KR102120679B1 - Mediated electrochemical removal method of sulfur hexafluoride, and its system - Google Patents

Abstract

The present invention relates to a mediated electrochemical removal method for sulfur hexafluoride (SF_6), to effectively decompose and remove SF_6 without generating a secondary toxic contaminant and a system thereof. According to the present invention, the mediated electrochemical removal method for SF_6 comprises the following steps of: a) inputting a catholyte including a precursor of a first electron mediator in a catholyte storage tank and inputting an anolyte including a precursor of a second electron mediator in an anolyte storage tank; b) injecting the catholyte including the precursor of the first electron mediator into a catholyte chamber, injecting the anolyte including the precursor of the second electron mediator into an anolyte chamber, and applying a current to reduce the precursor of the first electron mediator and, at the same time, oxidize the precursor of the second electron mediator to manufacture the catholyte including the first electron mediator and the anolyte including the second electron mediator; c) dissolving SF_6 in the catholyte including the first electron mediator to make the first electron mediator react with SF_6 to remove the SF_6 through mediated electrochemical reduction (MER) and produce a reaction product; and d) dissolving the generated reaction product in the anolyte including the second electron mediator to react the second electron mediator with the reaction product to remove the reaction product through mediated electrochemical oxidation (MEO).

Description

Mediated electrochemical removal method of sulfur hexafluoride, and its system

The present invention relates to a method for mediating electrochemical removal of SF ₆ , and a system thereof.

Sulfur hexafluoride (SF ₆ ) has a global warming index of 23,900 and is known to be the largest of the six greenhouse gases.

SF ₆ is mainly used as an insulation medium for high-voltage power equipment because it has excellent insulation at room temperature as well as at high temperatures. Etching and surface treatment are used to remove circuit patterns developed in semiconductor manufacturing processes by chemical or physical methods. It is used in the cleaning process to treat impurities.

SF ₆ is a non-toxic and non-combustible gas, but it is extremely inert and stays in the atmosphere for a long period of time (atmospheric lifetime: 800 to 3,200 years), but has a major disadvantage of causing global warming. The use of SF ₆ is inevitable until other alternatives are available.

Due to this lack of alternatives to SF _6, such a trend, interest in the administration and removal of SF ₆ from the industrial resources, which further increases.

SF ₆ is currently processed by methods such as pyrolysis, plasma, catalyst, adsorption, combustion, and membrane separation.

Pyrolysis technology is a technology that thermally decomposes SF ₆ at temperatures above 1200℃ and then removes it by quenching, which has the advantage that secondary contaminants such as dioxin are not generated, but has a drawback that energy consumption for maintaining a high temperature is very large. .

To reduce the energy consumption of the pyrolysis technology, a catalyst or plasma method was used. As a catalyst, a solid acid catalyst is mostly used, and a catalyst in which γ-Al ₂ O ₃ is loaded with a transition metal such as Ni, Co, Fe, Zn, Ce is mainly researched and used. In addition, studies on catalysts carrying inorganic acids such as sulfuric acid, phosphoric acid, and boric acid on γ-Al ₂ O ₃ are underway.

However, the decomposition of SF ₆ by catalyst or plasma method is S ₂ OF ₁₀ , CF ₄ , COF ₂ , F ₂ , HF, H ₂ S, SiF ₄ , S ₂ F ₁₀ , SF ₄ , SO ₂ F ₂ , SOF ₂ , It can also harm the human body by emitting various toxic substances such as SOF ₄ and S ₂ O ₃ F ₁₀ .

Among them, S ₂ F ₁₀ , F ₂ O, and SF ₄ are known to be highly toxic enough to regulate the limit of 8 hours at the American conference of governmental industrial hygienists (ACGIH).

Therefore, there is a need to develop a method capable of effectively decomposing and removing SF ₆ without releasing a second toxic pollutant, as well as simple SF ₆ decomposition.

On the other hand, Korean Patent Publication No. 10-2014-0056690 has been proposed as a similar precedent.

Republic of Korea Patent Publication No. 10-2014-0056690 (2014.05.12)

In order to solve the above problems, an object of the present invention is to provide an intermediate electrochemical removal method of SF ₆ and a system thereof that can effectively decompose and remove SF ₆ without discharging a second toxic pollutant. Is done.

One aspect of the present invention for achieving the above object is a) the catholyte solution containing the precursor of the first electronic medium is introduced into the catholyte storage tank, and the anolyte solution containing the precursor of the second electronic medium is introduced into the anolyte storage tank To do; b) by injecting a catholyte containing the precursor of the first electron mediator into the cathode chamber, and injecting a cathode liquid containing the precursor of the second electronic mediator into the anode chamber, and then applying a current to apply the current to the first electronic mediator Preparing a catholyte containing a second electron mediator by oxidizing the precursor of the second electron mediator while simultaneously preparing a catholyte containing the first electron mediator by reducing the precursor of the; c) the step of reacting the first electron mediator and the SF ₆ by dissolving the SF ₆ in the negative electrode mixture containing the first electron mediator through an intermediary electrochemical reduction removal of the SF ₆ and produce a reaction product ; d) dissolving the produced reaction product in the anolyte containing the second electron mediator to react the second electron mediator with the reaction product, thereby removing the reaction product through mediated electrochemical oxidation; The method relates to a method for mediating electrochemical removal of SF ₆ .

In one embodiment, the precursor of the first electron mediator is [M _a ^x+ (HA) _y ] ^z- , and the first electron mediator is [M _a ^{(x-1) +} (HA) _y ] ^{(z+ 1)-} (At this time, M _a is a transition metal, HA is a halogen material or a similar halogen material, x, y, and z may satisfy yx=z with a natural number of 2 to 10.) As a more specific example, the precursor of the first electron carrier is [Ni ²⁺ (CN) ₄ ] ^2- , and the first electron carrier from which the precursor of the first electron carrier is reduced is [Ni ¹⁺ (CN) ₄ ] ^3- can be.

In one embodiment, the precursor of the second electron mediator is a salt of M _b ⁿ⁺ , and the second electron mediator is a salt of M _b ^{(n+1)+ (where} M _b is a transition metal, n is 0) It is a natural number selected from 5). As a more specific example, the precursor of the second electron mediator is AgNO ₃ or Ag ₂ (NO ₃ ) ₂ , and the second electron mediator in which the precursor of the second electron mediator is oxidized is AgSO ₄ or Ag(NO ₃ ) ₂ Can be

In one embodiment, the anolyte solution may include an acidic solution, and may include a basic solution that is the catholyte solution, wherein the pH of the acidic solution is 1 or less, and the pH of the basic solution may be 13 or more.

In one aspect, the current in step b) may be applied with a current density of 1 to 100 mA/cm 2.

In addition, another aspect of the present invention is a catholyte (catholyte) reservoir containing the catholyte containing the first electronic medium, an anolyte (anolyte) reservoir containing the anolyte containing the second electronic medium, a diaphragm cell, and a power source An electrolytic cell including a supply part; A first wet scrubber provided above the catholyte reservoir and a second wet scrubber provided above the anolyte reservoir; An SF ₆ feeder for supplying SF ₆ to the lower end of the first wet scrubber through the upper end of the catholyte reservoir; Relates to the SF ₆ mediated electrochemical removal system containing; and Lee Dong - kwan gas connecting the upper end or the lower end portion of the second wet scrubber in the anolyte reservoir and the upper end portion of the first wet scrubber.

In another embodiment, the first electron mediator is [M _a ^(x-1)+ (HA) _y ] ^(z+1)- (where M _a is a transition metal, and HA is a halogen material or similar halogen Material, x, y, and z may satisfy yx=z with a natural number of 2 to 10.) As a specific example, the first electron mediator may be [Ni ¹⁺ (CN) ₄ ] ^3- . .

In another embodiment, the second electron mediator may be a salt of M _b ^{(n+1)+ (where} M _b is a transition metal, and n is a natural number selected from 0 to 5). For example, the second electronic medium may be AgSO ₄ or Ag(NO ₃ ) ₂ .

