KR102476213B1 - Method for selectively removing perfluorinated compound - Google Patents

Abstract

A method for selectively removing perfluorinated compounds according to an embodiment of the present invention can include the steps of: oxidizing and decomposing perfluorinated compounds contained in raw water through adsorption and electro-oxidation in an adsorption electro-oxidation tank including a reaction unit including a plurality of electrodes and granular activated carbon filled between the electrodes; and maintaining a water level in the reaction unit at or above the reaction height of the electrodes by a head control pipe unit.

Description

Method for selective removal of perfluorinated compounds {METHOD FOR SELECTIVELY REMOVING PERFLUORINATED COMPOUND}

This patent document relates to a method for selectively removing perfluorinated compounds, and more particularly, to a method for selectively and efficiently removing trace amounts of perfluorinated compounds contained in wastewater by adsorption electro-oxidation using granular activated carbon.

Among persistent organic pollutants (POPs), perfluorinated compounds (PFCs) are compounds having a perfluorinated (-C _n F2 _n+1 ) tail in which hydrogen is replaced by fluorine in the hydrocarbon basic skeleton structure. can be collectively referred to as Perfluorinated compounds include a wide range of homologs that have 4 to 15 carbon atoms, and can exist in various structures by converting forms through decomposition and synthesis processes. Representative examples of perfluorinated compounds include PFCAs (Perfluorocarboxlic acid, C _n F _{2n + 1} COOH) and PFASs (Perfluoroalkylsulfonic acid, C _n F _{2n + 1} SO ₂ OH).

Table 1 summarizes the physicochemical characteristics of exemplary perfluorochemical classes.

compound chemical formula Molecular Weight
(g/mol) solubility in water
(mg/L) pKa
PFCAs PFHxA C ₆ H F ₁₁ O ₂ 314 - - PFOA C ₈ H F ₁₅ O ₂ 414 3400 2.5 PFNA C ₉ H F ₁₇ O ₂ 464 9500 2-3
PFASs PFBS C ₄ HF ₉ SO ₃ 300 very high -3.94 PFHxS C ₆ HF ₁₃ SO ₃ 400 - - PFOS C ₈ HF ₁₇ SO ₃ 500 570 -3.27

PFHxA: Perfluorohexanoic acid

PFOA: Perfluorooctanoic acid

PFNA: Perfluorononanoic acid

PFBS: Perfluorobutane sulfonic acid

PFHxS: Perfluorohexane sulfonic acid

PFOS: Perfluorooctane sulfonic acid

In general, perfluorinated compounds are non-decomposable substances that are not easily decomposed due to their high chemical and thermal stability, and can accumulate in the environment and body for a long period of time. In addition, perfluorinated compounds generally have high solubility in water and thus are highly likely to migrate due to water discharge. Since perfluorinated compounds are used as coating agents in general industries such as clothing, electronics, and paints, the amount of perfluorinated compounds is also increasing. Concomitant with this increase in use and emission, awareness of the hazards of perfluorinated compounds is increasing. Currently, it is listed as a drinking water monitoring item in major countries and is being managed. The European Chemicals Agency (ECHA) hazard classifications and concerns for PFOS and PFOA are shown in Table 2 below.

PFOS PFOA Hazard Classification Serious health hazard, environmental pollution Corrosive, serious health hazard concerns Carcinogenicity, reproductive toxicity Carcinogenicity, Reproductive Toxicity, Bioaccumulation and Persistence European classification label Carcinogenicity 2, Reproductive toxicity 1B, Long-term toxicity RE1, Acute toxicity 4, Chronic aquatic toxicity 2 Carcinogenic Toxicity 2, Reproductive Toxicity 1B, Organ Toxicity RE1, Acute Toxicity 4, Eye Damage 1

Perfluorinated compounds are mainly present in water rather than in the atmosphere and tend to persist in soils with high organic carbon content. Recently, the harmfulness of perfluorinated compounds to the environment and health has become an issue, and research on effective treatment technologies has been conducted. However, there is a limit to the application of biological treatment technology due to structurally stable characteristics.

Perfluorinated compound removal technologies disclosed in the literature include ozone treatment, activated carbon adsorption, reverse osmosis, ion exchange, nanofiltration, membrane treatment, and oxidation treatment, but the removal efficiency by these technologies is not high. In addition, even in the case of some technologies disclosed as having high removal efficiency, according to the results of the demonstration review, it was confirmed that there is a limit to continuous operation and that the removal efficiency disclosed in the literature is not actually achieved. This is because wastewater contains trace amounts of perfluorinated compounds at the ppt (part per trillion) level, and substances with high concentrations such as TOC (total organic carbon) and ionic substances are first removed, reducing the removal efficiency of perfluorinated compounds. to be. In addition, even if the perfluorinated compound is partially decomposed, there is a problem in that only the form of the perfluorinated compound is changed and still remains as a different type of perfluorinated compound.

In the removal of perfluorinated compounds, considering these aspects, since perfluorinated compounds have a characteristic of being contained in a small amount in complex contaminants, it is expected that it will be difficult to apply a general-purpose water treatment technology, and due to the material characteristics of perfluorinated compounds, Biological treatment is also expected to have application limitations. Also, in the case of reverse osmosis and ion exchange technologies, the problem of handling the concentrated material remains.

Accordingly, there is a need to develop a technology for selectively removing perfluorinated compounds capable of continuously operating while selectively and efficiently removing only trace amounts of perfluorinated compounds among various materials.

An object to be solved by embodiments of the present invention is to provide a method for selectively and efficiently removing perfluorinated compounds contained in a small amount of wastewater, and capable of continuously performing the process.

A method for selectively removing perfluorinated compounds according to an embodiment of the present invention for solving the above problems is, in an adsorption electro-oxidation tank including a reaction unit including a plurality of electrodes and granular activated carbon filled between the electrodes, in raw water Oxidizing and decomposing the perfluorinated compound through adsorption and electro-oxidation; and maintaining the water level in the reaction unit at or above the reaction height of the electrode by a head control pipe unit.

In addition, a method for selectively removing perfluorinated compounds according to another embodiment of the present invention for solving the above problems includes pre-treating raw water; oxidizing and decomposing perfluorinated compounds contained in raw water through adsorption and electro-oxidation in an adsorption electro-oxidation tank including a plurality of electrodes and a reaction unit including granular activated carbon filled between the electrodes; and maintaining the water level in the reaction unit at or above the reaction height of the electrode by a head control pipe unit.

According to the above-described embodiments of the present invention, a perfluorinated compound capable of increasing selectivity for a perfluorinated compound and carrying out a continuous process in consideration of the characteristics of a perfluorinated compound that continues to exist even after being decomposed and contained in a small amount, A method for selectively removing compounds can be provided.

Therefore, according to embodiments of the present invention, it is possible to prevent harmful effects on the human body and the environment by selectively and efficiently removing perfluorinated compounds present in small amounts in wastewater.

In addition, according to the embodiments of the present invention, there is no need to use separate chemicals and no waste is generated in the removal of perfluorinated compounds, which is environmentally friendly.

In addition, according to the embodiments of the present invention, the granular activated carbon used for adsorption and removal of perfluorocompounds is rapidly electrochemically regenerated to secure stable treatment efficiency for perfluorocompounds and reach the breakthrough point. It can be applied to actual industrial sites in a cost-effective way because the time required to do so can be extended.

