A wastewater treatment method based on methane cracking hydrogen carbon material

Abstract

This invention relates to a wastewater treatment method based on carbon materials used in methane cracking for hydrogen production. The method involves cracking methane to produce hydrogen using an iron-based catalyst, collecting the carbon material byproducts, and utilizing the adsorption properties of carbon nanotubes in the byproducts and the catalytic properties of residual metals (such as iron) in the catalyst, combined with hydroxyl radicals (·OH) generated by the Fenton reaction, to achieve efficient removal of organic pollutants (such as dyes methylene blue and malachite green) from the wastewater. An external magnetic field can be applied to rapidly recover the carbon materials, enabling resource recycling.

Description

Technical Field

[0001] This invention relates to a high-efficiency wastewater treatment technology, specifically to the application of carbon materials, a byproduct of methane cracking for hydrogen production, in wastewater treatment. Background Technology

[0002] Methane cracking is a clean energy technology that decomposes methane into hydrogen and solid carbon. Because the process emits no carbon dioxide, it is considered an ideal low-carbon hydrogen production technology. Compared to traditional steam reforming and partial oxidation methods, methane cracking not only avoids CO2 release during fossil fuel combustion but also produces solid carbon byproducts with high added value. In recent years, how to utilize the solid carbon materials generated by methane cracking has become a research hotspot both domestically and internationally.

[0003] Carbon materials generated from methane cracking include carbon nanotubes, amorphous carbon, graphitic carbon, and carbon nanofibers. The specific properties of these materials depend on the choice of catalyst and the control of reaction conditions. Thanks to their excellent physicochemical properties, these carbon materials have been widely used in energy storage, composite materials, and catalyst supports. However, research on carbon materials for environmental remediation is still in its early stages, especially their potential in water treatment, which has not yet been fully explored.

[0004] Industrial wastewater commonly contains recalcitrant organic pollutants, such as methylene blue and malachite green in dyeing and printing wastewater. These pollutants pose a serious threat to aquatic ecosystems and human health. Traditional water treatment methods, including activated carbon adsorption, ozone oxidation, and biodegradation, while effective under certain conditions, often suffer from adsorption saturation, poor reaction selectivity, and the risk of secondary pollution. Therefore, developing an efficient, economical, and environmentally friendly treatment technology is urgently needed.

[0005] The Fenton reaction, as an advanced oxidation technology, has attracted much attention due to its ability to generate strong oxidants such as hydroxyl radicals (·OH), particularly for its significant effectiveness in treating recalcitrant organic pollutants. However, the Fenton reaction depends on Fe... 2+ The availability of iron sludge and the disposal of it after the reaction limit its widespread application. In recent years, some studies have attempted to combine the metal in the catalyst with the Fenton reaction to explore a water treatment technology that releases iron ions in situ, but this method still faces challenges in the development and optimization of metal-supported materials. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a wastewater treatment method based on methane cracking carbon materials. By utilizing the adsorption properties, catalytic effect of residual metals, and magnetic characteristics of the cracked carbon materials, combined with the Fenton reaction, highly efficient removal of organic pollutants is achieved. Simultaneously, the difficulty in separating the carbon materials is solved by applying an external magnetic field. This method not only improves water treatment efficiency but also maximizes the utilization of methane cracking byproducts, providing a novel technological pathway for wastewater treatment and resource recycling.

[0007] The technical solution to achieve the purpose of this invention is:

[0008] In a first aspect, the present invention provides a wastewater treatment method based on methane cracking to produce hydrogen carbon materials, comprising the following steps:

[0009] (1) Hydrogen is produced by cracking methane with an iron-based catalyst, and carbon material byproducts are collected;

[0010] (2) Add the carbon material byproducts to wastewater containing organic pollutants;

[0011] (3) Add hydrogen peroxide solution to the wastewater and adjust the pH of the wastewater to acidic;

[0012] (4) Organic pollutants are removed by Fenton reaction under stirring;

[0013] (5) Utilizing the magnetic properties of carbon material byproducts, rapid separation of carbon material byproducts from water is achieved by applying an external magnetic field.

