KR101978499B1 - A adsorbent based on hollow prussian blue magnetic nanoparticles for radioactive cesium, and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a composition for adsorbing radioactive cesium based on magnetic nanoparticles, a method for producing the same, and a method for adsorbing radioactive cesium using the composition, and more particularly, to a method for adsorbing radioactive cesium on a magnetic nanoparticle core, Due to the structural specificity and the large surface area, the coupled magnetic nanoparticles can adsorb radioactive cesium more efficiently and selectively than conventional Prussian blue. Accordingly, the magnetic nanoparticles combined with the Prussian blue particles having the porous structure according to the present invention can be usefully used for the removal of dissolved radioactive cesium such as widely contaminated streams, rivers, lakes, and wetlands.

Description

Technical Field The present invention relates to a composition for adsorbing radioactive cesium based on porous Prussian blue magnetic nanoparticles and a method for producing the same,

The present invention relates to a composition for adsorbing radioactive cesium based on porous Prussian blue magnetic nanoparticles and a method for producing the same. More specifically, the present invention relates to a radioactive cesium-adsorbing composition comprising a magnetic nanoparticle core and a porous blue- And a composition for adsorbing cesium.

March 2011 Fukushima Nuclear Power Plant accident in Japan caused serious environmental problems because soil, flora, fauna and waste were contaminated by radiation. Radioactive iodine and radioactive cesium are the main radioactive materials generated in the accident of a nuclear power plant.

Radioactive iodine has a half-life of about 8 days, whereas radioactive cesium has a half-life of 30 years, which is very long. Cesium is similar in chemical properties to potassium, and when absorbed, it concentrates in muscles and the like, resulting in immunodeficiency and various cancers (infertility, bone cancer, lung cancer, , Breast cancer, etc.), it is necessary to recover radioactive cesium at high efficiency when leaking to the external environment.

In addition, radioactive materials contained in fly ash contained in leachate and exhaust gas such as ash and waste landfill when treated with radioactive waste at an incinerator contain various types of radioactive materials. Radioactive cesium is a major cause of soil and water pollution .

In addition to these nuclear power plant accidents, much effort and expense are required for the safe treatment and management of high level radioactive waste generated at the time of operation of nuclear power plants. Especially, high level radioactive liquid waste contains a large amount of effective components. Is a major contributor to the recycling of high-level radioactive waste as well as strontium. Therefore, when it is recovered and recycled, it is beneficial not only in terms of cost reduction for disposal but also in terms of recycling of resources and also in terms of safety. The radioactive cesium contaminated in soil is in the form of cesium ion (Cs ⁺ ). It is strongly bound to clay, organic matter, and inorganic substances, making it extremely difficult to recover. Radioactive cesium ion contaminated in rivers and oceans is in low concentration There has been a limitation in selective adsorption because it exists.

Until now, natural materials such as zeolite, activated carbon or bentonite having a large surface area have been used for adsorption and removal of radioactive materials from radioactive waste liquids of nuclear power plants, or ion exchange resins, hollow fiber filters or reverse osmosis membranes have been used. However, there is a limitation in selectively adsorbing radioactive waste liquid or cesium distributed at a low concentration in water with high efficiency.

For the selective adsorption of radioactive cesium, a royal blue dye called prussian blue has been used. Prussian blue has been shown to reduce the biological half-life of Cs- ¹³⁷ from 110 days to 30 days as a hydrate of iron ferrocyanide, which has been used in refined cesium exposure to reduce exposure to cesium.

In addition, the Institute of Industrial Technology, an independent administrative agency in Japan, developed Prussian blue nanoparticles showing selective adsorption on cesium, and developed various compositions for adsorbing cesium in high concentration by selectively adsorbing cesium in contaminated water or leachate contaminated with radioactive cesium Respectively. This Prussian blue cesium adsorption mechanism has been known to selectively adsorb cesium hydrate as pores in Prussian blue crystals.

Korean Patent Laid-Open Publication No. 10-2005-120312 (Patent Document 1) discloses a method of adsorbing hexa-cyanophosphorus (II) which is an anion to an anion exchange resin and adsorbing Co, which is a transition metal, ≪ / RTI > capable of selective adsorption of < RTI ID = 0.0 > However, the ion exchanger disclosed in Patent Document 1 has a limitation in selectively adsorbing radioactive waste liquid or cesium distributed at a low concentration in water with high efficiency.

