KR20120037632A - The electrochemical continuous-flow wastewater treatment system by the electron emission of graphene electrode under water, and its apparatus - Google Patents

Abstract

PURPOSE: An electrochemical continuous flow type wastewater treating method and an apparatus for the same is provided to convert nitrogen oxide contained in wastewater into nitrogen gas based on emitted electrons and to discharge the nitrogen gas. CONSTITUTION: A reacting bath is formed by connecting an acidification reactor(12) and a reduction reactor(13). Wastewater to be denitrificated is introduced into the reacting bath. The cathode of the reduction reactor is coated with graphene. Water is electrolyzed in the acidification reactor and generates oxygen and satisfies biochemical and chemical oxygen demands in the reacting bath. The oxygen is reacted with nitrogen compound contained in the wastewater and generates nitrate ions. High electric potential difference negative current is supplied to the graphene coated cathode of the reduction reactor. Electrons are emitted from the surface of the graphene. The emitted electrodes are reacted with nitrogen positive electric charges, and nitrogen oxide is converted into nitrogen gas.

Description

The electrochemical continuous-flow wastewater treatment system by the electron emission of graphene electrode under water, and its apparatus}

The present invention relates to an electrochemical wastewater denitrification method using a direct reduction process by electrons emitted from a graphene cathode of a cathode, and a continuous flow wastewater treatment process including the apparatus.

Denitrification of wastewater is a reaction that is carried out only by the former, and can be classified into two types according to the prior art.

One is a microbial process using electrons emitted from a microorganism by a bioelectrochemical reaction, and the other is an indirect electrochemical process in which electrons are generated using an electrolytically eluted metal ion using an eluting electrode.

The microbial process employs a natural cycle of nitrogen, where anaerobic microbes ingest carbon as a food source, and are cross-linked by pi electrons or peptide bonds that form double bonds in the microbial cytoplasm. Protein is the process of applying the semiconductor characteristics of electron tunneling, the carbon fed by metabolism is ingested at the inlet, and the electrons of the carbon are discharged from the excretory through the electron electron tunneling of the cytoplasm to act as an electron donor It is a process using a bioelectrochemical energy conversion process of microorganisms.

However, microorganisms are difficult to control the temperature because the temperature is appropriate activity at 20 ~ 35 ℃ Celsius, there is a case of installing a constant temperature denitrification tank to maintain this temperature, which is difficult to manage and cost a lot.

And the range suitable for the activity of the microorganism is pH 6 ~ 8, because the drug must be added to adjust this, there is a problem that the addition of operating costs and fluctuations in the material balance due to the input drug may occur.

In addition, in microbial processes, carbon is a source of energy for microorganisms, and nitrogen is an important nutrient as a protein-forming factor, so there is a restriction to adjust the ratio of carbon to nitrogen (C / N ratio) contained in waste water.

In the denitrification process, NO ₃ ⁻ has an electron affinity, so it has a specific adsorption characteristic on the negative electrode having a potential difference. Since the specific adsorption process of NO ₃ ^- ions caused by the potential difference does not occur, a process of stirring activated sludge in a reaction tank is necessary to increase the probability of contact with microorganisms.

However, to carry out the agitation process requires a large plant scale, takes a long reaction time, and has limitations in efficiency.

Therefore, researches using microbial electrochemical processes have been conducted as a way to compensate for this (Korean Patent Publication Nos. 10-0609087, 10-0332496, and 10-0848331, US Pat. No. 7,572,369). number).

However, the microbial electrochemical process has a drawback of low current efficiency due to the use of activated sludge as an insulator between the electrodes, and the problem of contamination of the electrode by the generated sludge and the external charge generated from the electrode are the electron transfer system in the microorganism. The problem is raised that it may be a deterrent to disturbance.

Indirect electrochemical process uses eluted electrodes such as zinc, iron, aluminum, copper, etc. to generate electrons by reacting with OH ^- ions generated by electrolysis of water by electrolytically eluted metal ions as shown in Scheme 1 below. It is a process to do it.

However, since the indirect reduction process using a metal ion as a medium requires a large amount of metal ions in the high concentration denitrification process, it is difficult to predict the consumption life of the electrode due to electrolysis and may cause additional secondary contamination due to elution of the metal. There is a concern that it may be (Korean Patent Nos. 10-0779989 and 10-0891004).

Scheme 1

Therefore, there is a need for the development of a continuous flow wastewater treatment method including a wastewater denitrification method which can improve the above-mentioned problems of the denitrification reaction and can quickly treat a high concentration of nitrogen compounds in the wastewater with low energy.

