A method for preparing a high-yield tea residue derived porous carbon

Abstract

The present application relates to the technical field of waste biomass resource utilization, and discloses a method for preparing porous carbon material with high yield by taking tea dregs as raw material and application of the method in the field of environmental remediation.The resource utilization method takes tea dregs as a carbon precursor, and under the synergistic stabilization of p-xylene glycol, p-toluenesulfonic acid and calcium oxide, nano-porous carbon material is prepared with high yield.The present application is simple, efficient, low in cost, green and environmentally friendly, the prepared porous carbon has excellent adsorption and removal performance on macromolecular organic pollutants in water, and realizes "waste treatment by waste".

Description

Technical Field

[0001] This invention relates to the field of waste biomass resource utilization technology, and in particular to a method for preparing porous carbon materials with high yield using waste tea residue as raw material, and the application of the prepared porous carbon materials in the field of environmental remediation. Background Technology

[0002] Tea is one of the world's most popular beverages, generating a large amount of tea residue during its consumption. Currently, most of this waste tea residue is disposed of through landfills or incineration, resulting in resource waste and potential environmental burden. Tea residue, as a carbon-rich biomass (theoretically containing approximately 45%-50% carbon), is theoretically an ideal precursor for preparing porous carbon materials. However, direct pyrolysis and carbonization of tea residue typically yields low carbonization rates (approximately 15%-25%), and the resulting carbon materials exhibit insufficient pore structure development, limited specific surface area and pore volume, thus affecting their performance in applications such as adsorption and catalysis.

[0003] In existing technologies, physical activation methods (such as steam and CO2) or chemical activation methods (such as KOH, phosphoric acid, and ZnCl2) are commonly used to create pores in order to improve the porosity and performance of biomass carbon materials. However, regardless of whether physical or chemical activation methods are used, the yield of carbon materials obtained is usually low, and the yield of some activation methods is even less than 5%, which seriously affects the economics of preparation. In addition, the use of expensive and highly corrosive (strong acid and strong alkali) activating agents not only causes equipment corrosion but also increases the preparation cost, affecting its large-scale application.

[0004] Therefore, developing a simple, environmentally friendly, and low-cost method for preparing porous carbon derived from tea residue with high yield is of great application value for realizing the high-value resource utilization of waste gas biomass. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a simple, efficient, low-cost, green and sustainable high-yield method for preparing porous carbon derived from tea residue and its application in the field of environmental remediation.

[0006] This invention is achieved through the following technical solution: A method for preparing porous carbon derived from tea residue with high yield includes the following steps: (1) Wash, dry and crush the tea residue to obtain tea residue powder; (2) Mix a certain amount of tea residue powder, terephthalic acid, catalyst A and additive B evenly in a certain mass ratio; (3) Transfer the mixture obtained in step (2) into a rotary kiln. Under the protection of an inert atmosphere, first heat up to the stabilization treatment temperature and maintain it for a certain time. Then switch the inert atmosphere to carbon dioxide gas and continue to heat up to the preset temperature for carbonization. After carbonization is completed, cool to room temperature. (4) The carbonization product is washed with acid solution, then washed with deionized water until neutral, and dried to obtain high-yield porous carbon material.

[0007] A more preferred technical solution of the present invention is as follows: In step (1), the tea residue is one or a mixture of several types of black tea residue, green tea residue, and flower tea residue.

[0008] In step (2), the mass ratio of tea residue powder to terephthalic acid is 1:0.1-1:1; the catalyst A is p-toluenesulfonic acid, and the mass ratio of tea residue powder to catalyst A is 1:0.01-1:0.1; the auxiliary agent B is calcium oxide, and the mass ratio of tea residue powder to auxiliary agent B is 1:0.1-1:1.

[0009] In step (3), the heating rate is 1-5℃ / min; the stabilization temperature is 140℃-170℃, and the stabilization stage is maintained for 2h-8h; the carbonization temperature is 750℃-950℃, and the carbonization stage is maintained for 1h-4h.

