A controllable synthesis method of coal-based carbon material and application in organic wastewater treatment

Abstract

The application discloses a controllable synthesis method of coal-based carbon materials and application in organic wastewater treatment, and belongs to the technical field of water treatment. The cold extraction liquid added with metal active components is used to rapidly cool the calcined coal fine particles, and in the process, the metal active components are dispersed in large amounts and enter the surface of the coal fine particles, so that the effect of treating organic pollution is effectively improved. The problems of insufficient adsorption and catalytic degradation capacity of the existing coal-based carbon materials in organic wastewater treatment are effectively solved. After the material is saturated, activated persulfate is used to remove the adsorbed organic pollutants on the coal-based carbon materials, and the regeneration of the coal-based carbon materials is realized. The prepared carbon materials retain the phase at high temperature, have strong structural stability, and have uniform active component distribution, so that the problems of difficult treatment of large-volume wastewater and difficult regeneration of the saturated adsorption material of the carbon materials are overcome, and the carbon materials can be used for environmental pollution control.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a controllable synthesis method of coal-based carbon materials and their application in organic wastewater treatment. Background Technology

[0002] Water pollution treatment processes mainly include physical, chemical, and biological methods. These wastewater treatment methods each have their advantages, but also their disadvantages: (1) Physical methods transfer pollutants from the aqueous phase to other phases, but the pollutants themselves do not degrade, thus easily causing secondary pollution. In addition, the materials after saturated adsorption are difficult to regenerate; (2) Chemical methods mainly rely on strong oxidants to degrade pollutants, which is too expensive and difficult to treat large volumes of wastewater; (3) Biological treatment has a lower cost, but generally a long cycle, and is selective in degrading pollutants. Therefore, more and more researchers are committed to developing efficient, environmentally friendly, and inexpensive organic wastewater treatment materials and methods. Thus, single physical and chemical treatment methods have been abandoned, and a combined treatment method of "adsorption concentration + chemical degradation" with stable operation and lower cost has been adopted, that is, polycyclic aromatic hydrocarbons are first fixed on the surface of the material, and then chemically catalytically degraded.

[0003] Therefore, the materials used must possess both adsorption and catalytic properties. Carbon materials have a large specific surface area / pore size ratio, exhibiting strong affinity and adsorption for organic pollutants. Furthermore, research has revealed that some carbon materials with special structures, such as biochar, carbon nanotubes, graphene, and coke powder, are rich in sp2 and sp3 hybridization, π-π structures, oxygen-containing functional groups, and defect sites, giving them advantages such as activating persulfate / H2O2. Common carbon materials include activated carbon, carbon nanotubes, biochar, and hydrothermal carbon. However, the synthesis processes of carbon-based materials such as graphene and carbon nanotubes are complex and costly, making them unsuitable for large-scale applications. Biochar is characterized by low cost, good selectivity, and ease of transportation; however, its structural stability is poor, and it is prone to agglomeration and deactivation. Activated carbon adsorption is a typical advanced wastewater treatment technology. Early raw materials for activated carbon preparation mainly consisted of forest products such as wood, sawdust, and nutshells. Due to limited resources, the source of raw materials has gradually shifted to abundant and inexpensive coal. The development of activated carbon preparation using coal as a raw material has been rapid, with its application scope and quantity expanding quickly. Currently, the production of coal-based activated carbon has surpassed that of wood-based activated carbon. Therefore, the development of carbonaceous materials using coal as a raw material that combine low cost, high activity, high stability, and both adsorption and catalytic properties has broad application prospects for the control of polycyclic aromatic hydrocarbon pollution in water bodies. Furthermore, for carbonaceous materials possessing both adsorption and catalytic activity, a high fixed carbon content is required first, followed by high-temperature pyrolysis to generate hybrid structures, π-π structures, etc. Typical hydrothermal reaction temperatures are between 120 and 250℃. Although this can generate materials rich in oxygen-containing functional groups, it is difficult to achieve a large-scale pyrolysis of organic matter at this temperature, resulting in generally low structural stability of the generated hydrothermal carbon.

[0004] High-temperature calcination can achieve a large degree of pyrolysis of organic matter and obtain a stable structure, but the carbon materials prepared under this mode lack oxygen-containing functional groups, resulting in fewer active sites.

