KR102461840B1 - a Manufacturing method of strontium adsorbent using hydroxyapatite surface modification and adsorbent thereof - Google Patents

Abstract

The present invention provides a manufacturing method of a strontium adsorbent and an adsorbent according thereto, wherein the manufacturing method comprises the steps of: (1) preparing amorphous hydroxyapatite nanoparticles having an unmodified interior; and (2) modifying a surface of the amorphous hydroxyapatite nanoparticles by contacting a metal cation solution containing any one of sodium cations (Na^+), magnesium cations (Mg^(2+)), iron cations (Fe^(3+)), and barium cations (Ba^(2+)) with the amorphous hydroxyapatite nanoparticles. The strontium adsorbent can significantly improve strontium removal efficiency and economic feasibility.

Description

TECHNICAL FIELD [0002] A manufacturing method of strontium adsorbent using hydroxyapatite surface modification and adsorbent thereof

The present invention relates to a strontium adsorbent, and more particularly, to a method for manufacturing a strontium adsorbent capable of greatly improving the removal efficiency and economic efficiency of strontium even in the presence of competing ions, and to a strontium adsorbent according thereto.

In domestic nuclear power plants, clothing such as protective clothing and hats that need decontamination are generated due to contamination by radioactive substances. If radiation above a certain level is detected, they are discarded. used for decontamination. In general, an average of several tons (approximately 5 to 10 tons) of radioactive wastewater is generated per day per power plant. In particular, during the maintenance period, more than 10 times more contaminated laundry than usual is generated, and laundry wastewater is generated in proportion to this. Buildings, equipment, machinery, and structures contaminated with radioactive materials in this way cannot be simply buried or incinerated, but must be decontaminated and cut to remove radioactive materials, and then disposed of in accordance with the provisions of the Atomic Energy Act and the Environment Act. .

This wastewater is treated by evaporation, ion exchange, and adsorption, among which the evaporation method has a disadvantage in that it consumes a lot of energy to treat a vast amount of radioactive liquid waste. In addition, in the method of removing radionuclides in wastewater using an ion exchange resin and a filter, the efficiency of the ion exchange resin and the filter is low due to laundry soap, so they must be exchanged frequently. As a result, the generation of ion exchange resin waste is increasing.

In order to solve the disadvantages of the ion exchange resin method, research on an adsorbent with a high removal rate of radionuclides is in progress. As part of this effort, hydroxyapatite (Ca ₅ (PO ₄ ) ₃ OH) is used to Adsorbents for removing heavy metals or radionuclides present in surface water or groundwater have been introduced. Hydroxyapatite is a mineral known to have the property of exchanging calcium ions (Ca ²⁺ ) with cations in the liquid phase, and is a natural adsorbent ( adsorbent). In particular, it has been reported to be effective in removing strontium ions (Sr ²⁺ ) having the same divalent positive charge as calcium ions and having a similar ion size.

However, in the conventional technique for removing strontium using hydroxyapatite, when other cations are present in the aqueous system, other cations instead of strontium are adsorbed to hydroxyapatite, so the removal efficiency of the target strontium ion can be greatly reduced. . In the end, when other cations are present in the water system, not only a large amount of hydroxyapatite is required, but additional measures may be required because the adsorption efficiency is different depending on the type and concentration of competing cations, thereby lowering economic efficiency. .

Therefore, while improving the problems of the conventional method for removing strontium using hydroxyapatite, especially when hydroxyapatite is used for removing strontium in an aqueous system, the removal of strontium regardless of the presence of competing ions There is an urgent need to develop a strontium adsorbent capable of improving the efficiency.

Republic of Korea Publication No. 2011-0040389 (2011.07.26)

The present invention has been devised to overcome the above problems,

The first object of the present invention is to provide a method for manufacturing a strontium adsorbent capable of significantly improving the removal efficiency and economic efficiency of strontium regardless of the presence of competing ions by modifying the surface of amorphous hydroxyapatite nanoparticles. .

Another object of the present invention is to provide a strontium adsorbent capable of significantly improving the removal efficiency and economy of strontium regardless of the presence of competing ions by modifying the surface of the amorphous hydroxyapatite nanoparticles.