[0010] In step (4), the acid solution is either dilute hydrochloric acid or dilute nitric acid solution.

[0011] The porous carbon materials prepared by the above method have a yield of 40%-60% and a specific surface area of ​​100-2000 m². 2 / g; the cumulative pore volume of mesopores and macropores is greater than 0.5cm³. 3 / g, ash content less than 3%.

[0012] The porous carbon material prepared by the above method is applied in the continuous adsorption removal and dynamic regeneration of organic pollutants with large molecular size in water. The organic pollutants with large molecular size are one of tetracycline hydrochloride, methylene blue, Congo red, and rhodamine B, and the concentration of organic pollutants in the wastewater is 10-500 ppm.

[0013] This invention utilizes the synergistic stabilizing effect of tea residue raw material, terephthalic acid, p-toluenesulfonic acid catalyst, and calcium oxide additive to promote the formation of a stable structure in the tea residue raw material before pyrolysis, effectively inhibiting the decomposition and volatilization loss of the raw material during high-temperature processes, thereby achieving a high carbon yield. This method is simple to operate, uses inexpensive materials, and does not use any chlorine-containing raw materials, avoiding the generation of highly toxic substances during material pyrolysis. The prepared carbon material has a reasonable pore structure, suitable for the adsorption and removal of large-molecule organic pollutants, and represents an effective solution for the resource utilization of waste biomass. Attached Figure Description

[0014] The invention will now be further described with reference to the accompanying drawings.

[0015] Figure 1 This is a SEM image of TB-PC-3 in Example 3.

[0016] Figure 2 This is the N2 adsorption-desorption isotherm diagram of TB-PC-3 in Example 3.

[0017] Figure 3 This is a pore size distribution diagram of TB-PC-3 in Example 3.

[0018] Figure 4 This is a pore size distribution diagram of TPC-K in Example 6.

[0019] Figure 5 The image shows the dynamic adsorption breakthrough curves of the tetracycline hydrochloride solution in Example 12 over five consecutive cycles. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of this invention, the invention will be further described below in conjunction with embodiments.

[0021] Example 1 (1) Take 4000g of mixed tea residue, wash it with deionized water, dry it at 105℃ for 12 hours, and then crush it to obtain tea residue powder.

[0022] (2) Weigh 200g of the above tea residue powder, and mix it thoroughly with 20g of p-phenylenediethanol, 2g of p-toluenesulfonic acid and 20g of calcium oxide powder in a mixer to form a precursor.

[0023] (3) Transfer the mixture into a rotary kiln. Under nitrogen atmosphere (200 mL / min) protection, heat to 150°C at a rate of 1°C / min and maintain at this temperature for 8 hours. Then, switch the atmosphere to carbon dioxide (200 mL / min) and continue to heat to 750°C at the same rate and maintain at this temperature for 4 hours, then cool to room temperature.

[0024] (4) The carbonization product was thoroughly washed with dilute nitric acid solution, filtered, and then washed with deionized water until the filtrate was neutral. Finally, the material was dried at 110°C for 12 hours to obtain 84.2 g of porous carbon material, labeled as TB-PC-1, with a carbon yield of 42.1%.

[0025] The key structural properties of the prepared TB-PC-1 were analyzed using N2 low-temperature physical adsorption-desorption techniques. The results showed that the specific surface area and total pore volume of TB-PC-1 were 1373 m² / s. 2 / g, 1.05 cm 3 / g total pore volume and 0.89cm 3 / g mesopore volume. The ash content of TB-PC-1 was determined according to GB / T 12496.3-1999, and the ash content was 0.72%.

[0026] Example 2 (1) The same pretreated tea residue powder as in Example 1 was used.

[0027] (2) Weigh 200g of tea residue powder and mix it evenly with 50g of p-phenylenediethanol, 5g of p-toluenesulfonic acid and 50g of calcium oxide.