The present invention is to solve the above problems, the biochemical oxygen demand, chemical oxygen demand, suspended solids (SS) contained in the waste water, sterilization treatment and phosphorus (P) and nitrogen in the water of the negative electrode effectively treating the compound An object of the present invention is to provide a method and apparatus for treating electrochemical continuous flow wastewater by electron emission.

In order to achieve the above object, the present invention provides a wastewater requiring denitrification into a reaction tank connected to an oxidation reactor and a reduction reactor, wherein the reduction reactor has a first step of having a negative electrode coated with graphene; A second step of producing NO ₃ ⁻ ions by electrolyzing water in the oxidation tank to generate oxygen to meet biochemical and chemical oxygen demand in the reactor, and reacting the oxygen with nitrogen compounds contained in the waste water; A third step of supplying a high potential negative current of an electron emission device having a potential difference of 1 to 5 kV to the graphene-coated cathode of the reduction reactor to emit electrons from the graphene surface of the negatively polarized cathode Wow; The discharged electrons are reacted with the N ⁺⁵ positive charge of the NO ₃ ⁻ ions of the nitrogen oxides in the wastewater to convert the nitrogen oxides into nitrogen gas and be discharged; An electrochemical continuous flow type wastewater treatment method by discharge of electrons in water of a graphene cathode, which is made, is a technical gist.

Here, the negative electrode coated with the graphene of the reduction reaction tank of the first step (hereinafter referred to as 'graphene negative electrode') is a first negative electrode manufacturing process of blasting the insoluble metal plate to the surface roughness 50 ~ 75㎛; A second cathode manufacturing process of coating a mixture of PDMS (polydimethylsiloxane) and graphene on the blasted insoluble metal plate; the coated film is 200 to 250 ° C. in an oxygen-free nitrogen gas atmosphere for 6 to 8 hours. It is preferable to be a method for treating electrochemical continuous flow type wastewater by release of underwater electrons of the graphene negative electrode, characterized in that the third negative electrode manufacturing step of heat treatment during.

In addition, the third negative electrode manufacturing process includes a fourth negative electrode manufacturing step of activating the graphene by wet etching the heat-treated negative electrode with 6M nitric acid solution, electrochemical continuous flow by the electron emission of water in the graphene negative electrode, characterized in that It is preferable to become a food wastewater treatment method.

In addition, the coated coating film has a thickness of 100 to 200 μm and an average coating film thickness of about 150 μm.

In addition, the insoluble metal is preferably an electrochemical continuous flow wastewater treatment method by the electron emission of the water of the graphene cathode, characterized in that the titanium.

The present invention also outputs a flat wave current by converting three-phase alternating current into direct current in a reaction tank connected to an oxidation reaction tank and a reduction reaction tank in which the electrochemical continuous flow wastewater treatment method by the electron discharge of the graphene cathode is performed. A DC rectifier; A gate turn-off (GTO) thyristor for converting the flat wave current into a pulse current; An electron emission device connected to the cathode of the GTO thyristor to output a high potential difference current having a potential difference of 1 to 5 kV using the pulse current as an energy source; A reduction reactor connected to the electron emission device output unit to emit an electron from the negative electrode of the negatively polarized graphene; An oxidation tank connected with a cathode of the GTO thyristor to form NO ₃ ⁻ ions in nitrogen oxides in the wastewater; Another technical subject is an electrochemical continuous flow type wastewater treatment apparatus by discharge of underwater electrons of a graphene cathode, which is configured to include.

Here, it is preferable that the oxidation reaction vessel and the reduction reaction tank are electrochemical continuous flow type wastewater treatment apparatus by the release of underwater electrons of the graphene cathode, characterized in that a separator is provided between the anode and the cathode.

In addition, it is preferable that the anode of the oxidation reaction tank and the cathode of the reduction reaction tank are electrochemical continuous flow type wastewater treatment apparatuses by underwater electron emission of the graphene anode characterized in that a hole having a diameter of 10 to 15 mm is punched out.

In addition, it is preferable that the anode of the oxidation reactor and the cathode of the reduction reactor are electrochemical continuous flow type wastewater treatment devices by underwater electron emission of the graphene cathode, which is designed to have a baffled channel structure.

Electrochemical continuous flow wastewater treatment method by the discharge of electrons in the water of the graphene cathode to effectively treat the biochemical oxygen demand, chemical oxygen demand, suspended solids, sterilization and phosphorus and nitrogen compounds contained in the waste water by the present invention and There is an advantage that the device is provided.

