Iron-carbon-based catalyst, preparation method and application thereof

Abstract

This invention provides an iron-carbon based catalyst, its preparation method, and its application, relating to the field of wastewater treatment technology. The preparation method includes: S1, adding bamboo powder and humic acid to an alkaline solution and stirring to obtain a carbon precursor; S2, adding the carbon precursor to a glucose solution and carrying out a hydrothermal reaction to obtain a carbon complex; S3, adding an active iron source and an auxiliary agent to a humic acid solution to obtain a complex solution; S4, adding the carbon complex to the complex solution and performing gradient calcination under an inert atmosphere to obtain the iron-carbon based catalyst. The entire preparation process of this invention requires no external binder or pore-forming agent, reduces sintering temperature, and has low cost. The prepared sea urchin-type iron-carbon based catalyst exhibits extremely strong iron-carbon bonding, is not easily detached, and has high stability. Its structure provides a large number of active sites, and the radial nanospikes maximize the specific surface area, greatly promoting Fe... 3+ / Fe 2+ It can recycle and increase the yield of •OH, has strong catalytic activity, and can efficiently degrade recalcitrant organic pollutants.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to an iron-carbon based catalyst, its preparation method, and its application. Background Technology

[0002] With rapid industrial development, wastewater discharged from industries such as pharmaceuticals, chemicals, and electroplating has complex compositions, containing large amounts of recalcitrant organic pollutants, such as heterocyclic compounds, aromatic compounds, and antibiotics. This type of wastewater is characterized by high COD concentration, low BOD5 / COD ratio, high toxicity, and deep color. It also contains new pollutants, such as persistent organic pollutants, endocrine disruptors, antibiotics, and microplastics. Traditional biochemical treatment processes struggle to achieve ideal treatment results. Iron-carbon micro-electrolysis technology, due to its advantages of low cost, simple operation, and no secondary pollution, has been widely used in the treatment of recalcitrant wastewater. Its core principle is that iron-carbon materials form a galvanic cell, generating Fe... 2+ , OH and other reactive substances can oxidize and decompose organic pollutants. However, existing iron-carbon materials have the following technical drawbacks: 1. The iron and carbon bonds are not strong, and they are easy to fall off and pulverize during water treatment, resulting in catalyst loss and a rapid decrease in treatment efficiency over time; 2. Few reactive sites, Fe 2+ Slow generation rate Insufficient OH production limits the degradation efficiency for recalcitrant pollutants. 3. It is prone to caking, which can lead to reactor blockage and affect the continuous and stable operation of the treatment system; 4. Existing iron-carbon catalytic packings are relatively dense on both the surface and inside after pressing and sintering. The accumulation of recalcitrant substances on the surface of the packings to form a passivation film not only hinders the normal progress of the electrolysis reaction, but also makes backwashing of the packings difficult.

[0003] 5. The raw material selection is limited, mostly using a mixture of pure iron powder and ordinary activated carbon without optimizing the iron-carbon structure, which restricts the catalytic performance and service life. Summary of the Invention

[0004] Therefore, this invention proposes an iron-carbon based catalyst, its preparation method, and its application.

[0005] The technical solution of this invention is implemented as follows: A method for preparing an iron-carbon based catalyst includes the following preparation steps: S1. Add bamboo powder and humic acid to an alkaline solution, stir, filter, freeze dry, and obtain carbon precursor; S2. Add the carbon precursor to the glucose solution, place the system in a high-pressure reactor, and carry out a hydrothermal reaction to obtain the carbon complex. S3. Add the active iron source and additives to the fulvic acid solution to obtain a complex solution; S4. Add the carbon complex to the complexing solution, stir, filter, freeze dry, and perform gradient calcination under an inert atmosphere to obtain the iron-carbon based catalyst.

[0006] Furthermore, in step S1, the mass ratio of bamboo powder to humic acid is 3-5:1; The alkaline solution is a 30wt%-40wt% NaOH solution and anhydrous ethanol in a volume ratio of 1:1-3; The solid-liquid ratio of the fulvic acid and the alkaline solution is 1:10-15 g / mL.

[0007] Furthermore, in step S2, the solid-liquid ratio of the carbon precursor to the glucose solution is 1:8-10 g / mL, and the concentration of the glucose solution is 20wt%-30wt%. The hydrothermal reaction is carried out at a temperature of 180-200℃ for 10-12 hours.

[0008] Furthermore, in step S3, the auxiliary agent is copper chloride and nickel chloride in a mass ratio of 1:0.5-0.8; The mass ratio of the active iron source to the additive is 2-3:0.5; The solid-liquid ratio of the active iron source to the humic acid solution is 0.5:8-10 g / mL; The concentration of the humic acid solution is 10wt%-15wt%.

