JP3500399B2 - Method for producing highly functional activated carbon fiber having ion exchange properties - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a functional group on the surface of a carbon body of activated carbon fiber having a surface structure with well-developed surface polarity and excellent adsorption performance, which is subjected to a simple electrochemical surface treatment in an electrolytic solution. By introducing such a functional group, there is no change in the surface structure and adsorption performance by the introduction of such a functional group, and a method for producing a novel highly functional activated carbon fiber having excellent ion exchange characteristics with the development of surface polarity. Regarding

[0002] Adsorption / removal technology for various polar environmental pollutants is greatly influenced by the physical adsorption performance due to the pore structure of the adsorbent and the chemical properties of the surface.

[0003]

2. Description of the Related Art As existing treatment methods for imparting polarity to the surface of an adsorbent, dipping treatment with an acidic or alkaline solution at room temperature and introduction of functional groups by oxygen and ozone treatment at high temperature are known. Has become
No method has yet been reported for imparting ion exchange properties to the surface of carbon adsorbents by electrolysis of acidic and alkaline electrolytic solutions.

In the surface treatment method for existing adsorbents, the kinds of solution and gas for the surface treatment are limited depending on the surface properties and structure of the adsorbent itself, and are generally limited to the application in the liquid phase. . Also, the surface structure of the carbon material may change due to the etching effect of an acidic or alkaline solution, or the salt may form salts on the surface of the carbon body to lower its adsorption performance, thus deteriorating its function as an adsorbent. There is.

[0005]

Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art by adhering to the functional groups formed on the surface of the adsorbent while maintaining its adsorbing performance. Has excellent ion-exchange characteristics, and it is not only for the recovery and removal of various heavy metal ions having polarity in the liquid phase, but also for the activated carbon fiber having excellent adsorption selectivity for a trace amount of polar pollutants in the atmosphere. It is to provide a manufacturing method.

[0006]

According to the present invention, an activated carbon fiber as an adsorbing material is subjected to an electrochemical surface treatment in an electrolytic solution to give a functional group to the surface of the activated carbon fiber.
Provided is a method for producing a highly functional activated carbon fiber having ion exchange properties. An acidic solution or an alkaline solution can be used as the above-mentioned electrolytic solution, and any electrolytic solution may be used as long as it can introduce an acidic or alkaline functional group onto the surface of the carbon body by electrochemical surface treatment. A phosphoric acid (H ₃ PO ₄ ) solution is preferable as the acidic solution, and potassium carbonate (K ₂ C) is used as the alkaline solution.
O ₃ ) solutions are particularly preferred.

The concentration of the above-mentioned electrolytic solution is preferably 1 to 40% by weight, and when the concentration is less than 1% by weight, the concentration of the electrolyte dissociated by electrolysis is low, so that the functional groups formed on the surface of the carbon adsorbent. It is not preferable because the amount of groups is small and sufficient ion exchange properties cannot be provided. On the other hand, if the concentration exceeds 40% by weight, many of the dissociated electrolytes corrode the surface of the adsorbent or form salts to deteriorate the adsorption performance due to the change of the surface structure, which is not preferable.

As a preferable example of the above-mentioned electrochemical surface treatment method, a method of inducing electrolysis by applying an electric current to an electrolytic solution can be mentioned. A current of 0.1-5.0A is 2
It is particularly preferred to run for ~ 30 minutes. Supply current is 0.1A
When it is less than the above range, the concentration of the electrolyte dissociated by electrolysis is low, the amount of functional groups formed on the surface of the carbon adsorbent is small, and sufficient ion exchange characteristics are not provided, which is not preferable. On the other hand, when the supply current exceeds 5.0 A, many electrolytes that are dissociated corrode the surface of the adsorbent, or form a salt to deteriorate the adsorption performance due to a change in the surface structure, which is not preferable.

When the current supply time is less than 2 minutes, the electrolytic solution is not sufficiently dissociated by electrolysis, and the concentration of the electrolyte is low, so that the amount of functional groups formed on the surface of the carbon adsorbent is small and sufficient. It is not preferable because it does not give the ion exchange property. On the other hand, if the current supply time exceeds 30 minutes,
Whether many dissociated electrolytes corrode the surface of the adsorbent,
Alternatively, it is not preferable because a salt is formed to lower the adsorption performance due to the change of the surface structure.

