KR102224842B1 - Methods for manufacturing capacitive deionization electrodes - Google Patents

Abstract

A method of manufacturing a capacitive desalting electrode is prepared. This manufacturing method includes preparing activated carbon powder by pulverizing activated carbon, and preparing an electrode including the activated carbon powder, wherein the activated carbon powder has a volume of fine pores having a diameter within a predetermined range than before being pulverized. Increased, and the oxygen/carbon ratio can be increased.

Description

Method for manufacturing capacitive deionization electrodes {Methods for manufacturing capacitive deionization electrodes}

The technical idea of the present invention relates to a capacitive deionization electrode. More specifically, it relates to a capacitive desalting electrode containing activated carbon powder.

Typical wastewater treatment techniques include reverse osmosis, coagulation precipitation, and distillation. Reverse osmosis requires high energy to form a high pressure, and costs for managing the separation membrane are consumed. Coagulation precipitation is a significant cost to the chemical addition. The distillation method consumes high energy and may generate harmful substances during the process.

Electrochemical wastewater treatment technologies are being studied as a way to overcome these shortcomings, and representatively, electrodialysis (ED) and capacitive deionization (CDI) are available. Electrodialysis can treat relatively high concentration of wastewater, but has a disadvantage in that it consumes a lot of energy and there is a cost of maintaining an ion exchange resin. Capacitive desalination technology is a technology that uses the principle of adsorption and desorption of ions by electric force in an electric double layer (EDL) formed at the interface of a charged electrode, and consumes only a very small amount of energy. There is an advantage.

The problem to be solved by the technical idea of the present invention is to provide a method of manufacturing a capacitive desalting electrode with improved adsorption capacity and selectivity for specific ions, for example, sulfate ions.

In order to solve the above-described problems, a method of manufacturing a capacitive desalting electrode according to an embodiment of the technical idea of the present invention includes preparing activated carbon powder by pulverizing activated carbon, and preparing an electrode including the activated carbon powder. The activated carbon powder may have an increased volume of micropores having a diameter within a predetermined range than before being pulverized, and an oxygen/carbon ratio may be increased.

According to the method of manufacturing a capacitive desalination electrode according to the technical idea of the present invention, by pulverizing activated carbon, the volume of micropores having a predetermined size may be increased and the oxygen/carbon ratio may be increased compared to before pulverization. The capacitive desalting electrode including such activated carbon powder may have increased adsorption performance for specific ions than the capacitive desalting electrode including activated carbon before pulverization. In addition, since it is possible to manufacture a capacitive desalting electrode having improved adsorption performance even if an activated carbon with relatively inexpensive but relatively low adsorption performance is purchased, the cost can be reduced according to the manufacturing method of the capacitive desalting electrode according to the technical idea of the present invention. have.

1 is a flowchart illustrating a method of manufacturing a capacitive desalting electrode according to an embodiment of the inventive concept.
2 is a flow chart showing a step of manufacturing activated carbon powder in a method of manufacturing a capacitive desalting electrode according to an embodiment of the inventive concept.
3 are graphs of measurement results of sulfate ion concentration in effluent water according to measurement time in sulfate ion adsorption experiments for Comparative Examples and Examples.
4 is a plot comparing adsorption capacity for sulfate ions in Comparative Examples and Examples.

1 is a flowchart illustrating a method of manufacturing a capacitive desalting electrode according to an embodiment of the inventive concept. 2 is a flow chart showing a step of manufacturing activated carbon powder in a method of manufacturing a capacitive desalting electrode according to an embodiment of the inventive concept.

1 and 2, a method of manufacturing a capacitive desalination electrode according to an embodiment of the inventive concept includes a step of manufacturing an activated carbon powder 110 and a step 120 of manufacturing an electrode including the activated carbon powder. Can include.

The activated carbon powder manufacturing step 110 includes an activated carbon pulverization step 111, a step 112 of determining whether the volume of micropores having a diameter within a predetermined range and an oxygen/carbon ratio satisfy a predetermined condition (112), and as the pulverization time increases. Accordingly, it may include a step 113 of determining whether the volume of micropores having a diameter within a predetermined range increases.

Activated carbon can be prepared using any conventional method known in the art. For example, an activated carbon precursor selected from the group consisting of wood, sawdust, charcoal, fiber, palm, coke, or a combination thereof may be prepared. The activated carbon precursor may be carbonized by heat-treating the activated carbon precursor at a temperature of about 500° C. to about 1500° C. for about 2 to about 4 hours in an inert gas atmosphere. Subsequently, activated carbon may be prepared by mixing the carbide formed by the heat treatment with an activating agent such as potassium hydroxide (KOH) and sodium carbonate (Na ₂ CO ₃ ) and activating it at a temperature of about 60°C to about 100°C. However, the method for producing activated carbon is not limited thereto. For example, commercially available activated carbon can be used.

