KR20160101827A - Filter Media Coated by Nanosheet Graphene Oxide and Method for Manufacturing the Same - Google Patents

Abstract

The present invention relates to a filter media coated by nanosheet-type graphene oxide which has a simple production process, reduces production time, and can continuously filter, remove and treat toxic heavy metal ions and radioactive isotope ions, and to a producing method thereof. The filter media coated by nanosheet-type graphene oxide for removing heavy metal and radioactive substances comprises a carrier coated by the graphene oxide nanosheet.

Description

Technical Field [0001] The present invention relates to a nano-sheet type graphene oxide coating filtration medium and a method for manufacturing the same,

The present invention relates to nanosheet-type graphene oxide coated filtration media and methods for their manufacture. More particularly, the present invention relates to a nano-sheet-type graphene oxide-coated filtration medium which is simple in manufacturing process, shortened in manufacturing time, and capable of continuously filtering off toxic heavy metal ions and radioisotope ions, will be.

Graphene is a highly doped honeycomb structure of carbon atoms bonded to a single layer of sp ² hybrid orbital, which has excellent mechanical, optical and electrical properties, Sensors, nanocomposites and energy storage. Recently, it has become a matter of interest in environmental restoration and pollutant removal.

In addition, since various functional groups can be introduced through the chemical synthesis process, graphene oxide produced by the oxidation reaction of graphite under strong acidic conditions is a substitute for carbon nano tube, Has attracted much interest as a medium for application.

Typically, graphene produced from graphite is present as graphene oxide (GO) or reduced graphene oxide (RGO). RGO has a high conductivity but low solubility in water whereas GO has an oxygen-containing functional group such as carboxyl (-COOH), carbonyl (-C═O) and hydroxyl (-OH) And is known to have an efficient removal characteristic against cationic heavy metal ions and organic dyes having positive charge.

The graphene oxide with many functional groups has a large specific surface area, is hydrophilic and easily dispersed in water, and can be used as an effective adsorbent for heavy metals and organic dyes. However, it is difficult to use the graphene oxide itself as a continuous processing medium, and even when it is used as an adsorbent for water treatment, it requires a large amount of cost for solid-liquid separation as well as a complicated process, .

Therefore, in order to overcome these limitations, much research has been focused on developing a new medium having a magnetite (Fe ₃ O ₄ ) metal oxide complexed with graphene oxide. Studies related to graphene oxide have been carried out by combining a nanoparticle-type graphene oxide with a metal oxide or a magnetite having magnetism, and conducting a basic laboratory-scale study on heavy metal ion and organic dye treatment using the same and a graphene oxide To remove heavy metal ions.

In the water treatment process, some studies have been made on the simple separation, washing and reusability of the adsorbent using the permanent magnet after the adsorption. In recent years, a technique using a magnetic force has been applied to a technique that combines a separation technique using a magnetic force and an adsorption process of an adsorbent in water treatment technology, because it quickly and effectively recovers magnetic materials. The advantage of this technique is that it can treat large volumes of wastewater in a short period of time without generating additional contaminants.

However, complexing magnetite having such a magnetic force with graphene oxide is problematic in that it consumes a large amount of energy, has a problem of generation of unattached iron oxide-containing waste solution, that the active point of graphene oxide is reduced by magnetite attachment, A need for a new graphene oxide-based medium manufacturing method which can improve the complexity and difficulty in the processing process is required because a permanent magnet and a reactor design for separating the composite medium from the magnet are required. .

The background art of the present invention is disclosed in Korean Patent Laid-Open Publication No. 10-2011-0119270 (November 22, 2011, a method of forming a graphene nanosheet and a graphene nanosheet formed using the method).

The present invention provides a nano-sheet-type graphene oxide-coated filtration medium which is simple in manufacturing process, shortened in manufacturing time, and capable of continuously filtering off toxic heavy metal ions and radioisotope ions, and a method for producing the same.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention, claims and drawings.

An object of the present invention is achieved by preparing a filtration medium coated with a nanoparticle-type graphene oxide and using the produced filtration medium as a filtration medium for removing heavy metals or radioactive substances.

According to one aspect of the present invention, there is provided a nano-sheet type graphene oxide coated filtration medium for removing heavy metals and radioactive materials, comprising a carrier coated with graphene oxide nanosheet.