Korean Patent Registration No. 10-1172247 (Patent Document 2) discloses a method for converting radioactive carbon in an ionic form in a radioactive waste solution into radioactive carbon dioxide using an acidic solution, adsorbing the radioactive carbon dioxide in a composition for adsorbing radioactive carbon dioxide, A first decontamination step in which a radionuclide in the first decontamination waste paper and a radionuclide dissociated in the acidic solution in the first decontamination step are treated with supercritical carbon dioxide and a carbon dioxide- A second decontamination step of extracting and removing the complex with the complex (Co, Cs) and the metal substance extraction aid); and a drying step of heating and drying the decontaminated waste paper in the first decontamination step and the second decontamination step A method of decontaminating radioactive wastewater has been proposed. However, the above method is also effective in selectively adsorbing radioactive cesium and adsorbing it with high efficiency There boundaries.

Under these circumstances, the present inventors have made intensive efforts to develop a composition for adsorbing radioactive cesium capable of adsorbing radioactive cesium with high efficiency. As a result, when using magnetic nanoparticles combined with prussian blue particles having a porous structure, It is possible to remove radioactive cesium with high efficiency and high selectivity, thus completing the present invention.

KR publication number: 10-2005-120312 KR registration number: 10-1172247

An object of the present invention is to provide a magnetic nanoparticle core; And porous Prussian Blue bonded to the core. The present invention also provides a composition for adsorbing radioactive cesium.

Another object of the present invention is to provide a method for producing the composition for adsorbing radioactive cesium.

It is still another object of the present invention to provide a method for adsorbing radioactive cesium using the composition for adsorbing radioactive cesium.

In order to achieve the above object, the present invention provides a magnetic nanoparticle core; And porous Prussian Blue bonded to the core. The present invention also provides a composition for adsorbing radioactive cesium.

In addition,

(1) preparing a magnetic nanoparticle core;

(2) adding meso-crystalline prussian blue to an acid solution, and then heating at 100 ° C to 150 ° C to prepare porous prussian blue; And

(3) mixing the magnetic nanoparticle core of the step (1) and the porous prussian blue of the step (2) to prepare a composition for adsorbing radioactive cesium.

In addition,

(1) adding a composition for adsorbing radioactive cesium comprising magnetic nanoparticles bound with porous Prussian blue to a sample contaminated with radioactive cesium; And

(2) recovering the composition for adsorbing radioactive cesium by using the magnetic material in the step (1).

The magnetic nanoparticles having Prussian blue particles having a porous structure according to the present invention can adsorb radioactive cesium with high efficiency and high selectivity compared with Prussian blue due to its structural specificity and large surface area. Accordingly, the magnetic nanoparticles combined with the Prussian blue particles having the porous structure according to the present invention can be usefully used for the removal of dissolved radioactive cesium such as widely contaminated streams, rivers, lakes, and wetlands.

FIG. 1 is a view showing a process for producing Prussian blue-bonded magnetic nanoparticles having a porous structure.
FIG. 2 is a graph showing the results of observation of (A) PDDA-coated iron oxide, (B) mesophase Prussian blue and (C) hollow Prussian blue using a scanning electron microscope (TEM).
3 is a graph showing the results of measurement of Prussian blue-bonded magnetic nanoparticles having (A) a magnetic nanoparticle core and (B) a porous structure using Fourier-transform infrared (FT-IR) to be.
FIG. 4 is a graph showing changes in the color of a sample (right side) when a sample containing (A) porous prussian blue-bound magnetic nanoparticles is treated with a magnet and (B) FIG. 2 is a graph showing the removal efficiency of radioactive cesium removed by Prussian blue-bound magnetic nanoparticles having a cyanide-containing magnetic nanoparticle.

The present invention relates to a magnetic nanoparticle core; And porous Prussian Blue bonded to the core. The present invention also provides a composition for adsorbing radioactive cesium.

Hereinafter, the present invention will be described in detail.

In the present invention, the term " magnetic nanoparticles (MNP) " means a metal nanocomposite having magnetism and may be composed of a metal, a magnetic material, or a magnetic alloy. Materials that can constitute the magnetic nanoparticles may be included without limitation, for example, nanoparticles having a spinel structure or an inverse spinel structure may be magnetic materials.