In order to solve the first problem described above, the present invention provides the steps of (1) preparing amorphous hydroxyapatite nanoparticles that are not modified inside, and (2) sodium cations (Na ⁺ ) and magnesium cations in the amorphous hydroxyapatite nanoparticles. (Mg ²⁺ ), iron cation (Fe ³⁺ ), barium cation (Ba ²⁺ ) Strontium comprising the step of modifying the surface of the amorphous hydroxyapatite nanoparticles by contacting a metal cation solution containing any one A method for preparing an adsorbent is provided.

The method for manufacturing a strontium adsorbent according to an embodiment of the present invention may be characterized in that the amorphous hydroxyapatite nanoparticles in step (1) do not contain metal cations therein.

The method for preparing a strontium adsorbent according to another embodiment of the present invention may be characterized in that the step (1) is performed under a basic condition of pH 9 or higher.

The method for producing a strontium adsorbent according to another embodiment of the present invention may be characterized in that the amorphous hydroxyapatite nanoparticles in step (1) are formed by reacting calcium nitride and ammonium phosphate.

In the method for producing a strontium adsorbent according to an embodiment of the present invention, in the step of modifying the surface of step (2), a part of calcium in the amorphous hydroxyapatite nanoparticles is substituted with metal cations and the surface of step (2) The modified hydroxyapatite nanoparticles may be characterized in that the following relation 1 is satisfied.

[Relational Expression 1]

≤ 1.56 1.48 ≤

≤ 1.56

In the method for manufacturing a strontium adsorbent according to another embodiment of the present invention, the metal cation in step (2) may be characterized in that at least one of a magnesium cation (Mg ²⁺ ) and an iron cation (Fe ³⁺ ).

In the method for preparing a strontium adsorbent according to another embodiment of the present invention, the concentration of the metal cation solution in step (2) may be 0.05 M or more.

In addition, in order to solve the second object of the present invention, the surface of the hydroxyapatite nanoparticles whose interior is not modified is a sodium cation (Na ⁺ ), a magnesium cation (Mg ²⁺ ), an iron cation (Fe ³⁺ ), and barium. Cation (Ba ²⁺ ) Provided is a strontium adsorbent whose surface is modified by being partially or completely substituted with at least one metal cation.

The strontium adsorbent according to an embodiment of the present invention may be characterized in that the surface-modified hydroxyapatite nanoparticles satisfy Relational Equation 1 below.

[Relational Expression 1]

≤ 1.56 1.48 ≤

≤ 1.56

In the strontium adsorbent according to another embodiment of the present invention, the surface-modified hydroxyapatite nanoparticles have a hexagonal structure, and the metal cation is a magnesium cation (Mg ²⁺ ) or an iron cation (Fe ³⁺ ) It may be characterized by any one or more of them.

According to the manufacturing method of the strontium adsorbent according to the present invention, a high removal rate for strontium can be exhibited.

Furthermore, according to the method for manufacturing the strontium adsorbent according to the present invention, the adsorption capacity for strontium can be improved despite the presence of competing ions, thereby improving the efficiency and economic efficiency of the purification process for strontium-contaminated aqueous systems.

Furthermore, the adsorbent prepared by the method for manufacturing the strontium adsorbent according to the present invention can improve the removal efficiency of strontium by modifying only the surface of the hydroxyapatite nanoparticles, thereby greatly contributing to process simplification.

1 is a graph showing the adsorption capacity of metal cations according to an embodiment of the present invention.
2 is a graph showing the adsorption capacity according to the concentration of magnesium cations according to an embodiment of the present invention.
3 is a graph showing the results of X-ray diffraction (XRD) analysis of the surface-modified hydroxyapatite nanoparticles according to an embodiment of the present invention.
4 is a graph showing the adsorption capacity of hydroxyapatite nanoparticles before surface modification with magnesium cations and the adsorption capacity of hydroxyapatite nanoparticles after surface modification.
5 is a graph showing the removal rates for non-radioactive and radioactive strontium of hydroxyapatite nanoparticles surface-modified with magnesium cations according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