In accordance with another aspect of the present invention, Drying and drying the slurry of the graphene oxide nanosheet immersed with the carrier under reduced pressure; And hydrothermally reacting a slurry of the graphene oxide nanosheet immersed with the carrier concentrated under reduced pressure to coat the graphene oxide nanosheet on the surface of the support; Coated graphene oxide-coated filter media.

The present invention can provide a nano-sheet-type graphene oxide-coated filtration medium capable of continuously removing the toxic heavy metal ions and radioisotope ions by a simple manufacturing process, shortening the manufacturing time, and a manufacturing method thereof .

That is, in the manufacturing method of the present invention, a carrier is added to a slurry of a nano-thick graphene oxide sheet peeled off by ultrasonic irradiation to a slurry containing a graphene oxide powder having a three-dimensional multi-layer structure, The present invention relates to a simple manufacturing process in which a graphene oxide of a nanosheet type that is peeled off while evaporating moisture under the following heating conditions is coated on the surface of the carrier, and the manufacturing facility and the manufacturing process can be simplified.

In addition, since the nanoparticle-type graphene oxide is coated on the surface of the carrier through ultrasonic scanning, a filtration medium coated with a relatively uniform thickness of graphene oxide can be produced.

Further, according to an embodiment of the present invention, by using the graphene oxide-containing slurry solution separated by high concentration and ultrasonic wave, the volume of the reaction solution can be reduced and the facility capacity can be reduced, and the uncoated graphene oxide solution It can be reused because the stability is maintained. Therefore, it is possible to drastically reduce the amount of waste water generated in the production of Fe ₃ O ₄ -GO, thereby greatly reducing the cost of the process.

1 is a schematic view of a process for producing graphene oxide nanosheets from graphite according to an embodiment of the present invention.
2 is an electron micrograph (SEM) of a graphene oxide nanosheet according to an embodiment of the present invention.
3 is a graph showing FT-IR (Fourier Transform Infra-Red) analysis results for qualitative analysis of graphene oxide nanosheets according to an embodiment of the present invention in comparison with graphite.
4 is an X-ray photoelectron spectroscopy (XPS) analysis graph for qualitative analysis of graphene oxide nanosheets according to an embodiment of the present invention.
5 illustrates a process for fabricating a sand and ceramic ball filtration media coated with graphene oxide nanosheet according to an embodiment of the present invention.
FIG. 6 shows an experimental procedure for evaluating the mechanical strength (coating stability) of a graphene oxide nanosheet-coated sand and a ceramic ball filtration medium according to an embodiment of the present invention.
FIG. 7 is a graph showing a tendency of lead removal with time of a ceramic ball coated with graphene oxide nanosheet according to an embodiment of the present invention. FIG.
8 is a schematic diagram showing an ex situ treatment process of groundwater contaminated with heavy metals and radioactive materials using a column reactor packed with a filtration medium coated with a graphene oxide nanosheet according to an embodiment of the present invention .

 BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and particular embodiments are illustrated in the drawings and will be described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprises", "having", and the like are intended to specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a nanosheet-type graphene oxide coated filtration medium and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings, The same reference numerals denote the same elements, and a duplicate description thereof will be omitted.

For the sake of convenience of explanation, the direction of each constitution is based on the direction shown in the figure. However, the description in this direction is merely an example of the operating state, and the nanosheet-type graphene oxide coating filtration medium according to the present embodiment and the manufacturing method thereof are not limited.

According to one aspect of the present invention, nanosheets of graphene oxide coated filtration media for removing heavy metals and radioactive materials, including a carrier coated with graphene oxide nanosheets, can be produced.

According to an embodiment of the present invention, the carrier may include sand or ceramic balls. However, there is no particular limitation on the type, shape and size of the support, as long as the nanosheet-shaped graphene oxide can be coated.

According to one embodiment of the present invention, the coated carrier may be coated by a hydrothermal reaction of the nanosheet-shaped graphene oxide.

According to an embodiment of the present invention, the size of the carrier may be 1.0 mm to 4.0 mm. The coating and / or filtration efficiency can be improved when the size is within the above range. However, the present invention is not limited to this, and it may be suitably controlled in consideration of various parameters including coating and / or filtration efficiency depending on the kind of carrier.

According to another aspect of the present invention, there is provided a method of producing a graphite powder comprising: oxidizing powder graphite to powder graphene oxide; Peeling the graphene oxide with a single layer of graphene oxide nanosheet; Immersing the carrier in a slurry of the graphene oxide nanosheet; Drying and drying the slurry of the graphene oxide nanosheet immersed with the carrier under reduced pressure; And hydrothermally reacting a slurry of the graphene oxide nanosheet immersed with the carrier concentrated under reduced pressure to coat the graphene oxide nanosheet on the surface of the support; A method for manufacturing a nanosheet-shaped graphene oxide coated filtration medium can be provided.