The magnetic nanoparticle core may be an iron oxide (Fe ₂ O ₃ , Fe ₃ O ₄ ), an alloy (FePt, CoPt) or a ferrite (MnFe ₂ O ₄ , CoFe ₂ O ₄ , NiFe ₂ O ₄ or ZnFe ₂ O ₄ ) Preferably iron oxide, but is not limited thereto.

The magnetic nanoparticle core may have a diameter of 1 nm to 1000 nm, preferably 50 nm to 500 nm, but is not limited thereto.

The magnetic nanoparticle core may be made of polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydiallyldimethylammonium chloride (PDDA), polylysine (PLL) or polydiallyl dimethyl Ammonium (polydiallyldimethylammonium), PDADMA), but is not limited thereto.

In the present invention, the term " prussian blue " refers to a blue pigment whose main component is potassium hexacyanoferrate (II) iron (III) oxide.

The prussian blue may be in the form coated with polyvinylpyrrolidone (PVP), but is not limited thereto.

In the present invention, the term " porous " means that the solid is in the interior or the surface with a lot of small gaps, and the gaps are communicated to the outside. The porous structure may be, for example, mesoporous or hollow hollow structure, but are not limited thereto.

The term " radioactive cesium " in the present invention means cesium 134 and cesium 137, which are radioactive isotopes of cesium. These radioactive cesium is a radioactive substance released into the external environment by the accident of a nuclear power plant and has a half-life of about 2 years and about 30 years, respectively.

The term " adsorption " in the present invention refers to a phenomenon in which molecules of a gas or a solution adhere to a solid surface, and a solid material that receives the adsorption is referred to as an adsorbent. The adsorbent has a wide surface area to be adsorbed per unit volume and functions as an excellent adsorbent. The magnetic nanoparticles having Prussian blue particles having a porous structure according to the present invention can adsorb radioactive cesium with high efficiency and high selectivity compared with Prussian blue due to its structural specificity and large surface area.

In the present invention, the composition may further comprise a magnetic nanoparticle core and a porous prussian blue bonded to the core, as well as other compounds having a radioactive cesium adsorption effect. In addition, the composition may be used in a free form or in a form immobilized on a carrier or the like. The composition may also be used to remove radioactive cesium by immobilizing the composition on a carrier. The method of immobilizing the composition on a carrier or the like is not particularly limited and various applications are possible. For example, chemical methods such as a physical method such as an adsorption method and an inclusion method, a covalent bonding method, and a crosslinking method can be used.

The present invention also provides a process for producing a composition for adsorbing radioactive cesium.

Specifically,

(1) preparing a magnetic nanoparticle core;

(2) adding meso-crystalline prussian blue to an acid solution, and then heating at 100 ° C to 150 ° C to prepare porous prussian blue; And

(3) mixing the magnetic nanoparticle core of the step (1) and the porous prussian blue of the step (2) to prepare a composition for adsorbing radioactive cesium.

The step (1) is a step of manufacturing the magnetic nanoparticle core.

The magnetic nanoparticle core may be an iron oxide (Fe ₂ O ₃ , Fe ₃ O ₄ ), an alloy (FePt, CoPt) or a ferrite (MnFe ₂ O ₄ , CoFe ₂ O ₄ , NiFe ₂ O ₄ or ZnFe ₂ O ₄ ) But is not limited thereto.

The magnetic nanoparticle core may be made of polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydiallyldimethylammonium chloride (PDDA), polylysine (PLL) or polydiallyl dimethyl Ammonium (polydiallyldimethylammonium), PDADMA), but is not limited thereto.

The step of coating the magnetic nanoparticles may be performed at 30 ° C to 150 ° C, preferably at 60 ° C to 100 ° C.

In one embodiment of the present invention, PDDA-Fe ₃ O ₄ coated with polydiallyldimethylammonium chloride (PDDA) Magnetic nanoparticles were prepared. Specific preparation methods are described below in Example 1-1.

The step (2) is a step of thermally treating mesocrystalline Prussian blue with an acid solution to provide porous Prussian blue.

The acid may be sulfuric acid, hydrochloric acid, nitric acid, or a mixture thereof, but is not limited thereto.

The heat treatment may be performed at 100 ° C to 150 ° C, preferably at 130 ° C to 140 ° C.

