KR101975098B1 - Deionization electrode with oxidation resistance and method of operating the same - Google Patents

Abstract

The present invention relates to a method for manufacturing an oxidation-resistant desalting electrode and a method of operating the same, comprising the steps of: preparing an electrode material for preparing a carbon material, a metal oxide, and a salt including a ring structure; A carbonization step of carbonizing the electrode material; And a salt removal step of removing the salts contained in the electrode material, and a method of operating the oxidation-resistant desalination electrode.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an oxidation-resistant desalting electrode and a method of operating the same,

More particularly, the present invention relates to a method of manufacturing an oxidation-resistant desalting electrode having high durability and high desalting capacity and a method of operating the same.

The world is now increasing in value as a resource of water due to the deepening of drought phenomenon due to global warming, depletion of groundwater, progress of desertification, population increase, industrialization, and increase in industrial water usage. Therefore, desalination of sea water, And recycling are emerging as new issues. In addition, as interest in the production of ultra pure water for industrial use increases, the demand for clean water that can be eaten and washed increases in living, and research on the development of high efficiency ion removing apparatus is actively carried out.

In addition, when hard water is used as industrial water and domestic water, the detergent is not solved easily, and the formation of scales by cationic ions (Ca ^{2 +} , Mg ^{2 +,} etc.) causes industrial and hygienic problems. Therefore, in order to reduce the damage caused by the use of hard water, softening process is indispensable. In addition, removal of radioactive Cs + ions present in the water and recovery of Li + ions are recognized as important in environment and industrial sale

At present, technologies for removing ionic materials mainly use evaporation method, reverse osmosis membrane method and ion exchange resin method. Evaporation method and reverse osmosis method have operation cost and operation problem due to high energy consumption, and most widely used ion The exchange resin method has a disadvantage of producing secondary pollutants because it uses excess acid or salt (NaCl) during regeneration.

In order to overcome the disadvantages of existing ion-ion removal technologies and to develop a new ion-depletion technology of low energy consumption type, researches are being carried out in various countries around the world. Such ion-removing technologies include an electric storage which is being developed by US LLNL, Sabrex of Texas, Capacitive Deionization (CDI) technology.

CDI technology is a new environmentally friendly ion removal technology that does not require secondary cleaning because it requires less energy consumption compared to other methods and does not require cleaning by chemicals unlike conventional ion removal technology. It is easy to use and it is actively researched by next generation dissolved ion removal technology.

In the first CDI process, researchers at the University of Oklahoma in the US in the 1960s studied seawater desalination using porous activated carbon electrodes, and Johnson et al. Conducted CDI experiments using activated carbon. However, the development of the CDI process using carbon airgel electrodes in the mid-1990s at Lawrence Livermore National Laboratory (LLNL) in the United States was carried out. Research has also been conducted on the development of a CDI process using active carbon fibers and carbon nanotubes as an electrode active material.

When the carbon electrode is used, it has a large surface area and thus has a relatively stable capacity characteristic in the aqueous solution. However, it has a disadvantage in that the carbon itself has a low resistance and the surface property is hydrophobic, It tends to be somewhat slow in terms of speed, and durability is not good enough to be used for a long time.

Accordingly, it has been required to develop a desalting electrode having high durability while efficiently performing desalination.

It is an object of the present invention to provide an electrode capable of improving desalination capacity in a storage desalination process.

It is another object of the present invention to provide an electrode for desalination which is excellent in oxidation resistance and which can be used for a long time.

According to an aspect of the present invention, there is provided a method of preparing a carbon material, comprising: preparing an electrode material for preparing a carbon material, a metal oxide, and a salt; A carbonization step of carbonizing the electrode material; And a salt removing step of removing salts included in the electrode material.

According to another aspect of the present invention, there is provided a method of manufacturing an oxidation-resistant desalting electrode, further comprising a recrystallization step of heating to raise the degree of crystallization after the salt removing step.

According to the present invention, there is also provided a method for producing an oxidation-resistant desalting electrode characterized in that the carbon material is a saccharide including monosaccharides and disaccharides.

According to the present invention, the metal oxide is _{TiO 2, CuNiFe 2 O 4,} CuO, HfO 2, CeO 2, Gd 2 O 3, the oxidation resistance desalted electrode production method characterized in that included at least one from among Fe _x O .

According to the present invention, there is also provided a method of manufacturing an oxidation-resistant desalting electrode characterized in that the salt is one or more salts of NaCl, CaCl ₂ and ZnCl ₂ .

