阅读说明：本技术 一种自支撑碳材料及其制备方法和应用 (Self-supporting carbon material and preparation method and application thereof ) 是由 陈凤娟 段思聪 于 2020-12-25 设计创作，主要内容包括：本发明涉及一种自支撑碳材料及其制备方法和应用。本发明提供的自支撑碳材料具有自支撑木碳结构框架,贯穿自支撑木碳结构框架的微米级孔道以及分布在所述自支撑木碳结构框架上的纳米孔；所述纳米孔包括孔径为10纳米以下,优选为5纳米以下,更优选为2纳米以下的纳米孔。本发明提供的自支撑碳材料在维持木材原有宏观孔道结构同时引入纳米级微孔,作为电极材料,具有较高的电吸附容量,对无机阴离子的选择性高,可以适用但不限于工业含盐废水的废水电吸附脱盐,低含盐量地表水的电吸附脱盐,水中特定离子的选择性电吸附分离。(The invention relates to a self-supporting carbon material and a preparation method and application thereof. The self-supporting carbon material provided by the invention is provided with a self-supporting wood-carbon structural framework, micron-sized pore channels penetrating through the self-supporting wood-carbon structural framework and nano-pores distributed on the self-supporting wood-carbon structural framework; the nanopores include nanopores having a pore diameter of 10nm or less, preferably 5nm or less, more preferably 2nm or less. The self-supporting carbon material provided by the invention has the advantages that the original macroscopic pore structure of wood is maintained, and simultaneously, the nano-scale micropores are introduced, so that the self-supporting carbon material is used as an electrode material, has higher electro-adsorption capacity and high selectivity on inorganic anions, and can be suitable for but not limited to electro-adsorption desalination of industrial salt-containing wastewater, electro-adsorption desalination of surface water with low salt content and selective electro-adsorption separation of specific ions in water.)

1. A self-supporting carbon material having a self-supporting wood carbon structural framework, microscale channels extending through the self-supporting wood carbon structural framework, and nanopores distributed on the self-supporting wood carbon structural framework;

wherein the nanopores comprise nanopores having a pore diameter of 10nm or less, preferably 5nm or less, more preferably 2nm or less.

2. The self-supporting carbon material of claim 1, having one or more of the following characteristics:

the specific surface area of the self-supporting material is 100m²/g-1000m²A/g, preferably of 300m²/g-1000m²A/g, more preferably 500m²/g-1000m²(ii)/g; the pore volume of the self-supporting material is 0.2cm³/g-1cm³A/g, preferably 0.25cm³/g-0.8cm³/g；

The diameter of the micron-sized pore canal is 10-100 μm, preferably 20-80 μm;

the specific surface area of the nanopores with the pore diameter of less than 2nm accounts for more than 90 percent of the specific surface area of the self-supporting material, and preferably more than 95 percent;

the pore volume of nanopores with a pore diameter of 2nm or less accounts for 60% or more, preferably 70% or more of the pore volume of the self-supporting material;

the specific surface area of the nanopores with the pore diameter of less than 1nm accounts for more than 80 percent of the specific surface area of the self-supporting material, and preferably more than 85 percent;

the specific surface area of nanopores having a pore diameter of 1nm or less accounts for 85% or more, preferably 90% or more, of the specific surface area of nanopores having a pore diameter of 2nm or less;

the pore volume of the nanopores with the pore diameter of less than 1nm accounts for more than 35 percent, preferably more than 40 percent of the pore volume of the self-supporting material;

the pore volume of the nanopores having a pore diameter of 1nm or less accounts for 50% or more, preferably 55% or more, of the pore volume of the nanopores having a pore diameter of 2nm or less.

3. A method of making a self-supporting carbon material, comprising:

step A) treating wood with an activator aqueous solution to obtain a precursor, wherein the activator solution comprises an oxyacid salt, a chloride or an alkali metal hydroxide;

and B) carbonizing the precursor.

4. The method of claim 3, wherein the wood is selected from one or more of beech, basswood, robinia, eucalyptus, pine, cedar, poplar, willow, peach, apricot, apple, pear, banyan, camphor, locust, maple, cedar, oak, elm, birch, sandalwood, oak, fir, and phoenix wood, preferably beech.