That is, the present invention is to improve the problems of the existing denitrification reaction and to treat the pollutants contained in the wastewater in order to effectively treat the biochemical oxygen demand, chemical oxygen demand, suspended solids, sterilization and phosphorus and nitrogen compounds contained in the wastewater As a method that can be processed quickly with low energy, a pulsed direct current is supplied to the anode of the oxidation reactor, and a high potential difference current of the electron emission device is supplied to the cathode of the reduction reactor using graphene to provide Gauss' law. As a result, electrons are emitted from the inner surface (hereinafter referred to as 'graphene surface') at the interface by 0.77Å, the constituent carbon atom radius of graphene. Electrochemical continuous flow due to the emission of electrons in the water from the graphene cathode There is an advantage that is provided to cool the waste water treatment method and apparatus.

1 is a block diagram showing a structure when the cathode using carbon nanomaterial graphene is in contact with the wastewater of the electrolyte
2 is a conceptual diagram schematically illustrating a denitrification mechanism by energy band and electron emission during negative potential polarization of the graphene cathode of the present invention ( by the electric double layer model by Bockris - Devanathan - Muller ).
Figure 3 is a connection diagram of the oxidation reaction tank and the reduction reaction tank included in the reaction tank of the present invention
4 is a block diagram showing a device of the present invention;
5 is a cross-sectional structure diagram of a reduction reaction tank (denitration reaction tank) of the present invention.
(The oxidation reactor is configured such that the positive electrode and the negative electrode are switched with respect to the reduction reaction tank.)
6 is an electron scanning micrograph of a graphene-coated cathode surface of the present invention

Hereinafter, the present invention will be described with reference to the drawings. In the following description of the present invention, a detailed description of related arts or configurations will be omitted when it is determined that the gist of the present invention may be unnecessarily obscured will be.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to be exemplary, self-explanatory, allowing for equivalent explanations of the present invention.

The present invention is to provide an electrochemical continuous flow wastewater treatment method and apparatus including a direct reduction process by electrons emitted from the graphene surface of the cathode, the configuration of the present invention is largely, the oxidation reaction tank 12 and It comprises a reduction reactor 13, a direct current rectifier 9, a gate turn-off (GTO) thyristor 10, and an electron emitting device 11.

The reaction tank of the present invention is an electrochemical reaction tank in which a continuous flow is generated by connecting an oxidation reactor 12 and a reduction reactor 13, and the reactor receives wastewater requiring denitrification, and the reduction reactor 13 is The negative electrode has the characteristic of being coated with graphene.

The DC rectifier 9 of the present invention converts three-phase AC power into DC to output a flat wave current, and the flat wave current is converted into a pulse current by a GTO thyristor 10 connected to the DC rectifier 9. do.

The cathode of the oxidation reactor 12 and the cathode of the reduction reactor 13 are connected to the cathode of the GTO thyristor 10, and the oxidation reactor 12 and the reduction reactor 13 form only different polarities. Has the same characteristics.

Therefore, the anode of the oxidation reactor 12 and the cathode of the reduction reactor 13 have the same form, and the anode of the oxidation reactor 12 is effectively used to achieve the continuous flow type wastewater treatment apparatus pursued by the present invention in the reactor. And the cathode of the reduction reactor 13 is designed to have a baffled channel structure as shown in FIGS. 4 and 5, and the corresponding electrodes of the barrier plate flow path are respectively the cathode and the reduction reactor of the oxidation reactor 12. It becomes the anode of (13).

The anode of the oxidation reactor 12 and the cathode of the reduction reactor 13 are also punched out with holes of 10 to 15 mm in diameter to adjust the resistance and reactivity to the continuous flow of fluid in the reactor.

The electron emission device 11 of the present invention is a device for outputting a high potential negative current having a potential difference of 1 to 5 kV using the pulse current as an energy source, as shown in FIGS. 4 and 5. It is connected to the graphene cathode 15 of (13).

That is, the reduction reactor 13 has a cathode connected to the output of the electron emitting device 11 to emit electrons from the negative (-) potential polarized graphene surface.

In the oxidation reactor 12 of the present invention, the anode is connected to the cathode of the GTO thyristor 10 to form NO ₃ ⁻ ions in nitrogen oxide in the wastewater.

According to the present invention configured as described above, the oxidation reactor 12 is supplied with a pulsed DC current of 10 to 15 V having a period of 2 to 3 ms to the anode, and the reduction reactor 13 has a period of 2 to 3 ms. By supplying a high-potential negative current of the electron-emitting device 11 having a potential difference of ˜5 kV to the cathode to emit electrons from the graphene surface of the cathode, the nitrogen oxide in the wastewater is converted into nitrogen gas by the emitted electrons. An electrochemical wastewater treatment is carried out that includes a direct reduction process for releasing.

Hereinafter, the implementation of the apparatus will be described together with the electrochemical continuous flow type wastewater treatment method by the electron emission of water in the graphene cathode of the present invention.