According to the present invention, graphene or carbon nanotubes are added in the step of preparing the electrode material.

According to the present invention, there is also provided a method for producing an oxidation-resistant desalting electrode characterized in that carbonization is carried out at a temperature rise of 1 to 5 ° C / min in the carbonization step.

According to the present invention, there is also provided a method for producing an oxidation-resistant desalting electrode characterized in that carbonization is carried out by raising the temperature to 500 to 600 ° C in the carbonization step.

According to the present invention, there is also provided a method for manufacturing an oxidation-resistant desalting electrode, wherein the salt removing step is carried out through an activating step and a washing step in the salt removing step.

According to the present invention, there is provided a method of manufacturing an oxidation-resistant desalting electrode, wherein the activating step is performed by heating at 800 to 900 ° C. to vaporize and remove the salts.

According to the present invention, there is provided a method of manufacturing an oxidation-resistant desalting electrode, wherein the cleaning step is performed by washing the water with water to remove salts.

According to the present invention, there is also provided a method for producing an oxidation-resistant desalting electrode characterized in that the recrystallization step is carried out at a temperature of 1300 to 1400 ° C.

According to another aspect of the present invention, there is provided a desalting electrode operating method for conducting desalting by reversed-phase cross-charging and discharging using a desalting electrode manufactured by the above method.

The oxidation-resistant desalination electrode according to the present invention provides a carbon electrode for a desalination process with excellent oxidation resistance by producing the carbon electrode through a special process.

The oxidation-resistant desalination electrode according to the present invention is advantageous in that durability of the oxidation-resistant desalination electrode is improved by positioning the metal oxide between the carbon structures by injecting it in the electrode material preparing step before the carbonization step.

The oxidation-resistant desalination electrode according to the present invention can provide an electrode for desalting process which can operate for more than 50 hours by using a crystalline tin nanometer electrode having a porous structure.

1 schematically shows a manufacturing process of an electrode for a storage desalination process according to an embodiment of the present invention.
Fig. 2 shows a reverse-potential cross-charging system of a charge-coupled desalting electrode.
Fig. 3 shows the effluent conductivity of Example 1 and Comparative Example 1. Fig.
Fig. 4 shows the effluent conductivity of Example 2 and Comparative Example 2. Fig.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, in the drawings, it is noted that the same components or parts are denoted by the same reference numerals as possible. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted so as to avoid obscuring the subject matter of the present invention.

The terms " about ", " substantially ", etc. used to the extent that they are used herein are intended to be taken to mean an approximation of, or approximation to, the numerical values of manufacturing and material tolerances inherent in the meanings mentioned, It is used to prevent unauthorized exploitation by an unscrupulous infringer from disclosing the exact or absolute numerical value to help.

The present invention relates to an oxidation-resistant desalination electrode and a method of manufacturing the same, wherein the production of a desalting electrode comprises: preparing an electrode material for preparing a carbon material, a metal oxide, and a salt including a ring structure; A carbonization step of carbonizing the electrode material; And a salt removal step of removing salts contained in the electrode material, wherein the salt removal step further includes a recrystallization step of heating to increase the degree of crystallization.

1 schematically shows a manufacturing process of an oxidation-resistant desalting electrode according to an embodiment of the present invention.

Electrode material preparation step

First, in preparing the electrode material, a carbon material, a metal oxide, and a salt containing a ring structure are prepared as the electrode material.

As the carbon material, various saccharides including a cyclic structure are preferable, among which monosaccharides and disaccharides are more preferable.

In addition, the metal oxide is included in the preparation of the electrode material. When the carbonization proceeds in the carbonization step, the metal oxide particles naturally form a carbon material uniformly supported in the carbon structure. In this case, So that desalination performance and durability can be improved.

The metal oxide is deposited in the electrode material preparation step prior to the carbonization step, and is positioned between the carbon structures, thereby improving durability.

As such a metal oxide, at least one of TiO ₂ , CuNiFe ₂ O ₄ , CuO, HfO ₂ , CeO ₂ , Gd ₂ O ₃ , and Fe _x O can be used.

Also prepared are salts which are present between the carbons and can form pores. Examples of salts include one or more of chlorine-containing NaCl, CaCl ₂ , and ZnCl ₂ .

The solvent for mixing them is not particularly limited, and any solvent can be used as long as it is capable of dissolving the metal oxide and dissolving the carbon material and the salt. Water can be used as a preferable example of such a solvent. A carbon material and salts are dissolved in a sufficient amount of a solvent, and a metal oxide is dispersed to prepare an electrode material.