Therefore, as a preferred example according to the present invention, activated carbon fiber having excellent adsorption performance is used in a concentration of 1 to 40% by weight of phosphoric acid (H ₃ PO ₄ ) or potassium carbonate (K ₂ CO ₃ ).
2 each in the solution while applying a current of 0.1-5.0A.
There is a method of producing a high-performance carbon adsorbent having an excellent ion exchange property and an excellent adsorption selectivity by performing an electrochemical surface treatment for about 30 minutes.

The adsorption performance of the activated carbon fiber produced according to the present invention is maintained without any change of its surface structure, and the polarity of the activated carbon fiber in the liquid phase is changed by giving the ion exchange property by introducing the oxygen functional group on the surface of the carbon body. It has excellent adsorption selectivity not only for the recovery and removal of various heavy metal ions, but also for trace amounts of polar pollutants in the atmosphere. Therefore, another object of the present invention is to provide a method for adsorbing and removing a polar pollution source by the highly functional activated carbon fiber produced by the above method. The polar pollutants mentioned above include all types of pollutants that exist in polar states in the liquid as well as in the gas phase. As the removal method by adsorption, a known method of removing a pollution source using an adsorbent can be used.

Hereinafter, the present invention will be described in more detail by way of examples, but the scope of protection of the present invention is not limited to the examples.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Example 1 The activated carbon fiber used in the experiment is a felt type activated carbon fiber manufactured and sold by Uda Sangyo Co., Ltd. of Korea. As an electrolytic solution, H ₃ PO ₄ having a concentration of 1% by weight was used, and an electric current of 0.1 A was applied for 2 minutes to perform electrochemical surface treatment. The adsorption specific surface area of the activated carbon fiber thus obtained, the total dryness of the pores, the dryness of the fine pores, the average diameter of the pores, the iodine adsorption capacity, etc. are shown in Table 1, and the pH at the surface of the activated carbon fiber, the surface The acidity, surface basicity and ion exchange performance are shown in Table 2, respectively. As a result, the surface structure and iodine adsorption were almost unchanged, but the surface acidity and the surface basicity were increased by 108% each through the electrochemical surface treatment. This is because the electrochemical surface treatment according to the present invention does not change the surface structure and adsorption performance of the activated carbon fiber, but it is more polar due to the reaction between the surface carbon of the activated carbon fiber and the dissociated ionic component in the electrolytic solution. Surface functional groups are formed, resulting in 184% cation exchange performance and 2 anion exchange performance compared to untreated activated carbon fibers.
It can be confirmed that the increase is 60%.

Example 2 This example is an example except that H ₃ PO ₄ having a concentration of 10% by weight was used as an electrolytic solution and a surface treatment was electrochemically performed by applying a current of 0.5 A for 5 minutes. Same as 1. The adsorption specific surface area of the activated carbon fiber thus obtained,
The total dryness of the pores, the dryness of the fine pores, the average diameter of the pores, the iodine adsorption capacity, etc. are shown in Table 1, the pH of the activated carbon fiber surface,
Surface acidity, surface basicity and ion exchange performance are shown in Table 2, respectively. As a result, the surface structure and iodine adsorption capacity were almost unchanged, but the surface acidity was increased by 123% and the surface basicity was increased by 129% through the electrochemical surface treatment. This is because the electrochemical surface treatment according to the present invention does not change the surface structure and adsorption performance of the activated carbon fiber, while the surface carbon of the activated carbon fiber is more polar due to the reaction with the ion component dissociated in the electrolytic solution. Form a group and, as a result,
In case of cation exchange performance compared to untreated activated carbon fiber 4
It was confirmed that the increase was 58% and the anion exchange performance was 735%.