In the activated carbon pulverization step 111, the activated carbon may be pulverized using, for example, a ball mill process. In some embodiments, a dry ball mill process may be used. The dry ball mill process has the advantage of easier recovery of activated carbon powder than the wet ball mill process. However, in some other embodiments, a wet ball mill process may be used. In the ball mill process, zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ), or a container and ball made of a magnetic material may be used. In some embodiments, the diameter of the ball may be between about 0.5 mm and about 5 mm. In some embodiments, the ball mill container may be rotated at a speed of about 100 to about 1000 rpm.

After the activated carbon pulverization step 111 is performed for a predetermined time, the fine pore distribution and the oxygen/carbon ratio of the activated carbon powder may be measured. In the present specification, the oxygen/carbon ratio means the ratio of the number of oxygen/carbon atoms in the material, that is, the ratio of the number of moles. The micropore distribution can be measured using a conventional Brunauer-Emmett-Teller (BET) measuring equipment. The oxygen/carbon ratio can be measured using X-ray photoelectron spectroscopy or an elemental analyzer.

In step 112 of determining whether the volume of micropores having a diameter within a predetermined range and the oxygen/carbon ratio satisfy a predetermined condition (112), the volume of the micropores having a diameter within a predetermined range is greater than or equal to a specific value, and oxygen/carbon It can be determined whether the ratio is greater than or equal to a specific value. If the volume of the micropores having a diameter within a predetermined range and the oxygen/carbon ratio satisfy the predetermined conditions, the milling may be terminated. Otherwise, as the milling time increases, the micropores having a diameter within the predetermined range The step 113 of determining whether the volume increases may be performed.

During the pulverization process, the size distribution of the fine pores in the activated carbon powder may be changed. In some embodiments, as the grinding time increases, the volume of micropores having a diameter within a predetermined range in the activated carbon powder may increase and then decrease. Specific ions may be selectively adsorbed to micropores having a diameter within a predetermined range. For example, sulfate ions can be adsorbed into micropores having a diameter of about 0.6 nm to about 2 nm. Therefore, when sulfate ions capable of adsorbing to micropores having a diameter of about 0.6 nm to about 2 nm and chlorine ions capable of adsorbing to micropores having a smaller size coexist, the micropores having a diameter of about 0.6 nm to about 2 nm It is possible to increase the adsorption capacity and selectivity for sulfate ions by increasing the volume. That is, as the volume of micropores having a diameter within a predetermined range increases, adsorption capacity and selectivity for specific ions may increase.

In addition, oxidation of the surface of the activated carbon powder may proceed during the pulverization process. When oxidation of the surface of the activated carbon powder proceeds, functional groups such as -OH or -COOH are formed on the surface, and the oxygen/carbon ratio may increase. In some embodiments, the oxygen/carbon ratio may increase as the grinding time increases. These functional groups may be capable of interacting with certain ions, for example through hydrogen bonding, with sulfate ions. Thus, it may be possible to further improve the adsorption capacity and selectivity for certain ions, such as sulfate ions, by increasing the oxygen/carbon ratio.

Therefore, in the step 112 of determining whether the volume of micropores having a diameter within a predetermined range and the oxygen/carbon ratio satisfy a predetermined condition in order to obtain an activated carbon powder with improved adsorption capacity and selectivity for a specific ion, a predetermined It may be determined whether the volume of micropores having a diameter within a range is greater than or equal to a specific value, and whether the oxygen/carbon ratio is greater than or equal to a specific value. For example, in order to increase the adsorption capacity and selectivity for sulfate ions, it is determined whether the volume of micropores having a diameter of about 0.6 nm to about 2 nm is about 0.45 cm ³ /g or more and the oxygen/carbon ratio is 0.1 or more. Can be.

When the volume of micropores having a diameter within a predetermined range or the oxygen/carbon ratio does not satisfy the predetermined condition, determining whether the volume of the micropores having a diameter within a predetermined range increases as the grinding time increases ( 113) can be performed. When the volume of micropores having a diameter within a predetermined range increases as the grinding time increases, grinding may continue, otherwise, grinding may be terminated.

In this way, through the pulverization of the activated carbon, the volume of fine pores having a diameter within a predetermined range is increased, and activated carbon powder with an increased oxygen/carbon ratio can be obtained. Using such activated carbon powder, a capacitive desalting electrode having improved adsorption capacity and selectivity for specific ions, for example, sulfate ions, may be manufactured.