[0014] Preferably, the carbon material byproducts generated from methane cracking for hydrogen production are carbon nanotubes, amorphous carbon, graphite carbon, and mixtures thereof, which possess high specific surface area and abundant pore structure.

[0015] Preferably, the iron-based catalyst used is Fe2O3 / Al2O3, where Fe2O3 is the active component and Al2O3 is the support. It is prepared by a melt method. When the calcination temperature is 500℃-700℃ and the Fe2O3 loading is 43%-61%, the carbon nanotubes in the carbon material byproducts of hydrogen production from methane cracking by the iron-based catalyst have a diameter of 50-100nm, which exhibits the best adsorption properties.

[0016] Preferably, the organic pollutants in the wastewater include organic dyes such as methylene blue and malachite green.

[0017] Preferably, at least 0.5g of carbon material byproducts are added per 100ml of wastewater.

[0018] Preferably, at least 10 ml of hydrogen peroxide solution is added for every 100 ml of wastewater.

[0019] Ideally, the pH of the wastewater should be adjusted to below 2.

[0020] Preferably, the external magnetic field is generated by a permanent magnet or electromagnetic field device to adsorb and deposit carbon materials.

[0021] Compared with existing technologies, this invention aims to address the shortcomings of traditional wastewater treatment technologies in terms of treatment efficiency, economy, and environmental protection, and provides a highly efficient water treatment method based on carbon materials generated from methane cracking and hydrogen production byproducts. By innovatively combining the adsorption performance and catalytic characteristics of carbon materials with the oxidation effect of the Fenton reaction, and further utilizing the magnetic properties of carbon materials to achieve their separation and recovery, the water treatment efficiency and operability are significantly improved. Furthermore, the treated carbon sludge can be reused after magnetic recovery, while also opening up new avenues for the utilization of byproducts from methane cracking technology. Attached Figure Description

[0022] Figure 1 The graph shows the standard absorbance curves of methylene blue in all examples and comparative examples.

[0023] Figure 2 These are TEM images of the front (a) and cross-section (b) of the carbon products from methane cracking catalyzed by the Fe-Al catalyst in Example 1.

[0024] Figure 3 These are TEM images of the front (a) and cross-section (b) of the carbon products from methane cracking catalyzed by the pure Fe2O3 catalyst in Example 6.

[0025] Figure 4 The images show the Raman spectra of different carbon products in Examples 1 and 6.

[0026] Figure 5 This is a graph showing the magnetic sedimentation test of carbon mud in solution. Detailed Implementation

[0027] This invention effectively addresses the shortcomings of traditional technologies by utilizing carbon materials generated from methane cracking and their unique adsorption, catalytic, and magnetic properties, combined with advanced oxidation technologies such as the Fenton reaction. The Fenton reaction generates hydroxyl radicals through the reaction of residual metals (such as Fe, Co, and Ni) in the cracked carbon materials with hydrogen peroxide. In particular, the separation of the carbon materials from water using an external magnetic field further improves the simplicity and economy of the treatment process, providing a new solution for wastewater treatment. The magnetic component of the carbon materials originates from the residual iron-based catalyst in the methane cracking reaction. Simultaneously, the method maximizes the utilization of byproducts from the methane cracking process, significantly improving the overall economic efficiency of hydrogen production. This technology has broad industrial application prospects and environmental protection significance, especially suitable for treating industrial wastewater containing recalcitrant organic matter.

[0028] This invention provides a wastewater treatment method based on methane cracking to produce hydrogen carbon materials, comprising the following steps:

[0029] 1. Preparation of iron-based catalysts

[0030] 1.1 Weigh out a single Fe(NO3)3·9H2O and dissolve it in deionized water, or weigh out Fe(NO3)3·9H2O and Al(NO3)3·9H2O in a molar ratio, typically between 1:1 and 1:3, to optimize the catalyst's performance, and dissolve it in deionized water. Mechanically stir or ultrasonically vibrate to form a homogeneous metal salt solution.

