole was placed in a crucible and calcined in a muffle furnace at 550 °C for 3 h. The resulting sample was then dispersed in a 1 mol / L sulfuric acid solution and stirred for 12 h. After washing and drying, pure C3N5 catalyst was obtained.

[0028] Example 2: 10 g of 5-amino-1H-tetrazole and 0.3 g of glucose were ground thoroughly for 10 min. The resulting mixture was then transferred to a crucible and calcined in a muffle furnace at 550 °C for 3 h. The resulting sample was then dispersed in a 1 mol / L sulfuric acid solution and stirred for 12 h. After washing and drying, a graphite carbon-modified C3N5 catalyst was obtained, labeled as C3N5-C.

[0029] Example 3: 10 g of 5-amino-1H-tetrazole and 70 mg of manganese chloride tetrahydrate were dissolved in water, stirred at 70 °C for 1 h, and then evaporated to dryness at 110 °C. The evaporated sample was then thoroughly ground for 10 min. The resulting mixture was then transferred to a crucible and calcined in a muffle furnace at 550 °C for 3 h. The resulting sample was then dispersed in a 1 mol / L sulfuric acid solution and stirred for 12 h. After washing and drying, a manganese single-atom modified Mn-C3N5 catalyst was obtained, labeled as Mn-C3N5.

[0030] Example 4: 10 g of 5-amino-1H-tetrazole and 70 mg of manganese chloride tetrahydrate were dissolved in water, stirred at 70 °C for 1 h, and then evaporated to dryness at 110 °C. The evaporated sample and 0.3 g of glucose were placed in a mortar and ground thoroughly for 10 min. The resulting mixture was then transferred to a crucible and calcined in a muffle furnace at 550 °C for 3 h. The resulting sample was then dispersed in a 1 mol / L sulfuric acid solution and stirred for 12 h. After washing and drying, a C3N5 catalyst co-modified with graphite carbon and single-atom manganese was obtained, labeled as Mn-C3N5-C.

[0031] Example 5: 10 g of 5-amino-1H-tetrazole and 31 mg of manganese dioxide were dispersed in water, stirred at 70 °C for 1 h, and then evaporated to dryness at 110 °C. The evaporated sample and 0.3 g of glucose were placed in a mortar and ground thoroughly for 10 min. The resulting mixture was then transferred to a crucible and calcined in a muffle furnace at 550 °C for 3 h. The resulting sample was then dispersed in a 1 mol / L sulfuric acid solution and stirred for 12 h. After washing and drying, a C3N5 catalyst co-modified with manganese oxide and graphite carbon was obtained, labeled as MnO2-C3N5-C.

[0032] Example 6: 10 g of powdered activated carbon and 70 mg of manganese chloride tetrahydrate were dispersed in water, stirred at 70 °C for 1 h, and then evaporated to dryness at 110 °C. The evaporated sample was placed in a mortar and ground thoroughly for 10 min. The resulting mixture was then transferred to a crucible and calcined in a muffle furnace at 550 °C for 3 h. The resulting sample was then dispersed in a 1 mol / L sulfuric acid solution and stirred for 12 h. After washing and drying, a single-atom manganese-modified activated carbon catalyst was obtained, labeled as Mn-AC.

[0033] Application Examples: The following reactions were carried out using pure C3N5, C3N5-C, Mn-C3N5, Mn-C3N5-C, MnO2-C3N5-C, and Mn-AC as catalysts, respectively. 20 mg of catalyst was added to a 200 mL reactor, followed by 150 mL of simulated organic wastewater (containing phenol solution, p-nitrophenol solution, bisphenol A solution, p-chlorophenol solution, and oxalic acid solution, all at concentrations of 30 mg / L), and the mixture was stirred for 30 min to allow the catalyst adsorption to reach equilibrium. Ozone gas was then introduced into the reactor at a flow rate of 50 mL / min and a concentration of 10 mg / L to initiate the degradation and mineralization reaction. The reaction time was 60 min, with samples taken every 20 min. The samples were filtered through a 0.22 μm microporous membrane, and then a small amount of 0.1 mol / L Na2S2O3 solution was added to quench any residual O3 in the samples. The total organic carbon in the solution was analyzed using a TOC-V CPH analyzer (Shimadzu). After the reaction, the catalyst was recovered by filtration, washed three times each with deionized water and anhydrous ethanol, and dried for 4-5 hours. The resulting catalyst was then added back into the reactor for recycling.