The method of mediated electrochemical removal of SF ₆ according to the present invention removes SF ₆ through mediated electrochemical reduction using a first electron mediator generated through electrolysis, and simultaneously removes the reaction product produced by the decomposition of SF ₆ It has the advantage of being able to effectively decompose and remove SF ₆ without releasing the second toxic contaminant by removing it through a mediating electrochemical oxidation using a second electronic medium.

In addition, since there is no need for catalytic treatment, the process can be simplified to a single process system, and problems such as catalyst deactivation or fouling can be prevented, so that there is no need to periodically replenish the catalyst. In addition, there is an advantage that the process can be performed at room temperature because a high temperature operating temperature is not required.

1 schematically shows the construction of an electro-scrubbing process apparatus used for the removal of SF ₆ according to the present invention.
2 is analytical data when Ag(II) (in 5 MH ₂ SO ₄ aqueous solution) and Ni(I) (in 10 M KOH aqueous solution) are respectively generated in the positive half cell and the negative half cell, and the curve of FIG. 2 is shown. a(Ag(II)) and b(Ni(I)) are graphs of changes in redox potential (ORP, [mV]) according to the electrolysis time, and curves a'(Ag(II)) and b'in FIG. 2 (Ni(I)) is a graph of change in concentration (M) of each electron mediator according to the electrolysis time. At this time, the conditions of the electrolysis experiment were 600 ml of electrolyte volume; Pt coated Ti anode (49 cm 2) and Cu cathode (49 cm 2 ); Current density 25 mA/cm 2; Solution flow rate to the cell 2 L/min; Solution flow rate to wet scrubber 3 L/min; The precursor concentration of the electron mediator is 25 mM AgNO ₃ and 50 mM [Ni(II)(CN) ₄ ] ^2- .
3 is a data analyzing the concentration of SF ₆ gas discharged when 5 ppm of SF ₆ gas is continuously supplied and absorbed, and FIG. 3 a provides SF ₆ gas to a 10 M KOH aqueous solution without electrolysis and As a result of absorption, b of FIG. 3 is a result of supplying and absorbing SF ₆ gas to a 5 M aqueous solution of H ₂ SO ₄ without electrolysis, and c of FIG. 3 is electrolysis of a 10 M aqueous solution of KOH to DER to SF _{6 is} the result of performing gas removal, FIG. 3 d is a result of performing SF ₆ gas removal with DEO by electrolysis of 5 M H ₂ SO ₄ aqueous solution, and FIG. 3 e shows 50 mM of [Ni(II )(CN) ₄ ] This is the result of SF ₆ gas removal by MER by electrolysis of the catholyte containing ^2- . The experimental conditions not mentioned at this time are the same as the experimental conditions in FIG. 2.
Figure 4 shows the various gases emitted from the electro-scrubber according to the removal time (in seconds) of SF ₆ by mediated electrochemical reduction (Part I) and mediated electrochemical oxidation (Part II) measured by on-line FT-IR spectroscopy. Graph showing concentration (ppm), curve a is OF ₂ , curve b is SO ₂ , curve c is SOF ₂ , curve d is SO ₂ F ₂ , curve e is SF ₆ . The experimental conditions not mentioned at this time are the same as the experimental conditions in FIG. 2.
FIG. 5A is a graph showing the change in the concentration of Ni(I) during the generation of electron mediators through electrolysis and SF ₆ gas removal, and FIG. 5B is during the generation of electron mediators through electrolysis and SF ₆ gas removal. It is a graph showing the change in the concentration of Ag(II). The experimental conditions not mentioned at this time are the same as the experimental conditions in FIG. 2.
6 is a graph showing the product concentration change during SF ₆ gas removal according to the gas flow rate change in electric scrubbing by MER, curve a is SF ₆ , curve b is SOF ₂ , curve c is OF ₂ , curve d is SO _{It is 2} . The experimental conditions not mentioned at this time are the same as the experimental conditions in FIG. 2.
7 is a graph showing changes in product concentration during SF ₆ gas removal according to gas flow rate change in electric scrubbing by MEO, curve a is SF ₆ , curve b is SOF ₂ , curve c is OF ₂ , curve d is SO _{It is 2} . The experimental conditions not mentioned at this time are the same as the experimental conditions in FIG. 2.
8 is a graph showing the product concentration change during SF ₆ gas removal according to the SF ₆ supply concentration change in electric scrubbing by MER, curve a is SF ₆ , curve b is SOF ₂ , curve c is OF ₂ , curve d Is SO ₂ . The experimental conditions not mentioned at this time are the same as the experimental conditions in FIG. 2.
9 is a graph showing the change in product concentration during SF ₆ gas removal according to the change in SF ₆ supply concentration in electric scrubbing with MEO, curve a is SF ₆ , curve b is SOF ₂ , curve c is OF ₂ , curve d Is SO ₂ . The experimental conditions not mentioned at this time are the same as the experimental conditions in FIG. 2.
10 is a portable fluorine gas detector, a is a detector before the test, and b is a photograph of the detector after detecting fluorine gas from the exhaust gas during SF ₆ gas removal in electric scrubbing with MEO. At this time, the conditions of the electrolysis experiment were 600 ml of electrolyte volume; Pt coated Ti anode (49 cm 2) and Cu cathode 49 cm 2 ); Current density 25 mA/cm 2; Solution flow rate to the cell 2 L/min; Solution flow rate to wet scrubber 3 L/min; Precursor concentration of the electron mediator 25 mM AgNO ₃ and 50 mM [Ni(II)(CN) ₄ ] ^2- ; SF ₆ feed concentration 5 ppm; The gas flow rate is 0.5 L/min.
11 is a result of FTIR gas analyzer analysis of the presence or absence of H ₂ S and HF in the exhaust gas during SF ₆ gas removal in electric scrubbing by MEO.

Hereinafter, a method for mediated electrochemical removal of SF ₆ according to the present invention and a system thereof will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Therefore, the present invention is not limited to the drawings presented below, but may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. In addition, the same reference numbers throughout the specification indicate the same components.

At this time, unless there are other definitions in the technical terms and scientific terms to be used, those skilled in the art to which the present invention pertains have the meanings commonly understood, and the gist of the present invention in the following description and the accompanying drawings Descriptions of well-known functions and configurations that may be obscured are omitted.

In addition, in describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only for distinguishing the component from other components, and the nature, order, or order of the component is not limited by the term.

In addition, in describing the present invention, the term "diaphragm cell" may mean an electrochemical cell having a diaphragm or separator provided between an anode and a cathode, and may refer to a two-electrode system including an anode and a cathode. .

In describing the present invention, the term "positive electrode half reaction" may mean electron exchange between molecules around the positive electrode. As a specific example, the anodic half reaction may mean an oxidation reaction in which the median metal ion loses electrons.

In describing the present invention, the term "cathodic half reaction" may mean electron exchange between molecules around the cathode. As a specific example, the cathode half reaction may mean a reduction reaction in which the medial metal ion obtains electrons.

In the detailed description of the present invention, the term "electronic mediator" may refer to a material capable of participating in an electrochemical reaction by receiving (stimulating or reducing) electrons directly around an anode or a cathode.

SF ₆ is the substance with the largest global warming index among the six greenhouse gases, and is processed by methods such as thermal decomposition, plasma, catalyst, adsorption, combustion, and membrane separation.

Pyrolysis techniques as pyrolysis the SF ₆ at a temperature of at least 1200 ℃ There are a very large disadvantage consumption of energy for maintaining a high temperature, SF ₆ decomposition by a catalyst or a plasma method is _{S 2 OF 10, CF 4,} COF 2 , F ₂ , HF, H ₂ S, SiF ₄ , S ₂ F ₁₀ , SF ₄ , SO ₂ F ₂ , SOF ₂ , SOF ₄ , S ₂ O ₃ F _10, etc., there is a problem of discharging various toxic substances.

