KR102206876B1 - Cesium ion adsorbent, method for producing the same, and method for removing cesium ion using the same - Google Patents

Abstract

The present specification discloses a cesium ion adsorbent, a method for preparing the same, and a method for removing cesium ions using the same.

Description

Cesium ion adsorbent, manufacturing method thereof, and cesium ion removal method using the same {CESIUM ION ADSORBENT, METHOD FOR PRODUCING THE SAME, AND METHOD FOR REMOVING CESIUM ION USING THE SAME}

The present invention relates to a cesium ion adsorbent, a method for preparing the same, and a method for removing cesium ions using the same. More specifically, the present invention relates to a cesium ion adsorbent comprising a; graphene oxide complex having a hydrophilic group containing an alkali ion, a method for preparing the same, and a method for removing cesium ions using the same.

Cs-137, one of the radioactive nuclides, has a half-life of up to 30 years and is a major effluent material in a major accident at a nuclear power plant, so it requires adsorbent technology that can decontaminate quickly and efficiently.

Cs-137 and other radioactive wastes were present in the contaminated water from the Fukushima nuclear power plant accident that occurred in the northeastern part of Japan in 2011, and the existing zeolite decontamination technology was used to remove them.

However, due to the occurrence of additional problems such as generation of secondary contaminated water due to low removal efficiency and high concentration treatment, the development of a new treatment technology is required.

KR 10-2018-0004559 WO 2017/188564 A1 KR 10-2018-0037830 KR 10-1992-0014375 KR 10-2013-0116280 KR 10-2012-0108100 KR 10-2018-0004559 WO 2017/188564 A1 KR 10-2018-0037830 KR 10-1992-0014375 KR 10-2015-0037064 KR 10-2012-0108100 KR 10-2014-0091264

Journal of Materials Chemistry 2008, 18, 3628-3632 Bioresource Tehcnology, 2016, 218, 391-398 Bioresource Technology, 2016, 218, 294-300 Dalton Transaction, 2013, 42, 16049-16055 J Hazard Mater 2007, 143, 354-361.

It is an object of the present invention to provide a cesium ion adsorbent capable of efficiently removing cesium even at a low initial concentration, including graphene oxide complexes having a hydrophilic group containing alkali ions.

In an exemplary embodiment of the present invention, a graphene oxide complex having a hydrophilic group represented by COO ^- M ⁺ includes; wherein M is H, Li, Na, K, Rb or a quaternary amine, providing a cesium ion adsorbent do.

In an exemplary embodiment of the present invention, a method for preparing the above-described cesium ion adsorbent, comprising: synthesizing graphene oxide; Provides a process for the production of cesium ion adsorbent comprising a (wherein M ⁺ is H,; step for wet spinning a solution containing a salt represented by the composite oxide graphene composite material ^- and the oxidizing So the pin M ⁺ OH Li, Na, K, Rb or quaternary amine).

An exemplary embodiment of the present invention provides a method for removing cesium ions, including; removing cesium ions using the above-described cesium ion adsorbent.

The cesium ion adsorbent according to the present invention includes a graphene oxide complex having a hydrophilic group containing an alkali ion, and cesium ions are substituted with alkali ions in the hydrophilic group in an aqueous solution to effectively remove cesium ions.

In another aspect, the method for producing a cesium ion adsorbent according to the present invention can easily and economically manufacture a cesium ion adsorbent by producing graphene oxide fibers through wet spinning.

In another aspect, the method for removing cesium ions according to the present invention comprises regenerating the adsorbent used to remove cesium ions in an alkali salt solution to enable adsorption of cesium ions, thereby recycling the cesium ion adsorbent semi-permanently or rechargeable to Ion can be removed.

1 shows a method for preparing a cesium ion adsorbent according to an embodiment of the present invention and a method for removing cesium ions in an aqueous solution using the same.
Figure 2a is a view of the carbon fiber obtained by spinning a wet alkali metal salt aqueous solution (left), which was observed by Energy Dispersive Spectroscopy Mapping, showing the fiber surface consisting of carbon, oxygen and sodium (right).
In addition, Figure 2b is observed with a Scanning Electron Microscope (electron microscope), showing the state of the carbon fiber in the form of solidified graphene oxide (Graphene Oxide) of a two-dimensional structure is tightly intertwined.
3A to 3C are X-ray Photoelectron Spectroscopy (XPS) analysis results showing the chemical structure of the synthesized carbon fiber.
4A to 4C are graphs showing the results of an experiment for adsorption of cesium ions of the synthesized carbon fiber.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention disclosed in the text are exemplified for purposes of explanation only, and the embodiments of the present invention may be implemented in various forms and should not be construed as being limited to the embodiments described in the text. .

The present invention is not intended to limit the present invention to a specific disclosed form, as various changes can be added and various forms may be added, and all changes, equivalents or substitutes included in the spirit and scope of the present invention It should be understood to include.