As described above, despite the excellent adsorption capacity of hydroxyapatite, the conventional technique for removing strontium using hydroxyapatite is effective against strontium ions because other cations are adsorbed to hydroxyapatite instead of strontium when other cations are present in the aqueous system. There was a problem that the removal efficiency was greatly reduced. Therefore, while improving the problems of the above-described conventional method for removing strontium using hydroxyapatite, especially when hydroxyapatite is used for strontium removal in an aqueous system, the removal efficiency of strontium regardless of the presence of competing ions There is an urgent need to develop a strontium adsorbent that can improve the

Accordingly, the present invention relates to the steps of (1) preparing amorphous hydroxyapatite nanoparticles that are not modified inside, and (2) adding sodium cations (Na ⁺ ), magnesium cations (Mg ²⁺ ), and iron to the amorphous hydroxyapatite nanoparticles. To provide a method for producing a strontium adsorbent comprising the step of modifying the surface of the amorphous hydroxyapatite nanoparticles by contacting a metal cation solution containing any one of cations (Fe ³⁺ ) and barium cations (Ba ²⁺ ) A solution to the above-mentioned problem was sought.

Through this, the problems of the conventional adsorbent using hydroxyapatite can be improved, and the adsorption capacity for strontium can be improved despite the presence of competing ions, thereby improving the efficiency and economical efficiency of the strontium purification process.

Step (1) of the present invention is a step of preparing amorphous hydroxyapatite nanoparticles that are not modified inside.

Hydroxyapatite is one of the apatite-based materials and has advantages such as solubility, stability, and low cost. The structure of such hydroxyapatite exhibits stable cation removal ability by maintaining low solubility and high redox conditions after cation substitution.

On the other hand, strontium (Strontium) is a group 2 alkaline earth element with atomic number 38. Strontium in its natural state is not a radioactive element, but strontium-90, an isotope generated from nuclear fission of uranium and plutonium, spreads over a large area during an atmospheric nuclear test or a nuclear power plant accident. It is a hazardous substance that causes In the present invention, strontium is not limited to radioactive strontium, but may be preferably used to remove radioactive strontium.

At this time, it is known that the hydroxyapatite undergoes a substitution reaction between calcium (Ca) in its own structure and other cations present in the solution to efficiently remove strontium through an ion exchange reaction.

Accordingly, the amorphous hydroxyapatite nanoparticles according to the present invention use the above-described ion exchange reaction of calcium of hydroxyapatite and use the amorphous hydroxyapatite nanoparticles that are not modified inside, despite the presence of competing ions. It shows high removal efficiency for strontium.

That is, the present invention is to prevent a decrease in adsorption capacity in the presence of competing ions when conventional hydroxyapatite nanoparticles are used as strontium adsorbents. Similarly, hydroxyapatite nanoparticles with only the surface modified are used.

Specifically, the meaning that the interior of hydroxyapatite is not modified means that the calcium contained in the hydroxyapatite nanoparticles is not substituted with other types of cations, or materials that are directly produced when the hydroxyapatite nanoparticles are first manufactured. This means that it does not include preparing nanoparticles by separately mixing a cationic material for surface modification. For example, when hydroxyapatite nanoparticles are prepared by mixing calcium nitrate and ammonium chloride and the surface is modified with magnesium, magnesium is not mixed together during the initial preparation of nanoparticles, but a separate surface modification process after manufacturing nanoparticles It means to modify only the surface of the hydroxyapatite nanoparticles through Through this, the adsorption efficiency of hydroxyapatite nanoparticles modified to the inside for strontium is about 70%, whereas the adsorption efficiency for strontium of the hydroxyapatite nanoparticles modified only on the surface exceeds 90%, which is remarkably high. Even in the presence of competing ions, the adsorption efficiency for strontium is also increased.

That is, the amorphous hydroxyapatite nanoparticles prepared in step (1) of the present invention may not contain metal cations therein because the interior is not modified, and contain metal cations only on the surface of the hydroxyapatite.