1 is a diagram schematically illustrating a method for selectively removing perfluorinated compounds according to an embodiment of the present invention.
FIG. 2 is a diagram schematically illustrating an example of a device for selectively removing perfluorinated compounds used in a method for selectively removing perfluorinated compounds according to an embodiment of the present invention.
FIG. 3 is a detailed view of an adsorption electro-oxidation tank and head control pipe of the selective removal device for perfluorinated compounds of FIG. 2 .
FIG. 4 is a detailed view of a reaction unit of the adsorption electro-oxidation bath shown in FIG. 3 .
5 is a diagram schematically illustrating a method for selectively removing perfluorinated compounds according to another embodiment of the present invention.
6 is a diagram schematically illustrating an example of a device for selectively removing perfluorinated compounds used in a method for selectively removing perfluorinated compounds according to another embodiment of the present invention.
Figure 7a shows the concentration (ng / L) of PBFS in treated water according to BV (bed volume) in Examples and Comparative Examples, and Figure 7b shows the removal rate (%) of PBFS according to BV.
Figure 8a is a graph showing the change in pH after treatment by the device for selectively removing perfluorinated compounds according to an embodiment of the present invention.
8B is a graph showing a change in electrical conductivity after treatment by a device for selectively removing perfluorinated compounds according to an embodiment of the present invention.
8C is a graph showing a change in COD (Chemical Oxigen Demand) after treatment by the apparatus for selectively removing perfluorinated compounds according to an embodiment of the present invention.
FIG. 8D is a view showing a concentration change of total organic carbon (TOC) after treatment by the apparatus for selectively removing perfluorinated compounds according to an embodiment of the present invention.
8E is a graph showing the change in TN concentration after treatment by the apparatus for selectively removing perfluorinated compounds according to an embodiment of the present invention.
Figure 8f is a graph showing the change in concentration of NH ₃ -N after treatment by the device for selective removal of perfluorinated compounds according to an embodiment of the present invention.
8g is a graph showing a change in concentration of NO ₃ -N after treatment by the apparatus for selectively removing perfluorinated compounds according to an embodiment of the present invention.
FIG. 8H is a graph showing the concentration change of SO ₄ ^2- after treatment by the apparatus for selectively removing perfluorinated compounds according to an embodiment of the present invention.

Hereinafter, various embodiments are described in detail with reference to the accompanying drawings.

The drawings are not necessarily drawn to scale, and in some instances, the proportions of at least some of the structures shown in the drawings may be exaggerated in order to clearly show characteristics of the embodiments. In the following description, many specific details such as specific components are shown, which are provided to help a more general understanding of the present invention, and it is common knowledge in the art that the present invention can be practiced without these specific details. It will be self-evident to those who have. And, in describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

Embodiments of the present invention relate to methods for the selective removal of perfluorinated compounds from water systems such as wastewater. In the embodiments of the present invention, the basic mechanism of the selective removal of perfluorinated compounds is that oxidation and decomposition are simultaneously performed directly and indirectly through adsorption and electro-oxidation, and to maximize the selectivity and efficiency of perfluorinated compound removal. Additional processes may be added along with careful condition setting.

Adsorption refers to a phenomenon in which a substance present in a liquid or gas phase moves to the surface of an adsorbent and is concentrated. In embodiments of the present invention, the adsorbent used for adsorption electrooxidation may include granular activated carbon (GAC). Since the adsorption of perfluorinated compounds by granular activated carbon can be achieved by electrostatic attraction and hydrophobic interaction, conditions and additional processes that can increase the selectivity and efficiency of perfluorinated compound removal must be established in consideration of this.

Since the surface of the granular activated carbon is positively charged at a pH below the isoelectric point ( _pZC ), it is possible to selectively adsorb perfluorinated compounds exhibiting anionic properties by electrostatic attraction. Adsorbed perfluorinated compounds can be decomposed and removed by an oxidation process. In this case, when the pH of the solution increases, the surface of the granular activated carbon becomes negatively charged, and the adsorption capacity of the granular activated carbon for anionic substances may decrease.

On the other hand, since the surface of granular activated carbon does not have hydroxyl groups and exhibits hydrophobicity, non-polar molecules and weakly polar molecules can be adsorbed by hydrophobic interaction. In adsorption by hydrophobic interaction, contaminants with a high molecular weight or high concentration tend to be preferentially adsorbed, and thus selective adsorption of small amounts of perfluorinated compounds may be limited. In addition, in the case of adsorption by hydrophobic interaction, since PFSA is more hydrophobic than PFCA, and compounds with long C-F bonds are more hydrophobic than compounds with short C-F bonds, removal by adsorption can be smooth. However, since surface adsorption of perfluorinated compounds having a high carbon number is undesirable from the viewpoint of long-term continuous operation of the device, an oxidation process is applied together with adsorption to induce a low-molecular structure of the perfluorinated compound, which can be converted into molecules having a low carbon number. can Since perfluorinated compounds having a low carbon number can have hydrophilic and anionic properties, they can be selectively adsorbed on granular activated carbon by electrostatic attraction and can be decomposed and removed by application of an oxidation process.

Embodiments of the present invention are based on the basic mechanism as described above, and in this process, in consideration of the characteristics of perfluorinated compounds and granular activated carbon as an adsorbent, process steps and The configuration of the device used may vary. That is, the process steps may vary depending on the pH and SS (suspended solid) of the incoming raw water:

1) When the pH of raw water is less than the pH of granular activated carbon _PZC and SS is less than 500 mg/L

2) When the pH of the raw water exceeds the pH _PZC of the granular activated carbon and the SS exceeds 500 mg/L

In the case of 1), since the surface of the granular activated carbon as an adsorbent is dominated by positive charges, oxidation and decomposition of the perfluorinated compound can be simultaneously performed directly or indirectly through adsorption and electro-oxidation.

In the case of 2), since the SS content of the raw water is high, when it is put into the device where adsorption and electro-oxidation are performed without pretreatment, the SS in the raw water is attached between the granular activated carbon filled inside the device to increase the electrical resistance in the device, and the fluid Blockage of the device may occur, such as interfering with the movement of the device, making normal operation difficult. In order to solve this problem, a process for additional pretreatment may be added before adsorption and electrooxidation processes. In addition, since the pH of the raw water exceeds the pH _PZC of the granular activated carbon, a process for adjusting the pH can be added so that positive charges prevail on the surface of the granular activated carbon in order to selectively adsorb the perfluorinated compound by electrostatic attraction. .

A method for selectively removing a perfluorinated compound applied to each case of 1) and 2) will be described in detail below.

1 is a diagram schematically illustrating a method for selectively removing perfluorinated compounds according to an embodiment of the present invention.

The method for selectively removing perfluorinated compounds shown in FIG. 1 may be applied in the case of 1) above, that is, in the case where the pH of the raw water (W _in ) is less than the pH _PZC of the adsorbent and SS is less than 500 mg/L.

Referring to FIG. 1 , the method for selectively removing perfluorinated compounds according to an embodiment of the present invention may include adsorption electro-oxidation of perfluorinated compounds and regeneration of granular activated carbon (S11) and treated water collection (S12). have.

In the adsorption electro-oxidation of the perfluorinated compound and regeneration of the granular activated carbon (S11), the perfluorinated compound from the raw water (Win) is oxidized and decomposed directly or indirectly through adsorption and electro-oxidation, and at the same time the granular activated carbon can be regenerated. .

The adsorption electrooxidation of the perfluorinated compound and the regeneration of the granular activated carbon (S11) may be performed in an adsorption electrooxidation tank including a reaction unit including a plurality of electrodes and the granular activated carbon filled between the electrodes. The granular activated carbon is polarized by an electric field to form a microelectrode, so that perfluorinated compounds adsorbed on the surface of each granular activated carbon can be oxidized and decomposed. At this time, the adsorption electro-oxidation reaction may be accompanied by a water level control process by the head control pipe unit.

The adsorption electro-oxidation of the perfluorinated compound and the regeneration of the granular activated carbon (S11) include introducing raw water into the reaction unit through an inflow pipe disposed above the reaction unit; and discharging the treated water for which the reaction is completed in the reaction unit through an outflow pipe disposed below the reaction unit.

The step of maintaining the water level in the reaction part at or above the reaction height of the electrode by the head control pipe part may be performed by the head control pipe part including the first part and the second part. The first part is arranged in a vertical direction, the lower end is orthogonally connected to the outflow pipe, and may include a valve allowing air to flow from the upper end. The second part may have a bent shape, one end may be connected orthogonally to the first part at a predetermined height of the first part, and the other end may be disposed at the same level as the outflow pipe.