Accordingly, the applicant has repeatedly studied how to effectively decompose and remove SF ₆ without releasing the second toxic pollutant, and then mediated electrochemical reduction (MER) and mediated electrochemical oxidation When the (MEO, Mediated Electrochemical Oxidation) method is used at the same time, SF ₆ is effectively decomposed and removed, and it has been discovered that the second toxic product may not be discharged, thereby completing the present invention.

Specifically, the present invention comprises the steps of: a) introducing a catholyte solution containing a precursor of a first electron mediator into a catholyte storage tank, and anolyte solution containing a precursor of a second electronic mediator into a cathode liquid storage tank; b) by injecting a catholyte containing the precursor of the first electron mediator into the cathode chamber, and injecting a cathode liquid containing the precursor of the second electronic mediator into the anode chamber, and then applying a current to apply the current to the first electronic mediator Preparing a catholyte containing a second electron mediator by oxidizing the precursor of the second electron mediator while simultaneously preparing a catholyte containing the first electron mediator by reducing the precursor of the; c) the step of reacting the first electron mediator and the SF ₆ by dissolving the SF ₆ in the negative electrode mixture containing the first electron mediator through an intermediary electrochemical reduction removal of the SF ₆ and produce a reaction product ; d) dissolving the produced reaction product in the anolyte containing the second electron mediator to react the second electron mediator with the reaction product, thereby removing the reaction product through mediated electrochemical oxidation; The method relates to a method for mediating electrochemical removal of SF ₆ .

In other words, SF ₆ is removed through a median electrochemical reduction (MER) using a first electron mediator generated through electrolysis, and at the same time, a reaction product produced by decomposition of SF ₆ is mediated using a second electron mediator. It relates to a method of removal through electrochemical oxidation (MEO).

This method has the advantage of being able to effectively decompose and remove SF ₆ without releasing a second toxic contaminant.

In addition, since there is no need for catalytic treatment, the process can be simplified to a single process system, and problems such as catalyst deactivation or fouling can be prevented, so that there is no need to periodically replenish the catalyst. In addition, there is an advantage that the process can be performed at room temperature because a high temperature operating temperature is not required.

Hereinafter, each step of the mediated electrochemical removal method of SF ₆ according to the present invention will be described in more detail.

First, a) the catholyte solution containing the precursor of the first electron mediator may be introduced into the catholyte reservoir, and the anolyte solution containing the precursor of the second electron mediator may be introduced into the anolyte reservoir.

At this time, the catholyte storage tank and the anolyte storage tank may be those that follow the configuration of a conventional electrolytic cell, for example, the electrolytic cell may include an anolyte storage tank, a catholyte storage tank, a diaphragm cell, and a power supply. This will be described in more detail in the intermediate electrochemical removal system of SF ₆ described later.

In the catholyte containing the precursor of the first electron mediator according to an embodiment of the present invention, the precursor of the first electron mediator is a material that is reduced by electrolysis to become the first electron mediator, and the first electron mediator The precursor is [M _a ^x+ (HA) _y ] ^z- , and the first electron mediator is [M _a ^(x-1)+ (HA) _y ] ^(z+1)- (where M _a is a transition metal , HA is a halogen material or a similar halogen material, x, y, and z may satisfy yx=z with a natural number of 2 to 10.). More specifically, M _a may be any one or two or more selected from nickel (Ni), cobalt (Co), iron (Fe), copper (Cu), and zinc (Zn), but is well soluble in strong bases and relatively more It is preferably stable, less toxic nickel, cobalt or iron. HA may be any one or two or more selected from F, Br, Cl and CN, but is preferably CN in terms of improving the removal efficiency of SF ₆ .

Particularly preferably, the precursor of the first electron mediator is a nickel-based precursor [Ni ²⁺ (CN) ₄ ] ^2- , and the first electron mediator from which the precursor of the first electron mediator is reduced is [Ni ¹⁺ (CN ) ₄ ] ^3- The use of [Ni ¹⁺ (CN) ₄ ] ^3- can be less harmful to the human body and the environment, is well soluble in strong bases and is relatively more stable, effectively inducing oxidation/reduction reactions, through which SF ₆ It is better because the removal efficiency can be improved.

In the catholyte containing the precursor of the first electron mediator according to an example of the present invention, the catholyte may include a basic solution, and specifically, the pH of the basic solution may be 13 or more. The use of such a strong base can improve the production efficiency of the first electron mediator. In this case, the upper limit of the pH may be a maximum value of a commonly known pH, and specifically, may be pH 14. As a more specific and non-limiting example, the basic solution may be any one or two or more selected from sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, manganese hydroxide aqueous solution and alkylamines aqueous solution, and preferably potassium hydroxide aqueous solution. It may be, more preferably, an aqueous potassium hydroxide solution having a concentration of 1 to 50 mol/L, and more preferably an aqueous potassium hydroxide solution having a concentration of 5 to 20 mol/L.

In addition, in the anolyte containing the precursor of the second electron mediator according to an embodiment of the present invention, the precursor of the second electron mediator is a material that is oxidized by electrolysis to become the second electron mediator, the second electron mediator The precursor of may be a salt of M _b ⁿ⁺ , and the second electron carrier in which the precursor of the second electron carrier is oxidized is a salt of M _b ^{(n+1)+ (where} M _b is a transition metal, and n is 0 to 0). It is a natural number selected from 5.). More specifically, M _b may be any one or two or more selected from silver (Ag), cobalt (Co) and cerium (Ce), and more preferably silver (Ag). Particularly preferably, the precursor of the second electron carrier may be AgNO ₃ or Ag(NO ₃ ) ₂ , and the second electron carrier in which the precursor of the second electron carrier is oxidized is AgSO ₄ , Ag(NO ₃ ) ₂ , Ag ₂ SO ₄ or Ag ₂ (NO ₃ ) ₂ . The use of AgSO ₄ or Ag(NO ₃ ) ₂ can effectively remove the reaction product produced by the removal of SF ₆ .

In the anolyte containing the precursor of the second electron mediator according to an example of the present invention, the anolyte may include an acidic solution, and specifically, the pH of the acidic solution may be 1 or less. The use of such a strong acid can improve the production efficiency of the second electronic medium. In this case, the lower limit of the pH may be a minimum value of a commonly known pH, and specifically, may be pH 1. As a more specific and non-limiting example, the anolyte may be any one or two or more selected from an aqueous nitric acid solution, an aqueous sulfuric acid solution and an aqueous methanesulfonic acid solution, preferably an aqueous sulfuric acid solution, and more preferably 1 to 50 It is preferable to use an aqueous sulfuric acid solution having a concentration of mol/L, more preferably an aqueous sulfuric acid solution having a concentration of 3 to 10 mol/L.

Next, b) by injecting a catholyte containing the precursor of the first electron mediator into the cathode chamber, and injecting a cathode liquid containing the precursor of the second electron mediator into the anode chamber, and then applying a current to the agent Reducing the precursor of the 1 electron mediator to prepare a catholyte containing the first electronic mediator and simultaneously oxidizing the precursor of the second electronic mediator to prepare an anolyte containing the second electronic mediator. .

At this time, the cathode chamber and the anode chamber are included in the diaphragm cell, and the diaphragm cell may include an anode portion, a cathode portion, and a separator, and the anode portion includes an anode, an anode chamber, and an anode tab, and the cathode portion A cathode, a cathode chamber, and a cathode tab may be provided, but are not limited thereto. This will be described in more detail in the intermediate electrochemical removal system of SF ₆ described later.

In the catholyte containing the first electron mediator according to an example of the present invention, the first electron mediator is a material obtained by reducing the precursor of the first electron mediator of step a) through electrolysis, The precursor is a material that is reduced by electrolysis to become the first electron mediator, and the precursor of the first electron mediator is [M _a ^x+ (HA) _y ] ^z- , and the first electron mediator is [M _a ^{(x- 1)+} (HA) _y ] ^(z+1)- (In this case, M _a is a transition metal, HA is a halogen material or a similar halogen material, and x, y, and z are natural numbers of 2 to 10, and yx=z. I am satisfied.) More specifically, M _a may be any one or two or more selected from nickel (Ni), cobalt (Co), iron (Fe), copper (Cu), and zinc (Zn), but is well soluble in strong bases and relatively more It is preferably stable, less toxic nickel, cobalt or iron. HA may be any one or two or more selected from F, Br, Cl and CN, but is preferably CN in terms of improving the removal efficiency of SF ₆ .