In addition, in the present invention, nano-sized hydroxyapatite particles capable of securing an adsorption space for strontium by increasing a specific surface area capable of reacting with strontium in order to efficiently remove strontium are used. That is, according to one embodiment of the present invention, the size of the hydroxyapatite nanoparticles is 20 to 30 nm, and may be amorphous without taking a specific shape.

In addition, in the present invention, amorphous hydroxyapatite nanoparticles are used, but 'amorphous' means particles with a relatively low crystallinity of hydroxyapatite nanoparticles, and has a higher specific surface area than 'crystalline' particles with relatively high crystallinity It is possible to improve the adsorption efficiency by providing an adsorption space.

In order to synthesize such nano-sized hydroxyapatite, as the amorphous hydroxyapatite nanoparticles, a material for preparing general atypical hydroxyapatite nanoparticles capable of providing calcium and phosphorus, respectively, may be used, and a non-limiting example thereof is calcium. As the source, Ca(NO ₃ ) ₂ ·4H ₂ O, CaCl ₂ and the like may be used, and as the source of phosphorus, NH ₄ H ₂ PO ₄ , K ₂ HPO, etc. may be used. At this time, preferably calcium nitride and ammonium phosphate may be formed by reaction, and more preferably Ca(NO ₃ ) ₂ .4H ₂ O and NH ₄ H ₂ PO may be used as a source of calcium and phosphorus.

In this case, as the solvent in which the calcium and phosphorus sources can be mixed, a general solvent suitable for the purpose of preparing the hydroxyapatite nanoparticles may be used, and ultrapure water may be used as a non-limiting example thereof.

In addition, in the mixed solution, the calcium source, the phosphorus source and the solvent may be mixed in a molar ratio of 0.10 to 0.15: 0.05 to 0.10: 20 to 25, and for the purpose of the present invention, the role of the calcium source and the phosphorus source and the preparation of hydroxyapatite nanoparticles. It is not particularly limited as long as it conforms.

Thereafter, the prepared mixed solution is stirred in a conventional manner and separated and dried to prepare hydroxyapatite nanoparticles. In this case, step (1) may be performed under basic conditions for the preparation of amorphous hydroxyapatite nanoparticles having a relatively low crystallinity, and preferably at a basic condition of pH 9 or higher. If the amorphous hydroxyapatite nanoparticles are prepared at a pH of less than 9, there may be a problem in that the incident formation rate is too slow or crystalline particles having a low specific surface area are formed.

Next, in step (2) of the present invention, the amorphous hydroxyapatite nanoparticles are brought into contact with a metal cation solution containing any one of sodium cation, magnesium cation, iron cation, and barium cation to contact the surface of the amorphous hydroxyapatite nanoparticles. The step of reforming is the step of forming.

In this case, the step of modifying the surface of step (2) may be a step in which a portion of calcium in the amorphous hydroxyapatite nanoparticles is replaced with a metal cation.

The metal cation may be a general metal cation that may be substituted with the surface calcium of the hydroxyapatite nanoparticles, and preferably may be at least any one or more of a sodium cation, a magnesium cation, an iron cation, and a barium cation.

Meanwhile, FIG. 1 is a graph showing the adsorption capacity for strontium after replacing the surface of the hydroxyapatite nanoparticles with metal cations according to an embodiment of the present invention. As can be seen from FIG. 1 , the adsorption efficiency of hydroxyapatite nanoparticles without surface modification on strontium was only 85.7%, but in the case of hydroxyapatite nanoparticles surface-modified with sodium and barium cations, 89.7%, respectively. and 91.4%. Furthermore, hydroxyapatite nanoparticles surface-modified with iron cations have an adsorption capacity of 95.5%, and further, hydroxyapatite nanoparticles surface-modified with magnesium cations have the best adsorption capacity of 96.7%.

Accordingly, the metal cation that can be substituted with the surface calcium of the hydroxyapatite nanoparticles may be at least one of a magnesium cation and an iron cation, and most preferably a magnesium cation.

In this case, the hydroxyapatite nanoparticles surface-modified with the metal cation may satisfy Relational Equation 1 below.