In the present specification, when a certain part "includes" a certain constituent element, it means that other constituent elements may be further included rather than excluding other constituent elements unless otherwise specified.

Cesium ion adsorbent

In exemplary embodiments of the present invention, a graphene oxide complex having a hydrophilic group represented by COO ^- M ⁺ includes; wherein M is H, Li, Na, K, Rb or a quaternary amine, a cesium ion adsorbent Provides.

Referring to FIG. 1, the cesium ion adsorbent of the present invention removes cesium ions in the aqueous solution while alkali ions (M ⁺ ) of the hydrophilic group on the surface of the graphene oxide composite are replaced with cesium ions in the aqueous solution. Since hydrophilic groups, that is, alkali ion sites, are evenly dispersed on the surface of the cesium ion adsorbent, it is expected that more stable cesium ion adsorption is possible. For example, M may be preferably Na.

In exemplary embodiments, the cesium ions may be 137 Cs ⁺ ions having a half-life of about 30 years while being a major radioactive species present in particularly radioactive contaminated water.

In exemplary embodiments, the content of M may be 1 to 20% by weight, and preferably 2 to 8% by weight, based on the total weight of the graphene oxide composite.

In exemplary embodiments, the cesium ion adsorbent may be a graphene oxide fiber having a diameter of 100 to 500 μm, and may have a structure in which stability and adsorption properties are optimized within the above range. When the diameter is less than 100 μm, fiber stability and physical durability are deteriorated, and when the diameter is more than 500 μm, it is difficult to synthesize a uniform fiber.

In example embodiments, the graphene oxide composite may have a two-dimensional multilayer structure. Since the two-dimensional graphene composite is stacked in one or more layers, there is a synthetic advantage of realizing a three-dimensional porous structure through this.

Of cesium ion adsorbent Manufacturing method

In exemplary embodiments of the present invention, a method of preparing the above-described cesium ion adsorbent, comprising: synthesizing graphene oxide; Provides a process for the production of cesium ion adsorbent comprising a (wherein M is H, Li; step for wet spinning a solution containing a salt represented by the composite oxide graphene composite material ^- and the oxidizing So the pin M ⁺ OH , Na, K, Rb or a quaternary amine).

Graphene material, which is drawing attention as a next-generation semiconductor device, can be synthesized in various forms according to the process method. Among them, the graphene oxide process designed to obtain more efficient and high yield in solution is reduced graphene oxide through the process of re-reducing the exfoliated graphene structure through acid treatment in the liquid phase using graphite. To create a structure. If the process of reducing the graphene oxide is performed in a slow process through a weak reducing agent, it can be assembled into a three-dimensional porous structure based on a secondary structure of graphene oxide.

Accordingly, in the present invention, a technology for synthesizing graphene fibers containing an alkali metal was devised by using self-assembly of graphene oxide in a reducing environment. Referring to FIG. 1, the method for preparing a cesium ion adsorbent of the present invention is simple and economical without a separate process procedure, heat treatment or crosslinking aid by wet spinning a graphene oxide solution into a solution containing a salt represented by M ⁺ OH ^- . As a result, a cesium ion adsorbent can be prepared. When the wet spinning is performed, the reduction process is also performed at the same time.

In addition, a solution containing a salt represented by M ⁺ OH ^- is necessary for spinning carbon fibers in a more stable and uniform form. This is because the -OH functional groups present in the M ⁺ OH ^- solution so cooperate with various oxidizing functional groups (C-OH, COOH, C=O) present on the surface of graphene oxide to create a weak reducing environment. This is supported by the fact that homogeneous fibers cannot be synthesized in other salts containing M ⁺ such as sodium ions (eg NaCl).

In exemplary embodiments, the graphene oxide may be prepared by various modified methods based on Hummer's method in a general solution process, but is not limited thereto.

In exemplary embodiments, the synthesized graphene oxide may be in the form of a powder, and may be prepared in the form of a dispersion solution obtained by placing it in distilled water and dispersing it with ultrasonic waves, and then wet spinning, but is not limited thereto.

In exemplary embodiments, when the graphene oxide dispersion solution is wet-spinned, the solidification chamber may be rotated at a speed of 140 RPM to maintain the orientation of the graphene oxide structure, but is not limited thereto.

Cesium ion removal Way

In exemplary embodiments of the present invention, a method for removing cesium ions including; removing cesium ions using the aforementioned cesium ion adsorbent is provided.

In exemplary embodiments, the step of removing the cesium ions may be performed in an aqueous solution.

In an exemplary embodiment, the cesium ion removal method, the cesium ion adsorbent M ⁺ OH ^- reproducing and supported on a solution containing a salt represented by may further include (where: M is H , Li, Na, K, Rb or a quaternary amine.).

