Cellulose biochar supported graphite phase carbon nitride catalytic material and preparation method and application thereof

Abstract

A cellulose biochar loaded graphite phase carbon nitride catalytic material and a preparation method and application thereof are provided, and the specific method is as follows: cellulose and urea are uniformly mixed, the mass percentage of cellulose is controlled to be 2-20%, the mixture is placed in a muffle furnace for one-step pyrolysis at 500-600 DEG C, and the obtained product is the cellulose biochar loaded graphite phase carbon nitride catalytic material. The catalytic material takes carbon material as a support, graphite phase carbon nitride is loaded on the surface, the dispersibility is greatly improved, more active sites are exposed, high-efficiency activation of peroxymonosulfate (PMS) is realized under the catalytic condition without ultraviolet or visible light, degradation of ofloxacin in water environment is realized, a wide pH range can be adapted, the influence of background chloride ions and humic acid can be resisted, and the reusability is better. The raw material is easy to obtain and economic and environmental protection, the one-step pyrolysis method is simple in operation and high in repeatability, and the practical application range is wide.

Description

Technical Field

[0001] This invention relates to the field of functional composite materials technology, specifically to a cellulose biochar-supported graphite-phase carbon nitride catalytic material, its preparation method, and its application. Background Technology

[0002] Ofloxacin (OFL), a fluoroquinolone antibiotic, is widely used in the pharmaceutical field and is released into the environment through human metabolism and pharmaceutical wastewater. Because it is difficult to biodegrade and wastewater treatment systems cannot completely remove it, it poses a threat to the aquatic environment and human health.

[0003] Advanced oxidation technologies (AORs) are one of the traditional treatment techniques for removing antibiotics from water. Common AORs include Fenton oxidation, photocatalytic oxidation, ozone oxidation, and electrochemical oxidation. These technologies utilize hydroxyl radicals generated in the system, which have strong oxidizing properties and effectively remove recalcitrant organic pollutants. Persulfate (PS) AORs, compared to traditional hydroxyl radical-based AORs, exhibit higher reaction stability, greater adaptability to wastewater, and the persulfates used are easier to store and transport, thus attracting widespread attention from researchers in recent years. Commonly used persulfates include permonosulfate (PMS) and perdisulfate (PDS). PMS, with its asymmetric structure, is more easily activated than PDS. Studies have shown that ultraviolet light, heat, alkalis, and transition metals can activate persulfates; however, these activation methods suffer from drawbacks such as high energy consumption, high cost, harsh reaction conditions, and potential secondary pollution from heavy metals. Therefore, developing novel activators has become a hot topic in persulfate AOR research.

[0004] Graphitic carbon nitride (g-C3N4) is a conjugated polymer semiconductor with high stability, non-toxicity, and resistance to acids and alkalis. Its relatively narrow band gap (approximately 2.7 eV) endows it with excellent light absorption capabilities, thus it is commonly used as a photocatalyst. g-C3N4 is rich in carbon and nitrogen elements and has been attempted as an activator for PMS in recent years; however, its activation performance has generally been poor. Therefore, it is necessary to develop a novel graphitic carbon nitride composite material for activating PMS to degrade ofofloxacin in water under photocatalytic-free conditions. Summary of the Invention

[0005] Technical Problem Solved: Addressing the problems existing in the prior art, this invention proposes a cellulose biochar-supported graphitic carbon nitride catalytic material, its preparation method, and its applications. This catalytic material uses carbon materials as a support, with graphitic carbon nitride loaded on top, significantly improving dispersibility and exposing more active sites. It achieves highly efficient activation of PMS for the degradation of ofloxacin in the water environment under conditions without ultraviolet or visible light catalysis, and exhibits excellent reusability. The raw materials used in this invention are readily available, economical, and environmentally friendly. The one-step pyrolysis method is simple to operate, highly reproducible, and has a wide range of practical applications.