According to one embodiment of the present invention, the powdered graphene oxide may be oxidized using the Hummer's method. However, the type of the powdered graphene oxide of the present invention is not limited as long as it is capable of forming a powdery graphene oxide in addition to the above-mentioned humming method.

Although not limited thereto, powdered graphite is subjected to an oxidation process by adding sulfuric acid and hydrogen peroxide. Powder graphene in the process of oxidation is filtered to obtain a solid oxide, and the supernatant is discarded through centrifugation (8000 rpm, 1 h) The oxide is dried in an oven (105 DEG C) to obtain powdered graphene oxide.

According to an embodiment of the present invention, the step of stripping the graphene oxide into a monolayer of graphene oxide nanosheets includes ultrasonication of the graphene oxide to strip off the monolayer to a nanometer thickness .

Although not limited thereto, the slurry solution containing graphene oxide can be separated for 30 minutes to 1 hour by using an ultrasonic wave extractor. At this time, ultrasonic extraction is performed for a sufficient time (0.5-1 h) by using an ultrasonic wave extractor, thereby allowing the graphene oxide, which is a multi-layer structure, to be stripped in a single layer structure. At this time, though not limited thereto, ultrasound can be applied to the slurry once per second.

According to an embodiment of the present invention, the step of immersing the carrier in the slurry of graphene oxide nanosheets may be performed at a pH in the range of 6 to 8 by adding 5 to 7 kg of the carrier per liter of slurry of the graphene oxide nanosheet / RTI > ratio. ≪ / RTI >

According to an embodiment of the present invention, the step of concentrating the graphene oxide slurry while evaporating the moisture on the surface of the carrier may be performed by, but not limited to, a method in which the graphene oxide slurry solution, (Rotary Evaporator) and heated to 100 ° C or less, preferably 75 to 85 ° C under reduced pressure (0.2 to 0.3 atm).

According to an embodiment of the present invention, the step of coating the graphene oxide nanosheet on the surface of the support may include a step of hydrothermally treating the immersed support at about 100 to 170 ° C for 1 to 3 hours, Lt; / RTI >

According to one embodiment of the present invention, the carrier may comprise sand or ceramic balls. The carrier is not particularly limited as long as the nanosheet-shaped graphene oxide can be coated.

According to an embodiment of the present invention, after the filtration medium coated with the graphene oxide is prepared through the hydrothermal reaction, the incompletely coated graphene oxide and foreign matter may remain, and the filtration medium may be washed as water A post-drying step may be performed. The filtration medium may be washed with ultrapure water and then dried at about 90 to 110 DEG C, preferably about 105 DEG C for about 2 hours.

The present invention will now be described in more detail with reference to the following Examples, which are for the production of graphene oxide, the graphene oxide coating filtration media and the production method thereof.

[ Example ]

10 g of powdered graphite was placed in a beaker containing 50 mL of sulfuric acid, and the beaker was immersed in an ice bath and stirred for about 15 minutes while maintaining the temperature at about 0 ° C. Then, 6 g of potassium permanganate was added to the mixture in small portions to prevent rapid temperature rise, and the mixture was stirred for about 20 minutes while maintaining the temperature at about 18 to 22 캜. Then, when the ice was removed from the thermostat and the mixture was stirred for about 1 hour while maintaining the temperature at about 32-35 ° C., the mixture became dark green and viscous and gradually turned grayish brown.

Further, the mixture was stirred for 1 hour and diluted with 450 mL of distilled water. In order to suppress the sudden increase in temperature and the formation of bubbles, stirring was further performed for 1 hour while injecting a small amount of distilled water . After the stirring was completed, 7 mL of 30% hydrogen peroxide was added to the mixture, and the mixture was stirred at room temperature for 15 minutes. The well-stirred mixture was filtered using a filter paper, and the filtrate remaining in the filter paper was transferred to a beaker. 100 mL of 30% NH ₃ solution was added thereto, followed by centrifugation using a centrifuge for 1 hour. After discarding the supernatant, The oxide was dried in an oven at 100 to 105 DEG C to obtain powder graphene oxide.