[0031] 1.2 After impregnation, the sample is placed in an oven and dried at 80-120℃ for 4-8 hours to remove residual moisture.

[0032] 1.3 Place the dried sample in a tube furnace and calcine it in an inert atmosphere (such as argon or nitrogen). Calcination conditions: temperature 500-700℃, time 2-4 hours. The calcination process decomposes the metal salt into metal oxide (Fe2O3) and uniformly adheres to the surface of the support (Al2O3).

[0033] 2. The methane cracking reaction proceeds.

[0034] 2.1 Load 0.2g of catalyst into the middle of the reaction tube and fix the catalyst in the reaction area (usually clamped with quartz wool). Ensure that the catalyst is evenly distributed and avoid displacement or excessive compaction that may affect gas flow.

[0035] 2.2 Before the experiment, purge the system with nitrogen (N2) at a flow rate of 100 mL / min for 15 minutes to remove air and impurities.

[0036] 2.3 Start the heating device, set the reaction temperature to 800℃, and gradually increase the temperature to the target temperature at a heating rate of 10-20℃ / min.

[0037] 2.4 When the temperature stabilizes at 800℃, switch the gas to methane, adjust the flow rate to 50 mL / min, and start the tail gas collection system. Record the time when the methane gas enters the reactor and start timing.

[0038] 2.5 Methane undergoes a cracking reaction on the catalyst surface, producing hydrogen (H2) and solid carbon deposition: CH4 → C (solid) + 2H2

[0039] 2.6 After the reaction has been running for a specified time (e.g., 3-6 hours), turn off the methane gas source and switch back to nitrogen gas to purge the reactor for 15 minutes.

[0040] 2.7 Stop the heating device and allow the reaction system to cool naturally to room temperature.

[0041] 2.8 Collect solid carbon products from inside the condenser or reactor, weigh and characterize them.

[0042] 3. Water treatment process

[0043] 3.1 Wastewater sample preparation: Prepare the target wastewater (such as simulated dye wastewater containing methylene blue and malachite green) into a solution of a certain concentration (e.g., 0.1 g / 100 mL), dilute it with deionized water to ensure uniform water quality.

[0044] 3.2 Addition of carbon materials: According to the target wastewater volume, add an appropriate amount of carbon materials generated by methane cracking (e.g., 0.5g of carbon materials for 100mL of wastewater).

[0045] 3.3 Stir at low speed with a mechanical stirrer for 10-15 minutes to ensure that the carbon material is evenly dispersed in the wastewater.

[0046] 3.4 Addition of Auxiliary Reagents: Add hydrogen peroxide solution: Add a certain amount of 30% H2O2 solution to the wastewater (e.g., 10 mL H2O2 per 100 mL of wastewater). Adjust pH: Adjust the pH of the solution to 1-2 with dilute sulfuric acid to activate the metal components (Fe) in the carbon material. 2+ It also enhances the oxidizing power of the Fenton reaction.

[0047] 3.5 Stirring and reaction time: Maintain mechanical stirring and react for 24 hours (this can be adjusted appropriately according to the degradation of pollutants).

[0048] 3.6 Temperature control (optional): The reaction can be carried out at room temperature or heated to 40-60℃ to accelerate the degradation of pollutants.

[0049] 3.7 Centrifugation: Centrifuge the treated mixture at 3000 rpm for 10 minutes in a benchtop centrifuge to separate the solid carbon and liquid in the solution.

[0050] 3.8 Filtration: The supernatant after centrifugation is further filtered using a polytetrafluoroethylene (PTFE) filter to ensure complete removal of solid carbon. 3.9 Magnetic Separation: Because the reaction uses carbon materials rich in iron-based catalysts, carbon particles in the water can be adsorbed by an external magnetic field, improving separation efficiency.

[0051] 3.10 Move the magnet close to the container wall to allow the adsorbed carbon sludge to accumulate and then remove it. The adsorbed carbon sludge can be reused in the next batch of reaction.