5. The production method according to claim 3 or 4, wherein the salt of an oxyacid is selected from at least one of sodium thiosulfate, sodium sulfate, potassium nitrate, and sodium phosphate, preferably sodium thiosulfate; the melting point of the chloride is 200-900 ℃, and zinc chloride is preferred; the alkali metal hydroxide is selected from at least one of sodium hydroxide and potassium hydroxide;

preferably, the concentration of the active agent in the aqueous solution of the active agent is 0.5-1.6 mol/L.

6. Preparation method according to any one of claims 3 to 5, characterized in that the treatment in step A) is impregnation of the wood with an activator solution, preferably the impregnation comprises the following steps carried out in succession:

1) carrying out the first impregnation at 80-95 ℃, preferably the time of the first impregnation is 1-4 hours, more preferably 1.5-2.5 hours;

2) cooling to 20-40 ℃ for second impregnation, preferably, the second impregnation time is 1 minute-1 hour, more preferably 5 minutes-0.5 hour;

3) heating to 80-95 ℃ for third impregnation, wherein the third impregnation time is preferably 1-4 hours, and more preferably 1.5-2.5 hours;

3) and cooling to 20-40 ℃ for fourth impregnation, wherein the fourth impregnation time is preferably 1-24 hours, and more preferably 5-12 hours.

7. The method of any one of claims 3 to 6, wherein in step B), the carbonization temperature is 750 ℃ to 950 ℃, preferably 780 ℃ to 850 ℃; the carbonization time is 1 to 4 hours, preferably 1.5 to 4 hours.

8. The method of any one of claims 3-7, wherein the carbonizing comprises heating the precursor to a carbonizing temperature in an inert atmosphere at a ramp rate of 3-10 ℃ per minute.

9. Use of the self-supporting carbon material according to any one of claims 1 to 2 or prepared by the preparation method according to any one of claims 1 to 8 in the field of water treatment, in particular in electro-adsorption desalination.

10. Use according to claim 9, wherein the self-supporting carbon material is used as an electrode material and the salt comprises one or more of a sulphate, a nitrate and a chloride.

Technical Field

The invention relates to an electrode technology, in particular to a self-supporting carbon material and a preparation method and application thereof.

Background

Excessive interference of human activities, such as excessive use of agricultural fertilizers and large discharge of industrial sewage, causes rapid accumulation of inorganic salts in water bodies, and poses great threat to natural environment and human health. Because the salts have the characteristics of higher solubility and high stability in the water body, the water body self-repairing and purifying are only relied on, so that the repairing and purifying are very slow and difficult. Many techniques have been developed for removing inorganic salts from water bodies, including physical/chemical adsorption techniques, reverse osmosis techniques, solar distillation techniques, electrodialysis techniques, and the like.

The electro-adsorption (capacitive deionization) technology is a new seawater desalination and water treatment technology, and has the advantages of low energy consumption, environmental friendliness, simplicity and convenience in operation and the like. However, the existing electro-adsorption electrode material is often a powder material, the adsorption capacity is limited, the preparation process is complex, a binder is required, the long-term stability is poor, the cost is high, the obtained material cannot realize the selective separation of different ions, and the requirements of practical application cannot be met.

Disclosure of Invention

Aiming at the defects in the prior art, the inventor of the application carries out extensive and intensive research on the electrode material for electro-adsorption, and finds that the wood, preferably beech, can be used as a self-supporting electrode material after being impregnated and carbonized by different chemical reagents such as sodium thiosulfate, zinc chloride and the like, has higher electro-adsorption capacity, high adsorption speed, good selectivity and simple preparation flow; thereby breaking through the inherent view of the technicians in the field and achieving quite outstanding technical effects. Based on this, the present application is proposed.

In a first aspect, the present invention provides a self-supporting carbon material having a self-supporting wood carbon structural framework, microscale pores extending through the self-supporting wood carbon structural framework, and nanopores distributed on the self-supporting wood carbon structural framework; the nanopores include nanopores having a pore diameter of 10 nanometers or less.

According to some embodiments of the invention, the nanopores comprise nanopores having a pore size of 5nm or less, preferably 2nm or less. According to some embodiments of the invention, the nanopore comprises a nanopore having a pore size of 1nm or less.

According to some embodiments of the invention, the free-standing material is a metal alloyThe specific surface area of the material is 100-1000m²/g, preferably 300-²(iv)/g, more preferably 500-²/g。

According to some embodiments of the invention, the pore volume of the self-supporting material is from 0.2 to 1cm³In g, preferably from 0.25 to 0.8cm³/g。

According to some embodiments of the invention, the diameter of the micron-sized channels is 10-100 μm, preferably 20-80 μm;

according to some embodiments of the invention, the specific surface area of the nanopores having a pore size of 2nm or less accounts for 90% or more, preferably 95% or more of the specific surface area of the self-supporting material.

