Biomass-derived porous carbon with ion adsorption potential and preparation method thereof

Abstract

The invention provides a preparation method of biomass-derived porous carbon with ionic adsorption potential, which comprises the following steps: adding disodium ethylene diamine tetraacetate and ferrous chloride into water, and uniformly mixing to obtain EDTA-Fe; the preparation method comprises the following steps: sequentially adding an acetic acid-sodium acetate buffer solution and a biomass material into EDTA-Fe, uniformly mixing, adding aluminum chloride, carrying out a hydrothermal reaction to obtain a primary product, cleaning the primary product, and drying to obtain biomass hydrothermal carbon; the preparation method comprises the following steps: soaking biomass hydrothermal carbon in a saturated solution of potassium carbonate, then carrying out solid-liquid separation, firstly drying a solid obtained by separation, then calcining in a nitrogen atmosphere, and cleaning to obtain the biomass derived porous carbon. The biomass hydrothermal carbon prepared by the method has regular and controllable morphology, abundant surface functional groups and a stable carbon skeleton structure, and shows excellent electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of porous carbon preparation technology, specifically relating to a biomass-derived porous carbon with ion adsorption potential and its preparation method. Background Technology

[0002] Hydrothermal carbonization technology has attracted increasing attention for its economic and environmentally friendly advantages in the efficient conversion and application of biomass resources. This technology uses water as the reaction solvent and biomass as the raw material to synthesize carbon-rich solid products in a sealed pressure vessel at temperatures below 375 ℃ (typically 150-280 ℃). Due to the involvement of a subcritical water medium, the products obtained through hydrothermal carbonization possess many inherent advantages, such as uniform size, regular morphology, good physicochemical stability, and a surface rich in oxygen-containing functional groups. Therefore, hydrothermal carbon materials have wide applications in environmental remediation, catalyst supports, and supercapacitors. In terms of energy density, hydrothermal carbon is close to the quality of peat and lignite, and can be directly burned as a composite solid fuel. Furthermore, after undergoing certain hydrothermal cross-linking carbonization treatments, carbon with uniform size and good morphology can be obtained, which, through synthesis and modification, can be used as a highly efficient and stable nanoscale carbon functional material.

[0003] Due to the complex composition of biomass, hydrothermal carbonization reactions in pure water systems cannot produce carbon microspheres with complete and dispersed morphologies. Therefore, adding a catalyst to the hydrothermal system may be a feasible solution. To enable the added catalyst to function better, this invention proposes a controlled release scheme for the iron ion catalyst.

[0004] Currently, the main methods for converting hydrothermal carbon into porous carbon include physical activation and chemical activation. Physical activation often results in insufficient and unevenly distributed pore structures; chemical activation often uses highly corrosive reagents such as KOH and ZnCl2 as activators, which can form abundant pores, but also causes problems such as severe equipment corrosion, wastewater pollution, and difficulty in recovering the activators. In addition, due to the complex composition of biomass raw materials, the morphology and structure of the precursor hydrothermal carbon are not very consistent, resulting in poor morphology retention and low controllability of pore structure of the porous carbon obtained by subsequent calcination or activation, which seriously restricts its application performance.

[0005] To address the above problems, this invention provides a method for preparing biomass-derived porous carbon with regular morphology and stable structure. Summary of the Invention

[0006] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a method for preparing biomass-derived porous carbon with ion adsorption potential. This invention utilizes a controlled iron ion release strategy to construct a biomass hydrothermal carbon precursor with regular morphology and stable structure in the early hydrothermal stage. This precursor exhibits excellent structural inheritance during subsequent calcination. Its regular morphology and uniform composition facilitate the formation of a well-developed and uniformly distributed pore structure at high temperatures, while effectively maintaining the stability of surface functional groups. This avoids the dependence on strong corrosive reagents and the uncontrollable pore structure defects of traditional activation methods, ultimately yielding a porous carbon material with high specific surface area, excellent electrical conductivity, and stable chemical properties, significantly enhancing the added value and application potential of biomass carbon materials.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing biomass-derived porous carbon with ion adsorption potential, the preparation method comprising the following steps:

[0008] S1. Disodium ethylenediaminetetraacetate and ferrous chloride are added to water and mixed evenly to obtain EDTA-Fe;

[0009] S2. Add acetate-sodium acetate buffer solution to the EDTA-Fe obtained in S1, then add biomass material and mix evenly. Finally, add aluminum chloride to carry out hydrothermal reaction. After hydrothermal reaction, centrifuge to obtain the primary product. Wash the primary product and dry it to obtain biomass hydrothermal char.