In the method of the present invention, the wastewater requiring denitrification is introduced into a reaction tank in which an oxidation reaction tank 12 and a reduction reaction tank 13 are connected, and the reduction reaction tank 13 has a first step in which a cathode is coated with graphene. ; A second step of generating NO ₃ ⁻ ions by electrolyzing water in the oxidation reactor 12 to generate oxygen to meet biochemical and chemical oxygen demand in the reactor, and reacting the nitrogen with nitrogen compounds contained in the waste water Wow; By supplying a high potential difference negative current of the electron-emitting device 11 having a potential difference of 1 to 5 kV to the graphene-coated cathode of the reduction reactor 13, electrons are formed on the graphene surface of the negative-polarized cathode A third step of discharging; The discharged electrons are reacted with the N ⁺⁵ positive charge of the NO ₃ ⁻ ions of the nitrogen oxides in the wastewater to convert the nitrogen oxides into nitrogen gas and be discharged; Is done.

The first step of the present invention is a step of introducing wastewater requiring denitrification into a reaction tank in which an oxidation reactor 12 and a reduction reactor 13 are connected, which corresponds to a preparation step for implementation.

In the second step of the present invention, the oxygen is electrolyzed in the oxidation reactor 12 to generate oxygen to meet the biochemical and chemical oxygen demand in the reactor, and the oxygen reacts with the nitrogen compound contained in the waste water to reduce NO ₃ ^−. It is a step of producing ions.

As described above, the electrochemical reaction tank of the present invention is divided into an oxidation reaction vessel 12 and a reduction reaction vessel 13 as shown in FIG. 3, and the reaction in the oxidation reaction vessel 12 is performed as follows.

In the oxidation reaction tank 12, oxygen is generated as shown in Scheme 2 as water is electrolyzed.

Scheme 2

Oxygen generated at this time meets the biochemical and chemical oxygen demand,

 The chemical oxygen demand is treated as in Scheme 3.

Scheme 3

Nitrification of ammonia nitrogen is carried out as in Scheme 4.

Scheme 4

The nitrification of cyan ions is carried out via Schemes 5, 6 and 7.

Scheme 5

Scheme 6

Scheme 7

The suspended solids are filtered in a filtration tank through the flotation and flocculation process by oxygen bubbles generated in the oxidation reaction tank, and the phosphorus compounds generated in the oxidation reaction tank 12 are iron oxide / carbon nanotubes / aluminum / calcium oxide ( It is treated by filtration adsorption with a composite catalyst composed of Fe ₃ O ₄ / CNT / Al / CaOx).

The third step of the present invention is to supply a high-potential difference negative current of the electron-emitting device 11 having a potential difference of 1 ~ 5kV to the graphene-coated cathode of the reduction reactor 13 to negative (-) potential polarized The electron is emitted from the graphene surface of the step.

In the present invention, the cathode of the reduction reactor 13 is prepared by coating graphene on an insoluble metal plate as described above.

The graphene anode of the reduction reactor 13 is a first cathode manufacturing process of blasting the insoluble metal plate to the surface roughness 50 ~ 75㎛, the second negative electrode to coat the mixture of PDMS and graphene on the blasted insoluble metal plate In the manufacturing process, the coating film is subjected to a third negative electrode manufacturing process of heat-treating the coating film in an electric furnace in an oxygen-free nitrogen gas atmosphere for 6 ~ 8 hours at 200 ~ 250 ℃, specifically, insoluble metal plate surface roughness 50 ~ After blasting to 75㎛, the blasted insoluble metal plate is mixed with PDMS having a [-Si-O-Si-] n basic structure and graphene and coated with an injector.

At this time, the coating film thickness is adjusted to 100 ~ 200㎛ to adjust the average coating film thickness to about 150㎛.

Next, the coated coating film is heat-treated in an electric furnace in an oxygen-free nitrogen gas atmosphere for 200 to 250 ° C. for 6 to 8 hours to fabricate a cathode, which is wet etched with 6M nitric acid solution to impart hydrophilicity to graphene. And improve the electron emission function.

The insoluble metal is preferably titanium, but is not limited thereto.

The graphene is a pi electron conductor having a sp ² hybrid structure, and has a thickness of 3 to 30 nm and a current density of about 10 ⁸ A / cm 2, which is more than 100 times greater than copper, and its electron mobility is 15,000 cm 2? V ^-1. ? s ⁻¹ , the electrical resistance is 10 ⁻⁶ Ω · cm, and the energy bandgap is about 0.25 eV, indicating very good electrical properties.

The present invention exhibits excellent electrical properties and a low energy bandgap of 0.25 eV by using graphene having the above characteristics, so that the electron emission is very easily generated by less electrical energy.