[0028] (3) Under nitrogen protection (200 mL / min), the temperature was increased to 155℃ at 3℃ / min and maintained for 6 hours. After switching to carbon dioxide (200 mL / min), the temperature was increased to 850℃ at the same rate and maintained for 2 hours, and then cooled down.

[0029] (4) The carbonization product was thoroughly washed with dilute hydrochloric acid solution, filtered, and then washed with deionized water until the filtrate was neutral. After drying, 104.6 g of porous carbon material was obtained, labeled as TB-PC-2, with a carbon yield of 52.3%.

[0030] The key structural properties of the prepared TB-PC-2 were analyzed using N2 low-temperature physical adsorption-desorption techniques. The results showed that the specific surface area was as high as 1691 m². 2 / g, total pore volume is 2.03 cm³ 3 / g, with mesopore and macropore volumes reaching 1.82cm³. 3 / g. The ash content of TB-PC-1 was determined according to GB / T 12496.3-1999, and the ash content was 0.81%.

[0031] Example 3 (1) The same pretreated tea residue powder as in Example 1 was used.

[0032] (2) Weigh 200g of tea residue powder and mix it evenly with 80g of p-phenylenediethanol, 10g of p-toluenesulfonic acid and 80g of calcium oxide.

[0033] (3) Under nitrogen protection (200 mL / min), the temperature was increased to 160℃ at 5℃ / min and maintained for 8 hours. After switching to carbon dioxide (200 mL / min), the temperature was increased to 900℃ at the same rate and maintained for 1 hour, and then cooled down.

[0034] (4) Post-processing was the same as in Example 2. 117.4 g of porous carbon material was obtained, labeled as TB-PC-3, with a carbon yield of 58.7%.

[0035] The key structural properties of the prepared TB-PC-3 were analyzed using N2 low-temperature physical adsorption-desorption techniques. The results showed that the specific surface area was 1952 m². 2 / g, total pore volume is 2.46 cm³. 3 / g, the total pore volume of mesopores and macropores is 2.21 cm³. 3 / g. The ash content of TB-PC-1 was determined according to GB / T 12496.3-1999, and the ash content was 0.78%.

[0036] Example 4 (Comparative Example 1): (1) Take 200g of the same pretreated tea residue powder as in Example 1.

[0037] (2) Place the tea residue powder directly into a rotary kiln, and under nitrogen atmosphere (200 mL / min) protection, heat it to 150°C at a rate of 1°C / min and maintain it at that temperature for 8 hours. Then continue to heat it to 750°C at the same rate and maintain it at that temperature for 4 hours, and then cool it to room temperature.

[0038] (4) The carbonization product was thoroughly washed with dilute nitric acid solution, filtered, and then washed with deionized water until the filtrate was neutral. Finally, the material was dried at 110℃ for 12 hours. A total of 51g of carbon material was obtained, labeled as TPC-0. The carbon yield was 25.5%. Testing showed that the specific surface area of ​​TPC-0 was only 12 m². 2 / g, total pore volume of mesopores and macropores is less than 0.05 cm³. 3 / g. The ash content of TB-PC-1 was determined according to GB / T 12496.3-1999, and the ash content was 1.67%.

[0039] Example 5 (Comparative Experiment 2): (1) Weigh 80g of terephthalic acid, 10g of p-toluenesulfonic acid and 80g of calcium oxide and mix them evenly without adding tea residue powder.

[0040] (2) Transfer the mixture into a tube furnace and heat it to 160°C at a rate of 5°C / min under nitrogen protection (200 mL / min) and maintain the temperature for 8 hours. After switching to carbon dioxide (200 mL / min), heat it to 900°C at the same rate and maintain the temperature for 1 hour, then cool it down.

[0041] (3) The carbonization products were thoroughly washed with dilute hydrochloric acid solution and filtered. After filtration, no carbon material was found to remain.

[0042] Example 6 (Comparative Experiment 3): (1) Take 200g of pretreated tea residue powder, the same as in Example 1, and grind and mix it thoroughly with 50g of potassium hydroxide.