In example embodiments, the method for removing cesium ions may reach 160 mg/g within 10 minutes based on an initial concentration of 100 ppm.

The present invention will be described in more detail through the following implementation. However, the examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

Example

Cesium ion adsorbent Produce

<Example 1-Preparation of graphene oxide solution>

The graphene oxide solution was synthesized in a form slightly modified from the basic method of Hummer's method of exfoliating graphite by a general solution process. 1 g of graphite (flakes, +100 mesh, Sigma-Aldrich), 1 g of NaNO ₃ (≥99.0%, Sigma-Aldrich), and 50 mL sulfuric acid (ACS reagent grade, 95-98%, Sigma-Aldrich) at room temperature. Stirred. KMnO ₄ (Powder, 97%, Sigma-Aldrich) powder was added in small portions (50 mg/min) to the stirred mixed solution. After the powder was added, the mixed solution was further stirred at 35 degrees for 2 hours. Thereafter, the temperature was lowered to after 5 degrees using an ice bucket, and 20 mL of H ₂ O ₂ (reagent, 30%, JUNSEI) was added, followed by stirring for an additional 30 minutes. The reacted solution was washed in 4% HCl solution, followed by vacuum drying for 24 hours. The graphene oxide powder prepared by the above method was added to 500 mL per 1 g of Deionized H ₂ O, and a graphene oxide dispersion solution was synthesized through ultrasonic dispersion.

<Example 2-Preparation of graphene oxide composite>

After inserting 1.5 mL of the graphene oxide dispersion solution prepared in Example 1 into a 5 mL syringe, the PTFE tube was connected to a 0.5 mm diameter. The graphene oxide dispersion solution was sprayed onto 100 mL of 2wt% NaOH (Ethanol:H ₂ O=1:1) solution at a rate of 0.4 ml/min using a syringe pump. The solidification chamber was rotated at a speed of 140 RPM to maintain the orientation of the graphene oxide structure. This is for spinning the fibers in a smoother form, and spinning was performed in an environment at a constant speed. At too low a speed, no rotation, or an excessively high speed (more than 200 RPM), the uniformity of the fibers may decrease.

The spun fibers were washed in 50 mL 50% Ethanol solution for 5 minutes. It was dried naturally on a Teflon roller for 24 hours and then dried for 3 hours in a vacuum environment at 60°C.

<Example 3-Cesium ion removal experiment>

The graphene oxide composite (carbon fiber) synthesized in Example 2 was dispersed in a CsCl solution at a concentration of 100 ppm and stirred with an aqueous solution at a speed of 250 RPM. After each stirring reaction time, the fiber and the Cs solution were separated, and the difference in Cs concentration was analyzed through ICP-MS analysis.

<Example 4-Regeneration of cesium ion adsorbent>

The carbon fiber used as the Cs ion adsorbent in Example 3 was supported in a 0.1 M NaOH solution for 10 minutes, and the Cs ⁺ ions adsorbed on the carbon fiber surface were replaced with Na ⁺ ions to regenerate the adsorbent function. Thereafter, the regenerated carbon fiber was subjected to a cesium ion control experiment in the same manner as in Example 3, and the cesium removal efficiency was also calculated in the same manner by the same ICP-MS method.

Test example

<Observation of the prepared graphene oxide composite>

It was found through EDS mapping that the synthesized graphene oxide composite (Na-GO) fiber was evenly dispersed on the surface of both graphene oxide, which forms the basic skeleton, and Na ion sites that have functionality for adsorption of cesium ions (Fig. 2a). Reference). In addition, through electron microscopic analysis (SEM image), it was confirmed that this Na-GO fiber was composed of a multilayer structure of graphene oxide exfoliated in two dimensions (see FIG. 2B).

3A to 3C, it was confirmed through X-ray photospectroscopy (XPS) analysis that the hexagonal graphite sp2 carbon structure is maintained in graphene oxide during the fiberization process and oxygen functional groups present at the edge are also maintained. It can be (Fig. 3a and 3b), it can be confirmed the presence of the sodium element that performs the function of adsorption of cesium ions (Fig. 3c).

Specifically, FIG. 3A is a graph showing a graphene oxide structure forming a skeleton on a carbon fiber, and FIG. 3B is a graph showing a C-sp ² pick showing a graphene structure and oxidized functional groups C-OH, C=O, OC= It is a graph showing that the graphene oxide structure is maintained through the presence of the O structure, and FIG. 3C is a graph showing that the Na element on the surface of the graphene oxide complex exists in a monovalent state through a 1071 eV energy wavelength, so that it can be easily ion-substituted in an aqueous solution. It is a graph indicating that it is possible.