Particularly preferably, the precursor of the first electron mediator is a nickel-based precursor [Ni ²⁺ (CN) ₄ ] ^2- , and the first electron mediator from which the precursor of the first electron mediator is reduced is [Ni ¹⁺ (CN ) ₄ ] ^3- The use of [Ni ¹⁺ (CN) ₄ ] ^3- can be less harmful to the human body and the environment, is well soluble in strong bases and is relatively more stable, effectively inducing oxidation/reduction reactions, through which SF ₆ It is better because the removal efficiency can be improved.

In addition, in the anolyte containing the second electron mediator according to an embodiment of the present invention, the second electron mediator is a material obtained by oxidizing the precursor of the second electron mediator of step a) through electrolysis, the second electron The precursor of the mediator may be a salt of M _b ⁿ⁺ , and the second electron mediator in which the precursor of the second electron mediator is oxidized is a salt of M _b ^{(n+1)+ (where} M _b is a transition metal, and n is 0 It is a natural number selected from 5). More specifically, M _b may be any one or two or more selected from silver (Ag), cobalt (Co) and cerium (Ce), and more preferably silver (Ag). Particularly preferably, the precursor of the second electron carrier may be AgNO ₃ , and the second electron carrier of which the precursor of the second electron carrier is oxidized is AgSO ₄ , Ag(NO ₃ ) ₂ , Ag ₂ SO ₄ or Ag ₂ (NO ₃ ) May be ₂ . The use of AgSO ₄ or Ag(NO ₃ ) ₂ can effectively remove the reaction product produced by the removal of SF ₆ .

In an example of the present invention, the current may be applied by a power supply, specifically, in step b), the current may be applied at a current density of 1 to 100 mA/cm 2, preferably 10 It may be applied to a current density of 90 mA/cm 2, more preferably 15 to 50 mA/cm 2. It is possible to induce a stable electrolysis reaction in the above range.

Next, c) the first by dissolving the SF ₆ in the negative electrode mixture containing an electron mediator response to the first electronic media and the SF _6, mediated electrochemical through the reduction of the SF _6, and the reaction product The step of generating can be performed.

At this time, as described in the system to be described later, the SF ₆ is supplied to the lower end of the first wet scrubber by the SF ₆ feeder, and the catholyte is supplied to the upper end of the first wet scrubber through an injection pipe connected to the catholyte reservoir. SF ₆ can be dissolved in the catholyte. At this time, SF ₆ gas supplied to the lower end of the first wet scrubber is supplied directly to the lower end of the first wet scrubber or is pre-supplied to the upper end of the catholyte storage tank and then passes through the lower end of the first wet scrubber and exits to the upper end. It could be the way out.

In addition, in an example of the present invention, SF ₆ supplied for dissolution in step c) may be carried by a carrier gas. The carrier gas is not particularly limited as long as it is an inert gas, and may be, for example, nitrogen (N ₂ ), argon (Ar), or the like.

At this time, the carrier gas supply may be in the form of a general tank for supplying gas, and as shown in FIG. 1, the carrier gas is mixed with SF ₆ and connected to the SF ₆ supply to supply to the lower end of the first wet scrubber. Carrier gas supply pipes may be connected to the SF ₆ supply pipes, whereby SF ₆ and carrier gas mixed as one may be supplied to the first wet scrubber. In addition, the carrier gas supply pipe is also equipped with a mass flow controller (MFC) to control the concentration and flow rate of the carrier gas. At this time, SF ₆ and the carrier gas supplied to the lower end of the first wet scrubber are supplied directly to the lower end of the first wet scrubber or pre-supplied to the upper end of the catholyte storage tank and then passed through the first wet scrubber and drained to the top. It could be the way out.

A specific example of a feed concentration and flow rate of the SF _6, feed concentration of the SF ₆ may be a 1 to 100 ppm, more preferably from 2 to 20 ppm, more preferably from 3 to 10 ppm, most preferably from 4 to 6 ppm. In this range, SF6 can be almost decomposed and removed. At this time, the flow rate is not particularly limited, and in one embodiment, 0.1 to 10.0 L/min, more preferably 0.2 to 5.0 L/min, and more preferably 0.3 to 3.0 L/min, but is not limited thereto.

On the other hand, in one example of the present invention, the catholyte containing the first electronic medium may be supplied to the first wet scrubber provided on the top of the catholyte reservoir, wherein the flow rate of the catholyte is not particularly limited, It may be 0.1 to 50 L/min, preferably 0.5 to 20 L/min, and more preferably 1 to 10 L/min. In the above range, the oxidation/reduction reaction of the first electron mediator and SF ₆ is effectively induced, so that the efficiency of SF ₆ removal and reaction product generation can be improved.

Next, d) dissolving the produced reaction product in the anolyte containing the second electron mediator to react the second electron mediator and the reaction product, thereby removing the reaction product through mediated electrochemical oxidation. You can do

At this time, as described in the system to be described later, the reaction product is generated in the first wet scrubber through a gas transfer pipe connecting the upper end of the first wet scrubber and the upper end of the anolyte reservoir or the lower end of the second wet scrubber. It is supplied to the lower end of the second wet scrubber, and the anolyte solution is supplied to the upper end of the second wet scrubber through an injection tube connected to the anolyte reservoir, so that the reaction product can be dissolved in the anolyte. At this time, the reaction product supplied to the lower end of the second wet scrubber is directly supplied to the lower end of the second wet scrubber through the gas transfer pipe or pre-supplied to the upper end of the anolyte storage tank and then passed through the lower end of the second wet scrubber. It may be a way to escape to the top.

In one example of the present invention, the anolyte containing the second electronic medium may be supplied to a second wet scrubber provided on the top of the anolyte reservoir, wherein the flow rate of the anolyte is not particularly limited, but is 0.1 to It may be 50 L / min, preferably 0.5 to 20 L / min, more preferably 1 to 10 L / min. In the above range, the oxidation/reduction reaction of the second electron mediator and the reaction product is effectively induced, so that the efficiency of removing the reaction product can be improved.

In addition, another aspect of the present invention is a catholyte (catholyte) reservoir containing the catholyte containing the first electronic medium, an anolyte (anolyte) reservoir containing the anolyte containing the second electronic medium, a diaphragm cell, and a power source An electrolytic cell including a supply part; A first wet scrubber provided above the catholyte reservoir and a second wet scrubber provided above the anolyte reservoir; An SF ₆ feeder for supplying SF ₆ to the lower end of the first wet scrubber through the upper end of the catholyte reservoir; Relates to the SF ₆ mediated electrochemical removal system containing; and Lee Dong - kwan gas connecting the upper end or the lower end portion of the second wet scrubber in the anolyte reservoir and the upper end portion of the first wet scrubber.

In the mediated electrochemical removal system of SF ₆ according to an example of the present invention, the electrolytic cell may be the same or partially modified form that is conventionally used in the art, specifically, the electrolytic cell according to the present invention It may include a catholyte storage tank containing a catholyte containing the first electronic medium, an anolyte storage tank containing anolyte containing the second electronic medium, a diaphragm cell, and a power supply.

In the catholyte containing the precursor of the first electron mediator according to an example of the present invention, the precursor of the first electron mediator is a material that is reduced by electrolysis to become the first electron mediator, the precursor of the first electron mediator Is a material that is reduced by electrolysis to become the first electron mediator, the precursor of the first electron mediator is [M _a ^x+ (HA) _y ] ^z- , and the first electron mediator is [M _a ^{(x-1 )+} (HA) _y ] ^(z+1)- (In this case, M _a is a transition metal, HA is a halogen material or a similar halogen material, and x, y and z satisfy yx=z with a natural number of 2 to 10 It may be). More specifically, M _a may be any one or two or more selected from nickel (Ni), cobalt (Co), iron (Fe), copper (Cu), and zinc (Zn), but is well soluble in strong bases and relatively more It is preferably stable, less toxic nickel, cobalt or iron. HA may be any one or two or more selected from F, Br, Cl and CN, but is preferably CN in terms of improving the removal efficiency of SF ₆ .