[0006] Technical solution: A method for preparing cellulose biochar-supported graphite phase carbon nitride catalytic material, comprising the following steps: mixing cellulose and urea evenly, controlling the cellulose mass ratio to be 2-20%, placing the mixture in a muffle furnace for one-step pyrolysis at 500-600℃, and obtaining the product as cellulose biochar-supported graphite phase carbon nitride catalytic material.

[0007] Preferably, the cellulose content is controlled at 4%.

[0008] Preferably, cellulose and urea are mixed evenly and then transferred to a covered ceramic crucible, which is then placed in a muffle furnace for pyrolysis.

[0009] Preferably, the mixture is placed in a muffle furnace and heated from room temperature to the pyrolysis temperature of 500-600°C at a heating rate of 5-10°C / min, and held at this temperature for 1-3 hours. After natural cooling, it is removed and stored in a desiccator. The resulting product is cellulose biochar supported graphite phase carbon nitride catalyst.

[0010] Preferably, the mixture is placed in a muffle furnace and heated from room temperature to the pyrolysis temperature of 550°C at a heating rate of 5°C / min, and held at this temperature for 3 hours. After natural cooling, it is removed and stored in a desiccator. The resulting product is cellulose biochar supported graphite phase carbon nitride catalyst.

[0011] Cellulose biochar-supported graphite-phase carbon nitride catalytic material was prepared based on the above method.

[0012] Based on the above application of cellulose biochar-supported graphitic carbon nitride catalyst in the removal of ofloxacin from water by PMS activation under photocatalytic-free conditions, the optimal concentration of the cellulose biochar-supported graphitic carbon nitride catalyst is recommended to be 0.1-1 g / L, corresponding to a PMS concentration of 1-10 mmol / L and an ofloxacin concentration of 5-20 mg / L.

[0013] Beneficial effects: 1. Unlike other carbon materials combined with graphite phase carbon nitride, this invention uses 50μm commercial cellulose as a carbon source, which is directly mixed with urea and obtained by one-step pyrolysis. The raw materials are not only readily available, pure and inexpensive, but also do not require complicated pretreatment. The method is simple, economical, more repeatable and environmentally friendly.

[0014] 2. Unlike existing catalytic materials that have a narrow pH range and low degradation rate under acidic or alkaline conditions, the cellulose biochar-supported graphite-phase carbon nitride catalytic material provided by this invention has a wide range of adaptability. It can efficiently activate PMS and complete the degradation of ofloxacin in the pH range of 3 to 12, and is not affected by chloride ions and humic acid (HA) in the background water. In fact, the degradation of ofloxacin is promoted in the presence of chloride ions.

[0015] 3. Unlike the original graphitic carbon nitride and graphitic carbon nitride composite materials, which require UV or visible light catalysis to activate persulfate and have poor performance without UV or visible light catalysis, the cellulose biochar-supported graphitic carbon nitride catalytic material in this invention can efficiently activate PMS without photocatalysis and completely degrade ofloxacin in 120 min.

[0016] 4. The cellulose biochar-supported graphite-phase carbon nitride catalytic material provided by this invention has excellent stability. After five cycles, the final degradation rate of ofloxacin can still reach 94.6%. Attached Figure Description

[0017] Figure 1 The images show scanning electron microscope (SEM) images of the cellulose biochar-supported graphitic carbon nitride catalyst (4% CEB550 / g-C3N4) prepared in Example 1, and the original cellulose biochar and graphitic carbon nitride prepared in Comparative Examples 1 and 2, respectively. In the figure, (a) is the SEM image of the original cellulose biochar CEB550 prepared in Comparative Example 1, (b) is the SEM image of the graphitic carbon nitride g-C3N4 prepared in Comparative Example 2, and (c) is the SEM image of the cellulose biochar-supported graphitic carbon nitride catalyst 4% CEB550 / g-C3N4 prepared in Example 1.