Graphene used in the cathode of the reduction reactor 13 is a carbon nanomaterial, and has a structure as shown in FIG. 1 when contacted with wastewater, which is an electrolyte.

That is, the insoluble metal 1 and the graphene 2 form a Schottky contact, and the electrons of the power supply injected into the metal electrode have a quantum mechanical tunneling effect through the Schottky barrier, which is a space charge layer. tunneling effect) is injected into the graphene, and the conduction band electrons of the graphene move to the graphene surface and become electron-excess at the surface.

Hereinafter, the denitration mechanism by the energy band gap and the electron emission during the negative potential polarization of the negative electrode of the present invention will be described in detail with reference to FIG. 2.

Graphene is a carbon nanomaterial consisting of carbon with six electrons. When negative polarization is performed, conduction band electrons move to the graphene surface by the pie electron transfer structure, resulting in excess electrons on the surface. At the interface with, an electric double layer called a Helmholtz plane is formed on the electrolyte wastewater 3 side, which is symmetric to the graphene surface.

When joining an insoluble metal (eg titanium) and graphene, the work function of the space charge region as an electrical double layer is about 4.58 eV [titanium work function (4.33 eV) + graphene's energy bandgap (about 0.25 eV)], above about 7.34 ^-19 joules of electrical energy, the electrons of the power supply quantum mechanically tunnel through the energy barrier.

At this time, the width of the space charge layer is a Gaussian surface, which is 1.45 kV (titanium atomic radius (0.68 kPa) + graphene atomic radius (0.77 kPa), which is the sum of the respective atomic radii.

The current density by the applied electric field is shown in Equation 1 below, and corresponds to Fowler-Nordheim equation (hereinafter referred to as 'FN equation') [Niels de Jonge, Jean-Mark Bonard, "Carbon nanotube electron sources and application ", Phil. Trans. Soc. Lond. A, 2004, 2239-2266; Jean-Mark bonard et al., "Field emission from single-wall carbon nanotube films", Applied Physics Letters, 1998, vol. 73, No. 7, 918-920].

[Equation 1]

J: current density, E : electric field, Φ / e: work function of space charge layer

The electrons of the power supply device passing through the Schottky barrier, which is a space charge layer, by the tunneling effect, move the conduction band electrons of graphene, which are pie electron conductors, to the surface, causing the surface to be in an excess state of electrons. The energy bandgap of one graphene may be represented as bent toward the electrolyte interface. That is, on the basis of the Fermi level 5, the electrons of the conduction band 4 of graphene move to the graphene surface by the potential potential of the electrons supplied from the power supply device, and the electrons become excessive.

Meanwhile, as illustrated in FIGS. 4 and 5, an output of the electron emission device 11 is connected to the graphene cathode 15, and the electron emission device 11 has a high resistance having a resistance of 1 to 10 kΩ. Since the potential difference reaches about 1 to 5 kV, a negative potential high field is formed when the average film thickness of graphene is about 150 μm, and the excess electrons accumulated on the surface of the graphene cathode are formed. Is discharged into the waste water.

The electric field E, which is a driving force for moving the conduction band electrons in graphene when the potential is −1 kV, is calculated by the following equation.

[Equation 2]

≒

6.7 -6.7 × 10 ⁴ V cm ^-1

 V: dislocation, d: film thickness of graphene.

The potential of the electrode using graphene, a carbon nanomaterial, is equilibrated across the inside of the metal electrode and the graphene surface, regardless of what is contacted at the interface, but the height of the potential barrier on the graphene surface, That is, only the energy band gap of graphene is related.

Therefore, when pulsed electrical energy having a period of 2 to 3ms is instantaneously applied, an electric field E as shown in Equation 2 is formed on the graphene having a low energy bandgap of about 0.25 eV so that the conduction band electrons of the graphene are brought to the surface. The electrons on the surface are released to the electrolyte wastewater by the electrical energy of 0.4x10 ^-19 joule or more.

The maximum current density at this time is about 2.76x10 ⁴ A / cm 2 by Equation 1. Since the graphene has an electrical property that can sufficiently accommodate the maximum current density according to Equation 1, graphene can accommodate a large current of the electron emitting device and is effective for high concentration wastewater treatment.

Specifically, portion (-) electric potential when the graphene of the polarized cathode in contact with the electrolyte in the interface between waste NO ₃ ^- occurs specific adsorption of ions, NO ₃ ^- N ⁺⁵ positive charge of the ions, the electrons emitted from the surface And electron exchange occurs [NV Korovin et al., "Adatoms influence on overvoltage of Hydrogen", J. Res. Inst. Catalysis, Hokkaido Univ., 1981, Vol. 29, No. 1, 17-24; G. Rikken et al., “Schottky effect at a metal-polymer interface”, Appl. Phys. Lett. 1994, Vol. 65.2, 219-221.