During the operation of the adsorption electro-oxidation tank, the water level in the reaction unit may be maintained by opening the valve in the first part and using air pressure.

The step of maintaining the water level in the reaction unit to be equal to or higher than the reaction height of the electrode by the head control pipe unit may include maintaining the head control pipe unit to be equal to or higher than the height of the adsorption electro-oxidation tank.

The step of maintaining the water level in the reaction part by the head control pipe part to be equal to or higher than the reaction height of the electrode may include maintaining the height of the second part of the head control pipe within a range that is equal to or greater than the height of the reaction part and equal to or less than the height of the inflow pipe. can

In this specification, the reaction height of the electrode may be used interchangeably with the reaction area of the electrode, and may represent a region in which perfluorinated compounds adsorbed on the granular activated carbon can be decomposed and removed by an oxidation reaction on the electrode.

The adsorption electro-oxidation of the perfluorinated compound and the regeneration of the granular activated carbon ( S11 ) may further include a step of supplying power by a power supply device.

In the method for selectively removing perfluorinated compounds according to an embodiment of the present invention, the adsorption electro-oxidation of perfluorinated compounds and the regeneration of granular activated carbon (S11) are performed using an operating voltage of 7-12V and a current of 1-2.5mA/cm 2 . It can be performed under operating conditions with density. Such operating conditions are set to exert optimum effects for the selective and efficient removal of perfluorinated compounds.

The method for selectively removing perfluorinated compounds according to an embodiment of the present invention can exhibit a removal rate of 99% or more for perfluorinated compounds when processing a flow rate of 2,000 times or more relative to the volume of the granular activated carbon.

In the treated water collection step ( S12 ), the treated water from which the perfluorinated compound is removed by adsorption electro-oxidation and the granular activated carbon regeneration step ( S11 ) may be collected.

In this embodiment, the raw water to be treated (W _in ) may include wastewater or any liquid medium containing perfluorinated compounds, preferably trace amounts of perfluorinated compounds, but is not limited thereto. Examples of the raw water (W _in ) may include semiconductor wastewater or various industrial wastewater (clothing, electronics, paint, etc.), purified water, or sewage.

Perfluorinated compounds included in raw water (W _in ) may be collectively referred to as compounds having perfluorinated (-C _n F2 _n+1 ) tails in which hydrogen is substituted with fluorine in a hydrocarbon basic skeleton structure. Examples are Perfluorohexanoic acid (PFHxA), Perfluorooctanoic acid (PFOA), Perfluorononanoic acid (PFNA), Perfluorobutane sulfonic acid , PFBS), perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS), or a combination thereof.

The concentration of the perfluorinated compound contained in the raw water (W _in ) is not particularly limited, but in general, the perfluorinated compound may be present in wastewater in a trace amount, for example, at a ppt level.

The method for selectively removing perfluorinated compounds according to the present embodiment may be performed by the apparatus 100 for selectively removing perfluorinated compounds shown in FIG. 2 . Accordingly, with reference to FIGS. 1 to 4 , a method for selectively removing a perfluorinated compound according to the present embodiment will be described.

2 is a diagram schematically showing a device for selectively removing perfluorinated compounds that can be used in the method for selectively removing perfluorinated compounds according to the present embodiment.

Referring to FIG. 2 , the apparatus 100 for selectively removing perfluorinated compounds may include an adsorption electro-oxidation tank 101, a power supply unit 102, a head control pipe unit 103, and a treatment water tank 104. Connecting pipes, valves, and/or pumps may be provided between the adsorption electro-oxidation tank 101, the power supply unit 102, the head control pipe unit 103, and the treatment water tank 104.

Raw water (W _in ) may be transferred from a raw water tank (not shown) to the adsorption electro-oxidation tank 101 by an inlet pump.

In the adsorption electro-oxidation tank 101, perfluorinated compounds included in the raw water (W _in ) may be directly or indirectly oxidized and decomposed through adsorption and electro-oxidation. The adsorption electro-oxidation tank 101 will be described in more detail with reference to FIGS. 3 and 4 .

FIG. 2 is a view for explaining the adsorption electro-oxidation tank 101 and the head control pipe part 103 included in the selective removal device 100 for perfluorinated compounds.

Referring to FIG. 2 , the adsorption electric oxidation bath 101 includes a chamber 10, an inflow pipe 20, a reaction unit 30, an outflow pipe 40, an electrode current collector 50, an overflow pipe ( 60), a drain pipe 70 and a strainer unit 80.

In one embodiment, raw water (W _in ) may be introduced into the adsorption electro-oxidation tank 101 by an inlet pump installed at the front end and treated by gravity filtration.

In another embodiment, treated water (W _treated ) may be discharged through an outflow pump installed at the rear end of the adsorption electro-oxidation tank 101 .

The chamber 10 may serve to accommodate and support other components of the adsorption electro-oxidation bath 101, and may include a reaction unit 30 therein.

The inflow pipe 20 may serve to introduce raw water W _in into the reaction unit 30 . In this embodiment, the inflow pipe 20 is formed above the reaction part 30, and the raw water (W _in ) is introduced into the reaction part 30 through a natural flow method, and the head control pipe part 103 The water level can be maintained by

The outflow pipe 40 may play a role of discharging the treated water after the reaction in the reaction unit 30 . The outflow pipe 40 may be connected to the head control pipe unit 103 .

The electrode current collector 50 may supply DC power to the adsorption electro-oxidation tank 101 by being connected to a DC power supply, and may serve as a buffer to accommodate liquid overflow in the reaction unit 30 .

The overflow pipe 60 may also serve to deliver excess liquid overflowed to the drain pipe 70 . For example, in the electrode current collector 50, electrodes having the same polarity are bridge-connected to each other using two bolts and nuts, and then connected to a DC power supply to supply DC power.

The drain pipe 70 may play a role of discharging excess liquid when operation is finished or activated carbon is replaced.

The strainer unit 80 consists of an exterior and an interior, the exterior may serve to provide structural reinforcement, and the interior supports the granular activated carbon (see reference numeral 32 in FIG. 4) filled in the reaction unit 30 to It can play a role in preventing inflow into the lower part.

The reaction unit 30 may serve to oxidize and decompose the perfluorinated compound included in the raw water (W _in ) through adsorption and electro-oxidation, and to regenerate the granular activated carbon 32 as a conductive medium. The reaction unit 30 will be described in detail with reference to FIG. 4 .

Referring to FIG. 4 , the reaction unit 30 may include an electrode 31 and granular activated carbon 32 filled between the electrodes 31 .

As the raw water (W _in ) introduced into the reaction unit 30 passes through the filled granular activated carbon 32 , the perfluorinated compound included in the raw water (W _in ) may be adsorbed onto the granular activated carbon 32 . Adsorption to the granular activated carbon 32 may be achieved by electrostatic attraction and/or hydrophobic interaction. The perfluorinated compound adsorbed on the surface of the granular activated carbon 32 may be distributed into pores formed inside the granular activated carbon 32 by a screening action. The perfluorinated compound adsorbed on the granular activated carbon 32 by the radical generated from the electrode 31 by the current supplied by the power supply unit (see reference numeral 102 in FIG. 2) is oxidized to an inorganic form or a low molecular weight form can be broken down. The perfluorinated compound decomposed into a low molecular weight form can be decomposed into an inorganic form through adsorption, oxidation, and decomposition processes. Finally, the products of decomposition can be released in gaseous form. The decomposed products are discharged through a discharge port (not shown) provided in the lid of the adsorption electro-oxidation tank 101, or by making a hole in the lid and connecting a pipe (not shown). have. In addition, the granular activated carbon 32 can be regenerated simultaneously with the oxidation and decomposition of the perfluorinated compound. Therefore, the perfluorinated compound can be continuously adsorbed and decomposed in the reaction unit 30 .