[0018] Figure 2 The figures show the X-ray photoelectron spectroscopy (XPS) spectra of nitrogen and oxygen in the three carbon materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention. In the figures, (a) is the N1s spectrum of g-C3N4 prepared in Comparative Example 2, (b) is the N1s spectrum of 4%CEB550 / g-C3N4 prepared in Example 1, and (c) is the O1s spectrum of the three materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention.

[0019] Figure 3 The graph shows a comparison of the degradation efficiency of ofloxacin by the carbon materials prepared in Example 1 and Comparative Examples 1 and 2.

[0020] Figure 4 The graph shows a comparison of the degradation efficiency of ofloxacin by cellulose biochar-supported graphite-phase carbon nitride catalysts with different cellulose mass ratios prepared in Examples 1 and 2.

[0021] Figure 5 The graph shows a comparison of the activation efficiency of cellulose biochar-supported graphite-phase carbon nitride catalysts for the degradation of ofloxacin by PMS prepared at different temperatures in Examples 1 and 3.

[0022] Figure 6 The degradation efficiency of ofloxacin by 4% CEB550 / g-C3N4 provided in Example 1 of this invention under different pH conditions.

[0023] Figure 7 The figure shows the effect of the presence of chloride ions and humic acid on the degradation of ofloxacin by 4% CEB550 / g-C3N4 provided in Example 1 of the present invention. Figure (a) shows the effect of different concentrations of chloride ions on the degradation of ofloxacin by 4% CEB550 / g-C3N4 provided in Example 1 of the present invention, and (b) shows the effect of different concentrations of humic acid (HA) on the degradation of ofloxacin by 4% CEB550 / g-C3N4 provided in Example 1 of the present invention.

[0024] Figure 8 The diagram shows the cyclic stability of 4% CEB550 / g-C3N4 provided in Example 1 of this invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] The raw materials, reagents, sources, and specifications of this invention are as follows:

[0027] Cellulose, particle size 50 μm, analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0028] Urea, analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0029] Potassium persulfate (PMS), analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0030] All other reagents in this invention are commercially available products. Unless otherwise specified, the materials and reagents described in the following examples are all commercially available.

[0031] Cellulose was dried in a vacuum drying oven at 80°C for 24 hours before use, and then placed in a desiccator for later use. Newly opened, non-hygroscopic urea was also used. Deionized water was used in this experiment.

[0032] Example 1: Cellulose biochar-supported graphite-phase carbon nitride catalyst (4% CEB550 / g-C3N4)

[0033] The specific preparation method is as follows:

[0034] A certain amount of cellulose and urea were weighed and thoroughly mixed, with a total mass of 50g of cellulose and urea and a cellulose mass ratio of 4%. After uniform mixing, the mixture was transferred to a covered ceramic crucible and placed in a muffle furnace. The temperature was increased from room temperature to 550℃ at a rate of 5℃ / min. The mixture was then pyrolyzed at this temperature for 3 hours. After naturally cooling to room temperature, the product, cellulose biochar supported on graphite phase carbon nitride catalyst, was obtained and denoted as 4%CEB550 / g-C3N4.

[0035] Comparative Example 1: Cellulose Biochar (CEB550)

[0036] 50g of cellulose was weighed separately and placed in a covered ceramic crucible for high-temperature pyrolysis. The pyrolysis conditions were the same as those described in Example 1, and cellulose biochar was obtained, denoted as CEB550.

[0037] Comparative Example 2: Graphite-phase carbon nitride (g-C3N4)

[0038] 50g of urea was weighed separately and placed in a covered ceramic crucible for high-temperature pyrolysis. The pyrolysis conditions were the same as those described in Example 1, which yielded graphitic carbon nitride, denoted as g-C3N4.