Particularly preferably, the precursor of the first electron mediator is a nickel-based precursor [Ni ²⁺ (CN) ₄ ] ^2- , and the first electron mediator from which the precursor of the first electron mediator is reduced is [Ni ¹⁺ (CN ) ₄ ] ^3- The use of [Ni ¹⁺ (CN) ₄ ] ^3- can be less harmful to the human body and the environment, is well soluble in strong bases and is relatively more stable, effectively inducing oxidation/reduction reactions, through which SF ₆ It is better because the removal efficiency can be improved.

In the catholyte containing the precursor of the first electron mediator according to an example of the present invention, the catholyte may include a basic solution, and specifically, the pH of the basic solution may be 13 or more. The use of such a strong base can improve the production efficiency of the first electron mediator. In this case, the upper limit of the pH may be a maximum value of a commonly known pH, and specifically, may be pH 14. As a more specific and non-limiting example, the basic solution may be any one or two or more selected from sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, manganese hydroxide aqueous solution and alkylamines aqueous solution, and preferably potassium hydroxide aqueous solution. It may be, more preferably, an aqueous potassium hydroxide solution having a concentration of 1 to 50 mol/L, and more preferably an aqueous potassium hydroxide solution having a concentration of 5 to 20 mol/L.

In addition, in the anolyte containing the precursor of the second electron mediator according to an embodiment of the present invention, the precursor of the second electron mediator is a material that is oxidized by electrolysis to become the second electron mediator, the second electron mediator The precursor of may be a salt of M _b ⁿ⁺ , and the second electron carrier in which the precursor of the second electron carrier is oxidized is a salt of M _b ^{(n+1)+ (where} M _b is a transition metal, and n is 0 to 0). It is a natural number selected from 5.). More specifically, M _b may be any one or two or more selected from silver (Ag), cobalt (Co) and cerium (Ce), and more preferably silver (Ag). Particularly preferably, the precursor of the second electron carrier may be AgNO ₃ , and the second electron carrier of which the precursor of the second electron carrier is oxidized is AgSO ₄ , Ag(NO ₃ ) ₂ , Ag ₂ SO ₄ or Ag ₂ (NO ₃ ) May be ₂ . The use of AgSO ₄ or Ag(NO ₃ ) ₂ can effectively remove the reaction product produced by the removal of SF ₆ .

In the anolyte containing the precursor of the second electron mediator according to an example of the present invention, the anolyte may include an acidic solution, and specifically, the pH of the acidic solution may be 1 or less. The use of such a strong acid can improve the production efficiency of the second electronic medium. In this case, the lower limit of the pH may be a minimum value of a commonly known pH, and specifically, may be pH 1. As a more specific and non-limiting example, the anolyte may be any one or two or more selected from an aqueous nitric acid solution, an aqueous sulfuric acid solution and an aqueous methanesulfonic acid solution, preferably an aqueous sulfuric acid solution, and more preferably 1 to 50 It is preferable to use an aqueous sulfuric acid solution having a concentration of mol/L, more preferably an aqueous sulfuric acid solution having a concentration of 3 to 10 mol/L.

In one example of the present invention, the anolyte storage tank or the catholyte storage tank may include an inlet pipe and an outlet pipe on one side or the other, and the inlet pipe and the outlet pipe independently of each other may be an anode chamber, a cathode chamber, or an upper portion of each reservoir. It may be in communication with the wet scrubber provided in. Accordingly, the anolyte and catholyte solutions of the present invention can be continuously supplied and circulated to the anodic part, the cathodic part, or a wet scrubber through the injection tube and the discharge tube, respectively, and a pump is attached to the injector tube to provide The flow rate can be controlled. This is illustrated in more detail in FIG. 1.

In one example of the present invention, the diaphragm cell may include an anode portion, a cathode portion, and a separator, and the anode portion includes an anode, an anode chamber, and an anode tab, and the cathode portion includes a cathode, a cathode chamber, and a cathode. A tab may be provided, but is not limited thereto. In addition, the separator may be formed in a plate-like shape including a front side and a rear side of the opposite side, and the front side of the separator may be opposite to the anode, but is not limited thereto. The type of the separation membrane is not greatly limited in achieving the object of the present invention, but a material capable of delivering hydrogen ions is sufficient, and a material stable in a strong acid and a strong base solution is more preferable. As a specific and non-limiting example, the separator may be a Nafion polymer separator comprising one or more ionic functional groups selected from the group consisting of sulfonate, carboxylate, and phosphate. In addition, the positive electrode may be made of one or more metals or alloys selected from the group consisting of platinum (Pt), silver (Ag), titanium (Ti) and copper (Cu), and the negative electrode may include silver (Ag) and It may be made of one or more metals or alloys selected from the group consisting of copper (Cu) or the like. Preferably, the positive electrode may be a metal coated with platinum (Pt) or platinum (Pt), and the negative electrode may be copper (Cu), but is not limited thereto.

In one example of the present invention, the power supply may be electrically connected to a positive electrode tab extending from the positive electrode and located on one side of the positive electrode, and a negative electrode tab extending from the negative electrode and located on one side of the negative electrode. This is a device for controlling electrical signals, such as current density, which is a major factor in the removal of SF ₆ of the present invention and its reaction products, and when an electrical signal is applied, the precursor of the first electron mediator reacts half of the cathode in the cathode chamber of the cathode part. It is reduced by, the precursor of the reduced first electron mediator, that is, the first electron mediator reacts with SF ₆ to oxidize the first electron mediator again, and SF ₆ is reduced to produce a reaction product. At the same time, the precursor of the second electron mediator is oxidized by an anodic half reaction in the anode chamber of the anode unit by the application of an electrical signal, and the precursor of the oxidized second electron mediator, that is, the second electron mediator reacts with the reaction product, thereby The electron mediator is reduced again, and the reaction product can be oxidized and removed.

At this time, in the application of the current by the power supply, the current may be applied with a current density of 1 to 100 mA/cm 2, preferably 10 to 90 mA/cm 2, more preferably 15 to 50 mA/cm 2 It may be applied to the current density of. It is possible to induce a stable electrolysis reaction in the above range.

In addition, in the mediated electrochemical removal system of SF ₆ according to an example of the present invention, the first wet scrubber and the second wet scrubber may be used without particular limitation as long as they are commonly used in the SF ₆ removal process. At this time, the first wet scrubber is provided at the upper end of the catholyte storage tank, and the upper end of the catholyte storage tank is provided with an outlet independently of each other, so that the first wet scrubber and the outlet may be in communication structure. In addition, the second wet scrubber is provided at the upper end of the anolyte reservoir, and the upper end of the anolyte reservoir is provided with an outlet independently of each other, so that the second wet scrubber and the outlet may be in communication.

Further, in SF ₆ medium electrochemical removal system according to one embodiment of the present invention, the SF ₆ feeder may be a common tank type for supplying a gas, wherein the SF ₆ through the upper end of the catholyte reservoir 1 To supply to the lower end of the wet scrubber, the SF ₆ feeder and the upper end of the catholyte reservoir may be connected to the SF ₆ supply pipe. At this time, a mass flow controller (MFC) is attached to the SF ₆ supply pipe to control the concentration and flow rate of SF ₆ .

In addition, in the mediated electrochemical removal system of SF ₆ according to an example of the present invention, the system may further include a carrier gas supplier for supplying carrier gas carrying SF ₆ . The carrier gas is not particularly limited as long as it is an inert gas, and may be, for example, nitrogen (N ₂ ), argon (Ar), or the like.