[0005] Coal is widely available and inexpensive. Coal-based carbon materials made from coal have high mechanical strength, high chemical stability, well-developed pores, abundant oxygen-containing functional groups, and are rich in SP. 2 / sp 3 Hybridized carbon and π electrons possess characteristics such as high adsorption capacity, excellent catalytic activity, easy regeneration, and strong stability, making them promising candidates for water treatment. The main principle of the quenching method is to heat and hold samples of different compositions at a series of predetermined temperatures for an extended period, allowing them to reach their equilibrium structural state at the corresponding temperatures. Then, the samples are rapidly cooled. Because phase transformation does not have time to occur, the cooled samples retain their equilibrium structural state from the high-temperature temperature. The quenching method has the following effects: 1. Refining grains; 2. Expanding the solid solution region; 3. Increasing the number of grain boundaries and crystal defects; 4. Eliminating segregation and increasing the disorder of substituted atomic sites; 5. Generating supersaturated solid solutions, metastable phases, quasi-crystalline phases, and amorphous phases. Summary of the Invention

[0006] To address the shortcomings of existing technologies, a simple and effective controlled synthesis method for coal-based carbon materials is provided for use in organic wastewater treatment. This method can effectively degrade organic pollutants and significantly improve the adsorption effect of pollutants.

[0007] The objective of this invention is mainly achieved through the following technical solutions:

[0008] A controllable synthesis method for coal-based carbon materials includes the following steps:

[0009] S1. Grind the coal into fine particles and screen it, while ensuring it is dry;

[0010] S2. The screened coal fines are calcined and pyrolyzed in an anaerobic environment at a temperature of 800-1000℃.

[0011] S3. The calcined coal particles are taken out at high temperature and quickly placed in a cold extraction agent containing active components for cold extraction to prevent the calcined coal particles from cooling before entering the cold extraction agent. A large amount of metal active components are introduced into the calcined coal particles through cold extraction. During this process, the metal ions in the active components undergo a reduction reaction and are dispersed in the form of a phase on the surface of the calcined carbon material particles, making the carbon material particles more active.

[0012] S4. After the reaction is complete, the cooled solid is taken out, washed and dried to obtain the finished coal-based carbon material.

[0013] Furthermore, in S1, the coal is lignite and coking coal.

[0014] Furthermore, in S1, the carbon content of the coal is higher than 80%.

[0015] Furthermore, in S1, the coal particle size is below 100 mesh and the moisture content is ≤10%.

[0016] Furthermore, in S2, the calcination time is 2 to 3 hours.

[0017] Furthermore, in step S3, after the calcination time is reached, the calcined coal particles must be removed within 3 minutes and placed in a cold extraction agent for cold extraction.

[0018] Furthermore, in step S3, the cold extraction agent is an active component solution without dissolved oxygen, the temperature of the cold extraction agent is 1 to 10°C, the active components in the cold extraction agent include ferrous, iron, manganese, and molybdenum metal salts, and the concentration of the active components in the cold extraction agent is 0.5 to 2 g / L.

[0019] Furthermore, in step S3, the mass of the cold extraction agent is 100 to 200 times the mass of the fine coal particles after calcination.

[0020] A method for the controlled synthesis of coal-based carbon materials.

[0021] An organic wastewater treatment application uses coal-based carbon materials to adsorb organic pollutants in wastewater. After the materials are saturated, activated persulfate is used to remove the adsorbed organic pollutants from the coal-based carbon materials, thereby regenerating the coal-based carbon materials.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] 1) This invention first grinds and sieves the coal, then calcines it in a high-temperature anaerobic environment, and then removes it at high temperature and places it in a cold extraction agent. After washing and drying, the finished product is a coal-based carbon material. The prepared carbon material retains the phase at high temperature, has strong structural stability, and has a uniform distribution of active ingredients.

[0024] 2) The coal-based carbon material of the present invention removes organic pollutants from water bodies through the means of "enrichment-quenching". That is, the organic pollutants in the water body are first enriched on the surface of the carbon material. After saturation adsorption, most of the treated water is removed. Then, persulfate is added to generate active free radicals by activating the persulfate to catalyze the degradation of organic pollutants adsorbed on the surface of the carbon material. This overcomes the problem that carbon materials are difficult to treat large volumes of wastewater and the problem that the material is difficult to regenerate after saturation adsorption. It can be used for environmental pollution control.

[0025] 3) Compared with the impregnation method, the quenching method can introduce more uniform distribution of active ingredients into carbon materials, and the amount of active ingredients is larger, and more active sites are exposed. Therefore, the final product of coal-based carbon materials has better performance.