Manufacturing an electrode including activated carbon powder 120 may include preparing a slurry 121, coating the slurry on a current collector 122, and removing a solvent 123. . In the step 121 of preparing a slurry, a slurry may be prepared by mixing activated carbon powder, a binder, and a solvent. The binder may include, for example, polyvinylidene fluoride (PVDF), polystyrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyurethane (PU), or a combination thereof. The solvent may include, for example, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone (NMP), acetone, chloroform, dichloromethane, trichloroethylene, ethanol, methanol, normal hexane, or a combination thereof. I can. In the step 122 of coating the slurry on the current collector, for example, a doctor blade method may be used. In the step 123 of removing the solvent, for example, the electrode coated with the slurry may be dried so that the solvent is volatilized.

In the following, examples and comparative examples, a method of manufacturing a capacitive desalting electrode according to an embodiment of the present invention will be described in more detail. However, the present invention is not limited to the following examples.

[Example]

5 g of commercial activated carbon (product of P-60 obtained from Daedong AC) and 50 g of alumina balls were placed in an alumina pot and sealed. Ball milling was performed by varying the grinding time at 500 rpm (20h: first example, 40h: second example, 60h: third example). Thereafter, the activated carbon powder and the balls were sieved to obtain activated carbon powder. Activated carbon powder and binder polyvinylidene fluoride (PVDF) were mixed in a ratio of 9:1 and dissolved in a solvent N-methyl-2-pyrrolidone (NMP) to prepare a slurry. The slurry was coated on the current collector in a doctor blade method, and the current collector coated with the slurry was dried at 120° C. for 8 hours or more in order to remove N-methyl-2-pyrrolidone (NMP).

[Comparative Example]

Commercial activated carbon and binder PVDF were mixed in a ratio of 9:1, which was not pulverized (ie, pulverization time 0h), and dissolved in a solvent NMP to prepare a slurry. The slurry was coated on the current collector in a doctor blade method, and the current collector coated with the slurry was dried at 120° C. for 8 hours or more in order to remove NMP.

[Evaluation Example 1]

For the comparative examples and examples, the BET value, the size distribution of the micropores, and the oxygen/carbon ratio were measured. The results are shown in Table 1 below. Referring to Table 1, the volume of micropores having a diameter of 0.6 nm to 2 nm in the first example (20h), the second example (40h), and the third example (60h) compared to the comparative example (0h) Was observed to be large. It can be seen that as the grinding time increases, the volume of micropores having a diameter of 0.6 nm to 2 nm in the activated carbon powder increases and then decreases after 40 h. In addition, it was observed that the oxygen/carbon ratio of the second example (40h) and the third example (60h) was larger than that of the comparative example (0h). It can be seen that as the grinding time increases, the oxygen/carbon ratio of the activated carbon powder increases.

Comparative example Embodiment 1 Embodiment 2 Embodiment 3 Grinding time (h) 0 20 40 60 BET (m ² /g) 1316.8 1435.2 1499.9 1313.4 Volume less than 0.6nm (cm ³ /g) 0.22 0.246 0.248 0.19 0.6nm~2nm volume (cm ³ /g) 0.433 0.476 0.496 0.471 2nm~50nm volume (cm ³ /g) 0.152 0.15 0.164 0.133 Volume over 50nm (cm ³ /g) 0.805 0.872 0.908 0.794 Oxygen/carbon ratio 0.085 0.083 0.11 0.12

[Evaluation Example 2]

For the Comparative Examples and Examples, the sulfate ion adsorption experiment was conducted. Specifically, while the electrodes according to Examples and Comparative Examples were installed in a polypropylene cell having a diameter of 4 cm, a cell voltage of 1 V was applied, and _{influent water containing 1000 ppm Na 2} SO ₄ was flowed at a rate of 3 mL/min, The concentration of sulfate ions in the effluent was measured three times for 20 minutes each.

3 are graphs of measurement results of sulfate ion concentration in effluent water according to measurement time in a sulfate ion adsorption experiment. Referring to FIG. 3, the concentration of sulfate ions in the effluent water gradually decreases from the initial concentration of 1000 ppm as the sulfate ions are adsorbed to the electrode. However, when the adsorption capacity is saturated and the sulfate ions are no longer adsorbed to the electrode, the ion concentration in the effluent water is again increased to 1000 ppm. In the graphs of Fig. 3, the area between the 1000 ppm line and the graph is proportional to the adsorption capacity. It could be observed that the area between the 1000pppm line and the graph of Example 1 (20h), Example 2 (40h), and Example 3 (60h) was larger than that of Comparative Example 1 (0h). That is, it could be observed that the adsorption capacity of Example 1 (20h), Example 2 (40h), and Example 3 (60h) was greater than that of Comparative Example 1 (0h).