[Relational Expression 1]

≤ 1.56 1.48 ≤

≤ 1.56

The substituted metal cation in Relation 1 means the total content of surface-modified metal cations such as sodium cation, magnesium cation, iron cation, and barium cation and calcium cation present on the surface of the hydroxyapatite nanoparticles, The phosphorus (Phosphorus) means the content of the surface of the hydroxyapatite nanoparticles derived from the artificial source in step (1) described above.

In this case, if the value of Relation 1 is less than 1.48, there may be a problem that the particle structure is collapsed or changed, and if it exceeds 1.56, it can be considered that the desired surface modification is not sufficiently performed.

In addition, as the method for modifying the surface of the amorphous hydroxyapatite nanoparticles, a conventional surface modification method suitable for the purpose of preparing the amorphous hydroxyapatite nanoparticles for strontium removal of the present invention may be used, and preferably hydroxyapatite nanoparticles A method of bringing the apatite nanoparticles into contact with a solution containing the metal cation may be used. As a non-limiting example, hydroxyapatite nanoparticles having a surface-modified surface with the metal cation may be obtained by dissolving the metal cation solution through a salt bound to chlorine (Cl), followed by stirring and centrifugation.

Meanwhile, FIG. 2 is a graph showing the adsorption capacity according to the concentration of magnesium cations surface-modified of the hydroxyapatite nanoparticles according to an embodiment of the present invention. As can be seen from Figure 2, the concentration of the metal cation may be 0.05 M to 5 M, preferably 0.05 M to 1.5 M. If the concentration of magnesium cations surface-modified with hydroxyapatite nanoparticles is 0.05 M or less, there may be a problem in that the amount of magnesium required for surface modification is not sufficient.

In this case, a method of immersing the hydroxyapatite nanoparticles in a solution containing the metal cations may be used for surface modification of the hydroxyapatite nanoparticles into metal cations, and a known solvent suitable for the purpose of removing strontium of the present invention may be used.

As described above, according to the manufacturing method of the strontium adsorbent according to the present invention, a high removal rate for strontium can be exhibited, and the adsorption capacity for strontium can be improved despite the presence of competing ions, so that the efficiency of the purification process for strontium-contaminated water systems and Economic efficiency can be improved at the same time.

Next, the strontium adsorbent will be described.

In the strontium adsorbent according to the present invention, the surface of the hydroxyapatite nanoparticles that are not modified inside is a sodium cation, a magnesium cation, an iron cation, and a barium cation. The surface is modified by being partially or completely substituted with at least one metal cation.

Hereinafter, in order to avoid duplication, parts having the same technical idea in the above-described manufacturing method of the strontium adsorbent will be replaced with the description of the manufacturing method.

3 is a graph showing the results of X-ray diffraction analysis after surface modification of the amorphous hydroxyapatite nanoparticles according to the present invention with each metal cation, and Table 1 below shows the analysis results using inductively coupled plasma emission spectroscopy.

Referring to Table 1, as a result of surface-modifying the amorphous hydroxyapatite nanoparticles according to the present invention with each metal cation, it can be seen that the value of Relation 1 is 1.48 to 1.56. From this, it can be seen that the crystal structure of hydroxyapatite is maintained as a hexagonal structure even after surface modification.

Referring to FIG. 3 , in contrast to the case in which the amorphous hydroxyapatite according to the present invention is modified with a sodium cation or a barium cation, when the amorphous hydroxyapatite is modified with a magnesium cation and an iron cation, the cations are partially substituted with calcium on the surface of the amorphous hydroxyapatite, and the unit It can be seen that the height of the grid is decreased.

As described above, in the strontium adsorbent according to the present invention, the surface of the hydroxyapatite nanoparticles whose interior is not modified is partially or completely substituted with at least one metal cation selected from sodium cation, magnesium cation, iron cation, and barium cation, so that the surface is modified. Preferably, it may be at least one of a magnesium cation and an iron cation, and most preferably a magnesium cation.

In this case, as described in Table 1, the hydroxyapatite nanoparticles surface-modified with the metal cation may satisfy Relational Equation 1 below.