[0034] Figure 1The XRD patterns of the catalysts prepared in Examples 1-6 are shown. Two characteristic diffraction peaks are visible in the C3N5 spectrum, located at 13.6° and 27.4°, corresponding to the (100) and (002) crystal planes, respectively. Furthermore, no other diffraction peaks were observed after the introduction of single-atom manganese and graphitized carbon, indicating that the modified catalysts maintained the structural integrity of C3N5 and that the supported manganese species were highly dispersed. In addition, the intensity of the (002) diffraction peak was significantly weakened in the Mn-C3N5, C3N5-C, and Mn-C3N5-C samples, indicating that the co-modification of manganese and graphitized carbon increased the degree of disorder in the C3N5 structure.

[0035] Figure 2 The Fourier transform infrared (FTIR) spectra of the catalysts prepared in Examples 1-6 are shown. As can be seen from the MnO2-C3N5-C spectrum, the overall molecular structure of C3N5 was not disrupted after the introduction of single-atom manganese and graphitic carbon.

[0036] Figure 3 The image shows aberration-corrected transmission electron microscopy (TEM) image of Mn-C3N5-C prepared in Example 4. The image confirms that manganese atoms are incorporated into C3N5 in the form of isolated single atoms.

[0037] Figure 4 The figures show the activity of the catalysts in Examples 1-6 in the phenol mineralization reaction with activated ozone. The figures indicate that the Mn-C3N5-C catalyst has a significantly higher efficiency in mineralizing phenol than the C3N5, C3N5-C, Mn-C3N5, MnO2-C3N5-C, and Mn-AC catalysts.

[0038] Figure 5 The images show the experimental activity of the catalysts used in Examples 1-4 for the cyclic mineralization of phenol. The results indicate that Mn-C3N5-C maintains high activity after five cycles, outperforming pure C3N5, C3N5-C, and Mn-C3N5.

[0039] Figure 6 The graph shows the cyclic activity and manganese ion leaching concentration of the Mn-C3N5-C mineralized phenol prepared in Example 4. As can be seen from the graph, the manganese ion leaching concentration of Mn-C3N5-C is less than 0.04 mg / L.

[0040] Figure 7 The figure shows the cycling activity and manganese ion leaching concentration of the MnO2-C3N5-C mineralized phenol prepared in Example 5. As can be seen from the figure, the activity of MnO2-C3N5-C decreased significantly after five cycles, and the manganese ion leaching concentration was relatively high, indicating that Mn-C3N5-C has a better anchoring effect on manganese ions.

[0041] Figure 8The figure shows the cyclic activity of mineralized phenol with Mn-AC prepared in Example 6 and the manganese ion leaching concentration. As can be seen from the figure, the activity of Mn-AC also decreased significantly after five cycles, and the manganese ion leaching concentration was 0.3-0.5 mg / L.

[0042] Figure 9 The figures show the mineralization rates of different organic pollutants after 60 minutes of reaction for pure C3N5, C3N5-C, Mn-C3N5, and Mn-C3N5-C prepared in Examples 1-4. The data in the figures show that the Mn-C3N5-C catalyst exhibits good versatility in the treatment of organic wastewater.

[0043] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A carbon nitride catalyst co-modified with graphite carbon and single-atom manganese, characterized in that: A C3N5 catalyst co-modified with graphite carbon and manganese was obtained by thermal polymerization of 5-amino-1H-tetrazole, manganese chloride and glucose. The introduced graphite carbon increased the conductivity of the catalyst, while manganese was dispersed in the C3N5 framework in the form of single atoms and served as an active site to activate ozone to degrade organic pollutants.

2. The carbon nitride catalyst according to claim 1, characterized in that: The mass ratio of manganese chloride to 5-amino-1H-tetrazole used is 1:100~200, and the mass ratio of glucose to 5-amino-1H-tetrazole used is 1:10~100.

3. The carbon nitride catalyst according to claim 1, characterized in that: The thermal polymerization method involves heating the material to 500-600 °C at a rate of 5-10 °C / min in an air atmosphere and then holding it at that temperature for 2-10 h.

4. The application of a carbon nitride catalyst co-modified with graphite carbon and single-atom manganese as described in claim 1 in the catalytic ozone-activated degradation of organic pollutants in water.

5. The application according to claim 4, characterized in that: The conditions for the catalytic reaction are an ozone concentration of 5-50 mg / L and a catalyst dosage of 0.1-0.3 g / L.

6. The application according to claim 4, characterized in that: The organic pollutants include phenol, p-nitrophenol, bisphenol A, p-chlorophenol, and oxalic acid.

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