According to some embodiments of the invention, the pore volume of nanopores having a pore diameter of 2nm or less comprises 60% or more, preferably 70% or more of the pore volume of the self-supporting material.

According to some embodiments of the invention, the specific surface area of the nanopores having a pore size of 1nm or less accounts for 80% or more, preferably 85% or more of the specific surface area of the self-supporting material.

According to some embodiments of the present invention, the specific surface area of the nanopores having a pore size of 1nm or less accounts for 85% or more, preferably 90% or more of the specific surface area of the nanopores having a pore size of 2nm or less.

According to some embodiments of the invention, the pore volume of nanopores having a pore diameter of 1nm or less comprises 35% or more, preferably 40% or more of the pore volume of the self-supporting material.

According to some embodiments of the present invention, the pore volume of nanopores having a pore diameter of 1nm or less accounts for 50% or more, preferably 55% or more, of the pore volume of nanopores having a pore diameter of 2nm or less.

In a second aspect, the present invention provides a method of preparing a self-supporting carbon material, comprising:

step A) treating wood with an activator solution to obtain a precursor, wherein the activator solution comprises an oxyacid salt, a chloride, or an alkali metal hydroxide;

and B) carbonizing the precursor.

According to some embodiments of the method of making of the present invention, the wood is selected from one or more of beech, basswood, robinia, eucalyptus, pine, cedar, poplar, willow, peach, apricot, apple, pear, banyan, camphor, locust, maple, cedar, oak, elm, birch, sandalwood, oak, fir, and phoenix tree. According to some particularly preferred embodiments, the wood is beech.

According to some embodiments of the production method of the present invention, the salt of an oxyacid is at least one selected from the group consisting of sodium thiosulfate, sodium sulfate, potassium nitrate and sodium phosphate. According to some most preferred embodiments, the activator is sodium thiosulfate.

According to some embodiments of the preparation method of the present invention, the melting point of the chloride is 200-900 ℃, and preferably the chloride is zinc chloride.

According to some embodiments of the preparation method of the present invention, the alkali metal hydroxide is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide.

According to the present invention, the amount of the activating agent and the treatment temperature can be selected according to the process conditions in the specific application such as scale of production and production equipment. In some embodiments, the active agent is used in an amount of 0.5 to 1.6mol/L (i.e., 0.05 to 0.16mol active agent per 100mL of aqueous solution), preferably 0.7 to 1.3mol/L, based on the volume of the aqueous solution.

According to some embodiments of the method of making of the present invention, the treating in step a) is impregnation of the wood with an activator solution.

According to some preferred embodiments of the preparation method of the present invention, the impregnation comprises the following steps carried out in sequence:

1) carrying out the first impregnation at 80-95 ℃, preferably the time of the first impregnation is 1-4 hours, more preferably 1.5-2.5 hours;

2) cooling to 20-40 ℃ for second impregnation, preferably, the second impregnation time is 1 minute-1 hour, more preferably 5 minutes-0.5 hour;

3) heating to 80-95 ℃ for third impregnation, preferably, the third impregnation time is 1-4 hours, more preferably 1.5-2.5 hours;

3) and cooling to 20-40 ℃ for fourth impregnation, wherein the fourth impregnation time is preferably 1-24 hours, and more preferably 5-12 hours.

According to some embodiments of the method of manufacturing of the present invention, the impregnation comprises the following steps carried out in sequence:

1) carrying out first impregnation at the temperature of 80-95 ℃, wherein the time of the first impregnation is 1-4 hours;

2) cooling to 20-40 ℃ for second impregnation, wherein the second impregnation time is 1 minute-1 hour;

3) heating to 80-95 ℃ for third impregnation, wherein the time of the third impregnation is 1-4 hours;

3) cooling to 20-40 ℃ for fourth impregnation, wherein the time of the fourth impregnation is 1-24 hours.

According to some embodiments of the method of manufacturing of the present invention, the impregnation comprises the following steps carried out in sequence:

1) carrying out first impregnation at 85-95 ℃, wherein the time of the first impregnation is 1.5-4 hours;

2) cooling to 25-40 ℃ for second impregnation, wherein the second impregnation time is 5-30 minutes;

3) heating to 85-95 ℃ for third impregnation, wherein the time of the third impregnation is 1.5-4 hours;

3) cooling to 25-40 ℃ for fourth impregnation, wherein the time of the fourth impregnation is 5-12 hours.