[0043] (2) The mixture was placed in a tube furnace and heated to 150°C at a rate of 1°C / min under a nitrogen atmosphere (200 mL / min) and maintained at that temperature for 8 hours. The temperature was then increased to 750°C at the same rate and maintained at that temperature for 4 hours, before being cooled to room temperature. The quartz furnace tubes showed significant corrosion.

[0044] (3) The carbonization product was thoroughly washed with dilute nitric acid solution, filtered, and then washed with deionized water until the filtrate was neutral. Finally, the material was dried at 110℃ for 12 hours. A total of 6.48g of carbon material was obtained, labeled as TPC-K, with a carbon yield of only 3.24%. The specific surface area of ​​TPC-K was tested to be 1443 m². 2 / g, total pore volume is 0.91 cm³ 3 / g, with mesopore and macropore volumes of 0.23 cm³. 3 / g. The TPC-K ash content was determined according to GB / T 12496.3-1999, and the ash content was 1.14%.

[0045] Example 7 (Comparative Experiment 4): (1) Take 200g of the same pretreated tea residue powder as in Example 1, mix it evenly with 2g of p-toluenesulfonic acid and 20g of calcium oxide powder, without adding p-phenylenediamine.

[0046] (2) Subsequent steps were the same as in Example 1. The obtained carbon material was labeled TB-PC-S1. The carbon yield was determined to be 20.7%.

[0047] Example 8 (Comparative Experiment 5): (1) Take 200g of the same pretreated tea residue powder as in Example 1, and mix it thoroughly with 20g of terephthalic acid and 2g of p-toluenesulfonic acid in a mixer without adding calcium oxide.

[0048] (2) Subsequent steps were the same as in Example 1. The obtained carbon material was labeled TB-PC-S2. The carbon yield was determined to be 28.6%.

[0049] Example 9 (Comparative Experiment 6): (1) Take 200g of pretreated tea residue powder, the same as in Example 1, mix it with 100g of 50% phosphoric acid, and impregnate it to form a precursor.

[0050] (2) Transfer the mixture into a tube furnace and heat it to 150°C at a rate of 1°C / min under nitrogen atmosphere (200 mL / min) protection. Maintain this temperature for 8 hours, then continue to heat it to 750°C at the same rate and maintain this temperature for 4 hours. Cool it to room temperature.

[0051] (3) The carbonization product was thoroughly washed with dilute hydrochloric acid solution, filtered, and then washed with deionized water until the filtrate was neutral. After drying, 71.6 g of porous carbon material was obtained, labeled as TPC-P, with a carbon yield of 35.8%. The specific surface area of ​​TPC-P was tested to be 1440 m². 2 / g, total pore volume is 1.21 cm³ 3 / g, with mesopore and macropore volumes of 0.63 cm³. 3 / g. The ash content of TPC-P was determined according to GB / T 12496.3-1999, and the ash content was 5.23%.