[0052] Example 1

[0053] Weigh out 4.04 g of Fe(NO3)3·9H2O and 3.75 g of Al(NO3)3·9H2O, i.e., the molar ratio of Fe to Al is 1:1, and the loading is 43%. Add an appropriate amount of deionized water until completely dissolved, ultrasonically vibrate and mechanically stir, then evaporate to dryness. Place in a tube furnace, heat from room temperature to 700℃ at 10℃ / min, and maintain at 700℃ for 3 hours. Grind the calcined catalyst, take out 0.2 g and put it into a reactor for methane cracking reaction. The reaction temperature is 800℃, the methane gas flow rate is 50 mL / min, and the reaction time is 3 hours. After the reaction is completed, take out 0.5 g of product carbon, add it to 100 mL of 0.1 g / 100 mL methylene blue solution, then add 10 mL of 30% H2O2 solution, and then add dilute sulfuric acid to adjust the pH value to about 2. Stir mechanically for 24 hours, and detect the water treatment results of the carbon product by spectrophotometry. The absorbance of methylene blue solutions at different concentrations was measured, and a standard absorbance curve of methylene blue (diluted 100 times) was plotted. Figure 1 As shown in the figure. The electron micrograph of the morphology of the carbon material prepared using the catalyst in this embodiment is shown in the figure. Figure 2 As shown, Figure 2 (a) in the image is a TEM image of the front of the carbon material. Figure 2 (b) in the image is a TEM image of a cross-section of carbon material. A large number of carbon nanotubes can be found in both images.

[0054] Examples 2-5

[0055] The preparation and testing methods of the catalysts in Examples 2-5 are similar to those in Example 1. The calcination temperature and molar ratio of different catalysts are distinguished. The test results of all catalysts are shown in Table 1.

[0056] Table 1 Comparison of water treatment results in Examples 1-5

[0057]

[0058] Comparing Examples 1, 2, and 3, it can be found that, under the same conditions, the carbon material prepared by the catalyst at a calcination temperature of 700℃ in Example 1 exhibits the best water treatment performance. When the calcination temperature is kept constant, adjusting the molar ratio of Fe to Al in the catalyst, comparing Examples 1, 4, and 5, it can be found that, in Example 1, the carbon material prepared at a molar ratio of Fe to Al of 1:1 exhibits the best water treatment performance.

[0059] Example 6

[0060] In this embodiment, no Al element was added to the catalyst. Only 10.00 g of Fe(NO3)3·9H2O was weighed. The remaining preparation steps and methane cracking reaction conditions were the same as in Example 1. After the reaction was completed, 0.5 g of the product carbon was taken out and added to 100 mL of a 0.1 g / 100 mL methylene blue solution, followed by 10 mL of a 30% H2O2 solution. Then, dilute sulfuric acid was added to adjust the pH to around 2, and the mixture was mechanically stirred for 24 h. The test results showed an absorbance of 0.069 and a residual methylene blue concentration of 334 mg / L. The electron microscope image of the carbon material morphology prepared by the catalyst used in this embodiment is shown below. Figure 3 As shown, Figure 3 (a) in the image is a TEM image of the front of the carbon material. Figure 3 (b) is a TEM image of a cross-section of the carbon material. Figure 3 In (a), onion carbon material is seen coating the outer surface of the catalyst particles, but no obvious carbon nanotube morphology is observed. However, carbon nanotubes are visible in the cross-section of the onion carbon. Figure 3 As can be seen in (b), the carbon material has a low carbon nanotube content.

[0061] Raman spectroscopy characterization was performed on the two different carbon materials in Examples 1 and 6, and the results are as follows: Figure 4 As shown. In pure Fe catalyst (Fe2O3), I D / I G The ratio is 0.79; in a catalyst with an added Al and a Fe to Al molar ratio of 1:1, I D / I G The ratio is 0.46; in contrast, carbon materials with added Al have more defects, which increase the specific surface area of ​​the carbon materials, thereby increasing their adsorption capacity for organic dyes in wastewater.

