Preparation method and application of pine-based activated carbon with high specific surface area and high mesoporous volume

Abstract

The method comprises the following steps: taking pine wood powder as a carbon source, introducing triphenylphosphine oxide TPPO as a polymerization inhibitor and a carbon structure optimizer, mixing with the pine wood powder, carrying out hydrothermal modification, mixing with potassium hydroxide, and carrying out high-temperature activation to obtain the high-specific-surface-area high-mesoporous-volume pine-based activated carbon. And finally, pickling, washing and drying. Through the synergistic effect of activation of TPPO and KOH, the contradiction between high specific surface area and high mesoporous volume is reconciled, synchronous optimization of a pore structure is realized under the condition that a template agent is not used, and the specific surface area and mesoporous volume of the pine-based activated carbon are improved. The adsorption capacity of the activated carbon to high-concentration bisphenol A reaches up to 434.48 mg / g, and compared with pine-based activated carbon without TPPO action, the adsorption capacity is remarkably improved. The method is simple in process and environment-friendly, and the prepared activated carbon has a wide application prospect in the aspect of efficiently adsorbing and removing organic pollutants in a water body.

Description

Technical Field

[0001] This invention relates to the field of high-value utilization of biomass resources and preparation of advanced adsorption materials. Specifically, it relates to a method and application for preparing activated carbon with high specific surface area and high mesopore volume using pine wood as raw material through synergistic modification and activation strategies. Background Technology

[0002] Activated carbon, due to its well-developed pore structure, high specific surface area, stable chemical properties, and abundant surface functional groups, is widely used in environmental remediation, energy storage, catalysis, and other fields. Especially in water treatment, activated carbon is crucial for the adsorption and removal of organic pollutants such as dyes, phenolic compounds, pharmaceuticals, and personal care products.

[0003] For adsorption processes, the pore structure of activated carbon is a key factor determining its adsorption performance. Generally, a high specific surface area provides more adsorption sites, while a well-developed mesoporous structure (pore size 2-50 nm) facilitates the diffusion and transport of macromolecular pollutants, reducing mass transfer resistance. However, in conventional preparation processes, it is often difficult to simultaneously achieve high specific surface area and high mesopore volume. For example, activated carbon with extremely high specific surface area (>1500 m² / g) can usually be prepared using strong base (such as KOH) chemical activation methods, but its pores are mainly micropores (pore size <2 nm), with a microporosity often exceeding 65%, which is not conducive to the entry of macromolecules. While chemical activators such as phosphoric acid (H3PO4) can promote the development of mesopores and macropores (total pore volume ≤1.4 cm³), the results are not ideal. 3 While the mesopore content can reach up to 35%, the specific surface area of ​​the activated carbon prepared using this method is typically limited (≤1500 m² / g). In short, the formation of high mesopores often comes at the cost of reduced specific surface area, making it difficult to balance high specific surface area with high mesopore content. This severely limits its practical application in the removal of macromolecular pollutants. This "trade-off" contradiction restricts the efficient adsorption of large amounts of macromolecular or hydrophobic organic pollutants (such as bisphenol A and some dyes) present in water by traditional activated carbon.

[0004] Pine wood, as a widely available, renewable, and inexpensive forestry residue or processing byproduct, is an excellent carbon precursor for the preparation of biomass activated carbon. How to simultaneously increase the specific surface area and mesopore volume of pine-based activated carbon through green and efficient modification methods, thereby achieving targeted control of its pore structure and significantly enhancing its adsorption capacity for typical macromolecular pollutants, is a pressing technical problem in this field, and also has significant economic and environmental benefits. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art in preparing pine-based activated carbon, which makes it difficult to achieve both high specific surface area and high mesopore volume. It provides a method for preparing pine-based activated carbon with high specific surface area and high mesopore volume. Another objective of the present invention is to provide pine-based activated carbon with excellent pore structure parameters prepared by the method, and further disclose its application in the efficient adsorption and removal of typical macromolecular organic pollutants (such as bisphenol A) in water.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing pine-based activated carbon with high specific surface area and high mesoporous volume includes the following steps:

[0008] (1) Pretreatment and mixing: Dry pine wood powder and triphenylphosphine oxide (TPPO) are thoroughly and uniformly mixed at a certain mass ratio (0.5-1):1 to obtain a mixture;

[0009] (2) Hydrothermal modification: The mixture obtained in step (1) is placed in a hydrothermal reactor, an appropriate amount of deionized water is added, and after sealing, it is placed in an oven or muffle furnace. The mixture is then subjected to hydrothermal reaction at a certain temperature for a period of time. This process causes the cellulose, hemicellulose and lignin components in pine wood to undergo hydrolysis, dehydration and condensation reactions, initially forming hydrothermal carbon rich in oxygen functional groups. At the same time, TPPO may play a role in inhibiting excessive polymerization and optimizing the formation of carbon skeleton during this process. After the reaction is completed, the mixture is naturally cooled, and the obtained solid product is washed to remove soluble impurities, and then dried to obtain modified carbon.

[0010] (3) Alkali mixing: The modified carbonaceous material obtained in step (2) is mixed with solid potassium hydroxide (KOH) at a certain mass ratio of (1.5-2):1 to obtain a blend, so as to ensure the effective progress of the subsequent activation reaction;

[0011] (4) Activation: The blend obtained in step (3) is placed in a container resistant to high temperature and alkali corrosion (such as a nickel boat), and then transferred to a high-temperature device such as a tube furnace. Under an inert protective gas atmosphere (such as nitrogen or argon), the temperature is programmed to rise to a certain temperature at a heating rate not exceeding 10℃ / min, and then held at the target temperature for a period of time for activation. At this high temperature, KOH undergoes a violent redox reaction with carbonaceous material, etching a large amount of carbon skeleton, thereby creating pores.

[0012] (5) Post-processing: After activation, the product activated in step (4) is cooled to room temperature and then acid washed to completely remove residual potassium salt and ash. Then it is washed with deionized water until the filtrate is neutral and then dried to constant weight to obtain the high specific surface area and high mesoporous volume pine wood-based activated carbon.

[0013] As a further improvement of the present invention, in step (1), the mass ratio of triphenylphosphine oxide to pine powder is 0.5:1, 0.75:1 or 1:1, and the mixing is carried out by ball milling for 15-30 minutes to ensure that the two are mixed evenly and that preliminary physical interaction may occur.

[0014] As a further improved technical solution of the present invention, step (2) specifically involves: placing the mixture obtained in step (1) in a hydrothermal reactor and hydrothermally reacting it at 200°C for 2 hours. After the reaction is completed, the product is washed and dried to obtain modified carbonaceous material.

[0015] As a further improvement of the present invention, in step (3), the mass ratio of the modified carbon to solid potassium hydroxide is 1.5:1, 1.75:1 or 2:1, and the mixing method is grinding.

[0016] As a further improved technical solution of the present invention, step (4) specifically involves: placing the blend obtained in step (3) in a high-temperature furnace under nitrogen atmosphere protection, heating it to 800 ℃ at a heating rate of ≤10 ℃ / min, and activating it at this temperature for 60 minutes.

[0017] As a further improvement of the present invention, the high-temperature furnace is a tube furnace, and the blend is placed in a nickel boat for activation.

[0018] As a further improvement of the present invention, in step (5), the pickling is carried out using hydrochloric acid with a concentration of 0.1M.

[0019] The high specific surface area and high mesoporous volume pine-based activated carbon prepared according to the above preparation method has a specific surface area of ​​1827.48-1969.28 m² / g, a total pore volume of 1.33-1.43 cm³ / g, a mesoporous volume of 0.56-0.60 cm³ / g, and a mesopority of 40.84%-42.10%.