The adsorption capacity for sulfate ions was calculated from the area between the 1000 ppm line and the graph obtained from FIG. 3. The results are shown in FIG. 4. Referring to FIG. 4, it was confirmed that Example 1 (20h), Example 2 (40h), and Example 3 (60h) had higher adsorption capacity for sulfate ions than Comparative Example (0h). In addition, as the grinding time increases, the adsorption capacity for sulfate ions increases, but decreases after 40 h. This is similar to the tendency of the volume of micropores of 0.6 nm to 2 nm diameter with the grinding time.

[Evaluation Example 3]

The maximum adsorption amount of chlorine ions and the maximum adsorption amount of sulfate ions were measured using influent water containing ₁₀ mM NaCl and 10 mM Na ₂ SO 4. The results are shown in Table 2 below. Referring to Table 2, Example 1 (20h), Example 2 (40h), and Example 3 (60h) achieve a higher maximum adsorption amount of sulfate ions/maximum adsorption amount of chlorine ions compared to Comparative Example (0h). Was observed. That is, it was observed that Example 1 (20h), Example 2 (40h), and Example 3 (60h) have improved selectivity for sulfate ions compared to Comparative Example (0h).

Grinding time(h) Chlorine ion
Maximum adsorption amount (mg/g) Sulfate ion
Maximum adsorption amount (mg/g) Maximum adsorption amount of sulfate ions / Maximum adsorption amount of chlorine ions Comparative example 0 2.44 4.855 1.99 Example 1 20 2.2 5.36 2.44 Example 2 40 2.495 5.89 2.36 Example 3 60 2.57 6.275 2.44

The embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to describe it, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

110: activated carbon powder production step, 111: activated carbon pulverization step, 112: determining whether the volume of fine pores having a diameter within a predetermined range and the oxygen/carbon ratio satisfy a predetermined condition, 113: predetermined as the grinding time increases Determining whether the volume of micropores having a diameter within the range of increases, 120: preparing an electrode including activated carbon powder, 121: preparing a slurry, 122: coating a slurry on a current collector, 123: Step of removing the solvent

Claims (10)

Preparing activated carbon powder by pulverizing activated carbon; And
Preparing an electrode including the activated carbon powder; Including,
The activated carbon powder has an increased volume of micropores having a diameter within a predetermined range than before being pulverized, and an oxygen/carbon ratio is increased,
The electrode including the activated carbon powder increases adsorption capacity and selectivity for specific ions than the electrode including the activated carbon before pulverization,
The predetermined range is in the range of 0.6nm to 2nm,
The specific ion is a sulfate ion,
The selectivity is a method of manufacturing a capacitive desalting electrode, characterized in that the selectivity of sulfate ions to chlorine ions. The method of claim 1,
As the grinding time increases, the volume of the fine pores having a diameter within the predetermined range increases and then decreases. The method of claim 1,
As the grinding time increases, the oxygen/carbon ratio increases. delete delete delete The method of claim 1,
The step of preparing activated carbon powder by pulverizing the activated carbon,
Pulverizing the activated carbon; And
The method of manufacturing a capacitive desalting electrode comprising: terminating the pulverization when the volume of the micropores having a diameter within the predetermined range and the oxygen/carbon ratio satisfy a predetermined condition. The method of claim 7,
The step of preparing activated carbon powder by pulverizing the activated carbon,
When the volume of micropores having a diameter within the predetermined range or the oxygen/carbon ratio does not satisfy a predetermined condition,
When the volume of the micropores having a diameter within the predetermined range increases as the grinding time increases, the grinding is continued,
When the volume of the fine pores having a diameter within the predetermined range does not increase as the grinding time increases, the method of manufacturing a capacitive desalting electrode, further comprising: terminating the grinding. The method of claim 1,
The step of preparing an electrode including the activated carbon powder,
Preparing a slurry by mixing the activated carbon powder, a binder, and a solvent;
Coating the slurry on a current collector; And
The method of manufacturing a capacitive desalting electrode comprising; removing the solvent from the slurry. The method of claim 1,
The step of producing activated carbon powder by pulverizing the activated carbon is a method of manufacturing a capacitive desalting electrode, characterized in that using a ball mill process.

Images