According to some embodiments of the preparation method of the present invention, in step B), the carbonization temperature is 750-950 ℃, preferably 780-850 ℃. According to some embodiments. The carbonization temperature is 780 ℃, 800 ℃, 810 ℃, 820 ℃ or the like.

According to some embodiments of the preparation method of the present invention, in step B), the carbonization time is 1 to 4 hours, preferably 1.5 to 4 hours.

According to some embodiments of the preparation method of the present invention, in step B), the carbonizing includes heating the precursor to a carbonization temperature in an inert atmosphere at a heating rate of 3 to 10 ℃ (e.g., 3, 4, 5, 6, 7, 8 ℃) per minute.

According to some embodiments of the production method according to the present invention, further comprising washing and drying the carbonized product after step B). Specifically, the carbonized product is washed with hydrochloric acid and deionized water for many times to be neutral, dried and polished to a required size.

According to some embodiments of the preparation method according to the present invention, the prepared self-supporting carbon material has a self-supporting wood carbon structural framework, micro-scale pores penetrating through the self-supporting wood carbon structural framework, and nano-scale pores distributed on the self-supporting wood carbon structural framework; the pore diameter of the nano-scale pores is 10nm or less, preferably 5nm or less, more preferably 2nm or less, for example 1nm or less. Namely, the self-supporting carbon material according to the first aspect described above can be obtained by the production method of the present invention.

In a third aspect, the present invention provides the use of the self-supporting carbon material according to the first aspect of the present invention or the self-supporting carbon material prepared by the preparation method according to the second aspect of the present invention in the field of water treatment, in particular in electro-adsorption desalination.

In some embodiments of the uses of the present invention, the self-supporting carbon material serves as an electrode material.

In some embodiments of the uses of the invention, the salt comprises one or more of a sulfate, such as sodium sulfate, a nitrate, such as sodium nitrate, and a chloride, such as sodium chloride.

According to an embodiment of the invention, the self-supporting carbon material has a self-supporting wood carbon framework with a graded pore size distribution, the pores comprising: first, uniform nano-scale pores randomly distributed on the overall structure of the wood-carbon framework; the micron-sized holes are arranged in order, penetrate through the whole wood-carbon framework and are large enough to enable the self-supporting electrode to form a fluid flow path, and water flow can be pushed to flow through the whole self-supporting electrode; the ultramicropores are used for capturing inorganic salt molecules carried in water flowing through the self-supporting wood-carbon framework.

The self-supporting carbon material provided by the invention has the advantages that the original macroscopic pore structure of wood is maintained, and simultaneously, the nano-scale micropores are introduced, so that the self-supporting carbon material is used as an electrode material, has higher electro-adsorption capacity and high selectivity on inorganic anions, and can be suitable for but not limited to electro-adsorption desalination of industrial salt-containing wastewater, electro-adsorption desalination of surface water with low salt content and selective electro-adsorption separation of specific ions in water.

The preparation method has the advantages of simple process, low manufacturing cost and good stability. The self-supporting electro-adsorption electrode can effectively improve the electro-adsorption performance of the electrode, has excellent mechanical strength, and has high application value and practicability in the field of capacitance deionization.

Drawings

FIG. 1 is a scanning electron micrograph of a longitudinal section of the material prepared in example 1,

FIG. 2 is a cross-sectional scanning electron micrograph of the material prepared in example 1.

FIG. 3 is a graph of the beta test for the material prepared in example 1.

Figure 4 is a cv plot of the material prepared in example 1 in various anionic solutions.

Figure 5 is a cv plot of the material prepared in example 2 in various anionic solutions.

Figure 6 is a cv plot of the material prepared in example 3 in various anionic solutions.

FIG. 7 is a cv plot of the material prepared in example 1 at different sweeping speeds in 1M NaCl solution.

FIG. 8 is a graph of cp for different sweep rates in a 1M NaCl solution of the material prepared in example 1.

Detailed Description

The invention is further illustrated and described with reference to specific examples, which are not intended to be limiting.