At this time, the carrier gas supply may be in the form of a general tank for supplying gas, and as shown in FIG. 1, the carrier gas is mixed with SF ₆ and connected to the SF ₆ supply to supply to the lower end of the first wet scrubber. Carrier gas supply pipes may be connected to the SF ₆ supply pipes, whereby SF ₆ and carrier gas mixed as one may be supplied to the first wet scrubber. In addition, the carrier gas supply pipe is also equipped with a mass flow controller (MFC) to control the concentration and flow rate of the carrier gas. At this time, SF ₆ and the carrier gas supplied to the lower end of the first wet scrubber are supplied directly to the lower end of the first wet scrubber or pre-supplied to the upper end of the catholyte storage tank and then passed through the first wet scrubber and drained to the top. It could be the way out.

A specific example of a feed concentration and flow rate of the SF _6, feed concentration of the SF ₆ may be a 1 to 100 ppm, more preferably from 2 to 20 ppm, more preferably from 3 to 10 ppm, most preferably from 4 to 6 ppm. In this range, SF6 can be almost decomposed and removed. At this time, the flow rate is not particularly limited, and in one embodiment, 0.1 to 10.0 L/min, more preferably 0.2 to 5.0 L/min, and more preferably 0.3 to 3.0 L/min, but is not limited thereto.

In addition, in the mediated electrochemical removal system of SF ₆ according to an embodiment of the present invention, the gas transfer pipe is for removing the reaction product generated by the decomposition of SF ₆ in the first wet scrubber to the second wet scrubber As an example, the upper end of the first wet scrubber may be connected to the upper end of the anolyte storage tank or the lower end of the second wet scrubber. At this time, the location of the specific gas transfer pipe may not be specified, and one side or one end of the upper end of the first wet scrubber and one side of the upper end of the anolyte storage tank are connected, or one side or one end of the first wet scrubber and the second wet type It may be provided to connect one side of the lower end of the scrubber.

Hereinafter, the method for mediating electrochemical removal of SF ₆ according to the present invention and the system will be described in more detail through examples. However, the following examples are only one reference for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of effectively describing specific embodiments and is not intended to limit the present invention. In addition, the unit of the additive not specifically described in the specification may be weight%.

[Example 1]

1.1 Creation of electronic media

As shown in FIG. 1, two electronic media, Ag(II)(AgSO ₄ ) and Ni(I)([N ¹⁺ (CN) ₄ ] ^3- ), are narrow gap and split configurations of plate and frame type. It was simultaneously generated using an electrolytic cell.

In detail, 10 mM Ag(I) (AgNO ₃ ) as the anolyte Aqueous solution storage tank containing 0.6 L of aqueous solution (in 5 MH ₂ SO ₄ aqueous solution) and 10 mM Ni(II) ([Ni ²⁺ (CN) ₄ ] ^2- ) aqueous solution as an anode solution 0.6 L (in 10 M KOH aqueous solution) ) Was prepared to accommodate the catholyte storage tank.

The anolyte and catholyte are continuously flowed through the anode chamber and cathode chamber of the diaphragm cell at a constant flow rate of 2 L/min using a magnetic pump (Pan World Co., Ltd, Taiwan) through the narrow gap of the divided cell. Circulated (divided by Nafion@324 membrane). The active electron mediators Ni(I) and Ag(II) were generated with a constant current by applying a constant current density of 25 mA/cm2 using a DC power supply (Korea Switching Instruments), and the effective surface area of each electrode exposed to the solution was 49. It was cm2. Ti coated with a mesh-type Pt was used as the anode, and mesh-shaped Cu was used as the cathode. All measurements were repeated 3 times at 20°C.

1.2 Quantification of electronic media

5 ml of the catholyte containing Ni(I) was periodically collected during electrolysis, and the resulting Ni(I) concentration was the redox potential (ORP) electrode (model number EMC133 (6 mm Pt with Ag/AgCl reference electrode). Use and gel electrolyte, Germany)) and pH/ISE meter (iSTEK, pH-240L, USA) using the potentiometric method for [Fe(III)(CN) ₆ ] ^3- (1 mM) to titrate The end point was confirmed. During each titration, the addition of [Fe(III)(CN) ₆ ] ^3- is stopped when the measured ORP shifted to a negative value returns to -150 mV before electrolysis as the Ni(I) concentration increases. Became. The Ni(I) concentration was calculated from the concentration of [Fe(III)(CN) ₆ ] ^3- titrant consumed. The Ni(I) concentration measured in this way was reproducible within ±0.02 mM.

In a similar manner, the concentration of Ag(II) generated in the anolyte was determined by titration with Fe(II)SO ₄ (1 mM). The initial ORP value of the Ag(II)-containing solution was about 600 mV, and gradually increased as the Ag(II) concentration increased. The concentration of Ag(II) was calculated from the concentration of Fe(II)SO ₄ titrant. The Ag(II) concentration measured in this way was reproducible within ±0.02 mM.

1.3 Electro-scrubber setup

A column with a diameter of 5.5 cm and a height of 40 cm, having an empty bed volume of 0.95 L, was filled with a Teflon tube (1 cm 2) as a packing material to a height of 30 cm to a specific surface area of 437 m 2 /m 3 A scrubber column having a was prepared.

As shown in Figure 1, the scrubber column was attached to the top of the anolyte reservoir and the anolyte reservoir for SF ₆ gas decomposition experiment, respectively. The exhaust gas is real-time using an online gas chromatography (GC) analyzer from FT-IR (USA MIDAC Corporation, USA) and BDI-TCD (SHIMADZU, 2010 plus model form SHIMADZU Corporation) for identification of products. Was measured directly.

The Ni(I)-containing catholyte and Ag(II)-containing catholyte were separately pumped into a scrubber column provided at the top of each reservoir at a flow rate of 3 L/min. SF ₆ gas is mixed with argon (Ar) carrier gas and is controlled by mass flow controllers (MFCs; Line Tech., model M3030V R, Korea), to the lower end of the scrubber column provided at the top of the catholyte reservoir with the set gas flow rate. Was introduced.

At this time, the SF ₆ to Ar ratio obtained using the mass flow controller was confirmed before performing the experiment, and the scrubbing solution was recycled through an electrochemical cell to regenerate Ni(I) or Ag(II). Before starting the SF ₆ removal experiment, the electrochemical cell was operated until Ni(I) or Ag(II) conversion reached a steady state, and then the scrubbing solution was pumped into the scrubber column.

[Result Analysis]

1.1 Confirmation of creation of electronic media

Ni(I) and Ag(II), homogeneous catalysts, were electrochemically produced at a current density of 25 kV/cm 2.

Figure 2 Ag (I) (AgNO ₃ ) (in 5 MH ₂ SO ₄ aqueous solution) and Ni (II) ([Ni ²⁺ (CN) ₄ ] ^2- ) (in 10 M KOH aqueous solution) is a positive half cell and As a result of electrolysis when each is present in the negative half cell, the Ag(II) and Ni(I) electron mediators in each half cell have an oxidation-reduction potential (ORP) of the electrolytic solution at 1.5 V for 30 minutes (curve in FIG. 2). It was confirmed that it was formed by initial shifting to a) and -0.7 V (curve b in FIG. 2). The concentrations of Ag(II) and Ni(I) were confirmed as shown in curves a'and b'of FIG. 2 through potentiometric titration according to the change of ORP. After 3 hours of electrolysis under the given conditions, Ni(I) reached a concentration of about 5 mM and Ag(II) reached a concentration of about 6.5 mM.

In addition, the initial Ni(II) solution was changed from light yellow to dark red, and the colorless Ag(I) solution was changed to dark green, and it was confirmed that each electron mediator was well formed through electrolysis. At this time, the conditions of the electrolysis experiment were 600 ml of electrolyte volume; Pt coated Ti anode (49 cm 2) and Cu cathode (49 cm 2 ); Current density 25 mA/cm 2; Solution flow rate to the cell 2 L/min; Solution flow rate to wet scrubber 3 L/min; The precursor concentrations of the electron mediator were 25 mM Ag(I) and 50 mM Ni(II).