[0010] S3. The biomass hydrothermal carbon obtained in S2 is soaked in a saturated solution of potassium carbonate, and then solid-liquid separation is performed to collect the solid. The solid is first dried, and then calcined in a nitrogen atmosphere. After calcination, it is washed to obtain biomass-derived porous carbon.

[0011] Preferably, the molar ratio of disodium ethylenediaminetetraacetate and ferrous chloride in S1 is 1:1, and the molar volume ratio of disodium ethylenediaminetetraacetate and water is 0.0015 mol: 60 mL.

[0012] Preferably, the mass-volume ratio of EDTA-Fe, the acetate-sodium acetate buffer solution, and the biomass material in S2 is 60 mL: 5 mL: 1 g, and the biomass material is straw.

[0013] Preferably, the molar ratio of aluminum chloride in S2 to disodium ethylenediaminetetraacetate in S1 is 1:1.

[0014] Preferably, the hydrothermal reaction in S2 is carried out at a temperature of 180 °C for 24 h; the initial product is washed with distilled water; the drying temperature is 60 °C for 8-12 h; and the centrifugation speed is 6000-8000 r / min for 5-10 min.

[0015] Preferably, in step S3, the biomass hydrothermal char is soaked in a saturated potassium carbonate solution for 24 hours; the drying temperature is 60 °C for 12 hours; the calcination temperature is 800 °C for 2 hours; and distilled water is used for cleaning.

[0016] The present invention also provides a biomass-derived porous carbon, which is prepared by the above-mentioned method for preparing a biomass-derived porous carbon with ion adsorption potential.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. In this invention, iron ions are added as a catalyst for the hydrothermal reaction to better promote the formation of regular morphologies during the hydrothermal process. As the hydrothermal reaction proceeds, due to the reaction between EDTA and Al... 3+ Its binding ability is slightly higher than that of EDTA and Fe. 2+ The ability of Al to combine 3+ Slowly taking away Fe 2+ The combined EDTA forms EDTA-Al, while simultaneously transferring Fe 2+ Released, the released Fe 2+ It will participate as a catalyst in the carbonization reaction of biomass materials. Due to the interaction between EDTA and Al... 3+ The complexation rate is very slow, Fe 2+ The release rate will be slow and controllable, which is conducive to the formation of controllable morphology of hydrothermal carbon and the generation of surface functional groups.

[0019] 2. The biomass hydrothermal char prepared by this invention exhibits good structural order and chemical stability, and possesses a regular morphology. After high-temperature calcination, it demonstrates excellent electrochemical performance. Furthermore, the unique morphology and abundant oxygen-containing functional groups of the biomass hydrothermal char are also beneficial for preparing higher-performance biomass-derived porous char.

[0020] 3. The biomass-derived porous carbon prepared by this invention has a regular and controllable morphology, abundant surface functional groups and a stable carbon framework structure, exhibiting excellent electrochemical performance, including high specific capacity and excellent rate performance. At the same time, its good surface chemical properties also help to improve adsorption capacity, making it a multifunctional carbon material with excellent comprehensive performance.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a SEM image of the hydrothermal carbon obtained in S2 of Example 1 of the present invention.

[0023] Figure 2 This is a SEM image of the biomass-derived porous carbon prepared in Example 1 of the present invention.

[0024] Figure 3 The data represent the CV and charge / discharge data of the supercapacitor assembled using biomass-derived porous carbon as electrodes prepared in Example 1 of this invention.

[0025] Figure 4 lgK' of EDTA complex MY -pH curve.

[0026] Figure 5 The image shows a SEM image of the hydrothermal carbon prepared in Comparative Example 1.

[0027] Figure 6 This is a SEM image of the porous carbon prepared in Comparative Example 2.