[0052] Example 10: Adsorption Performance Test 1 A 300 mg / L methylene blue aqueous solution was prepared. 0.02 g of each of the following carbon materials (TB-PC-1, TB-PC-2, TB-PC-3, TPC-0, TPC-K, and TPC-P) were weighed and added to 100 mL of the solution. The mixture was shaken at 25°C and 150 rpm for 12 hours to allow adsorption. The concentration of methylene blue in the solution was monitored using a UV-Vis spectrophotometer, with a detection wavelength of 664 nm. The adsorption capacities of the obtained carbon materials for methylene blue were: TB-PC-1 (479.39 mg / g), TB-PC-2 (517.22 mg / g), TB-PC-3 (565.76 mg / g), TPC-0 (21.46 mg / g), TPC-K (432.18 mg / g), and TPC-P (465.92 mg / g). Among the materials, TB-PC-1, TB-PC-2, and TB-PC-3 showed significantly higher adsorption capacities for methylene blue than the control group, with TB-PC-3 exhibiting the highest adsorption capacity, indicating optimal adsorption performance. This may be attributed to its unique structural regulation (such as high specific surface area and abundant mesopores and macropores), which facilitates the capture and fixation of large-sized dye molecules. In the control group, TPC-0 showed the lowest adsorption capacity, at only 21.46 mg / g, indicating that the unmodified tea residue-based carbon material has limited pore structure, fewer surface active sites, and weaker adsorption capacity. TPC-K showed significantly higher adsorption capacity than TPC-0, thanks to KOH activation which creates pores and expands the specific surface area, enhancing the adsorption of dyes. TPC-P showed higher adsorption capacity than TPC-K. Phosphoric acid activation may introduce phosphorus-containing functional groups or form a specific pore size distribution, resulting in higher mesopore and macropore content than TPC-K, which is beneficial for the adsorption of large-sized dye molecules. However, the porous carbon prepared by phosphoric acid activation has a higher ash content, making post-processing difficult. The methylene blue adsorption test results show that the porous carbon material prepared in this invention has excellent adsorption capacity for typical macromolecular dyes (methylene blue molecules are relatively large), and the adsorption performance is positively correlated with the specific surface area of ​​the material, especially the pore volume of mesopores and macropores. This verifies the application feasibility described in the claims, that is, the prepared high-yield, high-pore-volume material is suitable for removing macromolecular organic pollutants from water.

[0053] Example 11: Adsorption performance test 2 A 300 mg / L tetracycline hydrochloride aqueous solution was prepared. 0.02 g of each of the following carbon materials (TB-PC-1, TB-PC-2, TB-PC-3, TPC-0, TPC-K, and TPC-P) were weighed and added to 100 mL of the solution. The mixture was shaken at 25°C and 150 rpm for 12 hours for adsorption. The concentration of tetracycline hydrochloride in the water was monitored using a UV-Vis spectrophotometer, with a detection wavelength of 355 nm. The adsorption capacities of the obtained carbon materials for tetracycline hydrochloride were: TB-PC-1 (385.58 mg / g), TB-PC-2 (433.14 mg / g), TB-PC-3 (471.82 mg / g), TPC-0 (16.69 mg / g), TPC-K (351.23 mg / g), and TPC-P (369.68 mg / g). Among the three materials, TB-PC-1, TB-PC-2, and TB-PC-3 showed significantly higher adsorption capacities for tetracycline hydrochloride than the control group, with TB-PC-3 exhibiting the highest adsorption capacity, indicating optimal adsorption performance. This may be attributed to its unique structural regulation (such as high specific surface area and abundant mesopores and macropores), which facilitates the capture and immobilization of large-sized drug molecules. In the control group, TPC-0 showed the lowest adsorption capacity, at only 16.69 mg / g, indicating that the unmodified tea residue-based carbon material has limited pore structure, fewer surface active sites, and weaker adsorption capacity. TPC-K showed significantly higher adsorption capacity than TPC-0, thanks to KOH activation which creates pores and expands the specific surface area, enhancing the adsorption of dyes. TPC-P showed higher adsorption capacity than TPC-K. Phosphoric acid activation may introduce phosphorus-containing functional groups or form a specific pore size distribution, resulting in higher mesopore and macropore content than TPC-K, which is beneficial for the adsorption of large-sized drug molecules. However, the porous carbon prepared by phosphoric acid activation has a higher ash content, making post-processing difficult. The adsorption test results of tetracycline hydrochloride show that the porous carbon material prepared in this invention has excellent adsorption capacity for typical macromolecular drugs, and the adsorption performance is positively correlated with the specific surface area of ​​the material, especially the pore volume of mesopores and macropores.