Conventional electro-oxidation processes require a large electrode surface area because oxidation occurs only on the surface of the anode. However, in the embodiments of the present invention, the granular activated carbon 32, which is a conductive medium filled between the electrodes 31, is polarized to form a microelectrode under the influence of an electric field formed at an appropriate voltage, so that each granular phase Electrooxidation and decomposition may be performed on the surface of the activated carbon 32 . Therefore, it is possible to secure a significantly increased electro-oxidation reaction area compared to a conventional electro-oxidation process, and thus, the removal efficiency of perfluorinated compounds can be increased.

In addition, in the conventional electrooxidation process, when the electrical conductivity in raw water (W _in ) is low, additional chemicals are required to secure conductivity. However, in the embodiments of the present invention, the conductivity required for electrooxidation and decomposition can be secured without additional chemical input by using the granular activated carbon 32, which is a conductive medium filled between the electrodes 31.

In addition, since the granular activated carbon 32 can be rapidly regenerated at the same time as the perfluorinated compound adsorbed on the granular activated carbon 32 is electrically oxidized and decomposed, the time required to reach the breakthrough point compared to the conventional adsorption process It is possible to secure stable treatment efficiency for perfluorinated compounds that are delayed and newly introduced. The breakthrough point refers to the point at which the adsorbent reaches the limit of adsorbing and removing the adsorbed substance, and can generally indicate the point at which the outflow concentration reaches 5-10% of the inflow concentration. In this embodiment, since the replacement cycle of the granular activated carbon capable of ensuring the perfluorinated compound removal performance can be increased due to the high regeneration efficiency of the granular activated carbon 32, cost efficiency is increased and effective application to large-scale processes is possible. it becomes possible

In this embodiment, it is characterized in that the electrode 31 and the granular activated carbon 32 are selected and combined to exert an optimized selective and efficient adsorptive oxidation removal effect of perfluorinated compounds. That is, the granular activated carbon 32 has a large specific surface area, so that the contact time for electro-oxidation of the perfluorinated compound can be increased. In addition, in order to compensate for the relatively low electrical conductivity of the granular activated carbon 32, the electrode 31 may be formed in a multi-electrode structure, and in addition, in order to increase the lifespan and efficiency of the electrode 31, it may be formed as a DSA electrode. have.

The granular activated carbon 32 included in the reaction unit 30 functions as a conductive medium for adsorption electro-oxidation, and adsorption, oxidation, and decomposition of perfluorinated compounds can be performed in the granular activated carbon 32 . That is, in this embodiment, for the selective and efficient removal of perfluorinated compounds, the characteristics of perfluorinated compounds themselves, the fact that they are contained in a small amount in wastewater, the method for removing perfluorinated compounds, the specific surface area of the conductive media, and the catalytic activity , stability, etc. are all comprehensively considered, and it is characterized by using granular activated carbon 32 as a conductive medium for adsorption electro-oxidation.

According to this embodiment, the granular activated carbon 32 may include any commercially available granular activated carbon 32 product or any manufacturable granular activated carbon material. The granular activated carbon 32 is granular porous carbon, and there are countless pores of 1 nm to 10 μm inside. Pores can be classified according to their sizes into micropores (pores with a diameter of 20 Å or less), mesopores (pores with a diameter of 20-1000 Å), and macropores (pores with a diameter of 1000 Å).

The granular activated carbon 32 can be produced by activating a carbonaceous raw material. Examples of the raw material of the granular activated carbon 32 include vegetable matter such as palm kernels, wood, sawdust, and charcoal, coal quality such as bituminous coal, anthracite, peat, lignite, lignite, and bituminous coal, petroleum residue, sulfuric acid sludge, and oil carbon. quality, or a combination thereof, and the like, but is not limited thereto. Examples of the activation method may include, but are not limited to, a gas activation method, a drug activation method, a drug gas combination activation method, and the like.

An example of detailed characteristics of the granular activated carbon 32 is shown in Table 3 below. However, the characteristics of the granular activated carbon 32 that can be used in this embodiment are not limited thereto.

Characteristic Packing Density (g/cc) 0.35-0.55 Electrical conductivity (Ω ^-1 cm ^-1 ) 0.01-0.2 Size (mesh) 4-30 Hardness(%) 85% or more Loss on drying (%) 0.5-6 Isoelectric point (pHPZC) 4-10 Specific surface area (㎡/g) 650-1500 Urea adsorption capacity (mg/g) 850-1200

The granular activated carbon 32 is rapidly regenerated as the adsorbed perfluorocompound is electro-oxidized, so that the breakthrough time is delayed and stable treatment efficiency for the newly introduced perfluorocompound can be exhibited.

The electrode 31 included in the reaction unit 30 may perform adsorption electro-oxidation by supplying an appropriate voltage. In this embodiment, for the selective and efficient removal of perfluorinated compounds, the characteristics of perfluorinated compounds themselves, the fact that they are contained in a small amount in wastewater, the method for removing perfluorinated compounds, and the electrocatalytic activity and operation of the electrode 31 It is characterized in that the electrode 31 including a specific structure and material is used in comprehensive consideration of lifespan and stability.

A typical electro-oxidation process has an electrode structure in which a cathode and an anode are respectively disposed on both sides. On the other hand, in this embodiment, the electrode 31 may have a multi-electrode structure. The multi-electrode structure may represent a structure in which an anode and a cathode are alternately disposed. For example, the electrode 31 having three electrodes may have a structure of anode-cathode-anode, and the electrode 31 having five electrodes may have a structure of anode-cathode-anode-cathode-anode. there is. In this way, since the electrode 31 has a multi-electrode structure, characteristics such as electrocatalytic activity, operation life, and stability can be improved, and accordingly, the efficiency of adsorption electro-oxidation can be further increased.

An anode and a cathode included in the electrode 31 may include the same material in order to increase efficiency during operation.

In one embodiment, one or more separators (not shown) may be further formed between the electrodes 31 . The separator is for physically separating the granular activated carbon 32 filled between the electrodes 31 .

In this embodiment, the electrode 31 may include a dimensionally stable anode (DSA). In this way, by using DSA as the electrode 31, the selective and efficient removal of perfluorinated compounds can be further improved.

The DSA electrode represents an anode that is physically, thermally, and electrochemically stable. DSA electrodes have a relatively low _Potenital for O ₂ Evolution (VOER) and long lifetime. The DSA electrode has excellent physical, thermal and electrochemical stability and low _VOER , so it was used for the chlorine generating electrode in the chlor-alkali process. Most DSA electrodes are manufactured by coating on a Ti substrate, and Ru, Ir, Ta, Pb, Sn, Pt, etc. may be used as a coating transition metal material. In particular, IrO ₂ with good stability and RuO ₂ with good reactivity were mainly used. Most of the electrode manufacturing methods have been reported using a pyrolysis method by coating a precursor on a substrate, and recently, an IL (Ionic Liquid) method, a Pechini method, an electrodeposition method, and the like have been reported.

According to this embodiment, the DSA used as the electrode 31 may include all commercially available DSA electrodes or all DSA electrodes that can be manufactured.

Referring back to FIG. 3 , a process of adjusting the water level by the head control pipe unit 103 will be described.

The head control pipe part 103 maintains the liquid in the reaction part 30 at a level higher than the reaction height of the electrode 31 during the operation of the selective removal device 100 for perfluorinated compounds, and treats the liquid after the reaction. It can serve to deliver to the water tank (104).

In this specification, the reaction height of the electrode 31 may be used interchangeably with the reaction area of the electrode 31, and the perfluorinated compound adsorbed on the granular activated carbon 32 is decomposed and decomposed by an oxidation reaction on the electrode 31. Areas that can be removed can be indicated.

The head control pipe part 103 may include a first part 103-1 and a second part 103-2.

The first part 103-1 is disposed in the vertical direction, the lower end can be connected orthogonally to the outflow pipe 40 of the adsorption electro-oxidation tank 101, and a valve V that allows air to flow therein can have During the operation of the adsorption electro-oxidation tank 101, by opening the valve V and using air pressure, the liquid in the reaction unit 30 can be maintained at a level equal to or higher than the reaction height of the electrode 31.