To the dried powdered graphene oxide, add 100 mL of distilled water. A mono-layer or multi-layer structure of graphene oxide is stripped off as a single layer by ultrasonication once per second by ultrasonic wave using an ultrasonic disperser to form a graphene oxide nanosheet So that ultrasonic waves were sufficiently injected for about 30 minutes.

An electron micrograph (SEM, JSM 5410LV, Japan) was taken for the analysis of the surface morphology of the graphene oxide nanosheet prepared according to the above examples and is shown in Fig. Further, FT-IR (IFS 66 / S) and XPS analysis were carried out to analyze the characteristics of the surface of the graphene oxide nanosheet surface according to the above examples on the functional groups, the crystallinity of the surface and the mineral form, .

In order to coat the carrier with the graphene oxide nanosheet prepared according to the above example, sand and ceramic balls were used as the carrier.

As a first carrier, the order specimens were used. In order to use sand of a certain particle size, the particle size of the sand was classified into a range of 1.0 mm to 2.0 mm by using a standard particle size separator.

A granular ceramic ball was used as the second carrier, and ceramics in the range of 2.0 mm to 4.0 mm were selected for use of ceramics having a certain diameter.

The custom crystal and ceramic balls used as the carrier were sequentially washed with 0.1 N hydrochloric acid solution and water to remove impurities on the surface of the carrier.

10 mL (1%) of the graphene oxide nanosheet slurry and 10 g of the sand or ceramic balls were put in a rotary evaporator to prepare a slurry. The slurry is stirred at a constant stirring rate of 30 rpm while the temperature of the water tank containing the rotary evaporator is maintained at about 75 to 85 캜 under a reduced pressure of 0.2 to 0.3 atm to evaporate water in the slurry, The evaporated sand or ceramic balls were placed in a heating furnace at about 150 ° C and then heated and fired for about 2 hours to obtain graphene oxide coated gos (GOS) and graphene oxide coated ceramics (GOC) . The prepared GOS and GOC were washed with ultrapure water and then dried at about 105 DEG C for about 2 hours.

The graphene oxide content of the graphene oxide nanosheet-coated filtration media prepared by the method of the above example was measured by mass difference before and after coating.

In order to measure the coating stability (coating strength) of the prepared GOS and GOC, 100 mL of ultrapure water was placed in a flask, 10 g of GOS or GOC was injected, and the mixture was mechanically and continuously shaken at about 200 rpm for about 2 hours The graphene oxide desorbed in the mixed solution was separated by a filter paper, and mass analysis was carried out.

Pb (II) standard reagent (PbCl ₂ , Merck Co.) and ultrapure water (Milli) were used to measure the adsorption capacity of each graphene oxide coated filtration media (GOS and GOC) -Q water) of 10 mg / L of lead contaminated water.

The initial pH of the 50 mL of lead-contaminated water having an ionic strength (0.01 M NaNO ₃ ) adjusted to 50 mL in a polypropylene conical tube was fixed to 5.5, and then the graphene oxide-coated filter medium (GOS And GOC) (0.05 g, 1 g / L) were injected into the reactor, and the mixture was stirred at 30 rpm using a nuclear rotator. The reaction was carried out for about 6 hours.

The experimental results of the above embodiment will be described below.

Table 1 shows the specific surface area and average grain size of graphite, graphene oxide nanosheets, ordered crystals, and ceramic balls as raw materials.

    material Specific surface area (BET, m ² / g) Average particle diameter (nm)   Order Champion 0.1024 1 to 2 mm   ceramic 1.556 3855   Graphite 0.573 10466   Graphene oxide nanosheet 1.831 3277

FIG. 3 shows FT-IR spectroscopic analysis results for the qualitative analysis of graphene oxide nanosheets produced by the Hummer's method, showing that graphite, which has no absorption peak at all, It was confirmed that a functional group was generated. These results are very similar to the FT-IR spectroscopic results of various conventional graphene oxides reported after the production by the humming method.

FIG. 4 shows XPS spectroscopic analysis results for the qualitative analysis of graphene oxide nanosheets prepared by the humming method. Graphite showed a single carbon peak at a binding energy of 284.5 eV. In graphene oxide nanosheets, A peak appears and suggests that the hybrid orbit has a different carbon atom.

FIG. 5 illustrates a process for manufacturing a GOC coated with graphene oxide nanosheets and a ceramic ball coated with graphene oxide nanosheets according to an embodiment of the present invention.