On the other hand, in addition to the carbon material, graphene or carbon nanotube may be added in the electrode material preparation step. The added amount can be added in the ratio of 1: 1 ~ 3: 2 mass ratio of graphene or carbon nanotube to carbon material. The electrode manufactured when the graphene or the carbon nanotube is added can improve the electrical conductivity and the specific surface area.

Carbonization step

The prepared electrode material has a carbonization step by applying heat.

The carbonization step is a step of carbonizing the carbon source separated in a monomolecular state to form a skeleton. Structures are made with carbon connections, salts do not react and exist in salt state. Characteristic pores can be formed by forming various clusters according to the type of salt.

During the carbonization step, carbonization can be carried out by raising the temperature at a slow rate of about 1 to 5 ° C / min. Carbonization is carried out by increasing the temperature gradually from room temperature to about 600 ° C.

The reason for raising the temperature at a slow rate is to have a higher degree of crystallinity when a carbonaceous material composed of a monosaccharide or a disaccharide is carbonized.

Salt removal step

After the carbonization is generated, the salt is removed.

The electrochemical desalination technique is a desalination technique which utilizes the fact that ions are adsorbed while forming an electric double layer on the electrode surface when a potential is applied to a pair of electrodes. Therefore, it is necessary to maximize the specific surface area of the electrode material. The specific surface area of the electrode material depends on the degree of pore development. The specific surface area per unit mass or unit volume tends to increase as the number of fine pores develops, and the mobility of ions in the electrode increases when the mesopores and large pores are developed.

The electrode of the present invention can increase the desalination performance by generating as many pores as possible to widen the specific surface area. The pores can be formed by removing salts trapped between the carbon structures in the carbonization step.

The salt removal can be accomplished through an activation step and a washing step.

In the activation step, some of the carbon is oxidized or etched by chlorine to form pores. That is, the temperature is raised to about 800 to 900 ° C to remove the salts by vaporization. At this time, it is not necessary to apply heat slowly, and it is possible to reach 900 ° C in a short time. In this case, the vaporization of the salts occurs, and the sites where the vaporized and removed salts are pores are formed.

Further, pores may be additionally formed through a subsequent washing step. After the heat-applied material is cooled to room temperature, it is washed to remove salts.

The washing step can be carried out using water, and the salt in the space between the carbon atoms can be formed as pores while the salt between the carbon atoms is dissolved in the water.

Recrystallization step

The completed carbon material may be further activated to increase the amount of pores. If the carbon material is heated, the carbon material may be heated at a temperature of 1300 to 1400 ° C in the recrystallization step. When the carbon material is heated at the above temperature, Thereby contributing to improvement of durability.

In the meantime, the present invention can proceed desalination using a desalting electrode in a crossing reversing manner. In other words, when desalting is performed by the reverse-potential cross-charging and discharging method, the electrode can be used for a long time.

Fig. 2 shows a reverse-potential cross-charging system of a charge-coupled desalting electrode.

In the case of a typical storage type desalination electrode system, a positive voltage is applied to both electrodes and a short circuit is made at the time of discharging.

On the other hand, in the case of reversed-phase cross-over charging, the short-circuiting is the same in the case of reversed-phase cross-over charging, but the charging can be alternately performed once at the time of charging and once at the time of charging.

In the case of CDI without ion-exchange membranes, short-circuit discharges can occur and positive and negative voltages (= reverse potential) can be alternately applied during charging. If the negative voltage is discharged instead of the short circuit, the ions move in the opposite direction without being discharged, and the ions are adsorbed again. The reversed (negative voltage) cross-charging method in the CDI without the ion exchange membrane is shown in FIG. 2 (a).

In addition, in CDI (MCDI) in which an ion exchange membrane or an ion exchange polymer is grafted, negative voltage can be applied in the discharge process. In this operating mode, negative voltage is applied as shown in Fig. 2 (b) without shorting at the time of discharging. However, if a negative voltage is applied during discharging, it is possible to take out all the ions remaining in the short circuit, thereby increasing the performance.

In the case where the negative potential is alternately applied, the durability is improved. In this regard, the electrochemical reaction is reversed to partially regenerate the electrode, and the material which damages the electrode is removed to improve the durability . Also, in the case of the anode, the electrode is oxidized and an imbalance occurs between the two electrodes of the cathode and the anode, which causes the imbalance of the system, thereby decreasing the desalination performance. However, since the electrochemical reaction occurs equally in both electrodes when a cross potential is applied, the durability of the system can be increased and the electrode can be used for a long time because the initial electrode can be maintained in a well-balanced state.