[0020] This invention also provides the application of the above-mentioned high specific surface area and high mesoporous volume pine-based activated carbon in the adsorption and removal of organic pollutants in water, especially suitable for the adsorption and removal of phenolic compounds, and most preferably used for the adsorption and removal of bisphenol A (BPA).

[0021] The beneficial effects of this invention are as follows:

[0022] (1) Synergistic optimization of pore structure: This invention innovatively introduces triphenylphosphine oxide (TPPO) as a polymerization inhibitor and carbon structure optimizer, which intervenes in the formation process of carbon skeleton during the hydrothermal pretreatment stage, and produces a synergistic effect with the subsequent KOH activation step. This synergistic effect effectively breaks the opposition between high specific surface area and high mesopore volume in traditional methods. While significantly increasing the specific surface area of ​​the product (up to 1969.28 m² / g), it also greatly increases the total pore volume (up to 1.43 cm³ / g), mesopore volume (up to 0.60 cm³ / g), and mesopore rate (up to 42.10%).

[0023] (2) Simple and efficient process, environmentally friendly: The method of this invention has a simple process, which includes only one hydrothermal pretreatment and one high-temperature activation. It does not require the use of expensive or difficult-to-remove hard / soft template agents, nor does it require complex secondary activation, thus reducing production costs and process complexity. The raw material is biomass waste, realizing the value-added utilization of resources.

[0024] (3) Excellent adsorption performance: Thanks to the unique "high specific surface area-high mesopore volume" composite pore structure, the activated carbon prepared by this invention exhibits excellent adsorption performance for macromolecular organic pollutants such as bisphenol A. The adsorption capacity is significantly higher than that of the control sample without TPPO modification (the increase can reach 113.79 mg / g), and it has broad application prospects in the field of deep water pollution treatment.

[0025] (4) Adjustable product performance: By adjusting key parameters such as the initial mass ratio of TPPO to pine powder, the amount of KOH, the activation temperature and time, the specific surface area, pore volume and pore size distribution of the final activated carbon can be controlled within a certain range to meet the specific needs of adsorption of different pollutants. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the method for preparing high specific surface area and high mesoporous volume pine-based activated carbon according to the present invention.

[0027] Figure 2 The nitrogen adsorption-desorption curves are for the different pine-based activated carbon samples prepared in Examples 1-4.

[0028] Figure 3 The graph shows the pore size distribution of different pine-based activated carbon samples prepared in Examples 1-4.

[0029] Figure 4 The graph shows the adsorption performance of bisphenol A (BPA) on different pine-based activated carbon samples prepared in Examples 1-4. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods.

[0031] Raw materials: Pine wood powder (commercially available, particle size 80-100 mesh), triphenylphosphine oxide (Shanghai Maclean Biochemical Technology Co., Ltd.).

[0032] Main equipment: reaction vessel, muffle furnace, high-temperature tube furnace, drying oven, Autosorb-iQ fully automatic gas adsorption analyzer, etc.

[0033] Example 1 (Comparative example, without TPPO):

[0034] As a comparison, 5 g of pine wood powder was placed in a polytetrafluoroethylene reaction vessel, 60 mL of deionized water was added, and the mixture was stirred until it was evenly dispersed. The reaction vessel was then placed in a muffle furnace at 200 ℃ and kept at that temperature for 2 h. After the reaction was completed, the mixture was cooled to room temperature, the reaction vessel was opened, and the resulting solid product was washed several times with deionized water and then dried to obtain modified pine wood powder.

[0035] Modified pine powder was thoroughly ground and mixed with 5 g of KOH to obtain a blend. The blend was transferred to a nickel boat and placed in a tube furnace. Under a nitrogen atmosphere (50 mL / min), the temperature was slowly increased from room temperature to 800 °C at a rate of 10 °C / min and held at this temperature for 60 min. After activation, the mixture was naturally cooled to room temperature under continuous nitrogen purging.

[0036] The activated product was removed, repeatedly washed with 0.1 M hydrochloric acid, then washed with deionized water until neutral and dried to obtain pine-based activated carbon (labeled as PC) sample.