1.2 SF ₆ Removal and product analysis

Before removing SF ₆ with MER using an electrogenerated electron mediator, SF ₆ is highly alkaline (10 M KOH) and acid (5 MH ₂ SO ₄ ) in a countercurrent scrubbing process by a single pass method. Absorbed into solution.

FIG. 3 shows the result of the concentration of SF ₆ gas discharged when 5 ppm of SF ₆ gas is continuously supplied and absorbed, and FIG. 3 a provides SF ₆ gas to a 10 M KOH aqueous solution without electrolysis and As a result of absorption, b in FIG. 3 is a result of supplying and absorbing SF ₆ gas in a 5 M aqueous solution of H ₂ SO ₄ without electrolysis, and c in FIG. 3 is directly electrochemically electrolyzing a 10 M KOH aqueous solution. the result of performing the SF ₆ gas to remove the reducing (DER) results, and the electrochemical oxidation (DEO) directly by electrolysis of H ₂ SO ₄ aqueous solution of 5 M diagram of a 3 d is performed to remove SF ₆ gas, the 3e is a result of performing SF ₆ gas removal with MER by electrolyzing a catholyte containing 50 mM Ni(II).

At this time, the conditions of the electrolysis experiment were 600 ml of electrolyte volume; Pt coated Ti anode (49 cm 2) and Cu cathode (49 cm 2 ); Current density 25 mA/cm 2; Solution flow rate to the cell 2 L/min; Solution flow rate to wet scrubber 3 L/min; Precursor concentration of the electron mediator 50 mM Ni(II); SF ₆ feed concentration 5 ppm; The gas flow rate was 0.5 L/min.

Referring to a of FIG. 3, in the initial 5 minutes, SF ₆ was absorbed by about 12%, which rapidly decreased to 0% absorption in 30 minutes, and was maintained until the end of the experiment. In other words, the concentration of SF ₆ released after 30 minutes has reached the supply concentration, which means that SF ₆ is completely discharged without further absorption, and although SF ₆ is very hydrophobic, it has a very low concentration in 10 M KOH aqueous solution. It shows that it is absorbed.

SF ₆ is an SF _2, but an inert gas, reacting the intermediate product forms an SOF ₂ and SO ₂ F ₂ compound, with toxicity as shown in the following, to readily react with molecular O ₂ in the atmosphere formula 1 and 2. At the same time, as shown in equations 3 and 4 below, when SF ₂ reacts with atomic oxygen (O( ³ P)), SO ₂ is produced.

(Equation 1) SF ₂ + O → SOF ₂

(Equation 2) SF ₂ + O ₂ → SO ₂ F ₂

(Equation 3) SF ₂ + O( ³ P) → SOF + F

(Equation 4) SOF + O( ³ P) → SO ₂ + F

In addition, when looking at b of FIG. 3, the removal of SF ₆ through absorption in 5 MH ₂ SO ₄ hardly occurred, and only about 0.2 ppm of SF ₆ was absorbed and maintained.

3c is observed as a result of absorption and discharge of SF ₆ during electrolysis of 10 M KOH, the absorption of SF ₆ suddenly increases to 21% in 4 minutes, and then rapidly decreases to 0% in 35 minutes. , This indicates that there is no removal of SF ₆ by direct electrochemical reduction (DER) in KOH aqueous solution.

3d shows the absorption and discharge of SF ₆ during the electrolysis of 5 MH ₂ SO ₄ , the absorption of SF ₆ was not observed.

On the other hand, e of FIG. 3 is a result of absorption and discharge of SF ₆ during electrolysis of a catholyte containing Ni(II), leaving only 0.2 ppm at the end of the experiment time, and 95% of SF ₆ removed within 5 minutes. , This confirms that the removal of SF ₆ was caused by a uniform low voltage electron mediator.

In addition, as shown in Part 1 of FIG. 4, in the Ni(I) reduction process, SF ₆ supplied at 5 ppm was removed by 95%, but the product was SOF ₂ 3 ppm, SO ₂ F ₂ 4 ppm, OF _It was found to be ₂ 7 ppm and SO ₂ 3 ppm. These are all poisonous toxic gases, similar to products produced by plasma technology.

Producing toxic gases from strong non-toxic greenhouse gases combined with an additional removal process called mediated electrochemical oxidation (MEO) by the electron mediator Ag(II) produced in the anode half-cell, as it is another environmental risk. .

Ag(II) produced at the same time as Ni(I) production was brought into contact with the gas reduced by MER by Ni(I) in the anode scrubbing column, and as a result, as shown in Part 2 of FIG. 4, the MER process SOF ₂ , SO ₂ F ₂ , OF ₂ and SO ₂ gases, including a small amount of SF ₆ present, were not present or discharged at almost 0%, confirming that the toxic gas products formed during the MER process were almost completely removed. .

Other products such as H ₂ S and HF among the gases that can be discharged as a final product were confirmed through an FTIR gas analyzer, and as shown in FIG. 11, none of H ₂ S and HF was found in the exhaust gas.

Fluorine gas (F ₂ ), which can be discharged as a final product, cannot be analyzed by FTIR due to symmetry factors, and thus, a fluorine gas detection test is performed at the exit gas using a portable fluorine gas detector, as shown in FIG. 10. It was confirmed that the fluorine gas was not discharged as the portable fluorine gas detector was not discolored from pale yellow (a) to brown (b). At this time, the portable fluorine gas detector was tested for exhaust gas using a portable gas fluorine gas detector No. 17 from Japan GASTEC and the gas sampling pump GV-1105 system.

In addition, as fluorine may exist in solution form, it was analyzed using a fluorine sensor ion selective electrode. Under pH 5, fluorine gas forms HF ₂ ^- ions with hydrogen, which may explain that the resulting fluorine gas did not escape from the solution. As the SF ₆ removal time increased, the concentration of the fluoride ion in the solution increased from 11.8 ppm to 120 ppm through a fluorine sensor ion selective electrode, indicating that the final fluorine product was in the form of fluoride. At this time, the fluorine or fluorine ion selection electrode was used according to the manufacturer's instructions using the electrode model F001502003B (iSTEK, USA).

In addition, since no sulfur-containing gaseous products such as H ₂ S and SO ₂ , SOF ₂ and SO ₂ F ₂ have been found, the remaining possible final product may be SO ₄ ^2- .

Regarding the above, the reaction pathways for final product formation from SF ₆ are shown in the following equations 5 to 8.

MER:

(Equation 5) Ni(Ⅱ) + e- → Ni(Ⅰ)

(Equation 6) 24Ni(Ⅰ) + 3SF ₆ + 12H ₂ O → 24Ni(Ⅱ) + 7OF ₂ + SOF ₂ + SO ₂ F ₂ + SO ₂ + 24H ⁺

MEO:

(Equation 7) Ag(Ⅰ) → Ag(Ⅱ) + e-

(Equation 8) 9Ag (Ⅱ) + 7OF 2 + SOF 2 + SO 2 F 2 + SO 2 + 9H + → 9Ag (Ⅰ) + 9HF 2 - + 3SO 4 2-

FIG. 5 is a graph showing the concentration change of Ni(I) and Ag(II) during electron mediator generation and SF ₆ gas removal through electrolysis. The concentration of Ni(I) generated during SF ₆ removal is 6 mM. At 4 mM, and the Ag(II) concentration was changed from 3 mM to 2 mM. From this it was confirmed once again that SF ₆ removal follows the MER and MEO procedures.

[Example 2]

The experiment was conducted in the same manner as in Example 1, but the gas flow rate was changed. Specifically, the conditions for the electrolysis experiment were: electrolyte volume of 600 ml; Pt coated Ti anode (49 cm 2) and Cu cathode (49 cm 2 ); Current density 25 mA/cm 2; Solution flow rate to the cell 2 L/min; Solution flow rate to wet scrubber 3 L/min; The precursor concentrations of the electron mediator were 25 mM Ag(I) and 50 mM Ni(II), the SF ₆ supply concentration was 5 ppm, and the gas flow rates were 0.2, 0.5, 1.0, 1.5 and 2.0 L/min, respectively.