Hereinafter, the production process of the electrode for desalting process of the present invention will be described with reference to specific examples.

Example 1

As a carbon material, glucose, TiO ₂ as a metal oxide, and NaCl as a salt are prepared and mixed with water (electrode material preparation step).

To start heating at room temperature, the temperature is gradually raised at about 2 DEG C / min and raised to about 600 DEG C. (Carbonization step)

After the carbonization step, additional heat is applied to raise the temperature to 900 ° C. to vaporize the salts, and further lower the temperature to room temperature, followed by washing with water to remove any remaining salts.

After the salt removal step, heat was applied to 1300 ° C to increase the durability of the electrode (recrystallization step).

Capacity was measured by using this material for storage type desalting electrode.

Example  2

The electrode prepared in Example 1 was subjected to a charge and discharge process by a charge reversal method. That is, at the time of charging, the battery was charged alternately once with positive voltage and once with negative voltage, and was short-circuited during discharging.

Comparative Example  One

General activated carbon was used for the electrode material and used for the desalting electrode.

Comparative Example  2

The electrode manufactured in Comparative Example 1 was subjected to a charge and discharge process using a reversed charge reversal method. That is, at the time of charging, the battery was charged alternately once with positive voltage and once with negative voltage, and was short-circuited during discharging.

Fig. 3 shows the effluent conductivity of Example 1 and Comparative Example 1, and Fig. 4 shows the effluent conductivity of Example 2 and Comparative Example 2. Fig.

Referring to FIG. 3, the use of the electrode according to Example 1 of the present invention showed better performance stability in a long-term operation.

The decrease in the solution conductivity of the effluent is due to the adsorption of ions on the electrode and the concentration of ions contained in the solution. A further decrease in effluent conductivity means better desalination performance.

The adsorption performance for the initial 0 to 30 minutes of the CDI of the storage type desalination electrode was not much different between the electrodes of Example 1 and Comparative Example 1 but the adsorption performance of the electrode manufactured in Example 1 was much better at 2700 to 2730 minutes .

4, there was almost no difference in the adsorption performance between the electrodes of Example 2 and Comparative Example 2 during the initial 0 to 30 minutes of the storage type desalination electrode, but the adsorption performance of the electrode of Example 2 was 2970 to 3000 minutes It is good to know.

From this, it was found that the durability was improved due to the oxidation resistance even when the electrode according to Example 1 of the present invention was used for a long period of time. According to the second embodiment of the present invention, It can be seen that durability is superior to the conventional method.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. It will be clear to those who have knowledge of.

110: carbon material
120: metal oxide
130: Salt

Claims (13)

Preparing an electrode material for preparing a carbon material, a metal oxide and a salt containing a ring structure;
A carbonization step of carbonizing the electrode material;
And a salt removal step of removing salts included in the electrode material,
The carbon material is a saccharide containing a cyclic structure or a saccharide containing a disaccharide,
The salts use one or more salts of NaCl, CaCl ₂ and ZnCl ₂ ,
Characterized in that pores are formed by removing the salts located between the carbon structures in the carbonization step in the salt removal step
A method for producing an oxidation resistant desalting electrode.
The method according to claim 1,
Further comprising a recrystallization step of heating to raise the degree of crystallization after the step of removing the salt.
delete The method according to claim 1,
Wherein the metal oxide comprises at least one of TiO ₂ , CuNiFe ₂ O ₄ , CuO, HfO ₂ , CeO ₂ , and Gd ₂ O ₃ .
delete The method according to claim 1,
Wherein graphene or carbon nanotubes are added in the step of preparing the electrode material.
The method according to claim 1,
Wherein carbonization is carried out at a temperature rise of 1 to 5 占 폚 / min in the carbonization step.
The method according to claim 1,
In the carbonization step, carbonization is carried out by raising the temperature to 500 to 600 ° C.
The method according to claim 1,
In the salt removal step, the salt removal is carried out through an activation step and a washing step,
Wherein the activating step is carried out by heating at 800 to 900 DEG C to vaporize and remove the salts.
delete 10. The method of claim 9,
Wherein the cleaning step removes salts by washing through water.
3. The method of claim 2,
Wherein the heating is carried out at a temperature of 1300 to 1400 캜 in the recrystallization step.
A desalting electrode manufactured by any one of claims 1, 2, 4, 6, 7, 8, 9, 11, A desalting electrode operating method for conducting desalting by charging and discharging.

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