[0037] Nitrogen adsorption tests were performed on the PC sample, and the specific surface area of ​​PC was 1749.23 m². 2 / g, total pore volume is 0.91 cm³ 3 / g, micropore volume is 0.55 cm³ / g, mesopore volume is 0.15 cm³ / g. 3 / g, with mesoporous components accounting for 16.48%.

[0038] From Table 1 and Appendix Figure 4 It can be seen that PC has an adsorption capacity of 320.69 mg / g for bisphenol A (100 mg / L) within 90 min.

[0039] Figure 1 This is a process flow diagram of the method for preparing high specific surface area and high mesoporous volume pine-based activated carbon according to the present invention. The flow diagrams for Examples 2-4 are shown below. Figure 1 As shown.

[0040] Example 2:

[0041] 5 g of pine wood powder and 2.5 g of triphenylphosphine oxide (TPPO) were ball-milled for 20 min and then placed in a polytetrafluoroethylene reaction vessel. 60 mL of deionized water was added and the mixture was stirred until homogeneous. The reaction vessel was then placed in a muffle furnace at 200 ℃ and kept at that temperature for 2 h. After the reaction was completed, the mixture was cooled to room temperature, the reaction vessel was opened, and the resulting solid product was washed several times with deionized water and then dried to obtain a mixture.

[0042] The mixture was ground with 5 g of KOH to obtain a blend. The blend was transferred to a nickel boat and placed in a tube furnace. Under a nitrogen atmosphere (50 mL / min), the temperature was increased from room temperature to 800 °C at a slow heating rate (10 °C / min) and held at this temperature for 60 min. After activation, the mixture was naturally cooled to room temperature under continuous nitrogen purging.

[0043] After the product is activated, it is first washed repeatedly with 0.1 M hydrochloric acid, then washed with deionized water until neutral and dried to obtain pine-based activated carbon (PC-1).

[0044] The specific surface area of ​​PC-1 was measured to be 1958.49 m². 2 / g, total pore volume is 1.42 cm³ 3 / g, micropore volume 0.47 cm³ / g, mesopore volume 0.58 cm³ / g 3 / g, mesoporous content 40.84%.

[0045] From Table 1 and Appendix Figure 4 It can be seen that PC-1 has an adsorption capacity of 382.41 mg / g for bisphenol A (100 mg / L) within 90 min.

[0046] Example 3:

[0047] 5 g of pine wood powder and 3.75 g of triphenylphosphine oxide (TPPO) were ball-milled for 20 min and then placed in a polytetrafluoroethylene reaction vessel. 60 mL of deionized water was added and the mixture was stirred until homogeneous. The reaction vessel was then placed in a muffle furnace at 200 ℃ and kept at that temperature for 2 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction vessel was then opened, and the resulting solid product was washed several times with deionized water and then dried to obtain a mixture.

[0048] The mixture was ground with 5 g of KOH to obtain a blend. The blend was transferred to a nickel boat and placed in a tube furnace. Under a nitrogen atmosphere (50 mL / min), the temperature was increased from room temperature to 800 °C at a slow heating rate (10 °C / min) and held at this temperature for 60 min. After activation, the mixture was naturally cooled to room temperature under continuous nitrogen purging.

[0049] After the product is activated, it is first washed repeatedly with 0.1 M hydrochloric acid, then washed with deionized water until neutral and dried to obtain pine-based activated carbon (PC-2).

[0050] The specific surface area of ​​PC-2 was measured to be 1827.48 m². 2 / g, total pore volume is 1.33 cm³ 3 / g, micropore volume 0.42 cm³ / g, mesopore volume 0.56 cm³ / g 3 / g, mesoporous content 42.10%.

[0051] From Table 1 and Appendix Figure 4 It can be seen that PC-2 has an adsorption capacity of 434.48 mg / g for bisphenol A (100 mg / L) within 90 min.