Example 1

1. Synthesis of nitrate radical selective adsorption electrode

The beech wood chips were immersed in a 1.2M sodium thiosulfate solution heated to 90 ℃ and maintained at this temperature for 2 hours, cooled to room temperature, heated again to 90 ℃ and maintained at this temperature for 2 hours, cooled to room temperature and left to stand overnight. And (3) placing the impregnated wood chips into a tube furnace, heating to 800 ℃ at a heating rate of 5 ℃ per minute in an argon atmosphere, maintaining for 2 hours, cooling to room temperature, and washing with hydrochloric acid and deionized water for multiple times in sequence to be neutral. Drying and grinding to the required size to obtain the self-supporting electrode material.

The characterization data of the self-supporting electrode material of this example are shown in table 1.

TABLE 1

2. Evaluation of electrochemical Properties

A self-supporting electrode (1cm x 1mm) is used as a working electrode, a platinum sheet is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, and GCD test and cyclic voltammetry test are carried out in 1M NaCl solution to test the electrochemical performance of the electrode.

Paired self-supporting electrodes were inserted with 50mM NaCl/25mM Na₂SO₄/50mM NaNO₃In salt solution; cyclic voltammetric scans were performed in the range-0.6V to test their selectivity to different anions. The data are shown in Table 2.

Fig. 1 is a scanning electron microscope image of a longitudinal section of the material prepared in this example, and fig. 2 is a scanning electron microscope image of a cross section of the material prepared in this example, it can be observed that the material well maintains the original channel structure of beech, which is beneficial to the transmission of solution and the diffusion of ions. FIG. 3 is a graph of beta testing of the material prepared in this example. After activation, the nanopores of the material are mainly ultramicropores smaller than 1 nanometer, which is beneficial to the selective adsorption of anions. Fig. 4 is a cv diagram of the material prepared in this example in different anion solutions, showing a larger capacitance and a certain ion selectivity. In addition, the EDX of the material was tested and showed that after activation, the material was sulfur doped, improving its wettability, conductivity.

Example 2

The only difference from example 1 is that the sodium thiosulfate solution has a concentration of 1.0M. The data are shown in Table 2. Fig. 5 shows cyclic voltammetry curves of the material prepared in this example in different anionic solutions, showing smaller capacitance and stronger ion selectivity.

Example 3

The difference from example 1 is only that the concentration of the sodium thiosulfate solution is 1.4M. The data are shown in table 2 and fig. 6.

Example 4

1. Synthesis of nitrate radical selective adsorption electrode

Beech chips were immersed in a 1.2M sodium thiosulfate solution heated to 90 ℃ and maintained at this temperature for 4 hours, cooled to room temperature and left to stand overnight. And (3) placing the impregnated wood chips into a tube furnace, heating to 800 ℃ at a heating rate of 5 ℃ per minute in an argon atmosphere, maintaining for 2 hours, cooling to room temperature, and washing with hydrochloric acid and deionized water for multiple times in sequence to be neutral. Drying and grinding to the required size to obtain the self-supporting electrode material.

2. Electrochemical performance was evaluated as in example 1. The data are shown in Table 2.

Example 5

1. Synthesis of nitrate radical selective adsorption electrode

The beech wood chips were immersed in a 1.2M sodium thiosulfate solution heated to 70 ℃ and maintained at this temperature for 2 hours, cooled to room temperature, heated again to 70 ℃ and maintained at this temperature for 2 hours, cooled to room temperature and left to stand overnight. And (3) placing the impregnated wood chips into a tube furnace, heating to 800 ℃ at a heating rate of 5 ℃ per minute in an argon atmosphere, maintaining for 2 hours, cooling to room temperature, and washing with hydrochloric acid and deionized water for multiple times in sequence to be neutral. Drying and grinding to the required size to obtain the self-supporting electrode material.

2. Electrochemical performance was evaluated as in example 1. The data are shown in Table 2.

Example 6

The only difference from example 1 is that beech wood chips were replaced with balsa wood chips. The data are shown in Table 2.

Example 7

The only difference from example 1 is that beech wood chips were replaced with basswood chips. The data are shown in Table 2.

Example 8

The only difference from example 1 is that beech wood chips were replaced with locust wood chips. The data are shown in Table 2.

Example 9

The only difference from example 1 is that the sodium thiosulfate solution was replaced with a 1.2M zinc chloride solution. The data are shown in Table 2.

Example 10

The only difference from example 1 is that the sodium thiosulfate solution was replaced with a 0.7M potassium hydroxide solution. The data are shown in Table 2.

Comparative example 1

The difference from example 1 is that the carbonization was carried out without using a chemical agent. The data are shown in Table 2.

TABLE 2

It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.