Example 3 This example is the same as Example 3 except that H ₃ PO ₄ having a concentration of 30% by weight was used as an electrolytic solution and a surface treatment was performed electrochemically by applying a current of 2.0 A for 10 minutes. Same as 1. The adsorption specific surface area of the activated carbon fiber thus obtained,
Table 1 shows the total dryness of the pores, the dryness of the fine pores, the average diameter of the pores, the iodine adsorption capacity, etc.
Surface acidity, surface basicity and ion exchange performance are shown in Table 2, respectively. As a result, the surface structure and iodine adsorption capacity were almost unchanged, but the surface acidity was increased by 151% and the surface basicity was increased by 155% through the electrochemical surface treatment. While the electrochemical surface treatment according to the present invention does not change the surface structure and adsorption performance of the activated carbon fiber, the surface of the activated carbon fiber has a more polar surface due to the reaction between the carbon on the surface and the ionic component dissociated in the electrolytic solution. It was confirmed that functional groups were formed, and as a result, the cation exchange performance increased by 747% and the anion exchange performance increased by 1,320% as compared with the untreated activated carbon fiber.

Example 4 This example is an example except that H ₃ PO ₄ having a concentration of 40% by weight was used as an electrolytic solution and a surface treatment was electrochemically applied by applying a current of 5.0 A for 30 minutes. Same as 1. The adsorption specific surface area of the activated carbon fiber thus obtained,
Table 1 shows the total dryness of the pores, the dryness of the fine pores, the average diameter of the pores, the iodine adsorption capacity, etc.
Surface acidity, surface basicity and ion exchange performance are shown in Table 2, respectively. As a result, the surface structure and iodine adsorption capacity were almost unchanged, but the surface acidity was increased by 191% and the surface basicity was increased by 195% through the electrochemical surface treatment. This is because the electrochemical surface treatment according to the present invention does not change the surface structure and adsorption performance of the activated carbon fiber, while the surface carbon of the activated carbon fiber is more polar due to the reaction with the ion component dissociated in the electrolytic solution. Form a group and, as a result,
It was confirmed that the cation exchange performance increased by 1,026% and the anion exchange performance increased by 1,860% as compared with the untreated activated carbon fiber.

Example 5 This example is an example except that 1% by weight concentration of K ₂ CO ₃ was used as an electrolytic solution, and a surface treatment was performed electrochemically by applying a current of 0.1 A for 2 minutes. Same as 1.
The adsorption specific surface area of the activated carbon fiber thus obtained, the total dryness of the pores, the dryness of the fine pores, the average diameter of the pores and the iodine adsorption capacity are shown in Table 1, where the pH of the active carbon fiber surface, the surface acidity, The surface basicity and the ion exchange performance are shown in Table 2, respectively. As a result, the surface structure and iodine adsorption capacity were almost unchanged, but the surface acidity was increased by 102% and the surface basicity was increased by 119% through the electrochemical surface treatment. This is because the electrochemical surface treatment according to the present invention does not change the surface structure and adsorption performance of the activated carbon fiber, while the surface carbon of the activated carbon fiber is more polar due to the reaction with the ion component dissociated in the electrolytic solution. 147 in the case of cation exchange performance compared to untreated activated carbon fiber, forming groups.
%, It was confirmed that the anion exchange performance increased by 230%.

Example 6 In this example, 10% by weight of K ₂ CO ₃ was used as an electrolytic solution, and a surface treatment was electrochemically applied by applying a current of 0.5 A for 5 minutes. Same as 1. The adsorption specific surface area of the activated carbon fiber thus obtained,
The total dryness of the pores, the dryness of the fine pores, the average diameter of the pores, the iodine adsorption capacity, etc. are shown in Table 1, the pH of the activated carbon fiber surface,
Surface acidity, surface basicity and ion exchange performance are shown in Table 2, respectively. As a result, the surface structure and iodine adsorption capacity were almost unchanged, but the surface acidity was increased by 113% and the surface basicity was increased by 128% through the electrochemical surface treatment. This is because the electrochemical surface treatment according to the present invention does not change the surface structure and adsorption performance of the activated carbon fiber, while the surface carbon of the activated carbon fiber is more polar due to the reaction with the ion component dissociated in the electrolytic solution. Form a group and, as a result,
In case of cation exchange performance compared to untreated activated carbon fiber 3
It was confirmed that 95% and 640% in the case of anion exchange performance increased.