[0052] Example 4:

[0053] 5 g of pine wood powder and 5 g of triphenylphosphine oxide (TPPO) were ball-milled for 20 min and then placed in a polytetrafluoroethylene reaction vessel. 60 mL of deionized water was added and the mixture was stirred until homogeneous. The reaction vessel was then placed in a muffle furnace at 200 ℃ and kept at that temperature for 2 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction vessel was then opened, and the resulting solid product was washed several times with deionized water and then dried to obtain a mixture.

[0054] The mixture was ground with 5 g of KOH to obtain a blend. The blend was transferred to a nickel boat and placed in a tube furnace. Under a nitrogen atmosphere (50 mL / min), the temperature was increased from room temperature to 800 °C at a slow heating rate (10 °C / min) and held at this temperature for 60 min. After activation, the mixture was naturally cooled to room temperature under continuous nitrogen purging.

[0055] After the product is activated, it is first washed repeatedly with 0.1 M hydrochloric acid, then washed with deionized water until neutral and dried to obtain pine-based activated carbon (PC-3).

[0056] The specific surface area of ​​PC-3 was measured to be 1969.28 m². 2 / g, total pore volume is 1.43 cm³ 3 / g, micropore volume 0.49 cm³ / g, mesopore volume 0.60 cm³ / g 3 / g, mesoporous content is 41.96%.

[0057] From Appendix 1 and Appendix Figure 4 It can be seen that PC-3 has an adsorption capacity of 413.18 mg / g for bisphenol A (100 mg / L) within 90 min.

[0058] Table 1 shows the pore structure parameters and bisphenol A adsorption performance of pine-based activated carbon.

[0059] Activated carbon <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Total pore volume (cm 3 / g)]]> <![CDATA[Micropore volume (cm 3 / g)]]> <![CDATA[Mesopore volume (cm 3 / g)]]> Mesopority (%) Bisphenol A adsorption capacity (mg / g) PC 1749.23 0.91 0.55 0.15 16.48 320.69 PC-1 1958.49 1.42 0.47 0.58 40.84 382.41 PC-2 1827.48 1.33 0.42 0.56 42.10 434.48 PC-3 1969.28 1.43 0.49 0.60 41.96 413.18

[0060] Combining the data in Table 1 and the attached figures, it can be seen that:

[0061] Pore ​​structure evolution ( Figure 2 , Figure 3 Table 1): Through Figure 2 The nitrogen adsorption curves confirmed that the material contains abundant micropores and mesopores. Compared with the comparative PC, the adsorption capacity of TPPO-modified samples PC-1, PC-2, and PC-3 was significantly increased in the high-pressure region, corresponding to a substantial increase in their total pore volume and mesopore volume. Figure 3 The pore size distribution curves more intuitively show that the mesopore peak of the PC sample is very weak in the 2-5 nm range, while the PC-1, PC-2, and PC-3 samples show significant and broad mesopore distribution peaks in this region, especially in the 2-10 nm range where the pore volume contribution is prominent.

[0062] Structure and Performance Correlation: Comparison of the pore structure parameters and adsorption data of PC and PC-1 / 2 / 3 reveals that although PC has a relatively high specific surface area (1749 m² / g), its mesopore volume is extremely small (0.15 cm³ / g) and its mesoporous ratio is low (16.48%), limiting the diffusion of BPA macromolecules into its internal microporous regions, resulting in a relatively low adsorption capacity. However, after introducing TPPO, although the specific surface area of ​​some samples (such as PC-2) decreased slightly, the mesopore volume (0.56-0.60 cm³ / g) and mesoporous ratio (>40%) of all modified samples were increased several times, forming an ideal structure of "high specific surface area - high mesoporous ratio". This structure provides BPA molecules with rapid transport mesoporous channels and a large number of accessible microporous adsorption sites, thus achieving a leap in adsorption capacity.