[0039] Figure 1 Scanning electron microscope (SEM) images of the cellulose biochar-supported graphitic carbon nitride catalyst (4% CEB550 / g-C3N4) prepared in Example 1, and the pristine cellulose biochar and graphitic carbon nitride prepared in Comparative Examples 1 and 2, respectively. Figure 1 It can be seen that the original cellulose biochar CEB550 exhibits a relatively regular spherical shape, while g-C3N4 exhibits an irregular flaky and granular aggregate shape with a large aggregate volume. The 4% CEB550 / g-C3N4 retains some of the shape of g-C3N4, and the overall structure shows a shape in which carbon material is supported and graphitic carbon nitride is attached to it, which greatly improves the dispersion of graphitic carbon nitride and thus enhances the exposure of active sites.

[0040] Figure 2XPS spectra of N and O elements of the 4% CEB550 / g-C3N4 provided in Example 1, as well as the original cellulose biochar CEB550 and original graphitic carbon nitride g-C3N4 provided in Comparative Examples 1 and 2, are shown. The results show that cellulose and graphitic carbon nitride were successfully combined. The 4% CEB550 / g-C3N4 retains the nitrogen-containing functional groups of g-C3N4 very well. The introduction of cellulose greatly increases the total oxygen content of the material compared with the original g-C3N4, and the CO / C=O content is significantly increased.

[0041] Example 2: Cellulose biochar-supported graphitic carbon nitride catalytic materials with different cellulose mass ratios (2% CEB550 / g-C3N4, 10% CEB550 / g-C3N4, 20% CEB550 / g-C3N4, 40% CEB550 / g-C3N4)

[0042] The preparation method is as follows:

[0043] Weigh out a certain amount of cellulose and urea and mix them thoroughly. The total mass of cellulose and urea is 50g. Control the mass ratio of cellulose to 2%, 10%, 20%, and 40%, respectively. The remaining steps are the same as in Example 1. The resulting product is cellulose biochar supported graphite phase carbon nitride catalyst material, which is denoted as 2%CEB550 / g-C3N4, 10%CEB550 / g-C3N4, 20%CEB550 / g-C3N4, and 40%CEB550 / g-C3N4, respectively.

[0044] Example 3: Cellulose biochar-supported graphite-phase carbon nitride catalysts (4% CEB500 / g-C3N4, 4% CEB600 / g-C3N4, 4% CEB700 / g-C3N4) calcined at different temperatures

[0045] The preparation method is as follows:

[0046] A certain amount of cellulose and urea were weighed and thoroughly mixed, with a total mass of 50g of cellulose and urea, and the mass percentage of cellulose being 4%. After uniform mixing, the mixture was transferred to a covered ceramic crucible and placed in a muffle furnace. The temperature was increased from room temperature to 500℃, 600℃, and 700℃ at a rate of 5℃ / min, respectively. The mixture was then pyrolyzed at these temperatures for 3 hours. After naturally cooling to room temperature, the mixture was removed to obtain the cellulose biochar-supported graphite-phase carbon nitride catalytic material, which was designated as 4%CEB500 / g-C3N4, 4%CEB600 / g-C3N4, and 4%CEB700 / g-C3N4, respectively.

[0047] Experimental Example 1: Comparison of the activation efficiency of three carbon materials prepared in Example 1 and Comparative Examples 1-2 in degrading of ofloxacin by PMS.

[0048] Add 5 mmol of PMS to 100 mL of ofloxacin solution with an initial concentration of 5 mg / L and shake well. Then weigh 0.05 g of each of the three carbon materials (CEB550, g-C3N4, and 4%CEB550 / g-C3N4) and add them to the solution. Then place the solution in a constant temperature shaker at 25 °C and 120 r / min and shake. Take samples at 15, 30, 60, 120, 180, and 300 min. Inject 1 mL of the sample into a 2.0 mL syringe and filter it through a 0.22 μm nylon membrane. Inject the filtrate into a liquid chromatography vial and cap it. Detect the concentration of residual ofloxacin in the sample using high performance liquid chromatography.

[0049] Depend on Figure 3 It can be seen that, compared with the original cellulose biochar CEB550 and the original g-C3N4, the cellulose biochar supported graphite phase carbon nitride catalyst material 4%CEB550 / g-C3N4 activated PMS prepared in this invention has a significant improvement in the degradation of ofloxacin. In this invention, 4%CEB550 / g-C3N4 can completely degrade ofloxacin in 120 min.