[0028] Figure 7 The graph shows the charge-discharge data of the porous carbon prepared in Comparative Example 2. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment provides a method for preparing biomass-derived porous carbon with ion adsorption potential, the method comprising the following steps:

[0032] S1. Add 0.0015 mol disodium ethylenediaminetetraacetate (EDTA) and 0.0015 mol ferrous chloride (FeCl2) to 60 mL of water and mix well to obtain EDTA-Fe;

[0033] S2. Add 5 mL of acetate-sodium acetate buffer solution to 60 mL of EDTA-Fe obtained in S1, controlling the pH to be between 4 and 5. Then add 1 g of straw and mix well. Finally, add 0.0015 mol of aluminum chloride (AlCl3) and carry out a hydrothermal reaction at 180℃ for 24 h. After the hydrothermal reaction, centrifuge at 7000 r / min for 8 min to obtain the primary product. Wash the primary product with distilled water and dry it in an oven at 60℃ for 9 h to obtain biomass hydrothermal char.

[0034] S3. The biomass hydrothermal carbon obtained in S2 is soaked in a saturated potassium carbonate solution for 24 h, and then solid-liquid separation is performed to collect the solid. The solid is first dried at 60 ℃ for 12 h, and then calcined at 800 ℃ in a nitrogen atmosphere for 2 h. After calcination, it is washed with distilled water to obtain biomass-derived porous carbon.

[0035] The drying time in S2 of this embodiment can also be 8h, 8.5h, 9.5h, 10h, 10.5h, 11h, 11.5h or 12h; the centrifugal separation speed can also be 6000 r / min, 6500 r / min, 6900 r / min, 7500 r / min, 7800 r / min or 8000 r / min, and the time can also be 5 min, 6 min, 7 min, 8.5 min, 9 min or 10 min.

[0036] Figure 1 The image shows the SEM image of the biomass hydrothermal char obtained in Example S2 of this embodiment. It can be seen from the image that the biomass hydrothermal char obtained in this embodiment has a uniform morphology and particle size.

[0037] As the reaction proceeds, due to the interaction between EDTA and Al... 3+ Its binding ability is slightly higher than that of EDTA and Fe. 2+ The binding ability of Al (as shown in Table 1) 3+ Slowly taking away Fe 2+ The combined EDTA forms EDTA-Al, while simultaneously transferring Fe 2+ Released, the released Fe 2+ It will participate as a catalyst in the carbonization reaction of biomass materials.

[0038] Throughout the hydrothermal reaction process, in order to maintain the relationship between EDTA and Al 3+ Its binding ability is consistently slightly higher than that of EDTA and Fe. 2+ The binding capacity requires the pH to be consistently maintained between 2 and 5. Figure 4(As shown). However, if the acidity is too low, it will affect the decarboxylation and other reactions during the hydrothermal reaction. Therefore, it is necessary to control the pH between 4 and 5 and add an acetate-sodium acetate buffer solution to maintain the pH stability of the solution.

[0039] Table 1 EDTA and Al 3+ Fe 2+ The ability to combine

[0040]

[0041] The biomass hydrothermal char obtained in S2 was pore-formed by immersing it in a saturated potassium carbonate solution. The presence of functional groups on the surface of the biomass hydrothermal char improved its wettability in the saturated potassium carbonate solution, which facilitated the adsorption of the pore-forming agent potassium carbonate. The uniform morphology of the biomass hydrothermal char further promoted the uniform adsorption of the pore-forming agent potassium carbonate. After immersion, solid-liquid separation was performed. Distilled water was not used for washing at this stage to prevent the adsorbed pore-forming agent potassium carbonate from being washed away. The char was then calcined and washed with distilled water.

[0042] The morphology of the biomass-derived porous carbon obtained in this embodiment is shown in the figure below. Figure 2 As shown in the figure, biomass porous carbon has a uniform porous structure as an electrode material.

[0043] Using the biomass-derived porous carbon obtained in this embodiment as electrodes, the CV and charge-discharge data of the assembled supercapacitor are as follows: Figure 3 As shown in the figure, the biomass-derived porous carbon material exhibits good double-layer behavior and highly reversible charge-discharge behavior.

[0044] Comparative Example 1

[0045] This comparative example provides a conventional method for preparing hydrothermal char, which includes the following steps:

[0046] 6 g of pulverized bamboo raw material, 0.6 g of Fe2(SO4)3, and 60 mL of deionized water were weighed and mixed in a polytetrafluoroethylene liner. After sonication for 15 min at room temperature, the mixture was sealed in a stainless steel reactor. The reactor was then placed in a muffle furnace and heated to 180 °C for 24 h. After the reaction was complete, the product was vacuum filtered, washed repeatedly with deionized water and ethanol until the filtrate was clear, and finally dried in an oven at 105 °C for 12 h to obtain hydrothermal carbon.