[0063] Effect of TPPO dosage: As can be seen from Examples 2-4, the addition of TPPO is key to improving mesopore size. Within a certain range (mass ratio of 0.5:1 to 1:1), activated carbon with high specific surface area and high mesopore volume can be effectively prepared. Among them, when the mass ratio of TPPO to pine powder is 0.75:1 (PC-2), the product exhibits the best adsorption performance for BPA (bisphenol A) while maintaining a high specific surface area, indicating the existence of an optimized ratio range.

[0064] In summary, this invention successfully prepared pine-based activated carbon with both high specific surface area and high mesopore volume by introducing a strategy of TPPO synergistic modification and KOH activation, and exhibited excellent adsorption capacity for the macromolecular pollutant bisphenol A, solving the problem that traditional methods cannot achieve both simultaneously.

[0065] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technical principles and concepts disclosed in the present invention, such as using other coniferous wood powders, adjusting the hydrothermal temperature or time, employing other inert atmospheres, or using the activated carbon to adsorb other macromolecular organic pollutants (such as dyes like Congo red and methylene blue, or antibiotics like tetracycline), should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing pine-based activated carbon with high specific surface area and high mesoporous volume, characterized in that, Includes the following steps: (1) Pretreatment: Pine wood powder and triphenylphosphine oxide are mixed evenly to obtain a mixture; (2) Hydrothermal modification: The obtained mixture is placed in a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, the product is washed and dried to obtain modified carbonaceous material. (3) Alkali mixing: The obtained modified carbonaceous material is uniformly mixed with solid potassium hydroxide to obtain a blend; (4) Activation: The obtained blend is activated in a high-temperature furnace under an inert atmosphere; (5) Post-processing: Cool the activated product to room temperature, then acid wash and water wash until neutral, and then dry to constant weight to obtain the high specific surface area and high mesoporous volume pine wood-based activated carbon.

2. The method for preparing high specific surface area and high mesoporous volume pine-based activated carbon according to claim 1, characterized in that, In step (1), the mass ratio of triphenylphosphine oxide to pine powder is (0.5-1):1, the mixing method is ball milling, and the ball milling time is 15-30 minutes.

3. The method for preparing high specific surface area and high mesoporous volume pine-based activated carbon according to claim 1, characterized in that, The specific steps (2) are as follows: the mixture obtained in step (1) is placed in a hydrothermal reactor and hydrothermally reacted at 200°C for 2 hours. After the reaction is completed, the product is washed and dried to obtain modified carbonaceous material.

4. The method for preparing high specific surface area and high mesoporous volume pine-based activated carbon according to claim 1, characterized in that, In step (3), the mass ratio of the modified carbonaceous material to solid potassium hydroxide is (1.5-2):1, and the mixing method is grinding.

5. The method for preparing high specific surface area and high mesoporous volume pine-based activated carbon according to claim 1, characterized in that, The specific steps (4) are as follows: the blend obtained in step (3) is placed in a nickel boat and placed in a high-temperature tube furnace under nitrogen atmosphere protection, heated to 800 ℃ at a heating rate of ≤10 ℃ / min, and held at this temperature for 60 minutes for activation.

6. The method for preparing high specific surface area and high mesoporous volume pine-based activated carbon according to claim 1, characterized in that, In step (5), the pickling is performed using hydrochloric acid with a concentration of 0.1M.

7. High specific surface area and high mesoporous volume pine-based activated carbon prepared by the preparation method according to any one of claims 1-6.

8. The high specific surface area and high mesoporous volume pine-based activated carbon according to claim 7, characterized in that: Its specific surface area is 1827.48-1969.28 m² / g, total pore volume is 1.33-1.43 cm³ / g, mesopore volume is 0.56-0.60 cm³ / g, and mesopore rate is 40.84%-42.10%.

9. The application of the high specific surface area and high mesoporous volume pine-based activated carbon according to any one of claims 7-8 in the adsorption and removal of organic pollutants in water.

10. The application according to claim 9, characterized in that: The organic pollutant is a phenolic compound, and the phenolic compound is bisphenol A.

Images