[0054] Example 12: Evaluation Experiment of Continuous Adsorption Removal and Dynamic Regeneration of Drugs in Water A 100 mg / L tetracycline hydrochloride standard aqueous solution was prepared. 0.1034 g of TB-PC-3 prepared in Example 3 was accurately weighed, and a small amount of anhydrous ethanol was added to form a slurry. This slurry was then packed into a 50 mm long, 4.6 mm inner diameter stainless steel column using a wet packing method, with both ends sealed with clean quartz sand. The 50 mg / L tetracycline hydrochloride standard aqueous solution was continuously pumped into the stainless steel packed column using a horizontal flow pump at a flow rate of 2 mL / min. The concentration of tetracycline hydrochloride in the effluent was monitored in real time using a UV-Vis spectrophotometer. The detection wavelength for tetracycline hydrochloride was 355 nm. The continuous adsorption operation temperature was 25 °C. After adsorption saturation, the carbon adsorbent in the packed column was dynamically regenerated using anhydrous methanol. During the regeneration process, the packed column was placed in a water bath at a constant temperature of 60 °C. The desorption flow rate was 1.5 mL / min. After the desorption regeneration was completed, dynamic adsorption evaluation was performed again. Repeat the above dynamic adsorption-regeneration cycle five times consecutively. Plot the dynamic breakthrough curve.

[0055] Evaluation results show that TB-PC-3 exhibits excellent dynamic adsorption capacity and regenerability in 5 consecutive dynamic adsorption-regeneration cycles. After 5 consecutive adsorption-regeneration cycles, the dynamic adsorption performance did not change significantly from the initial state, demonstrating good potential for practical application.

Claims

1. A high-yield method for preparing porous carbon derived from tea residue, characterized in that, The process includes the following steps: (1) washing, drying, and crushing tea residue to obtain tea residue powder; (2) mixing a certain amount of tea residue powder, terephthalic acid, catalyst A, and additive B in a certain mass ratio; (3) transferring the mixture obtained in step (2) into a rotary kiln, and under the protection of an inert atmosphere, first heating to the stabilization treatment temperature and maintaining it for a certain time, then switching the inert atmosphere to carbon dioxide gas, and continuing to heat to the preset temperature for carbonization, and cooling to room temperature after carbonization; (4) washing the carbonization product with an acid solution, then washing it with deionized water until neutral, and drying it to obtain a high-yield porous carbon material.

2. The method according to claim 1, characterized in that, In step (1), the tea residue is one or a mixture of several types of black tea residue, green tea residue, and flower tea residue.

3. The method according to claim 1, characterized in that, In step (2), the mass ratio of tea residue powder to terephthalic acid is 1:0.1-1:

1.

4. The method according to claim 1, characterized in that, In step (2), the catalyst A is p-toluenesulfonic acid, and the mass ratio of tea residue powder to catalyst A is 1:0.01-1:0.

1.

5. The method according to claim 1, characterized in that, In step (2), the auxiliary agent B is calcium oxide, and the mass ratio of tea residue powder to auxiliary agent B is 1:0.1-1:

1.

6. The method according to claim 1, characterized in that, In step (3), the heating rate is 1-5℃ / min; the stabilization temperature is 140℃-170℃, and the stabilization stage is maintained for 2h-8h; the carbonization temperature is 750℃-950℃, and the carbonization stage is maintained for 1h-4h.

7. The method according to claim 1, characterized in that, In step (4), the acid solution is either dilute hydrochloric acid or dilute nitric acid solution.

8. The method according to claim 1, characterized in that, The prepared porous carbon materials had a yield of 40%-60% and a specific surface area of ​​100-2000 m². 2 / g; the cumulative pore volume of mesopores and macropores is greater than 0.5cm³. 3 / g; ash content less than 3%.

9. The application of the porous carbon material prepared by the method according to claim 1 in the continuous adsorption removal and dynamic regeneration of organic pollutants with large molecular size in water.

10. The application according to claim 8, characterized in that: The organic pollutants with large molecular size are one of tetracycline hydrochloride, methylene blue, Congo red, and rhodamine B, and the concentration of organic pollutants in the wastewater is 10-500 ppm.

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