The height of the first portion 103-1 of the head control pipe part 103 may be set to be equal to or greater than the height H1 of the adsorption electro-oxidation tank 101 in order to prevent liquid from overflowing.

The second part (103-2) may have a bent shape, and one end is the first part (103-1) in the opposite direction to the outflow pipe (40) at a predetermined height (H3) of the first part (103-1). ), and the other end may be connected to the treatment tank 104 at the same level as the outflow pipe 40.

The height H4 of the second part 103-2 of the head control pipe part 103 should be designed in consideration of the head difference with the inflow pipe 20 so that the liquid can pass by gravity, and also the reaction part It should be designed to maintain the water level above the reaction height (reaction area) of the electrode 31 in (30). Therefore, the height H4 of the second part 103-2 of the head control pipe part 103 is greater than the height H3 of the reaction part 30 and less than the height H2 of the inflow pipe 20. can be set to Here, the heights H1 , H2 , H3 , and H4 may be based on the bottom surface of the perfluorinated compound selective removal device 100 .

Referring again to FIG. 2, the power supply unit 102 will be described.

The power supply unit 102 may serve to supply power for operation of the adsorption electro-oxidation tank 101 .

Power and current density conditions for the operation of the adsorption electro-oxidation tank 101 should be set to optimize the adsorption electro-oxidation of the perfluorinated compound. The granular activated carbon 32 included in the reaction unit 30 is polarized by an electric field formed by application of an appropriate voltage to form a microelectrode, so that an electrical oxidation reaction can be performed on the surface of each granular activated carbon 32 particle. Specific power and current density conditions may be appropriately selected depending on the material and structure of the electrode 31, the characteristics of the granular activated carbon 32, the flow rate of the introduced raw water (Win), the residence time, and the like.

In one embodiment, the adsorption electro-oxidation bath 101 may be operated under conditions of a voltage of 7-12V and a current density of 1-2.5 mA/cm 2 to optimize the electro-adsorption oxidation of perfluorinated compounds. Such operating conditions are set to exert optimum effects for selectively and efficiently removing perfluorinated compounds in consideration of the characteristics of the perfluorinated compounds as a result of intensive research by the present inventors.

The treatment water tank 104 may play a role of receiving and receiving the liquid for which the electro-adsorption reaction in the adsorption electro-oxidation tank 101 has been completed through the head control pipe 103 .

The treated water (W _treated ) from the treated water tank 104 may be discharged to the outside.

According to the method for selectively removing perfluorinated compounds according to the present embodiment, oxidation and decomposition of perfluorinated compounds can be simultaneously performed directly or indirectly through adsorption and electro-oxidation, and accordingly, it is possible to selectively and efficiently remove perfluorinated compounds. In addition, according to the method for selectively removing perfluorinated compounds of this embodiment, perfluorinated compounds can be selectively treated without additional chemicals, and as the granular activated carbon 32 is continuously regenerated, the breakthrough time is delayed, and stable treatment efficiency is achieved. can exert

Next, a method for selectively removing perfluorinated compounds according to another embodiment of the present invention will be described with reference to FIG. 5 .

The method for selectively removing perfluorinated compounds shown in FIG. 5 is applied in the case of 2) described above, that is, when the pH of the raw water (W _in ) exceeds the pH _PZC of the adsorbent and the SS exceeds 500 mg/L. can The embodiment shown in FIG. 5 is different from the embodiment shown in FIG. 1 in that it further includes an additional pretreatment process before adsorption and electrooxidation processes. The additional pretreatment may include one or more selected from the group consisting of flocculation, precipitation, filtration and pH adjustment.

In the embodiment shown in FIG. 5, the additional pretreatment includes all steps of coagulation, precipitation, filtration, and pH adjustment, but in another embodiment, one or more selected from the steps of coagulation, precipitation, filtration, and pH adjustment may be optionally included. .

The method for selectively removing perfluorinated compounds according to this embodiment includes coagulation step (S23), precipitation step (S24), primary treated water collection step (S25), filtration step (S26), pH adjustment step (S27), perfluorination It may include an adsorption electro-oxidation step of the compound (S21) and a secondary treatment water collection step (S22).

In the aggregation step (S23), the SS may be agglomerated to prevent clogging of the adsorption electro-oxidation tank 201 by the high content of SS contained in the raw water (W _in ).

The aggregation step (S23) may be performed using an aluminum-based coagulant, a polymer coagulant, or a coagulant including a combination thereof.

In the precipitation step (S24), the aggregates aggregated in the aggregation step (S23) may be precipitated.

The settling step (S24) may be performed using an inclined plate. For example, the settling step may be performed using an inclined plate having an area set to adjust the surface load to 40 m/hr to 60 m/hr.

In the primary treated water collection step (S25), the primary treated water that has undergone coagulation and precipitation reactions may be collected.

In the filtration step (S26), aggregates precipitated from the primary treated water collected in the primary treated water collection step (S25) may be filtered.

The filtration step (S26) may be performed by selecting an appropriate method among various filtration methods known in the art.

In the pH adjustment step (S27), the pH of the primary treated water filtered in the filtration step (S26) may be adjusted within a predetermined range. In the pH adjustment step (S27), the pH of the primary treatment water may be adjusted in the range of pH 6.5-8 for the efficiency of adsorption electro-oxidation, which is a subsequent process. Adjustment of the pH may be performed using an appropriate pH adjuster according to the pH of the primary treated water.

In one embodiment, when the pH of the primary treatment water filtered in the filtration step (S26) is within the above range, the pH adjustment step (S27) may be omitted.

The adsorption electrooxidation of the perfluorinated compound and the regeneration of the granular activated carbon (S11) may be performed in an adsorption electrooxidation tank including a reaction unit including a plurality of electrodes and the granular activated carbon filled between the electrodes. The granular activated carbon is polarized by an electric field to form a microelectrode, so that perfluorinated compounds adsorbed on the surface of each granular activated carbon can be oxidized and decomposed. At this time, the adsorption electro-oxidation reaction may be accompanied by a water level control process by the head control pipe unit.

The adsorption electro-oxidation of the perfluorinated compound and the regeneration of the granular activated carbon (S11) include introducing raw water into the reaction unit through an inflow pipe disposed above the reaction unit; and discharging the treated water for which the reaction is completed in the reaction unit through an outflow pipe disposed below the reaction unit.

The step of maintaining the water level in the reaction part at or above the reaction height of the electrode by the head control pipe part may be performed by the head control pipe part including the first part and the second part. The first part is arranged in a vertical direction, the lower end is orthogonally connected to the outflow pipe, and may include a valve allowing air to flow from the upper end. The second part may have a bent shape, one end may be connected orthogonally to the first part at a predetermined height of the first part, and the other end may be disposed at the same level as the outflow pipe.

During the operation of the adsorption electro-oxidation tank, the water level in the reaction unit may be maintained by opening the valve in the first part and using air pressure.

The step of maintaining the water level in the reaction unit to be equal to or higher than the reaction height of the electrode by the head control pipe unit may include maintaining the head control pipe unit to be equal to or higher than the height of the adsorption electro-oxidation tank.

The step of maintaining the water level in the reaction part by the head control pipe part to be equal to or higher than the reaction height of the electrode may include maintaining the height of the second part of the head control pipe within a range that is equal to or greater than the height of the reaction part and equal to or less than the height of the inflow pipe. can

The adsorption electro-oxidation of the perfluorinated compound and the regeneration of the granular activated carbon ( S21 ) may further include a step of supplying power by a power supply device.

In the method for selectively removing perfluorinated compounds according to an embodiment of the present invention, the adsorption electro-oxidation of perfluorinated compounds and the regeneration of granular activated carbon (S21) are performed using an operating voltage of 7-12V and a current of 1-2.5mA/cm 2 . It can be performed under operating conditions with density. Such operating conditions are set to exert optimum effects for the selective and efficient removal of perfluorinated compounds.