Example 7 This example is the same as Example 7 except that K ₂ CO ₃ having a concentration of 30% by weight was used as an electrolytic solution and a surface treatment was performed electrochemically by applying a current of 2.0 A for 10 minutes. Same as 1. The adsorption specific surface area of the activated carbon fiber thus obtained,
Table 1 shows the total dryness of the pores, the dryness of the fine pores, the average diameter of the pores, the iodine adsorption capacity, etc.
Surface acidity, surface basicity and ion exchange performance are shown in Table 2, respectively. As a result, the surface structure and iodine adsorption capacity were almost unchanged, but the surface acidity was increased by 125% and the surface basicity was increased by 135% through the electrochemical surface treatment. This is because the electrochemical surface treatment according to the present invention does not change the surface structure and adsorption performance of the activated carbon fiber, but the surface carbon of the activated carbon fiber is more polar due to the reaction with the dissociated ionic component in the electrolytic solution. Form a group and, as a result,
In case of cation exchange performance compared to untreated activated carbon fiber 8
It was confirmed that 11% and 1,160% in the case of anion exchange performance increased.

Example 8 This example is an example except that 40% by weight concentration of K ₂ CO ₃ was used as an electrolytic solution and the surface treatment was electrochemically performed by applying a current of 5.0 A for 30 minutes. Same as 1. The adsorption specific surface area of the activated carbon fiber thus obtained,
The total dryness of the pores, the dryness of the fine pores, the average diameter of the pores, the iodine adsorption capacity, etc. are shown in Table 1, the pH of the activated carbon fiber surface,
Surface acidity, surface basicity and ion exchange performance are shown in Table 2, respectively. As a result, the surface structure and iodine adsorption capacity were almost unchanged, but the surface acidity was increased by 143% and the surface basicity was increased by 146% through the electrochemical surface treatment. This is because the electrochemical surface treatment according to the present invention does not change the surface structure and adsorption performance of the activated carbon fiber, while the surface carbon of the activated carbon fiber is more polar due to the reaction with the ion component dissociated in the electrolytic solution. Form a group and, as a result,
It was confirmed that the cation exchange performance increased by 1,074% and the anion exchange performance increased by 1,575% as compared with the untreated activated carbon fiber.

Each of the electrochemically surface-treated activated carbon fibers was washed with distilled water at room temperature for 2 to 3 times, and then 1
It is dried in an oven at 00 ° C. for about 12 hours or more before use, and the adsorption specific surface area, pH, surface acidity, surface basicity of the activated carbon fibers obtained from the above examples and the existing activated carbon fibers which are not treated, and An ion exchange characteristic experiment was performed as follows, and the results are shown in each table.

Method for measuring BET specific surface area: About 0.2 g of a sample was taken in an atmosphere of liquid nitrogen at −196 ° C., and the adsorption amount was measured by increasing the concentration of nitrogen gas as an adsorption substance. When P / Po (where P is the partial pressure and Po is the saturated vapor pressure) is about 0.05 to 0.3, it shows a linear slope with respect to the adsorption amount, and then the BET specific surface area and the roughness of the fine pores are calculated. I asked.

Method for measuring iodine adsorption capacity: ASTM D4
According to 607, the amount of iodine adsorbed with respect to different weights for each sample and the residual concentration of iodine in the solution due to this are measured, and the iodine when the residual concentration becomes 0.02N is measured. The amount of adsorption was defined as its adsorption capacity. First, before the measurement, a 5 wt% HCl solution, a 0.100N sodium thiosulfate solution, a 0.100 ± 0.001N standard iodine solution and a 0.100N potassium iodoate solution were prepared, and then A
Used as a standard solution by STM method. Precisely take 0.1, 0.3, 0.5, and 1.0 g of the prepared samples, etc., put them in an Erlenmeyer flask, and prepare the prepared 5 wt% HC.
After adding 10 ml of 1-solution, the solution was gradually warmed for about 30 seconds, and then 50 ml of standard iodine solution was added. About 15 ~ at room temperature
After shaking for 20 minutes, the solution was filtered and the filtrate was titrated with 0.100N sodium thiosulfate solution. At this time, titration was performed until the yellow color of iodine disappeared, and mg of adsorbed iodine was determined with respect to the weight of each sample.