The porous Prussian blue is characterized by having a hollow or mesoporous structure.

In one embodiment of the present invention, prussian blue and polyvinylpyrrolidone (PVP) were mixed in an acid solution to obtain mesocrystalline prussian blue. The obtained mesophyll Prussian blue was mixed again with polyvinylpyrrolidone (PVP) in an acid solution, and then heat-treated at 135 ° C to obtain Prussian blue having a porous structure. Specific production methods are described in Examples 1-2 and 1-3 below.

In the step (3) , the magnetic nanoparticles prepared in the above step (1) and prussian blue having the porous structure prepared in the step (2) are mixed to form Prussian blue-bonded magnetic nanoparticles .

The weight ratio (g / g) of the magnetic nanoparticles and Prussian blue having a porous structure in the mixing may be 1: 1 to 10, preferably 1: 2 to 5.

In one embodiment of the present invention, the PDDA-coated iron oxide (Fe ₃ O ₄ ) prepared in the step (1) is mixed with prussian blue having a porous structure at pH 6.0 to prepare a prussian blue Magnetic nanoparticles were obtained. Specific production methods are described in Examples 1-4 below.

In addition,

(1) adding to the sample a composition for adsorbing radioactive cesium comprising magnetic nanoparticles bound with porous Prussian blue; And

(2) recovering the composition for adsorbing radioactive cesium by using the magnetic material in the step (1).

The step (1) is a step of adding a composition for adsorbing radioactive cesium containing magnetic nanoparticles bonded with porous Prussian blue to a sample contaminated with radioactive cesium.

In the step (1), the radioactive cesium contained in the sample is adsorbed and removed on a large surface area due to the porous structure of the composition for adsorbing radioactive cesium of the present invention.

The sample of step (1) may be collected from polluted rivers, rivers, lakes, or wetlands where radioactive cesium is dissolved, but is not limited thereto.

The step (1) may be carried out at a pH of from 2.0 to 12.0, preferably at a pH of from 6.0 to 8.0, more preferably at a pH of 7.0.

In one embodiment of the present invention, the degree of adsorption of radioactive cesium was compared at pH 4.0, 7.0, and 10.0, and it was confirmed that the adsorption efficiency was the highest at pH 7.0. As described above, when the radioactive cesium is removed using the radioactive adsorption composition of the present invention, the radioactive cesium can be removed more efficiently by adjusting the pH.

The step (2) is a step of recovering the radioactive cesium adsorbing composition of the step (1) using a magnetic material.

In the step (2), the radioactive cesium-adsorbed composition for radioactive adsorption is recovered to remove radioactive cesium in the sample.

The radioactive adsorption composition of the present invention includes magnetic nanoparticle cores, and the radioactive cesium-adsorbing composition to which radioactive cesium is bound can be easily removed using a magnetic material.

The magnetic material may be, for example, a magnet, but is not limited thereto.

In one embodiment of the present invention, it has been confirmed that magnetic nanoparticles having porous Prussian blue can be easily removed using a magnet as a magnetic substance.

Hereinafter, the present invention will be described in more detail by way of examples. It should be noted, however, that the following examples are provided to further illustrate the present invention and are not intended to limit the scope of the present invention.

Example 1. Preparation of Prussian blue-bonded magnetic nanoparticles having a porous structure

1-1. PDDA-Fe ₃ O ₄  Manufacture of Magnetic Nanoparticle Core

Polydiallyldimethylammonium chloride (PDDA) -Fe ₃ O ₄ magnetic nanoparticle cores were prepared according to a known method (see Jang, SC, Hong, SB, Yang, HM, Lee, KW, Moon , JK, Seo, BK, Huh, YS, Roh, C., 2014. Removal of radioactive cesium using prussian blue magnetic nanoparticles, Nanomaterials 4, 894-901.). Specifically, 20 ml of a solution containing FeCl ₃揃 6H ₂ O (2.16 g), FeCl ₂揃 4H ₂ O (0.8 g) and PDDA (1.0%, v / v) was bubbled in a nitrogen gas for 10 minutes Followed by heating at 80 占 폚. NH ₄ OH (28%) was added rapidly to the heated solution and stirred for 1 hour. After stirring, the solution heated at room temperature was cooled, and the formed PDDA-Fe ₃ O ₄ magnetic nanoparticles were separated in a magnetic field and washed with deionized water for 3 hours to obtain a pure PDDA-coated Fe ₃ O ₄ .