In the fourth step of the present invention, the emitted electrons are reacted with the N ⁺⁵ positive charge of the NO ₃ ⁻ ions of the nitrogen oxides in the wastewater, whereby the nitrogen oxides are converted into nitrogen gas and released.

NO ₃ ^- electron affinity of the ion corresponds to a very high ion as 3.0eV, NO ₃ ^- N ⁺⁵ striking a positive charge of the ions inside the Helmholtz plane (6) located on (hereinafter referred to as 'IHP' also Inner Helmholtz Plane) time to reach equilibrium boundaries by receiving electrons emitted from the surface up to 2NO _{3 ^{- + 4e - ---> 2NO 2}} - + 2e - ---> 2NO + 2e - ---> N 2 O + 2e - - -> Proceed to N ₂ . That is, graphene acts as an electron donor and NO ₃ ⁻ ions act as an electron acceptor.

If this is represented by chemical reaction formula, it becomes like Reaction Scheme 8 below.

Scheme 8

At this time, the center of NO ₃ ⁻ , which has an ion radius of 2.6 특이 adsorbed specifically at the interface of the cathode, is located on the IHP of the electric double layer, which is about 3 으로부터 away from the interface, and the center of the H ⁺ ions hydrated by hydronium ions is It is located on the outer Helmholtz plane 7 (hereafter referred to as 'OHP': Outer Helmholtz Plane).

As described above, electrons on the negatively polarized graphene surface are quantum-mechanically electron-emitted by the electrical attraction due to the relative positive potential of the anode with a relatively high energy level. Is called Schottky effect electron field emission by high electric field [Xiomara Calderon-Colon et al., "A Carbon nanotube field emission cathode with high current density and long-term stability", 2009 Nanotechnology 20.325707 (PP5 ), Zhanling Lu et al., "The field Emission Properties of Graphene Aggregates Films Deposited on Fe-Cr-Ni alloy Substrates", Journal of Nanomaterials, doi: 10.1155 / 2010/148596, Jianhui Dong et al., "Field Emission from Few-Layer Graphene Nanosheets Produced by Liquid Phase Exfoliation of Graphite ", Journal of Nanoscience and Nanotechnology, Vol. 10, 5051-5055, 2010].

The dipole monolayer of water between the interface and the IHP is called the first aqueous layer, and its dielectric constant is 6, and the electrons emitted from the surface are hopped at an average free stroke of 3 electrons with little interference. It is located on the IHP of the electric double layer about 3 Å away from the interface and causes electron exchange reaction with specifically adsorbed NO ₃ ^- ions.

Looking at this from the viewpoint of ion conductivity takes place in electron affinity with an electrolyte, an electron affinity of H ⁺ ions in the electric double layer of the OHP is a 0.76eV NO ₃ ^- the reaction of the former and because less than (3.0eV) is NO ₃ ^- At first, electron exchange occurs, and H ⁺ acts as a positive charge carrier and graphene acts as a condenser to form a displacement current. Therefore, H ⁺ gives a positive charge to graphene and loses its charge. Is released as H ₂ .

It is concluded that this is not used for direct denitrification of wastewater by electron emission as a rectifier with a flat wave because it only transfers charges moving from positive to negative in the electrolyte.

Summarizing the present invention, ammonia nitrogen and cyan ions in the oxidation reaction tank 12 are nitrified and introduced into the reduction reaction tank 13, and the electrons emitted from the graphene surface of the negative electrode polarized with negative (-) potential As a result, direct denitrification is carried out as in Scheme 8.

On the other hand, electrons emitted from the surface of the graphene of the cathode penetrate the cell protoplasts through the spore membrane of bacteria present in the water and disrupt the metabolism of bacteria to sterilize pathogenic microorganisms in the water.

The electrochemical treatment method of the present invention described above must have energy, and electricity is used as the energy source. The apparatus of the present invention will be described in detail again with reference to FIGS. 4 to 5.

As described above, the DC rectifier 9 converts three-phase AC power into DC to output a flat wave current, and the GTO (Gate turn-off) thyristor 10 converts the flat wave current into a pulse current. The energy supply source is constituted by an electron emission device 11 using the pulse current of the GTO thyristor 10 as an energy source, and the anode of the oxidation reactor 12 and the cathode of the reduction reactor 13 are connected.

The energy source uses a three-phase AC power (380V or 220V) as a basic energy source to convert to DC through the DC rectifier 9 to output a flat wave current of 10 ~ 15V.