Method for measuring pH : The pH of the activated carbon fiber electrochemically surface-treated in acidic and alkaline electrolytic solutions of H ₃ PO ₄ and K ₂ CO ₃ according to the strength of various electric currents is measured according to the ASTM D3838 method. Measured by About 0.5 g of each dried sample was added to 20 ml of distilled water boiled at 100 ° C., shaken for about 12 hours or longer, and each solution was filtered with a filter, and then the upper layer solution was adjusted to pH- It was measured with a meter.

Method of measuring surface acidity and surface basicity : The surface acidity and surface basicity due to the functional groups formed on the surface of the surface-treated activated carbon fiber were measured by titration by the selective neutralization method. First, in the case of surface acidity, 1.0 g of each sample was accurately taken and transferred to a 250 ml Erlenmeyer flask, and then 100 ml of 0.1N NaOH solution was added to each flask. Then, after completely sealing in order to prevent natural oxidation by oxygen in the air, the mixture was shaken for 48 hours or more. After filtering this shaking solution through a filter, 20 ml of the upper layer solution was taken and titrated with a 0.1N HCl solution. Similarly, the measurement of the surface basicity is performed by the same process as the measurement of the surface acidity.
HCl was used, 0.1N NaOH was used as the titration solution, and the phenolphthalein standard solution was used as the indicator for each titration.

Method of Measuring Ion Exchange Performance The ion exchange performance by the polar surface functional groups formed on the surface of the activated carbon fiber by the surface treatment was measured by the Mohr precipitation measuring method. In the measurement of cation exchange performance, since the ionic form of the polar surface functional group formed on the fiber surface is a hydroxyl group (OH-), first, a pretreatment process for substituting this with a chlorine anion (Cl-) form is performed. After that, it was used for titration. Precisely about 0.5 g of the pretreated sample was transferred to a 100 ml volumetric flask,
Approximately 25 ml of pH 7 ultrapure water is placed in each flask. Approximately 2 g of sodium nitrate (NaNO ₃ ) was added to this, and after completely dissolving, a small amount of 0.1 M potassium chromate (K ₂ CrO ₄ ) solution was added as an indicator to a 0.1 N silver nitrate (AgNO ₃ ) solution. The amount of silver nitrate solution used for titration at the end point was measured to determine the cation exchange value. The anion exchange capacity is measured by directly titrating the polar functional groups formed on the surface of the polar functional groups as hydrogen cations (H +) without the need for pretreatment. First, take about 0.5g of sample accurately,
After transferring to a 100 ml capacity flask, about 25 ml of ultrapure water of pH 7 is added to each flask. About 2 g of sodium chloride (NaCl) was added here, and after completely dissolving, a small amount of 0.01% methyl orange solution was added as an indicator and titrated with 0.1 N sodium hydroxide (NaOH) solution to end point. The anion exchange value was determined by measuring the amount of sodium hydroxide (NaOH) solution used for the titration in step.

[0027]

[Table 1]

[0028]

[Table 2]

Analysis of Experimental Results The activated carbon fibers produced according to the present invention did not significantly change the surface properties, that is, the physical properties such as the adsorption specific surface area and the pore structure, as compared with the existing untreated activated carbon fibers, but the surface polarity. It was confirmed that the ion exchange characteristics in the liquid phase were greatly improved due to the remarkable development of the. In Table 2, H ₃
In the case of activated carbon fiber surface-treated with PO ₄ electrolytic solution, activated carbon which is not treated in surface acidity due to oxygen functional groups formed on the surface due to increase of concentration of electrolytic solution, treatment time and intensity of applied current It can be seen that there is a difference of at least 1.1 times and at most 1.9 times that of fibers. Such an increase in surface acidity gives the activated carbon fiber, which is an adsorbent, further ion exchange characteristics, and in the case of cation exchange characteristics compared to untreated activated carbon fiber, it is at least 1.8 times and at most 10.3 times. It was confirmed that the number increased. Also,
In the case of anion exchange characteristics, the minimum is 2.6 times and the maximum is 18.
It was found to have increased up to 6 times. Similarly, in the case of activated carbon fibers surface-treated in a K ₂ CO ₃ electrolytic solution, the surface acidity due to the functional groups formed on the surface is not treated by increasing the concentration of the electrolytic solution, the treatment time and the strength of the applied current. Compared to activated carbon fiber, the minimum is 1.0 times and the maximum is 1.
It can be seen that the number has increased by four times. Such an increase in surface acidity further imparts ion exchange characteristics to the activated carbon fiber as an adsorbent and increases from a minimum of 1.5 times to a maximum of 10.7 times in the case of cation exchange characteristics as compared with untreated activated carbon fiber. I was able to confirm that I did. It was also found that the anion exchange property increases from a minimum of 2.3 times to a maximum of 15.8 times.