1-2. Manufacture of mesocrystal PB

3.0 g of polyvinylpyrrolidone (PVP) and 131.7 mg of K ₃ [Fe (CN) ₆ ] .3H ₂ O were added to a 0.1M HCl solution and stirred for 1 hour to obtain a clear solution. The obtained solution was heated in an electric oven at 80 DEG C for 20 hours, the precipitate formed using a centrifuge was collected, and washed twice with distilled water and ethanol. After washing, the collected precipitate was dried at room temperature for 12 hours to obtain mesocrystalline prussian blue.

1-3. Preparation of prussian blue with porous structure

20 mg of Prussian blue and 100 mg of PVP were added to a 1.0 M HCl solution in a Teflon vessel and stirred for 1 hour. The Teflon vessel was transferred to a stainless steel autoclave and heated at 135 ° C for 2.5 hours And heated. After heating, the precipitate formed using a centrifuge was collected and washed twice with distilled water and ethanol. Thereafter, the collected precipitate was dried at room temperature for 12 hours to obtain Prussian blue having a hollow structure.

1-4. Preparation of Prussian blue-bound magnetic nanoparticles with porous structure

1 g of the PDDA-coated iron oxide (Fe ₃ O ₄ ) prepared in Example 1-1 was added to 10 ml of distilled water and 0.01 M HCl was added to adjust the pH to 6.0. Then 3 g Prussian blue with a meso crystal or hollow structure was added to the distilled water and 0.01 M NaOH was added to adjust to pH 6.0. The resulting slurry was placed in a 50 ml polypropylene tube and thoroughly mixed at room temperature. 25 ml of distilled water was added to the mixture, and an excessive amount of Prussian blue not reacted with the magnetic nanoparticles was separated using a permanent magnet (1.4 tesla) to prepare functionalized Prussian blue-bound magnetic nanoparticles. FIG. 1 shows a process for preparing Prussian blue-bound magnetic nanoparticles having the porous structure.

Experimental Example 1, Confirmation of Structure and Characteristic of Magnetic Nanoparticle Core and Prussian Blue

The structure and characteristics of the magnetic nanoparticles prepared in Example 1-1 and Prussian blue prepared in Examples 1-2 and 1-3 and having a porous structure were confirmed as follows. The size and shape of the nanoparticles were observed using a transmission electron microscope (TEM) at an acceleration voltage of 300 keV (Tecnai G2 F30, USA). TEM images of (A) PDDA-coated iron oxide, (B) mesocrystalline prussian blue, and (C) hollow prussian blue are shown in FIG.

As shown in FIGS. 1 and 2, the magnetic Prussian blue-bound magnetic nanoparticles were confirmed to have a structure in which a porous Prussian blue was bonded to the surface of a smaller amount of positively charged PDDA-coated iron oxide .

The Fourier transform infrared (FT-IR) spectra of the nanoparticles were also measured using a Thermo Scientific Nicolet iS5 spectrometer, and the results are shown in FIG.

As shown in FIG. 3, a band peak appears at 1472 cm ^-1 due to the presence of PDDA of PDDA-coated iron oxide, and a strong band appears at around 2076 cm ^-1 due to the presence of Prussian blue. In particular, the peak of Prussian blue band with porous structure is higher than the peak of bands of meso-crystalline Prussian blue, so that magnetic nanoparticles combined with prussian blue with porous structure have better absorption capacity for radioactive cesium It is confirmed that the structure is a structure.

Experimental Example  2. Porosity Prussian Blue Combined  Radioactive cesium of magnetic nanoparticles Adsorption rate  Measure

The adsorption rate of the radioactive cesium of the porous prussian blue-bound magnetic nanoparticles prepared in Example 1-4 was measured as follows. First, the porous nanoparticles (2 mg) were added to 10 ml of ¹³⁷ Cs aqueous solution, and then the radioactive cesium ( ¹³⁷ Cs) in the solution before and after the treatment of the nanoparticles with HPGe (High-purity Germanium) ) Was measured. After removing radioactive cesium for 12 hours, the magnetic nanoparticles were removed using a magnetic bar. Table 1 shows the cesium concentration per gram (g) of the added Prussian blue nanoparticles.