However, since the flat wave current cannot contribute to electron emission, the flat wave current is applied to the gate turn-off (GTO) thyristor 10 by applying a signal input having a period of 2 to 3 ms, preferably having a 2.5 ms period. It is converted into a pulse current and supplied to the anode of the oxidation reactor.

At the same time, in order to facilitate electron emission on the graphene surface of the cathode, a negative current is supplied to the cathode of the reduction reactor with an electron emission device 11 having a potential difference of 1 to 5 kV.

In the reaction tank of the present invention, when electrolytic electrolyte wastewater is electrolyzed, oxygen is generated at the anode and hydrogen is generated at the cathode. A separation diaphragm 16 is installed between the anode and the cathode to suppress the recombination of the generated oxygen and hydrogen. do.

The anode of the oxidation reactor and the cathode of the reduction reactor, in which the main reaction occurs in the reactor, are punched out of holes having a diameter of 10 to 15 mm and designed in a baffled channel structure.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the examples.

Example  Of the present invention Graphene  Electrochemical Continuation with Cathode Flow  Wastewater Treatment Method

One. Graphene  Fabrication of Used Cathodes

Graphene was coated on an insoluble titanium plate to prepare a negative electrode. Specifically, after blasting the titanium plate so that the surface roughness 50 ~ 75㎛, PDMS and graphene was mixed with the blasted titanium plate and coated with an injector. At this time, the coating film thickness is adjusted to 100 ~ 200㎛ so that the average coating film thickness is about 150㎛. Then, the coated coating film was heat-treated at 200-250 ° C. for 6-8 hours in an oxygen-free nitrogen gas electric furnace, and wet etched the surface with 6M nitric acid solution and washed with fresh water to prepare an activated graphene coating film.

2. Fabrication of Anode

The anode was fabricated by heat treating a titanium plate at 450 ° C. for 6 hours in an electric furnace in an oxygen oxidation atmosphere to modify the surface with TiO ₂ .

3. Result of wastewater treatment

20 Lt of waste water is put into an oxidation tank (nitrification tank), and the supply power [current: 12 V / 30 A, current density: 22 mA /, 2.5 ms pulse wave] is adjusted to the anode by adjusting the flow of waste water at 1 Lt per minute by a metering pump. The cathode was grounded to perform an oxidation reaction. After the oxidation reaction, it is transferred to a reduction reactor, and the anode is grounded, and a reduction reaction is performed by applying supply power [current: -1 kV / -30 A, current density: 22 mA /, 2.5 ms pulse wave] by the electron emission device to the cathode. Was performed. The concentration of total nitrogen (T-N) in the wastewater was measured by ultraviolet absorbance photometry. Ultraviolet absorption spectroscopy is a method of quantifying total nitrogen by oxidizing nitrogen compounds in a sample with nitrogen nitrate at 120 ° C. in the presence of alkaline potassium persulfate and measuring nitrate nitrogen with ultraviolet light at 220 nm.

The results are shown in Table 1.

Item Wastewater Initial Concentration Final concentration Removal concentration COD 4921.8 ppm 2232.5 ppm 2689.3ppm T-N 2274.21ppm 1671.14ppm 603.07ppm

As shown in Table 1, wastewater having initial COD and TN concentrations of 4921.8 ppm and 2274.21 ppm, respectively, was treated according to the conditions and methods described above, and 2689.3 ppm and 603.07 ppm, respectively, were obtained. Since the electrochemical treatment efficiency is proportional to the amount of charged charge (current x time), it was confirmed that the higher the current, the higher concentration of the pollutant can be treated.

The electrochemical continuous flow wastewater treatment method using a direct reduction process by electron emission from the graphene surface of the cathode according to the present invention can achieve uniformity and stability of wastewater treatment because it uses electricity as an energy source. It is possible to minimize sludge generation without being affected by temperature, pH and pH, and it is possible to rapidly process high concentration nitrogen compounds in wastewater with low energy by the reduction process, and biochemical oxygen demand, Chemical oxygen demand can be met, and suspended solids and phosphorus compounds can be treated simultaneously through physical filtration process, which is suitable for high concentration wastewater treatment.

Bromine with bromine atoms with chloroform (CHCl ₃ ) with a chlorine atom with an electron affinity of 3.79 eV and bromine atoms with an electron affinity of 3.56 eV with specific adsorption at the cathode interface by the advanced wastewater treatment by electron emission as described above. Decomposition of bromoform (CHBr ₃ ) is possible, and phenol (Phenol: C ₆ H ₅ OH) with benzene can be decomposed.

In addition, electrons emitted from the surface of graphene penetrate the spore membrane of bacterial microorganisms and enter the cell protoplasts to inhibit the electron transport system of the microorganisms, and damage the cell membranes, which also involves the electrical sterilization of bacterial microorganisms.