[0009] Furthermore, the active iron source is reduced iron powder and nano-zero valent iron in a mass ratio of 1:1-2, wherein the particle size of the reduced iron powder is 150-200 mesh, and the particle size of the nano-zero valent iron is 50-100 mesh.

[0010] Furthermore, in step S4, the solid-liquid ratio of the carbon complex to the complexing solution is 1:8-10 g / mL; The stirring was performed by ultrasonic treatment at 30-40KHz and 350-450W for 20-30 minutes.

[0011] Furthermore, in step S4, the gradient calcination specifically involves: first raising the temperature to 350-450℃ at a heating rate of 2-5℃ / min and holding it for 40-60min; then raising the temperature to 650-750℃ at a heating rate of 1-3℃ / min and holding it for 20-40min; and finally raising the temperature to 800-900℃ at a heating rate of 5-8℃ / min and holding it for 20-30min.

[0012] Furthermore, in step S4, the iron-carbon based catalyst has a sea urchin-type structure.

[0013] An iron-carbon based catalyst, prepared by any of the methods described above.

[0014] Application of an iron-carbon based catalyst in the treatment of wastewater pollutants.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The bamboo powder of this invention has a fibrous structure and high mechanical strength, while fulvic acid is rich in oxygen-containing functional groups and aromatic structures, possessing high specific surface area, biodegradability, and sustainability. Both are excellent carbon sources, rich in oxygen-containing functional groups and natural microstructures, low in cost, and renewable. With proper regulation, they are more conducive to forming complex hierarchical channels. Activation of both in an alkaline solution followed by a hydrothermal reaction with a glucose solution generates a carbon complex with high mechanical strength and rich in active functional groups, serving as the "cholesterol" of a sea urchin-type iron-carbon based catalyst. Subsequent pyrolysis forms a porous, highly active carbon framework. By complexing the active iron source and additives with fulvic acid, its abundant functional groups can strongly chelate metal ions and adsorb them onto the carbon material surface, increasing subsequent loading uniformity and preventing agglomeration. Furthermore, fulvic acid acts as an excellent dispersant and structure-directing agent, guiding the active iron source and additives to mix and assemble with the carbon material into the "spine" of the sea urchin-type iron-carbon based catalyst. Simultaneously, fulvic acid can act as a natural electron mediator, promoting the Fe... 3+ / Fe 2+ Cycling enhances catalytic efficiency. A specific calcination process generates a radial "sea urchin-like" structure, with iron and carbon firmly bonded together.

[0016] The entire preparation process of this invention requires no external binder or pore-forming agent, reduces sintering temperature, and is low-cost. The prepared sea urchin-type iron-carbon based catalyst exhibits extremely strong iron-carbon bonding, is not easily detached, and has high stability. Its structure provides a large number of active sites, and the radial nanospikes maximize the specific surface area. The tight Fe-OC interface accelerates the transfer of electrons from carbon to iron, greatly promoting Fe... 3+ / Fe 2+ The catalyst of this invention features abundant internal pores and interconnected multi-level gradient channels, which prevent dense particle accumulation and avoid overall caking. This enhances the catalytic activity, resulting in improved •OH yield and efficient degradation of recalcitrant organic pollutants. Detailed Implementation

[0017] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0018] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0019] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0020] Example 1 A method for preparing an iron-carbon based catalyst includes the following preparation steps: S1. Add bamboo powder and fulvic acid in a mass ratio of 4:1 to a mixed solution of 35wt% NaOH solution and anhydrous ethanol in a volume ratio of 1:2. The solid-liquid ratio of fulvic acid to the mixed solution is 1:13 g / mL. Stir for 30 min, filter, wash, freeze dry to obtain carbon precursor. S2. The carbon precursor was added to a 25wt% glucose solution with a solid-liquid ratio of 1:9 g / mL and stirred. The system was placed in a high-pressure reactor and hydrothermally reacted at 190℃ for 11 h. The mixture was then filtered, washed, and dried to obtain the carbon complex. S3. Add an active iron source (reduced iron powder and nano-zero valent iron in a mass ratio of 1:2, with a particle size of 200 mesh for the reduced iron powder and 100 mesh for the nano-zero valent iron) and an auxiliary agent (copper chloride and nickel chloride in a mass ratio of 1:0.5) in a 13wt% fulvic acid solution and stir. The solid-liquid ratio of the active iron source to the fulvic acid solution is 0.5:9 g / mL to obtain a complex solution. S4. The carbon complex was added to the complexing solution at a solid-liquid ratio of 1:9 g / mL. The mixture was ultrasonically treated at 35 kHz and 400 W for 25 min, filtered, washed, and freeze-dried. The product was heated to 400 °C at a rate of 3 °C / min under a nitrogen atmosphere and held for 50 min. Then, it was heated to 700 °C at a rate of 2 °C / min and held for 30 min. Finally, it was heated to 850 °C at a rate of 5 °C / min and held for 25 min to obtain the iron-carbon based catalyst.