Table 2 shows the coated graphene oxide content and efficiency of the filtration media coated with graphene oxide nanosheets, according to one embodiment of the present invention, for the two different supports.

   carrier          The graphene oxide coating efficiency  Before coating (g)  After coating (g)  Coating amount (g) Coating efficiency (%)   Order Champion      10.008      10.060      0.0527 0.53   Ceramic Ball      9.999      10.173      0.1747 1.75

The coating amount of the graphene oxide nanosheet according to an embodiment of the present invention was about three times higher than that of sand in the same condition.

In order to investigate the coating strength (stability) of the graphene oxide nanosheet coated on the surface of the support, the prepared GOS and GOC were placed in a shaker and stirred at 200 rpm for about 1 hour, The amount of desorption and the rate of desorption are shown in Table 3.

    carrier The amount of desorption (g) Removal rate (%)     Order Champion 0.0478 90.70     Ceramic Ball 0.0021 1.20

In Table 3, when the GOS and GOC prepared according to an embodiment of the present invention are agitated at a speed of 200 rpm for about 1 hour, the desorption amount of the graphene oxide is measured to determine the amount of desorption of the coated graphene oxide as a percentage , It is found that the stability of the graphene oxide nanosheet is higher when the ceramic ball is used as the carrier than when the sand is used.

FIG. 6 shows an experimental procedure for measuring the desorption of graphene oxide according to agitation of GOS and GOC according to an embodiment of the present invention.

FIG. 7 shows the removal efficiency of 10 ppm Pb (II) over time under a pH of 5.5 (1.0 g / L) of GOS and GOC according to an embodiment of the present invention. As a result, a rapid increase of the removal rate was observed within the first 30 minutes, and then the adsorption equilibrium was reached. The adsorption capacity was 16.58 mg / g.

Figure 8 shows an ex-situ process flow diagram of groundwater by a filtration system filled with the nanosheet-type graphene oxide coated filtration media of the present invention.

In the present invention, a nanosheet-type graphene oxide-coated filtration medium and a method for manufacturing the same, which can overcome the limitations of separation and recovery in a water treatment process using only graphene oxide powder and the limitations in manufacturing and using the graphene oxide medium complexed with magnetite, And a manufacturing method thereof. In order to utilize as a continuous water-treatable filtration medium, embodiments of the present invention provide a fabricated filtration medium that coats a graphene oxide nanosheet onto a carrier such as sand and a ceramic ball and a method of making the same, The filtration media according to the examples were used to evaluate heavy metal removal capabilities. The filtration media coated with graphene oxide nanosheets according to an embodiment of the present invention allows continuous ex situ treatment of toxic heavy metals and groundwater contaminated with radioactive materials.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention as defined in the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

A nano-sheet type graphene oxide coated filtration media for removing heavy metals and radioactive materials, comprising a carrier coated with graphene oxide nanosheets. The method according to claim 1,
Wherein the carrier comprises sand or ceramic balls. The nanoclinic graphene oxide coated filtration media of claim 1, wherein the diameter of the carrier is 1.0 mm to 4.0 mm. The method according to claim 1,
Wherein the coated carrier is made by a hydrothermal reaction of the nanosheet-shaped graphene oxide. Immersing the carrier in a slurry of graphene oxide nanosheet;
Drying and drying the slurry of the graphene oxide nanosheet immersed with the carrier under reduced pressure; And
Coating the graphene oxide nanosheet on the surface of the support by hydrothermal reaction of a slurry of graphene oxide nanosheets immersed in the carrier concentrated under reduced pressure;
≪ / RTI > wherein the nano-sheet-type graphene oxide-coated filtration media is produced by a process comprising the steps of: 6. The method of claim 5,
Wherein the graphene oxide nanosheet is prepared by ultrasonication of graphene oxide to form a single layer with a nanometer thickness. 6. The method of claim 5,
The step of drying and concentrating the slurry of graphene oxide nanosheets, in which the carrier is immersed,
Lt; RTI ID = 0.0 > 75-85 C < / RTI > under 0.2 to 0.3 atm. 6. The method of claim 5,
The step of coating the graphene oxide nanosheet on the surface of the support comprises:
And hydrothermally reacting the immersed support at about 100 to 170 DEG C for 1 to 3 hours. 9. The method according to any one of claims 5 to 8,
Wherein the carrier comprises sand or ceramic balls. ≪ RTI ID = 0.0 > 8. < / RTI > 9. The method according to any one of claims 5 to 8,
Wherein the filtration medium is washed with water and then dried. ≪ RTI ID = 0.0 > 21. < / RTI >

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