The method for selectively removing perfluorinated compounds according to an embodiment of the present invention can exhibit a removal rate of 99% or more for perfluorinated compounds when processing a flow rate of 2,000 times or more relative to the volume of the granular activated carbon.

Secondary treated water from which perfluorinated compounds are removed by adsorption electrooxidation in step S21 of adsorption electrooxidation of perfluorinated compounds and regeneration of granular activated carbon in step S22 of collecting secondary treated water may be collected.

Steps S21 and S22 of the embodiment shown in FIG. 5 may correspond to steps S11 and S12 shown in FIG.

The method of selectively removing perfluorinated compounds shown in FIG. 5 may be performed using the apparatus 200 for selectively removing perfluorinated compounds shown in FIG. 6 . Accordingly, with reference to FIGS. 5 and 6 , a method for selectively removing perfluorinated compounds according to the present embodiment will be described. Detailed descriptions of the contents described with reference to FIGS. 1 to 4 are omitted to avoid repetition.

6 is a diagram schematically showing a device for selectively removing perfluorinated compounds that can be used in the method for selectively removing perfluorinated compounds according to the present embodiment.

Referring to FIG. 6, the device 200 for selectively removing perfluorinated compounds includes a coagulation tank 205, a precipitation tank 206, a primary treatment tank 207, a filtration tank 208, a pH adjusting tank 209, an adsorption electro-oxidation It may include a tank 201, a power supply unit 202, a head control pipe unit 203, and a secondary treatment water tank 204. Flocculation tank 205, sedimentation tank 206, primary treatment tank 207, filtration tank 208, pH adjustment tank 209, adsorption electric oxidation tank 201, power supply unit 202, head control pipe unit 203 ) and the secondary treatment water tank 204 may be provided with a connecting pipe, a valve, and/or a pump.

Raw water (W _in ) may be delivered to the flocculation tank 205 by an inlet pump from a raw water tank (not shown).

The coagulation tank 205 may serve to coagulate SS in order to prevent clogging of the adsorption electro-oxidation tank 201 by a high content of SS contained in the raw water (W _in ).

The coagulation reaction in the coagulation tank 205 may be performed using a coagulant. Preferably, the coagulant may include an aluminum-based coagulant, a polymeric coagulant, or a combination thereof.

Examples of aluminum-based coagulants may include poly aluminum chloride (PACl), alum, or combinations thereof.

Polymer coagulants can be classified into low polymerization degree and high polymerization degree according to molecular weight, and can be classified into cationic, anionic, and nonionic, respectively. Examples of polymer coagulants may include water-soluble polymers, polyacrylic acid, polyacrylamide, polyvinyl alcohol, or combinations thereof.

In this embodiment, an aluminum-based coagulant and a polymer coagulant may be appropriately selected from among commercially available products.

The settling tank 206 may serve to precipitate the agglomerates aggregated in the flocculation tank 205 .

For example, the settling tank 206 may use an inclined plate to minimize the site area, and the area may be set to adjust the surface load to 40 m/hr to 60 m/hr.

The primary treated water tank 207 may serve to accommodate the primary treated water in which flocculation and precipitation reactions have been performed.

The filter tank 208 may serve to filter aggregates precipitated from the primary treated water. The primary treated water may be transferred from the primary treated water tank 207 to the filtration tank 208 by a transfer pump.

Filtration performed in the filtration tank 208 may be used by selecting an appropriate method according to process conditions among various known filtration methods.

The pH adjusting tank 209 may serve to adjust the pH of the primary treated water that has passed through the filtration tank 208 within a predetermined range. In the pH adjusting tank 209, the pH of the primary treatment water may be adjusted in the range of pH 6.5-8 for the efficiency of adsorption electro-oxidation, which is a subsequent process. Adjustment of the pH may be performed using an appropriate pH adjuster according to the pH of the primary treated water.

In one embodiment, when the pH of the primary treated water that has passed through the filtration tank 208 is within the above range, the pH adjustment tank 209 may not be passed through.

Subsequently, an adsorption electrooxidation reaction of the perfluorinated compound may be performed in the adsorption electrochemical oxidation tank 201, and oxidation and decomposition may be simultaneously performed directly or indirectly through adsorption and electrooxidation of the perfluorinated compound. In addition, regeneration of the granular activated carbon (see reference numeral 32 in FIG. 4) is performed together with adsorption electro-oxidation of the perfluorinated compound, so that stable treatment efficiency can be exhibited.

The adsorption electro-oxidation tank 201, the power supply unit 202, the head control pipe unit 203, and the secondary treatment water tank 204 are respectively the adsorption electro-oxidation tank described in the embodiment shown in FIGS. 2 to 4 ( 101), the power supply unit 102, the head control pipe unit 103, and the treatment water tank 104.

In the embodiment shown in FIG. 6, as a pretreatment tank for pretreatment of raw water (W _in ), a coagulation tank 205, a precipitation tank 206, a primary treatment tank 207, a filtration tank 208, and a pH adjustment tank ( 209), but in another embodiment, one or more of them may be included.

According to the method for selectively removing perfluorinated compounds according to the present embodiment, oxidation and decomposition of perfluorinated compounds can be simultaneously performed directly or indirectly through adsorption and electro-oxidation, and accordingly, it is possible to selectively and efficiently remove perfluorinated compounds. In addition, according to the method for selectively removing perfluorinated compounds of this embodiment, when the SS content of the raw water is high and the pH exceeds the pH _PZC of the adsorbent, clogging of the device is prevented by a specific pretreatment, and electro-oxidation of perfluorinated compounds is adsorbed. selectivity and efficiency can be further increased. In addition, according to the device 200 for selectively removing perfluorinated compounds according to the present embodiment, perfluorinated compounds can be selectively treated without additional chemicals, and as the granular activated carbon 32 is continuously regenerated, the breakthrough time is delayed, Stable treatment efficiency can be demonstrated.

Hereinafter, the present invention will be described in more detail by examples based on experimental examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited to the following examples.

[Example]

1. Operating conditions of equipment used in selective removal of perfluorinated compounds

The treatment efficiency of perfluorinated compounds was evaluated by treating the raw water using the method for selectively removing perfluorinated compounds shown in FIG. 1 or 5 according to the pH and SS content of the raw water.

The operating conditions of the device used in the method for selectively removing perfluorinated compounds are as follows.

1) Flow: 1000L/hr

2) Granular activated carbon volume: 500L

3) Residence time: 20 min - 60 min

4) Power conditions: operating voltage 7-12V, current density 1-2.5mA/cm2

5) Electrode: DSA electrode with multi-electrode structure

6) Granular activated carbon conditions

division unit SPEC Test Results granularity % 8×30 mesh
95 or higher 98.5 loss on drying % below 10 6.7 joy % - 3.2 packing density g/mL - 0.48 iodine adsorption ml/g over 1000 1032

2. Evaluation of selective removal efficiency of perfluorinated compounds

The target material of the perfluorinated compound to be selectively removed was perfluorobutane sulfonic acid (PFBS). The structure of PFBS is as follows.

PFBS is one of the most stable materials, like other PFAS, due to the high thermodynamic stability of the C–F bond and the F2CF–SO3 bond. PFBS is a material that replaces the use of PFOS and is used in the semiconductor industry, paint/paint industry, and plating industry, and is used as a stain inhibitor in carpets, leather, furniture, and automobiles. It is known that PFBS is a non-degradable material and cannot be removed by general chemical and biological treatment methods.

Short-chain PFAS, such as PFBS, are mostly present in solution, unlike long-chain PFAS, which usually exist bound to particulate matter in solution, and thus can move over long distances in the aquatic environment, so they are not exposed to humans. There is a higher probability of being able to In addition, most studies have reported that short-chain PFAS species, such as PFBS, have slower adsorption rates than long-chain PFAS species.

Considering these aspects, in this experimental example, PFBS was set as a target material representing perfluorinated compounds to be removed.