[0021] Example 2 A method for preparing an iron-carbon based catalyst includes the following preparation steps: S1. Add bamboo powder and fulvic acid in a mass ratio of 3:1 to a mixed solution of 30wt% NaOH solution and anhydrous ethanol in a volume ratio of 1:1. The solid-liquid ratio of fulvic acid to the mixed solution is 1:10 g / mL. Stir for 30 min, filter, wash, freeze dry to obtain carbon precursor. S2. The carbon precursor was added to a 20wt% glucose solution with a solid-liquid ratio of 1:8 g / mL and stirred. The system was placed in a high-pressure reactor and hydrothermally reacted at 180℃ for 12 h. The mixture was then filtered, washed, and dried to obtain the carbon complex. S3. Add an active iron source (reduced iron powder and nano zero-valent iron in a mass ratio of 1:1, with a particle size of 150 mesh for the reduced iron powder and 50 mesh for the nano zero-valent iron) and an auxiliary agent (copper chloride and nickel chloride in a mass ratio of 1:0.5) to a 10wt% fulvic acid solution and stir. The solid-liquid ratio of the active iron source to the fulvic acid solution is 0.5:8 g / mL to obtain a complex solution. S4. The carbon complex was added to the complexing solution at a solid-liquid ratio of 1:8 g / mL. The mixture was ultrasonically treated at 30 kHz and 350 W for 20 min, filtered, washed, and freeze-dried. The product was heated to 350 °C at a rate of 2 °C / min under a nitrogen atmosphere and held for 40 min. Then, it was heated to 650 °C at a rate of 1 °C / min and held for 20 min. Finally, it was heated to 800 °C at a rate of 5 °C / min and held for 20 min to obtain the iron-carbon based catalyst.

[0022] Example 3 A method for preparing an iron-carbon based catalyst includes the following preparation steps: S1. Add bamboo powder and fulvic acid in a mass ratio of 5:1 to a mixed solution of 40wt% NaOH solution and anhydrous ethanol in a volume ratio of 1:3. The solid-liquid ratio of fulvic acid to the mixed solution is 1:15 g / mL. Stir for 30 min, filter, wash, freeze dry to obtain carbon precursor. S2. Add the carbon precursor to a 30wt% glucose solution with a solid-liquid ratio of 1:10 g / mL and stir. Place the system in a high-pressure reactor and hydrothermally react at 200℃ for 12 h. Filter, wash, and dry to obtain the carbon complex. S3. Add an active iron source (reduced iron powder and nano-zero valent iron in a mass ratio of 1:2, with a particle size of 150 mesh for the reduced iron powder and 100 mesh for the nano-zero valent iron) and an auxiliary agent (copper chloride and nickel chloride in a mass ratio of 1:0.8) in a 15wt% fulvic acid solution and stir. The solid-liquid ratio of the active iron source to the fulvic acid solution is 0.5:10 g / mL to obtain a complex solution. S4. The carbon complex was added to the complexing solution at a solid-liquid ratio of 1:10 g / mL. The mixture was ultrasonically treated at 40 kHz and 450 W for 30 min, filtered, washed, and freeze-dried. The product was heated to 450 °C at a rate of 5 °C / min under a nitrogen atmosphere and held for 60 min. Then, it was heated to 750 °C at a rate of 3 °C / min and held for 40 min. Finally, it was heated to 900 °C at a rate of 8 °C / min and held for 30 min to obtain the iron-carbon based catalyst.

[0023] Comparative Example 1 The difference from Example 1 is that the carbon-based material is replaced with activated carbon, and the catalyst is prepared according to conventional granulation methods. Otherwise, it is the same as the Example.

[0024] The preparation method of the iron-carbon based catalyst in this comparative example includes the following preparation steps: The active iron source (reduced iron powder and nano-zero valent iron in a mass ratio of 1:2, with a particle size of 200 mesh for the reduced iron powder and 100 mesh for the nano-zero valent iron), the additives (copper chloride and nickel chloride in a mass ratio of 1:0.5), activated carbon, and the pore-forming agent were added to a mixer and dry-mixed for 12 min. Water and sodium carboxymethyl cellulose binder were added and wet-mixed for 8 min. The material was then added to a granulator for granulation and kneading. After granulation, the material was air-dried at room temperature for 6 h and then dried at 80 °C for 11 h. Finally, the material was placed in a sintering furnace and heated to 1100 °C at a heating rate of 5 °C / min. The temperature was held for 60 min and then naturally cooled to 300 °C with the furnace before being removed and cooled to room temperature to obtain the iron-carbon based catalyst.