As it is possible to efficiently treat high concentration wastewater as described above, various industrial wastewater, livestock wastewater and sewage treatment plant wastewater discharged from chemical industry, oil refining industry, leather industry, food industry, pulp and paper industry, steel industry, dyeing industry, electronic industry, etc. Applicable.

It will be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Therefore, the present invention is not limited to the above-described embodiments, and various changes can be made by any person having ordinary skill in the art without departing from the gist of the present invention as claimed in the following claims. It will be said that the technical spirit of this invention is to the extent possible.

1. insoluble metal 2. graphene
3. Electrolyte Wastewater 4. Conduction Band
5. Fermi level 6. Inside Helmholtz floor
7. Outer Helmholtz layer 8. Hopping conduction
9. DC rectifier 10. GTO thyristor
11. Electron Emission Device 12. Oxidation Reactor (Nitrification Reactor)
13. Reduction reaction tank (denitrification reaction tank) 14. Anode of reduction reaction tank
15. Cathode or graphene cathode of reduction reactor
16. Separation Diaphragm

Claims (9)

A first step of introducing wastewater requiring denitrification into a reaction tank to which an oxidation reaction tank and a reduction reaction tank are connected, the reduction reaction tank having a negative electrode coated with graphene (hereinafter referred to as a 'graphene negative electrode');
A second step of producing NO ₃ ⁻ ions by electrolyzing water in the oxidation tank to generate oxygen to meet biochemical and chemical oxygen demand in the reactor, and reacting the oxygen with nitrogen compounds contained in the waste water;
Supplying a high potential negative current of an electron emission device having a potential difference of 1 to 5 kV to the graphene cathode of the reduction reactor so that electrons are emitted from the graphene surface of the negatively polarized cathode;
The discharged electrons are reacted with the N ⁺⁵ positive charge of the NO ₃ ⁻ ions of the nitrogen oxides in the wastewater to convert the nitrogen oxides into nitrogen gas and be discharged;
Electrochemical continuous flow type wastewater treatment method by underwater electron emission of the graphene cathode, characterized in that made. According to claim 1, wherein the graphene cathode of the reduction reaction tank of the first step
A first cathode manufacturing step of blasting the insoluble metal plate to have a surface roughness of 50 to 75 μm;
A second cathode manufacturing process of coating a mixture of PDMS and graphene on the blasted insoluble metal plate;
A third cathode manufacturing process of heat-treating the coated coating film in an electric furnace in an oxygen-free nitrogen gas atmosphere for 200 to 250 ° C. for 6 to 8 hours;
Electrochemical continuous flow type wastewater treatment method by the release of underwater electrons of the graphene cathode, characterized in that made by. The method of claim 2, wherein the third cathode manufacturing process
And a fourth cathode manufacturing step of wet etching the heat-treated cathode with a 6M nitric acid solution to activate graphene. 3. The method of claim 2, wherein the coated coating film has a thickness of about 100 μm to about 200 μm and an average thickness of about 150 μm. 3. The method of claim 2, wherein the insoluble metal is titanium. 6. To the reaction tank is connected to the oxidation reaction tank and the reduction reaction tank is subjected to the electrochemical continuous flow wastewater treatment method by the electron electron emission of the graphene cathode of claim 1,
A DC rectifier for converting three-phase AC power into direct current and outputting a flat wave current;
A gate turn-off (GTO) thyristor for converting the flat wave current into a pulse current;
An electron emission device connected to the cathode of the GTO thyristor to output a high potential difference current having a potential difference of 1 to 5 kV using the pulse current as an energy source;
A reduction reactor connected to the electron-emitting device output at a cathode to emit electrons at the negative potential polarized graphene surface;
An oxidation tank connected with a cathode of the GTO thyristor to form NO ₃ ⁻ ions in nitrogen oxides in the wastewater;
Electrochemical continuous flow type wastewater treatment apparatus by the electron electron emission of the graphene cathode, characterized in that comprising a. The method of claim 6, wherein the oxidation tank and the reduction tank
An electrochemical continuous flow type wastewater treatment device for discharging underwater electrons of a graphene cathode, characterized by providing a separation membrane between the anode and the cathode. The method of claim 7, wherein the anode of the oxidation reaction tank and the cathode of the reduction reaction tank
An electrochemical continuous flow type wastewater treatment apparatus by emitting electrons in water of a graphene cathode characterized in that a hole having a diameter of 10 to 15 mm is punched out. The electrochemical continuous flow wastewater treatment apparatus of claim 8, wherein the anode of the oxidation reactor and the cathode of the reduction reactor are designed in a baffled channel structure.

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