[0050] Experimental Example 2: Comparison of the activation efficiency of cellulose biochar-supported graphitic carbon nitride catalytic materials with different cellulose mass ratios prepared in Examples 1 and 2 for the degradation of ofloxacin by PMS.

[0051] 5 mmol of PMS was added to 100 mL of ofloxacin solution with an initial concentration of 5 mg / L and shaken well. Then, 0.05 g of several different cellulose biochar-supported graphite-phase carbon nitride catalysts with different cellulose mass ratios (2% CEB550 / g-C3N4, 4% CEB550 / g-C3N4, 10% CEB550 / g-C3N4, 20% CEB550 / g-C3N4, 40% CEB550 / g-C3N4) were weighed and added to the solution. The solution was then placed in a constant temperature shaker at 25 °C and 120 r / min and samples were taken at 15, 30, 60, 120, 180, and 300 min. 1 mL of the sample was injected into a 2.0 mL syringe and filtered through a 0.22 μm nylon membrane. The filtrate was injected into a liquid chromatography vial and capped. The concentration of residual ofloxacin in the sample was detected by high performance liquid chromatography.

[0052] Depend on Figure 4 It can be seen that when the cellulose mass ratio is 4%, the prepared cellulose biochar supported graphite phase carbon nitride catalyst 4% CEB550 / g-C3N4 activated PMS has the best effect on the degradation of ofloxacin. As the cellulose mass ratio increases, the degradation efficiency of ofloxacin shows a downward trend.

[0053] Experimental Example 3: Comparison of the activation efficiency of PMS degradation of ofloxacin by cellulose biochar supported on graphite-phase carbon nitride catalysts calcined at different temperatures prepared in Examples 1 and 3.

[0054] 5 mmol of PMS was added to 100 mL of ofloxacin solution with an initial concentration of 5 mg / L and shaken well. Then, 0.05 g of several cellulose biochar-supported graphite-phase carbon nitride catalysts calcined at different temperatures (4% CEB500 / g-C3N4, 4% CEB550 / g-C3N4, 4% CEB600 / g-C3N4, 4% CEB700 / g-C3N4) were weighed and added to the solution. The solution was then shaken in a constant temperature shaker at 25 °C and 120 r / min. Samples were taken at 15, 30, 60, 120, 180, and 300 min. 1 mL of each sample was injected into a 2.0 mL syringe and filtered through a 0.22 μm nylon membrane. The filtrate was injected into a liquid chromatography vial and capped. The concentration of residual ofloxacin in the sample was determined by high performance liquid chromatography.

[0055] Depend on Figure 5 It can be seen that as the calcination temperature increases, the efficiency of the prepared cellulose biochar-supported graphite phase carbon nitride catalyst in activating PMS to degrade ofofloxacin is improved. The material obtained by calcination at 550℃ and above can completely degrade ofofloxacin in 120 min, but after 550℃, the degradation rate of ofloxacin does not increase significantly with the increase of temperature.

[0056] Experimental Example 4: Effect of pH on the degradation of ofloxacin by 4% CEB550 / g-C3N4 activated PMS provided in Example 1

[0057] 100 mL of ofloxacin solution with an initial concentration of 5 mg / L was adjusted to pH 3 and 12 respectively with 1 mmol / L sodium hydroxide and 1 mmol / L sulfuric acid solution (the original ofloxacin solution had a pH of 8). 5 mmol of PMS was added and shaken well. Then, 0.05 g of 4% CEB550 / g-C3N4 provided in Example 1 was weighed and added to the solution. The solution was then placed in a constant temperature shaker at 25 °C and 120 r / min and shaken. Samples were taken at 15, 30, 60, 120, 180, and 300 min. 1 mL of the sample was injected into a 2.0 mL syringe and filtered through a 0.22 μm nylon membrane. The filtrate was injected into a liquid chromatography vial and capped. The concentration of residual ofloxacin in the sample was determined using an Agilent ultra-high performance liquid chromatograph.