Adsorption
Composition concentration
(mg mL ^-1 ) Meso crystal Prussian blue Hollow Prussian blue Before processing
Radioactive intensity
(Bq g ^-1 ) After processing
Radioactive intensity
(Bq g ^-1 ) Adsorption rate
(%) Before processing
Radioactive intensity
(Bq g ^-1 ) After processing
Radioactive intensity
(Bq g ^-1 ) Adsorption rate
(%) 0.2 93.97 4.07 95.67 85.18 0.2 99.77

As shown in Table 1, when the concentration of the adsorbing composition was 0.2 mg mL ^-1, it was 4.07 Bq g ^{-1 137} Cs after treatment at 93.97 Bq g ^{-1 137} Cs before the nanoparticle treatment in the case of mesocrystalline Prussian blue 95.67% adsorption rate). On the other hand, in the case of hollow prussian blue, it was confirmed to be purified at 0.28 Bq g ^{-1 137} Cs (99.77% adsorption rate) after treatment at 85.18 Bq g ^{-1 137} Cs before the nanoparticle treatment.

From the above results, it was confirmed that the Prussian blue particles having a porous structure had a higher cesium adsorption ratio than Prussian blue particles having a mesocrystalline structure due to their high surface absorption ability.

The ability to remove radioactive cesium from porous Prussian blue magnetic nanoparticles can be defined as the adsorption rate (%) and the partition coefficient (K _d ). The distribution coefficient K _d is defined as follows.

Here, C ₀ is the initial cesium concentration before the adsorption composition is treated, C _f is the final cesium concentration after the adsorption composition is treated, V is the volume of the solution, and M is the mass of the adsorption composition used. The radioactivity of 1 g of radioactive cesium is known to be 3.215 × 10 ¹² Bq, and C _{0 =} 2.65 × 10 ^-11 , As a result of calculating the partition coefficient from the experimental values of C _f = 8.087 × 10 ^-14 , V = 10 mL and M = 5 mg, the partition coefficient (K _d ) of the porous prussian blue- × 10 ⁵ mL / g, the values recorded in the reference (Steinhauser, G., Schauer, V., Shozugawa, K., 2013. Concentration of strontium-90 at selected hot spots in Japan. Which is higher than the adsorption partition coefficient of phosphorus blue of 7.3 × 10 ⁴ mL / g.

Experimental Example  3. Porosity Prussian blue  Removal of magnetic nanoparticles and removal of radioactive cesium by pH change

Fig. 4 (A) shows the result of observing the color change when a magnet is attached to the right side of the sample glass bottle containing the porous prussian blue-incorporated magnetic nanoparticles.

As shown in FIG. 4 (A), the porous Prussian blue magnetic nanoparticles were closely adhered to each other by the attraction force in the direction of the magnet, and the blue color of the sample became weaker. As a result, the porous Prussian blue magnetic nanoparticles were easily It can be removed.

The effect of radioactive cesium absorption on the pH of porous Prussian blue magnetic nanoparticles was measured as follows. The conditions for measuring the amount of radioactive cesium absorbed were measured under the conditions as described in Experimental Example 2, at the pH 4, 7, and 10, by the magnetic nanoparticles, and the results were shown in FIG. 4 (B) Respectively.

As shown in Fig. 4 (B), it was confirmed that the magnetic nanoparticles having porous Prussian blue bound exhibited the maximum cesium removal efficiency at pH 7.

According to the experimental results, the developed adsorption composition in which the porous prussian blue particles and the magnetic nanoparticles are combined can efficiently and rapidly remove the radioactive cesium in the solution, It was confirmed that the adsorption composition can be easily removed from the contaminants.

Claims (10)

delete delete delete delete delete delete (1) preparing a magnetic nanoparticle core;
(2) adding meso-crystalline prussian blue to an acid solution, and then heating at 100 ° C to 150 ° C to prepare porous prussian blue; And
(3) mixing the magnetic nanoparticle core of the step (1) and the porous prussian blue of the step (2). 8. The method of claim 7,
Wherein the acid is at least one selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid. (1) a magnetic nanoparticle core; And porous Prussian blue bonded to the core, to a sample having a pH of from 6.0 to pH 8.0; And
(2) recovering the composition for adsorbing a radioactive cesium using the magnetic material in the step (1). delete

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