<Cesium ion adsorption performance analysis>

It was confirmed that the synthesized Na-GO carbon fiber can very efficiently remove Cs ions present in the aqueous solution. Specifically, referring to the results of the time curve experiment of FIG. 4A, it can be seen that the carbon fiber reaches the saturation point within 10 minutes at the initial concentration of 100 ppm, and shows an adsorption of at most 160 mg/g. After that, it can be seen that the efficiency is shown at 120-130 mg/g and stable adsorption equilibrium (equilibrium) is maintained.

In addition, referring to the Pesudo-second order model matching result of FIG. 4B, Na functional groups present on the carbon fiber surface perform efficient ion substitution with Cs ions present in the aqueous solution, and chemisorptions as the main mechanism It can be seen that this is dominated (physical adsorption will dominate when matching with the Pesudo-first order model).

In addition, referring to Fig. 4c, which is the result of the experiment in which the same cesium ion adsorbent was repeated several cycles, when the cesium ion removal-regeneration cycle was repeated, the cesium removal efficiency did not decrease at all, and the reproducibility was excellent and the adsorption rate was stable. I could confirm that.

<Comparative Example>

Referring to the test example results, the cesium ion adsorbent of the present invention can control cesium ions faster than cesium decontamination materials that have been previously reported in academia (removal efficiency saturation time to 10 minutes, see Table 1 below). . The maximum adsorption capacity is higher than the previously reported graphene oxide-based adsorbent (G0-membrane on CaF ₂ ) or polymer-based adsorbent (PAN-KNiCF) (150-200 mg/g compared to the existing 112-148 mg/g), The Prussian Blue series of materials (PSMGPB, PB NP, Iron Ferrite, Table 1) showed higher reactivity even at an initial concentration (100 ppm cesium solution compared to the existing 100000 ppm or higher). In addition, it can be seen as a material that maximizes the efficiency of conventional adsorbents in that it can be used as a semi-permanent tablet through an easily available NaOH regenerant rather than one-time adsorption.

Qe Ci K _d t mg·g ^-1 ppm mL·g ^-1 h GO-membrane on CaF ₂ ^a 148.0 87.3 - 0.5~32 PSMGPB ^b 213.9 177300 5.0*10 ⁴ 24 PB NP ^c 127.7 13300 1.00*10 6 PAN-KNiCF ^d 110.3 20~240 1.46*10 ⁵ 24 iron ferrite 111.72 133~13300 8.15*10 ² 24 Na-GO fiber 150-200 100 1.64*10 ³ 0.2 Q _e = equilibrium adsorption capacity. C _i = initial Cs+ concentration. C _f = final concentration. E = removal efficiency. t = sorption saturation time
^a CaF ₂ supported by graphene oxide membrane. ^b pectin-stabilized magnetic graphene oxide Prussian blue nanocomposites. ^c Prussian-Blue nano particle. ^d PAN-based potassium nickel hexacyanoferrate (II) composite spheres. ^e Magnetic iron ferrite composite.

In terms of process, when compared with the cesium control agent synthesized using the existing complex processes and samples (KR 10-2013-00003314, KR 10-2018-0037830, KR 10-1992-0014375, KR 10-2013- 0116280) It can be said that it has a great advantage in that it is possible to synthesize a fibrous material through simple wet spinning in a dilute NaOH solution without a separate complicated process.

Claims (9)

As a cesium ion adsorbent,
Including; graphene oxide complex having a hydrophilic group represented by COO ^- M ⁺ ,
M is Li, Na, K, or Rb,
The cesium ion adsorbent is a graphene oxide fiber having a diameter of 100 to 500 µm, a cesium ion adsorbent.
The method of claim 1,
The content of M is 1 to 20% by weight based on the total weight of the graphene oxide composite, cesium ion adsorbent.
delete The method of claim 1,
The graphene oxide composite is characterized in that the two-dimensional multi-layer structure, cesium ion adsorbent.
A method for producing a cesium ion adsorbent according to any one of claims 1, 2 and 4, comprising:
Synthesizing graphene oxide; And
Synthesizing a graphene oxide complex by wet spinning the graphene oxide in a solution containing a salt represented by M ⁺ OH ^- ; Including,
The solution containing the salt represented by M ⁺ OH ^- contains a -OH functional group, a method for producing a cesium ion adsorbent.
(M is Li, Na, K, or Rb)
A method for removing cesium ions comprising; removing cesium ions by using the cesium ion adsorbent according to any one of claims 1, 2, and 4.
The method of claim 6,
The step of removing the cesium ions is characterized in that in an aqueous solution phase, cesium ion removal method.
The method of claim 6,
The cesium ion removal method,
Regenerating by supporting the cesium ion adsorbent in an aqueous solution represented by M ⁺ OH ^- and regenerating; characterized in that it further comprises, cesium ion removal method.
(M is Li, Na, K, or Rb.)
The method of claim 6,
The cesium ion removal method is characterized in that it reaches 160 mg/g within 10 minutes based on an initial concentration of 100 ppm.

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