[0058] Depend on Figure 6 It can be seen that ofloxacin can be completely degraded at 180 min under three pH conditions, indicating that the 4% CEB550 / g-C3N4 provided in Example 1 can adapt to a wide pH range and ensure a high degradation rate.

[0059] Experimental Example 5: Effects of chloride ions and humic acid on the degradation of ofloxacin by 4% CEB550 / g-C3N4 activated PMS provided in Example 1.

[0060] In a 100 mL of ofloxacin solution with an initial concentration of 5 mg / L, a certain mass of sodium chloride solid (5.85 mg or 58.5 mg) or sodium humate solid (0.5 mg or 1.5 mg) was added to make the chloride ion concentration in the reaction system 1 mmol / L or 10 mmol / L and the humic acid concentration 5 mg / L or 15 mg / L. The remaining steps were the same as in Experiment 1.

[0061] Depend on Figure 7 It can be seen that the addition of chloride ions has little effect on the degradation efficiency of ofloxacin, and both can be basically completely degraded at 120 min. In the presence of 10 mmol / L chloride ions, the degradation rate of ofloxacin is significantly accelerated. The increase of humic acid concentration has a slight inhibitory effect on the degradation of ofloxacin, but under the action of 15 mg / L humic acid, ofloxacin can still be completely degraded at 300 min. Therefore, the 4% CEB550 / g-C3N4 prepared in Example 1 has good stability.

[0062] Experimental Example 6: Investigation into the reusability of 4% CEB550 / g-C3N4 provided in Example 1.

[0063] Add 5 mmol of PMS to 100 mL of ofloxacin solution with an initial concentration of 5 mg / L and shake well. Weigh 0.05 g of 4% CEB550 / g-C3N4 and add it to the solution. Place the solution in a constant temperature shaker at 25℃ and 120 r / min and shake. Take samples at 15, 30, 60, 120, 180, and 300 min. Inject 1 mL of the sample into a 2.0 mL syringe and filter it through a 0.22 μm nylon membrane. Inject the filtrate into a liquid chromatography vial and cap it. Detect the concentration of residual ofloxacin in the sample using high performance liquid chromatography.

[0064] After the reaction was completed, the reaction solution was filtered through a 0.22 μm nylon membrane. The filtered catalyst was collected and dried in a vacuum drying oven at 80 °C. Then it was added to the next reaction and the process was repeated five times. Figure 8 The results show that the 4%CEB550 / g-C3N4 prepared in this invention has good reusability. After five repeated tests, the final degradation rate of ofloxacin can still reach 94.6%.

Claims

1. Application of a cellulose biochar supported graphite phase carbon nitride catalytic material in the activation of PMS under photocatalytic-free conditions to remove ofloxacin in water environment, characterized in that, The pH value of the water environment is 3-12, and the preparation method of the cellulose biochar loaded graphite phase carbon nitride catalytic material is as follows: cellulose and urea are uniformly mixed, the mass percentage of cellulose is controlled to be 2-20%, the mixture is placed in a muffle furnace, the temperature is raised from room temperature to pyrolysis temperature 500-600℃ at a temperature rising rate of 5-10℃ / min, and then kept at the temperature for 1-3h, and then naturally cooled, taken out and placed in a desiccator for storage, and the obtained product is the cellulose biochar loaded graphite phase carbon nitride catalytic material.

2. Use according to claim 1, characterized in that, The mass percentage of cellulose is controlled to be 4%.

3. Use according to claim 1, characterized in that, After the cellulose and urea are uniformly mixed, they are transferred to a covered ceramic crucible, and then pyrolysis is carried out in a muffle furnace.

4. Use according to claim 1, characterized in that, The mixture is placed in a muffle furnace, the temperature is raised from room temperature to pyrolysis temperature 550℃ at a temperature rising rate of 5℃ / min, and then kept at the temperature for 3h.

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