[0026] 4) Compared with materials that are calcined at high temperature and then cooled naturally, the materials synthesized by the method proposed in this invention have more defects, a higher degree of aromatization, more developed pores, and a better effect in removing pollutants.

[0027] 5) The raw materials of this invention include low-rank coal, which is inexpensive and readily available. The coal-based carbon materials invented are low in cost, simple in preparation method, and highly operable.

[0028] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of what is particularly pointed out in the written description.

[0029] Instruction manual illustrations

[0030] Figure 1 The image shows the XRD pattern of the coal-based carbon material prepared by the iron-containing quenching agent in Example 1 of this invention. Detailed Implementation

[0031] The embodiments of the present invention will be further described below:

[0032] Example 1: A method for synthesizing coal-based carbon materials:

[0033] 10g of lignite was ground into powder and sieved through a 100-mesh sieve. The powdered lignite was then placed in a tube furnace and calcined at 1000℃ for 3 hours under argon or nitrogen protection. Immediately after calcination, the material was removed and placed in 200mL of a 4℃ solution containing 1g / L ferric chloride. The mixture was then cold-extracted and stirred for 30 minutes under magnetic stirring. Subsequently, it was washed until the pH of the aqueous solution reached approximately 7, and then dried to obtain the coal-based carbon material. Figure 1 The image shows the XRD pattern of this coal-based carbonaceous material. As can be seen from the figure, the Fe in the quencher... 3+ Ions reduced to Fe 2+ Ferric chloride, dispersed on the surface of carbon materials in the form of ferric chloride (FeO), exhibits higher activity. Testing showed that 95% of the ferric chloride was successfully loaded into the structure of coal-based carbon materials.

[0034] Using the coal-based carbon material prepared in this embodiment, 10 g / L of naphthol was removed by enrichment, adsorption, and catalytic quenching at a dosage of 1 g / L. After reacting for 2 hours with the assistance of 5 mM persulfate, the naphthol removal rate was higher than 99%, and the TOC removal rate was 96%. Furthermore, no iron ion leaching was detected after the reaction, indicating that the coal-based carbon material has excellent stability.

[0035] Example 2: A method for synthesizing coal-based carbon materials:

[0036] 5g of lignite was ground into powder and sieved through a 100-mesh sieve. The powdered lignite was then placed in a tube furnace and calcined at 800℃ for 2 hours under argon or nitrogen protection. Immediately after calcination, the material was removed and placed in 100mL of a 6℃ solution containing 2g / L molybdenum nitrate. The solution was stirred magnetically for 40 minutes. The mixture was then washed until the pH of the aqueous solution reached approximately 7, and dried to obtain the coal-based carbon material. Testing showed that 98% of the molybdenum nitrate was successfully loaded into the structure of the coal-based carbon material.

[0037] Using the coal-based carbon material prepared in this embodiment, 50 g / L of aniline was removed by adsorption-catalysis at a concentration of 2 g / L. After 3 hours of reaction with the assistance of 10 mM persulfate, the aniline removal rate was higher than 99%, and the TOC removal rate was 88%. Furthermore, no molybdenum ion leaching occurred after the reaction, demonstrating the material's superior stability.

[0038] Example 3: A method for synthesizing coal-based carbon materials:

[0039] 5g of lignite was ground into powder and sieved through a 100-mesh sieve. The powdered lignite was then placed in a tube furnace and calcined at 900℃ for 2 hours under argon or nitrogen protection. Immediately after calcination, the material was removed and placed in 100mL of a 1g / L ferrous nitrate solution at 2℃, and stirred magnetically for 40 minutes. The solution was then washed until the pH reached approximately 7, and dried to obtain the coal-based carbon material. Testing showed that 99% of the ferrous nitrate was successfully loaded into the structure of the coal-based carbon material.

[0040] Using the coal-based carbon material prepared in this embodiment, 30 g / L of indole was removed by adsorption-catalysis at a concentration of 1 g / L. After 2 hours of reaction with the assistance of 10 mM persulfate, the indole removal rate was higher than 99%, and the TOC removal rate was 85%. Furthermore, no iron ion leaching occurred after the reaction, demonstrating the material's superior stability.