[0047] The morphology of the hydrothermal carbon obtained in this comparative example is as follows: Figure 5 It can be seen that the hydrothermal carbon has an uneven morphology and the carbon microspheres are aggregated.

[0048] Comparative Example 2

[0049] This comparative example provides a conventional method for preparing porous carbon, which includes the following steps:

[0050] Weigh 0.5 g of the hydrothermal carbon prepared in Comparative Example 1 and 3 g of KHCO3, grind and mix them thoroughly in a mortar, place them in a tube furnace, and calcine at 850 °C for 1 hour. After the reaction is complete, the product is washed with 1 mol / L HCl, then washed with deionized water until neutral, and finally dried in an oven at 105 °C for 12 hours to obtain porous carbon.

[0051] The morphology of the porous carbon obtained in this comparative example is as follows: Figure 6 As shown in the figure, the porous carbon obtained in this comparative example has an uneven structure as an electrode material.

[0052] Using the porous carbon obtained in this comparative example as the electrode, the charge-discharge curve is as follows: Figure 7 As shown in the figure, it can be seen that the number of charge-discharge cycles of the porous carbon obtained in this comparative example is much less than the number of charge-discharge cycles of the biomass-derived porous carbon material prepared in Example 1.

[0053] The data for the existing hydrothermal carbon preparation method in Comparative Example 1 and the existing porous carbon preparation method in Comparative Example 2 are both taken from the master's thesis (Xu Zenghua. Preparation and electrochemical performance of biomass hydrothermal carbon-based porous carbon [D]. Zhejiang University, 2021).

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing biomass-derived porous carbon with ion adsorption potential, characterized in that, The preparation method includes the following steps: S1. Disodium ethylenediaminetetraacetate and ferrous chloride are added to water and mixed evenly to obtain EDTA-Fe; S2. Add acetate-sodium acetate buffer solution to the EDTA-Fe obtained in S1, then add biomass material and mix evenly. Finally, add aluminum chloride to carry out hydrothermal reaction. After hydrothermal reaction, centrifuge to obtain the primary product. Wash the primary product and dry it to obtain biomass hydrothermal char. S3. The biomass hydrothermal carbon obtained in S2 is soaked in a saturated solution of potassium carbonate, and then solid-liquid separation is performed to collect the solid. The solid is first dried, and then calcined in a nitrogen atmosphere. After calcination, it is washed to obtain biomass-derived porous carbon.

2. The method for preparing biomass-derived porous carbon with ion adsorption potential according to claim 1, characterized in that, The molar ratio of disodium ethylenediaminetetraacetate (EDTA) and ferrous chloride in S1 is 1:1, and the molar volume ratio of disodium EDTA and water is 0.0015 mol: 60 mL.

3. The method for preparing biomass-derived porous carbon with ion adsorption potential according to claim 2, characterized in that, The mass-volume ratio of EDTA-Fe, the acetate-sodium acetate buffer solution, and the biomass material in S2 is 60 mL: 5 mL: 1 g, and the biomass material is straw.

4. The method for preparing biomass-derived porous carbon with ion adsorption potential according to claim 3, characterized in that, The molar ratio of aluminum chloride in S2 to disodium ethylenediaminetetraacetate in S1 is 1:

1.

5. The method for preparing biomass-derived porous carbon with ion adsorption potential according to claim 4, characterized in that, The hydrothermal reaction in S2 is carried out at a temperature of 180 °C for 24 h; the initial product is washed with distilled water; the drying temperature is 60 °C for 8-12 h; and the centrifugation speed is 6000-8000 r / min for 5-10 min.

6. The method for preparing biomass-derived porous carbon with ion adsorption potential according to claim 1, characterized in that, The biomass hydrothermal char described in S3 is soaked in a saturated potassium carbonate solution for 24 hours; the drying temperature is 60 ℃ and the time is 12 hours; the calcination temperature is 800 ℃ and the time is 2 hours; and distilled water is used for cleaning.

7. A biomass-derived porous carbon, characterized in that, It is prepared by the method for preparing biomass-derived porous carbon with ion adsorption potential as described in any one of claims 1-6.

Images