[0030]

As mentioned above, according to the present invention, an acidic or alkaline solution, preferably H ₃ PO ₄ or K ₂ C is used.
There is no change in its adsorption performance and surface structure through electrochemical surface treatment in an electrolytic solution of O ₃ , and the polar surface functional groups introduced on the surface further provide ion exchange characteristics, and gas phase and liquid phase It is possible to manufacture highly functional activated carbon fibers with significantly improved adsorption performance not only for the pollution sources of the above, but also for the pollution sources of polar organic and inorganic heavy metals.

Such an electrochemical surface treatment does not require a separate device in order to prevent side reactions due to the existing high temperature surface treatment, and the process is performed continuously, which makes the work easy and economical. Have.

[Brief description of drawings]

FIG. 1 is a process diagram schematically showing one process of surface-treating an activated carbon fiber by an electrochemical surface treatment according to the present invention.

FIG. 2 is a graph showing changes in the adsorption specific surface area of activated carbon fibers by electrochemical surface treatment in a phosphoric acid (H ₃ PO ₄ ) and potassium carbonate (K ₂ CO ₃ ) electrolytic solution according to the present invention.

FIG. 3 is a graph showing changes in ion exchange performance of activated carbon fibers by electrochemical surface treatment in a phosphoric acid (H ₃ PO ₄ ) electrolytic solution according to the present invention.

FIG. 4 is a graph showing changes in ion exchange performance of activated carbon fibers by electrochemical surface treatment in a potassium carbonate (K ₂ CO ₃ ) electrolytic solution according to the present invention.

[Explanation of symbols]

1: Activated carbon fiber 2: Anode roller 3: Anode electrolyzer 4: Graphite cathode plate 5: Electrolyte

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI D06M 10/00 D06M 10/00 A // D06M 101: 40 101: 40 (72) Inventor Kim Jie Dong, Yuseong-gu, Daejeon, South Korea Songji-dong 8-2 Hanyang Blue Rate Apartment No. 513-808 (56) Reference JP 57-74335 (JP, A) JP 8-151208 (JP, A) JP 63-135432 (JP, A) ) JP-A-54-124892 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) D06M 10/00-11/84 C08J 5/20 D01F 9/12-9/32 F-term (4L031, 4L037)

Claims (7)

(57) [Claims] 1. A highly functional activated carbon fiber having ion exchange characteristics by subjecting activated carbon fiber as an adsorbent material to electrochemical surface treatment in an electrolytic solution to give a functional group to the surface of activated carbon fiber. A method of manufacturing. 2. The method according to claim 1, wherein the electrolytic solution is an acidic solution or an alkaline solution. 3. The method of claim 2, wherein the acidic solution is a phosphoric acid (H ₃ PO ₄ ) solution and the alkaline solution is a potassium carbonate (K ₂ CO ₃ ) solution. 4. The method according to claim 1, wherein the concentration of the electrolytic solution is 1 to 40% by weight. 5. The method according to claim 1, wherein the electrochemical surface treatment method is performed by applying an electric current to the electrolytic solution to induce electrolysis. 6. The method according to claim 5, wherein a current of 0.1 to 5.0 A is applied for 2 to 30 minutes. 7. A method for selectively adsorbing and removing a polar pollution source by the highly functional activated carbon fiber produced by any one of claims 1 to 6.