[0025] The mass ratio of the above-mentioned active iron source, additives, activated carbon, pore-forming agent and binder is 3:0.4:4.5:0.3:1.2.

[0026] Comparative Example 2 The difference from Example 1 is that bamboo powder is missing; otherwise, it is the same as Example 1.

[0027] Comparative Example 3 The difference from Example 1 is that fulvic acid is missing; otherwise, they are the same as in Example 1.

[0028] Comparative Example 4 The difference from Example 1 is that glucose is missing; otherwise, it is the same as Example 1.

[0029] Comparative Example 5 The difference from Example 1 is that the carbon source of the iron-carbon based catalyst is carbon nanotubes, while the rest is the same as in Example 1.

[0030] Comparative Example 6 The difference from Example 1 is that the carbon source of the iron-carbon based catalyst is sludge carbon, while the rest is the same as in Example 1.

[0031] Test case Weigh 2g of the catalysts prepared in Examples 1-3 and Comparative Examples 1-6 respectively, add or fill them into the reactor, and run for 2 hours in wastewater with COD=2000mg / L and color=600 times. Calculate the COD removal rate and color removal rate. After running continuously for 12 hours, calculate the COD removal rate and observe the reactor blockage.

[0032] The results are shown in Table 1.

[0033] Table 1

[0034] As can be seen from Table 1, the catalyst of the present invention has high catalytic activity, effectively degrades refractory organic pollutants, has high mechanical strength, and does not clog the reactor during long-term operation.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an iron-carbon based catalyst, characterized in that, The preparation steps include the following: S1. Add bamboo powder and humic acid to an alkaline solution, stir, filter, freeze dry, and obtain carbon precursor; S2. Add the carbon precursor to the glucose solution, place the system in a high-pressure reactor, and carry out a hydrothermal reaction to obtain the carbon complex. S3. Add the active iron source and additives to the fulvic acid solution to obtain a complex solution; S4. Add the carbon complex to the complexing solution, stir, filter, freeze dry, and perform gradient calcination under an inert atmosphere to obtain the iron-carbon based catalyst.

2. The method for preparing an iron-carbon based catalyst as described in claim 1, characterized in that, In step S1, the mass ratio of bamboo powder to humic acid is 3-5:1; The alkaline solution is a 30wt%-40wt% NaOH solution and anhydrous ethanol in a volume ratio of 1:1-3; The solid-liquid ratio of the fulvic acid and the alkaline solution is 1:10-15 g / mL.

3. The method for preparing an iron-carbon based catalyst as described in claim 1, characterized in that, In step S2, the solid-liquid ratio of the carbon precursor to the glucose solution is 1:8-10 g / mL, and the concentration of the glucose solution is 20wt%-30wt%. The hydrothermal reaction is carried out at a temperature of 180-200℃ for 10-12 hours.

4. The method for preparing an iron-carbon based catalyst as described in claim 1, characterized in that, In step S3, the auxiliary agent is copper chloride and nickel chloride in a mass ratio of 1:0.5-0.8; The mass ratio of the active iron source to the additive is 2-3:0.5; The solid-liquid ratio of the active iron source to the humic acid solution is 0.5:8-10 g / mL; The concentration of the humic acid solution is 10wt%-15wt%.

5. The method for preparing an iron-carbon based catalyst as described in claim 4, characterized in that, The active iron source is reduced iron powder and nano-zero valent iron in a mass ratio of 1:1-2, wherein the particle size of the reduced iron powder is 150-200 mesh and the particle size of the nano-zero valent iron is 50-100 mesh.

6. The method for preparing an iron-carbon based catalyst as described in claim 1, characterized in that, In step S4, the solid-liquid ratio of the carbon complex to the complexing solution is 1:8-10 g / mL; The stirring was performed by ultrasonic treatment at 30-40KHz and 350-450W for 20-30 minutes.

7. The method for preparing an iron-carbon based catalyst as described in claim 1, characterized in that, In step S4, the gradient calcination specifically involves: first, raising the temperature to 350-450℃ at a heating rate of 2-5℃ / min and holding for 40-60min; then, raising the temperature to 650-750℃ at a heating rate of 1-3℃ / min and holding for 20-40min; and finally, raising the temperature to 800-900℃ at a heating rate of 5-8℃ / min and holding for 20-30min.

8. The method for preparing an iron-carbon based catalyst as described in claim 1, characterized in that, In step S4, the iron-carbon based catalyst has a sea urchin-type structure.

9. An iron-carbon based catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the iron-carbon based catalyst according to claim 9 in the treatment of wastewater pollutants.

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