Wastewater discharged from the semiconductor process is treated by the selective removal device for perfluorinated compounds of the present invention under the conditions of a granular activated carbon volume of 500L, an influent flow rate of 1000L/hr, an operating voltage of 7-12V, a current of 25A, and an anode surface area of 15,000 cm2. , the removal rate of PBFS, the target perfluorinated compound, was evaluated.

7A shows the concentration (ng/L) of PBFS in treated water according to BV (bed volume), and FIG. 7B shows the PBFS removal rate (%) according to BV. In FIGS. 7A and 7B, Comparative Examples show lab test results using a general activated carbon tank commonly used for semiconductor wastewater treatment, and Examples perform an adsorption electro-oxidation process using the selective removal method of perfluorinated compounds of the present invention. shows a result. BV shown in FIGS. 7A and 7B represents the injection flow rate of influent per activated carbon volume (injection flow rate/activated carbon volume), and may mean the flow rate of influent that can be treated by the filled volume of activated carbon.

Referring to FIGS. 7A and 7B , in the case of a comparative example using only adsorption by activated carbon, the concentration of PBFS in the treated water increased as the BV increased, resulting in a decrease in removal rate. On the other hand, in the case of the examples, the removal rate of PFBS in BV up to the time point tested was confirmed to be 100%.

Then, during the long-term operation of the apparatus for selectively removing perfluorinated compounds according to the present invention, the operation of the apparatus was continued to confirm the change in the concentration of PBFS. As a result, about 1,000,000 L or more of influent was treated, which can indicate that about 2,400 times the relative flow rate was treated when considering the volume of 500 L of the filled granular activated carbon. Even in the case of such a long-term operation, the method for selectively removing perfluorinated compounds of the present invention showed a removal rate of 99% or more for PFBS, which is a target perfluorinated compound. On the other hand, when the same relative flow rate was processed, it was confirmed that the case of using a general activated carbon tank as a comparative example showed a removal rate of about 50% with respect to PFBS, indicating a significantly lower efficiency than that of the present invention.

Therefore, in the case of using the method for selectively removing perfluorinated compounds according to the present invention, the period of reaching the breakthrough point of the granular activated carbon during long-term operation can be much longer than that of the comparative example using adsorption by general activated carbon. As a result, in the selective removal method of perfluorinated compounds of the present invention, since the replacement cycle of the granular activated carbon capable of ensuring the removal performance of perfluorinated compounds can be increased, cost efficiency can be increased and effective application to large-scale processes is possible. .

3. Evaluate the effect on influent characteristics and removal efficiency for other pollutants

In the treatment process using the selective removal method for perfluorocompounds of the present invention, effects on other contaminants other than perfluorocompounds and on the characteristics of influent were evaluated. As in the case of 2 above, the wastewater discharged from the semiconductor process was selectively treated with the perfluorinated compound of the present invention under the conditions of a granular activated carbon volume of 500L, an influent flow rate of 1000L/hr, an operating voltage of 7-12V, a current of 25A, and an anode surface area of 15,000 cm2. After treatment by the removal method, the following items were evaluated.

1) Change in pH

2) change in electrical conductivity

3) Change in COD (Chemical Oxigen Demand): Evaluated by COD _cr

4) Concentration change of TOC (Total organic carbon)

5) T-N concentration change

6) Change in the concentration of NH ₃ -N

7) NO ₃ -N concentration change

8) Change in concentration of SO ₄ ^2-

The evaluation results are shown in Figs. 8A to 8G.

Referring to FIG. 8A, the average pH of the raw water was about 4.8, and decreased to about 4.1 after treatment by the method for selectively removing perfluorinated compounds according to the present invention.

Referring to FIG. 8B, the average electrical conductivity of the raw water was 7.0 mS/cm, and was 7.0 mS/cm without change even after treatment by the method for selectively removing perfluorinated compounds according to the present invention. Therefore, it can be confirmed that the method for selectively removing perfluorinated compounds according to the present invention does not affect the electrical conductivity of raw water.

Referring to FIG. 8c, the average concentration of _COD in raw water was 69 mg/L, but decreased to about 36 mg/L after treatment by the method for selectively removing perfluorinated compounds according to the present invention. Therefore, it can be confirmed that the method for selectively removing perfluorinated compounds according to the present invention exhibits high selectivity and efficiency for removing perfluorinated compounds, and also affects COD reduction.

Referring to FIG. 8D, in the case of TOC, the concentration in raw water and treated water was about 531 mg/L, confirming that it was hardly affected by the method for selectively removing perfluorinated compounds according to the present invention.

Referring to FIG. 8E, in the case of T-N, the average concentration in raw water was about 771 mg/L, and showed a tendency to increase to about 826 mg/L after treatment by the selective removal method for perfluorinated compounds of the present invention.

Referring to FIG. 8f, in the case of NH ₃ -N, the average concentration in raw water was about 604 mg/L, and showed a tendency to increase to about 621 mg/L after treatment by the method for selectively removing perfluorinated compounds of the present invention. was The concentration change of NH ₃ -N showed a pattern similar to that of TN shown in FIG _.

Referring to FIG. 8G, in the case of NO ₃ -N, the proportion of total nitrogen was very low, and the average concentration in raw water was 0.3 mg/L. However, the effect on the total nitrogen concentration change was judged to be insignificant.

Referring to FIG. 8H, the average concentration of SO ₄ ^2- in raw water was 3053 mg/L, and slightly increased to 3064 mg/L after treatment by the method for selectively removing perfluorinated compounds according to the present invention.

Reduction efficiency for general pollutants such as pH, electrical conductivity, COD, TOC, TN, NH ₃ -N, NO ₃ -N, SO ₄ ^2- by treatment using the selective removal method for perfluorinated compounds of the present invention As a result of the analysis, as shown in FIGS. 8A to 8H , it was difficult to confirm the removal pattern of other general contaminants except for COD.

From the above experimental results, it can be confirmed that the method for selectively removing perfluorinated compounds of the present invention can remove perfluorinated compounds with very high selectivity and high efficiency compared to other contaminants. In addition, the method for selectively removing perfluorocompounds according to the present invention can maintain high removal performance for perfluorocompounds compared to general activated carbon adsorption when the same relative flow rate is processed by long-term operation of the device, so that the time to reach the breakthrough point is reduced. It can be confirmed that it can be extended, and the cost efficiency can be further increased.

Although the technical idea of the present invention has been specifically written according to the above preferred embodiments, it should be noted that the above embodiments are for explanation and not for limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical spirit of the present invention.

100, 200: selective removal device for perfluorinated compounds
101, 201: adsorption electro-oxidation tank 102, 202: power supply unit
103, 203: head control pipe part 104: treated water tank
204: secondary treatment tank 205: flocculation tank
206: sedimentation tank 207: primary treatment tank
208: filtration tank 209: pH adjustment tank
10: chamber 20: inflow pipe
30: reaction part 40: outflow pipe
50: electrode collector 60: overflow pipe
70: drain pipe 80: strainer part
31: electrode 32: granular activated carbon

Claims (38)