[0041] Example 4: A method for synthesizing coal-based carbon materials:

[0042] 4g of lignite was ground into powder and sieved through a 100-mesh sieve. The powdered lignite was then placed in a tube furnace and calcined at 900℃ for 1.5 hours under argon or nitrogen protection. Immediately after calcination, the material was removed and placed in 100mL of a 6℃ solution containing 2g / L manganese nitrate. The solution was stirred magnetically for 40 minutes. The mixture was then washed until the pH of the aqueous solution reached approximately 7, and dried to obtain the coal-based carbon material. Testing showed that 97% of the manganese nitrate was successfully loaded into the structure of the coal-based carbon material.

[0043] Using the coal-based carbon material prepared in this embodiment, 10 g / L of sulfadiazine was removed by adsorption-catalysis at a concentration of 1 g / L. After 2 hours of reaction with the assistance of 8 mM persulfate, the aniline removal rate was higher than 99%, and the TOC removal rate was 89%. Furthermore, no manganese ions were leached after the reaction, indicating that the material exhibits excellent stability.

[0044] Comparison Example 1

[0045] 10g of lignite was ground into powder and sieved through a 100-mesh sieve. It was then placed in a tube furnace and calcined at 1000℃ for 3 hours under argon or nitrogen protection. Instead of using a cold extraction solution, the calcined lignite was allowed to cool naturally before being placed in 200mL of a 4℃ solution containing 1g / L ferric chloride. The solution was stirred magnetically for 30 minutes. The mixture was then washed until the pH of the aqueous solution reached approximately 7, and dried to obtain the comparative coal-based carbon material. Testing showed that only 61% of the ferric chloride was successfully loaded as an active material into the structure of the carbon material.

[0046] Using 1 g / L of this material for adsorption-catalysis to remove 10 g / L of naphthol, the naphthol removal rate was approximately 59% and the TOC removal rate was 26% after 2 hours of reaction with the assistance of 5 mM persulfate. Furthermore, approximately 10% of the iron in the material leached into the solution after the reaction, indicating that the material's stability was generally moderate.

Claims

1. A controllable synthesis method for coal-based carbon materials, characterized in that, Includes the following steps: S1. Grind the coal into fine particles and screen it, while ensuring it is dry; S2. The screened coal fines are calcined and pyrolyzed in an anaerobic environment at a temperature of 800~1000℃. S3. The calcined coal particles are taken out at high temperature and quickly placed in a cold extraction agent containing active components for cold extraction to prevent the calcined coal particles from cooling before entering the cold extraction agent. By cold extraction, a large amount of active metal components are introduced into the fine particles of calcined coal. During this process, the metal ions in the active components undergo a reduction reaction and are dispersed in the form of a phase on the surface of the fine carbon material particles after calcination, thus giving the fine carbon material particles higher activity. The cold extraction agent is an active component solution without dissolved oxygen. The temperature of the cold extraction agent is 1~10℃. The active components in the cold extraction agent include ferrous, iron, manganese and molybdenum metal salts. The concentration of the active components in the cold extraction agent is 0.5~2 g / L. S4. After the reaction is complete, the cooled solid is taken out, washed and dried to obtain the finished coal-based carbon material.

2. The controllable synthesis method of coal-based carbon materials according to claim 1, characterized in that, In S1, the coal is lignite and coking coal.

3. The controllable synthesis method of coal-based carbon materials according to claim 1, characterized in that, In S1, the carbon content of the coal is higher than 80%.

4. The controllable synthesis method of coal-based carbon materials according to claim 1, characterized in that, In S1, the coal particle size is below 100 mesh and the moisture content is ≤10%.

5. The controllable synthesis method of coal-based carbon materials according to claim 1, characterized in that, In S2, the calcination time is 2-3 h.

6. The controllable synthesis method of coal-based carbon materials according to claim 1, characterized in that, In step S3, after the calcination time is reached, the calcined coal particles must be removed within 3 minutes and placed in a cold extraction agent for cold extraction.

7. The controllable synthesis method of coal-based carbon materials according to claim 1, characterized in that, In S3, the mass of the cold extraction agent is 100 to 200 times the mass of the fine coal particles after calcination.

8. A coal-based carbon material generated using the controllable synthesis method of the coal-based carbon material according to any one of claims 1-7.

9. An application for treating organic wastewater, characterized in that, The coal-based carbon material described in claim 8 is used to adsorb organic pollutants in wastewater. After the material is saturated, the organic pollutants adsorbed on the coal-based carbon material are removed by activating persulfate, thereby regenerating the coal-based carbon material.

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