[0062] Example 7

[0063] A comparative water treatment experiment was conducted using commercially available activated carbon (coconut shell carbon). Without requiring catalyst preparation or methane cracking, 0.5g of commercial activated carbon was directly weighed and added to 100ml of a 0.1g / 100mL methylene blue solution, followed by 10mL of a 30% H₂O₂ solution. Dilute sulfuric acid was then added to adjust the pH to approximately 2. The mixture was mechanically stirred for 24 hours, and the water treatment performance of the carbon product was measured using a spectrophotometer. After 24 hours, the absorbance was 0.096, and the remaining methylene blue concentration in the solution was 461mg / L. Compared to Example 1, the carbon material prepared in Example 1, after undergoing Fenton oxidation, exhibited significantly better water treatment performance than commercially available activated carbon.

[0064] Examples 8-11

[0065] Examples 8-11 used the catalyst prepared in Example 1, but changed the amount of dilute sulfuric acid added in the wastewater treatment experiment to change the pH value. The other conditions were the same as in Example 1. Water treatment tests were conducted, and the results are shown in Table 2.

[0066] Table 2 Comparison of water treatment results in Examples 1, 8, 9, 10, and 11

[0067]

[0068] The comparison revealed that carbon materials exhibited the best water treatment performance when the pH value was adjusted to be below 2 during water treatment.

[0069] This invention investigates the application effect of iron-based catalysts in the treatment of carbon products from methane cracking, and also explores their potential in environmental protection and resource recycling through experiments. When Fenton oxidation is introduced, FeAl carbon nanotubes with a diameter of 50-100 nm (i.e., calcination temperature of 500℃-700℃, Fe2O3 loading of 43%-61%, and Fe to Al molar ratio of 1:1-1:3) exhibit the best adsorption effect. The same catalyst also shows optimal water treatment performance at a pH below 2. Furthermore, this invention proposes a highly efficient and economical water treatment scheme by combining Fenton oxidation and magnetic sedimentation technology. The magnetic sedimentation of carbon materials in solution is demonstrated as follows: Figure 5 As shown, magnets can be used to adsorb carbon sludge in a solution, thus separating the carbon sludge from the wastewater for reuse. This not only helps improve water treatment efficiency but also enhances the economics of methane cracking reactions, providing a new solution for environmental protection and resource recycling. In the future, this research direction is expected to play a greater role in the fields of environmental protection and resource recycling.

Claims

1. A wastewater treatment method based on hydrogen production from methane cracking carbon material, characterized by, Includes the following steps: (1) Hydrogen is produced by cracking methane with an iron-based catalyst, and carbon material byproducts are collected; (2) Add the carbon material byproducts to wastewater containing organic pollutants; (3) Add hydrogen peroxide solution to the wastewater and adjust the pH of the wastewater to acidic; (4) Organic pollutants are removed by Fenton reaction under stirring; (5) Utilizing the magnetic properties of carbon material byproducts, rapid separation of carbon material byproducts from water is achieved by applying an external magnetic field.

2. The method as described in claim 1, characterized in that, The carbon material byproducts of methane cracking for hydrogen production include carbon nanotubes, amorphous carbon, graphite carbon, and mixtures thereof.

3. The method as described in claim 1, characterized in that, The iron-based catalyst used is Fe2O3 / Al2O3, in which Fe2O3 is the active component and Al2O3 is the support. It is prepared by melt method. When the calcination temperature is 500℃-700℃ and the Fe2O3 loading is 43%-61%, the carbon nanotubes in the carbon material byproducts of hydrogen production from methane cracking by the iron-based catalyst have a diameter of 50-100nm.

4. The method as described in claim 1, characterized in that, The organic pollutants in the wastewater are methylene blue or malachite green.

5. The method as described in claim 1, characterized in that, Add at least 0.5g of carbon material byproducts per 100ml of wastewater.

6. The method as described in claim 1, characterized in that, Add at least 10 ml of hydrogen peroxide solution for every 100 ml of wastewater.

7. The method as described in claim 1, characterized in that, Adjust the pH of the wastewater to below 2.

8. The method as described in claim 1, characterized in that, An external magnetic field is generated by a permanent magnet or electromagnetic field device to adsorb and deposit carbon materials.

Images