As a method for selectively removing perfluorinated compounds,
In an adsorption electro-oxidation tank including a dimensionally stable anode (DSA) electrode having a multi-electrode structure in which anode and cathode are alternately disposed and a reaction unit including granular activated carbon filled between the DSA electrodes, perfluorination contained in raw water oxidizing and decomposing the compound through adsorption and electro-oxidation; and
Maintaining the water level in the reaction unit above the reaction height of the DSA electrode by the head control pipe unit
Method for selective removal of perfluorinated compounds.
According to claim 1,
The perfluorinated compound includes a compound having a perfluorinated (-C _n F2 _n+1 ) tail in which hydrogen is substituted with fluorine in a hydrocarbon basic skeleton structure.
Method for selective removal of perfluorinated compounds.
According to claim 1,
The method for selectively removing perfluorinated compounds is applied to raw water having a pH less than the isoelectric point (pH _PZC ) of the granular activated carbon and a suspended solid (SS) content of less than 500 mg/L.
Method for selective removal of perfluorinated compounds.
According to claim 1,
The method for selectively removing perfluorinated compounds is performed under operating conditions with an operating voltage of 7-12V and a current density of 1-2.5 mA/cm 2 .
Method for selective removal of perfluorinated compounds.
According to claim 1,
The method for selectively removing perfluorinated compounds exhibits a removal rate of 99% or more for perfluorinated compounds when processing a relative flow rate of 2,000 times or more with respect to the volume of the granular activated carbon.
Method for selective removal of perfluorinated compounds.
According to claim 1,
introducing raw water into the reaction unit through an inflow pipe disposed above the reaction unit; and
Further comprising the step of discharging the treated water for which the reaction has been completed in the reaction unit by an outflow pipe disposed below the reaction unit.
Method for selective removal of perfluorinated compounds.
According to claim 6,
The step of maintaining the water level in the reaction unit at or above the reaction height of the DSA electrode by the head control pipe unit is performed by a head control pipe unit including a first part and a second part,
The first part is disposed in a vertical direction, the lower end is connected orthogonally to the outflow pipe, and includes a valve allowing air to flow from the upper end,
During the operation of the adsorption electro-oxidation tank, the valve of the first part is opened to maintain the water level in the reaction unit using atmospheric pressure.
Method for selective removal of perfluorinated compounds.
According to claim 7,
Maintaining the water level in the reaction unit by the head control pipe unit to be equal to or higher than the reaction height of the DSA electrode includes maintaining the head control pipe unit to be equal to or higher than the height of the adsorption electro-oxidation tank.
Method for selective removal of perfluorinated compounds.
According to claim 7,
The second part has a bent shape, one end is connected orthogonally to the first part at a predetermined height of the first part, and the other end is disposed at the same level as the outflow pipe,
The step of maintaining the water level in the reaction part by the head control pipe part to be equal to or greater than the reaction height of the DSA electrode, the height of the second part of the head control pipe being equal to or greater than the height of the reaction part and the height of the inflow pipe. Including keeping it in the range of
Method for selective removal of perfluorinated compounds.
According to claim 1,
Further comprising a separator disposed between the DSA electrodes
Method for selective removal of perfluorinated compounds.
According to claim 1,
The granular activated carbon has a size of 4-30 mesh, an isoelectric point (pH _PZC ) of 4-10, a specific surface area of 650-1500 m 2 / g and a packing density of 0.35-0.55 g / cc
Method for selective removal of perfluorinated compounds.
According to claim 1,
The granular activated carbon is polarized by an electric field to form a microelectrode, thereby oxidizing and decomposing the perfluorinated compound adsorbed on the surface of each granular activated carbon.
Method for selective removal of perfluorinated compounds.
According to claim 1,
By the step of oxidizing and decomposing the perfluorinated compound through adsorption and electro-oxidation, the granular activated carbon is regenerated simultaneously with the oxidation and decomposition of the perfluorinated compound.
Method for selective removal of perfluorinated compounds.
As a method for selectively removing perfluorinated compounds,
Pre-treating raw water;
In an adsorption electro-oxidation tank including a dimensionally stable anode (DSA) electrode having a multi-electrode structure in which anode and cathode are alternately disposed and a reaction unit including granular activated carbon filled between the DSA electrodes, perfluorination contained in raw water oxidizing and decomposing the compound through adsorption and electro-oxidation; and
Maintaining the water level in the reaction unit above the reaction height of the DSA electrode by the head control pipe unit
Method for selective removal of perfluorinated compounds.
According to claim 14,
In the preprocessing step,
A coagulation step of coagulating solids contained in raw water;
a precipitation step of precipitating aggregated aggregates;
a filtration step of filtering out the precipitated aggregates; and
Including at least one selected from the pH adjustment step of adjusting the pH of the filtered primary treatment water
Method for selective removal of perfluorinated compounds.
According to claim 14,
The perfluorinated compound includes a compound having a perfluorinated (-C _n F2 _n+1 ) tail in which hydrogen is substituted with fluorine in a hydrocarbon basic skeleton structure.
Method for selective removal of perfluorinated compounds.
According to claim 14,
The method for selectively removing perfluorinated compounds is applied to raw water having a pH exceeding the isoelectric point (pH _PZC ) of the granular activated carbon and having a suspended solid (SS) content exceeding 500 mg/L.
Method for selective removal of perfluorinated compounds.
According to claim 14,
The method for selectively removing perfluorinated compounds is performed under operating conditions with an operating voltage of 7-12V and a current density of 1-2.5 mA/cm 2 .
Method for selective removal of perfluorinated compounds.
According to claim 14,
The method for selectively removing perfluorinated compounds exhibits a removal rate of 99% or more for perfluorinated compounds when processing a relative flow rate of 2,000 times or more with respect to the volume of the granular activated carbon.
Method for selective removal of perfluorinated compounds.
According to claim 15,
In the coagulation step, coagulating SS (suspended solid) contained in the raw water to prevent clogging of the adsorption electrooxidation tank
Method for selective removal of perfluorinated compounds.
According to claim 15,
The coagulation step is performed using an aluminum-based coagulant, a polymer coagulant, or a coagulant comprising a combination thereof.
Method for selective removal of perfluorinated compounds.
According to claim 15,
The precipitation step is performed using an inclined plate
Method for selective removal of perfluorinated compounds.
According to claim 15,
The settling step is performed using an inclined plate having an area set to adjust the surface load to 40 m / hr to 60 m / hr
Method for selective removal of perfluorinated compounds.
According to claim 15,
In the pH adjustment step, the pH of the primary treated water is adjusted in the range of pH 6.5-8
Method for selective removal of perfluorinated compounds.
According to claim 14,
introducing raw water into the reaction unit through an inflow pipe disposed above the reaction unit; and
Further comprising the step of discharging the treated water for which the reaction has been completed in the reaction unit by an outflow pipe disposed below the reaction unit.
Method for selective removal of perfluorinated compounds.
According to claim 25,
The step of maintaining the water level in the reaction unit at or above the reaction height of the DSA electrode by the head control pipe unit is performed by a head control pipe unit including a first part and a second part,
The first part is disposed in a vertical direction, the lower end is connected orthogonally to the outflow pipe, and includes a valve allowing air to flow from the upper end,
During the operation of the adsorption electro-oxidation tank, the valve of the first part is opened to maintain the water level in the reaction unit using atmospheric pressure.
Method for selective removal of perfluorinated compounds.
The method of claim 26,
Maintaining the water level in the reaction unit by the head control pipe unit to be equal to or higher than the reaction height of the DSA electrode includes maintaining the head control pipe unit to be equal to or higher than the height of the adsorption electro-oxidation tank.
Method for selective removal of perfluorinated compounds.
The method of claim 26,
The second part has a bent shape, one end is connected orthogonally to the first part at a predetermined height of the first part, and the other end is disposed at the same level as the outflow pipe,
The step of maintaining the water level in the reaction part by the head control pipe part to be equal to or greater than the reaction height of the DSA electrode, the height of the second part of the head control pipe being equal to or greater than the height of the reaction part and the height of the inflow pipe. Including keeping it in the range of
Method for selective removal of perfluorinated compounds.
According to claim 14,
Further comprising a separator disposed between the DSA electrodes
Method for selective removal of perfluorinated compounds.
According to claim 14,
The granular activated carbon has a size of 4-30 mesh, an isoelectric point (pH _PZC ) of 4-10, a specific surface area of 650-1500 m 2 / g and a packing density of 0.35-0.55 g / cc
Method for selective removal of perfluorinated compounds.
According to claim 14,
In the adsorption electrooxidation tank, the granular activated carbon is polarized by an electric field to form a microelectrode, whereby the perfluorinated compound adsorbed on the surface of each granular activated carbon is oxidized and decomposed.
Method for selective removal of perfluorinated compounds.
According to claim 14,
In the adsorption electro-oxidation tank, the granular activated carbon is regenerated simultaneously with the oxidation and decomposition of the perfluorinated compound.
Method for selective removal of perfluorinated compounds. delete delete delete delete delete delete

Images