The results are shown in Figure 6 (MER) and Figure 7 (MEO).

As shown in FIG. 6, as a result of analyzing the change in the formation efficiency and reaction product of SF ₆ by MER, the released SF ₆ concentration is about 3.8 ppm at a gas flow rate of 0.5 L/min or more. As was almost constant. On the other hand, as can be seen from the curves b, c and d, the concentrations of SOF ₂ of 2.6 ppm, OF ₂ of 6.8 ppm, and SO ₂ of 3.7 ppm decrease to 0.5 ppm of SO ₂ , SOF ₂ and OF ₂ 0 ppm. The result was.

In addition, as illustrated in FIG. 7, as a result of analyzing the change in the efficiency of removal of SF ₆ by MEO and the formation of reaction products, the concentration of SF ₆ discharged as seen through curve a is about 0.5 L/min or more at a gas flow rate of about It was almost constant at 4.2 ppm. On the other hand, as can be seen from the curves b, c and d, the toxic reaction products SOF ₂ and OF ₂ were completely removed at all gas flow rates, and SO ₂ slightly increased to 0.5 ppm at the residual gas flow rates.

The increase in the concentration of SF ₆ during MEO can be explained by the concentrations of SO ₂ , SOF ₂ and OF ₂ , where F ₂ from SOF ₂ and OF ₂ will react with unremoved SF ₆ from MER at high gas flow rates. It means you can. In addition, the resulting S ₂ F ₁₀ , SO ₂ F ₂ or SOF ₂ product reacted with SF ₅ or SF ₄ again to generate SF ₆ again.

[Example 3]

The experiment was conducted in the same manner as in Example 1, but the SF ₆ feed concentration was changed. Specifically, the conditions for the electrolysis experiment were: electrolyte volume of 600 ml; Pt coated Ti anode (49 cm 2) and Cu cathode (49 cm 2 ); Current density 25 mA/cm 2; Solution flow rate to the cell 2 L/min; Solution flow rate to wet scrubber 3 L/min; The precursor concentration of the electron mediator was 25 mM Ag(I) and 50 mM Ni(II), the gas flow rate was 0.5 L/min, and the SF ₆ supply concentration was 5, 10, 15, 20, 25 and 30 ppm, respectively. Did.

The results are shown in Figure 8 (MER) and Figure 9 (MEO).

As shown in FIG. 8, as a result of analyzing the change in the efficiency of removal of SF ₆ and the formation of reaction products by MER, the discharged SF ₆ concentration increases as the SF ₆ supply concentration increases, as can be seen through the curve a. Did. On the other hand, as can be seen from the curves b, c and d, the OF _2, SOF ₂ and SO ₂ concentrations increased to 15 ppm SF _{6 and} then decreased.

At the same time, as shown in FIG. 9, as a result of analyzing the change in the efficiency of SF ₆ removal by MEO and reaction product formation, the reaction product by the MER process was completely removed at all feed concentrations during the MEO process, and 1 or 2 than the MER process. A higher SF ₆ concentration in ppm was found at each feed concentration.

Although the present invention has been described through specific matters and limited embodiments as described above, it is provided only to help a more comprehensive understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention pertains Those skilled in the art can make various modifications and variations from these descriptions.

Accordingly, the spirit of the present invention should not be limited to the described embodiments, and should not be determined, and all claims that are equivalent or equivalent to the scope of the claims as well as the claims to be described later belong to the scope of the spirit of the invention. .

Claims (13)

a) introducing a catholyte solution containing a precursor of the first electronic medium into the catholyte storage tank and anolyte solution containing a precursor of the second electronic medium into the anolyte storage tank;
b) by injecting a catholyte containing the precursor of the first electron mediator into the cathode chamber, and injecting a cathode liquid containing the precursor of the second electronic mediator into the anode chamber, and then applying a current to apply the current to the first electronic mediator Preparing a catholyte containing a second electron mediator by oxidizing the precursor of the second electron mediator while simultaneously preparing a catholyte containing the first electron mediator by reducing the precursor of the;
c) generating a reaction product from SF _6, while removing the second SF to dissolve the SF ₆ in the catholyte to one containing an electron mediator by the reaction of the first electron mediator and the SF ₆ through the medium electrochemical reduction ₆ ; And
d) dissolving the reaction product in the anolyte containing the second electron mediator to react the second electron mediator with the reaction product, thereby removing the reaction product through mediated electrochemical oxidation; Method of mediating electrochemical removal of SF ₆ . According to claim 1,
The precursor of the first electron mediator is [M _a ^x+ (HA) _y ] ^z- , and the first electron mediator is [M _a ^{(x-1) +} (HA) _y ] ^(z+1)- (where M _a is a transition metal, HA is a halogen material or a similar halogen material, x, y and z are natural numbers of 2 to 10 to satisfy yx=z.), a method of mediating electrochemical removal of SF ₆ . According to claim 2,
The precursor of the first electron mediator is [Ni ²⁺ (CN) ₄ ] ^2- , and the first electron mediator from which the precursor of the first electron mediator is reduced is [Ni ¹⁺ (CN) ₄ ] ^3- phosphorous, SF ₆ , mediated electrochemical removal method. According to claim 1,
The precursor of the second electron mediator is a salt of M _b ⁿ⁺ , and the second electron mediator is a salt of M _b ^{(n+1)+ (where} M _b is a transition metal, and n is a natural number selected from 0 to 5). Phosphorus, a method for the removal of mediated SF ₆ by electrochemical. The method of claim 4,
The precursor of the second electron mediator is AgNO ₃ or Ag ₂ (NO ₃ ) ₂ , and the second electron mediator in which the precursor of the second electron mediator is oxidized is AgSO ₄ or Ag(NO ₃ ) ₂ , the mediator of SF ₆ Electrochemical removal method. According to claim 1,
The anolyte solution includes an acidic solution, and the catholyte solution comprises a basic solution, the method of mediating electrochemical removal of SF ₆ . The method of claim 6,
The pH of the acidic solution is 1 or less, the pH of the basic solution is 13 or more, SF ₆ mediated electrochemical removal method. According to claim 1,
In step b), the current is applied at a current density of 1 to 100 mA/cm 2, the method of mediating electrochemical removal of SF ₆ . An electrolytic cell including a catholyte storage tank containing a catholyte containing a first electronic medium, an anolyte storage tank containing anolyte containing a second electronic medium, a diaphragm cell, and a power supply;
A first wet scrubber provided above the catholyte reservoir and a second wet scrubber provided above the anolyte reservoir;
An SF ₆ feeder for supplying SF ₆ to the lower end of the first wet scrubber through the upper end of the catholyte reservoir; And
It includes a gas transfer pipe connecting the upper end of the first wet scrubber and the upper end of the anolyte storage tank or the lower end of the second wet scrubber,
The gas transfer tube is to transfer the reaction product generated by the decomposition of SF ₆ in the first wet scrubber to the second wet scrubber to be removed, mediated electrochemical removal system of SF ₆ . The method of claim 9,
The first electron mediator is [M _a ^(x-1)+ (HA) _y ] ^(z+1)- (where M _a is a transition metal, HA is a halogen or similar halogen, x, y and z Is a natural number from 2 to 10, which satisfies yx=z.), the intermediate electrochemical removal system of SF ₆ . The method of claim 10,
The first electronic medium is [Ni ¹⁺ (CN) ₄ ] ^3- phosphorus, SF ₆ mediated electrochemical removal system. The method of claim 9,
The second electron mediator is a salt of M _b ^{(n+1)+ (where} M _b is a transition metal, and n is a natural number selected from 0 to 5), mediated electrochemical removal system of SF ₆ . The method of claim 12,
The second electronic medium is AgSO ₄ or Ag(NO ₃ ) ₂ , SF ₆ mediated electrochemical removal system.

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