[Relational Expression 1]

≤ 1.56 1.48 ≤

≤ 1.56

On the other hand, as described above, hydroxyapatite undergoes a calcium substitution reaction, in which case there are two positions at which calcium can be substituted. That is, the first adsorption site (Ca-1) and the second adsorption site (Ca-2) exist, and the adsorption capacity may be different for each position.

4 is a graph showing isothermal adsorption lines of the Bi-Langmuir model in which the adsorption sites of hydroxyapatite nanoparticles were selected as Ca-1 and Ca-2 two places, and Table 2 shows adsorption capacity according to adsorption positions before and after surface modification. .

Referring to FIG. 4 , it can be seen that the isothermal adsorption line of hydroxyapatite according to the present invention before and after surface modification behaves according to the Bi-Langmuir model.

Also, referring to Table 2, it can be seen that the adsorption capacity for strontium is improved at both the first adsorption site (Ca-1) and the second adsorption site (Ca-2) compared to before reforming, and in particular, the adsorption affinity for strontium It can be seen that the adsorption capacity of the position at the first adsorption site (Ca-1) with high adhesive affinity was greatly improved.

As described above, according to the strontium adsorbent according to the present invention, a high removal rate for strontium can be exhibited, and furthermore, the adsorption capacity for strontium can be improved despite the presence of competing ions, thereby improving the efficiency and economy of the purification process for strontium-contaminated aqueous systems. can be improved

Hereinafter, the present invention will be described in more detail through examples, but the following examples are not intended to limit the scope of the present invention, which should be construed to aid understanding of the present invention.

[Example 1] - Preparation of hydroxyapatite nanoparticles

In order to synthesize amorphous hydroxyapatite nanoparticles, 0.668 M Ca(NO ₃ ) ₂ .4H ₂ O 200ml is prepared and then NH ₄ OH is injected to adjust the pH to a basic condition of 9. Then, 200ml of 0.4 M NH ₄ H ₂ PO ₄ solution is injected into the solution at a flow rate of 1 mL/min for 200 minutes, and in this process, NH ₄ OH is used to maintain the pH of the mixed solution to be 9 or higher.

Then, the mixture is stirred for 72 hours or more, and the hydroxyapatite nanoparticles produced therefrom are recovered through centrifugation, washed with ultrapure water, and dried.

After quantifying 500 mg of hydroxyapatite nanoparticles for surface modification of the synthesized hydroxyapatite nanoparticles, 50 mL of a 0.1 M magnesium cation solution in which MgCl ₂ salt is dissolved in ultrapure water is added. Thereafter, the cation solution is dissolved in a salt bound to chlorine and stirred for 24 hours through a magnetic stirrer, then the particles are recovered by centrifugation, washed and dried, the inside is not modified and a part of the surface is modified with sodium cation. Loxiapatite nanoparticles were prepared.

[Example 2]

It was prepared in the same manner as in Example 1, but hydroxyapatite nanoparticles were prepared using iron, not magnesium, as a metal cation.

[Example 3]

It was prepared in the same manner as in Example 1, except that barium, not magnesium, was used as a metal cation, and then, hydroxyapatite nanoparticles were prepared using a barium salt combined with NO ₃ and not chlorine for preparing a cation solution.

[Example 4]

It was prepared in the same manner as in Example 1, but hydroxyapatite nanoparticles were prepared using sodium, not magnesium, as a metal cation.

[Examples 5 to 9]

Hydroxyapatite nanoparticles were prepared in the same manner as in Example 1, except that the concentration of magnesium cations was changed to 0.5 M, 1.0 M, 2.0 M, and 4.0 M, respectively.

[Comparative Example 1]

It was prepared in the same manner as in Example 1, except for the step of modifying the surface of the hydroxyapatite nanoparticles to prepare hydroxyapatite nanoparticles.

[Experimental Example 1]

To check the adsorption efficiency of metal cations, 100 mg of the hydroxyapatite nanoparticles prepared according to Examples 1 to 4 were reacted with 20 mL of a 10 ppm strontium solution for 24 hours, and then the concentration of strontium cations remaining in the solution was measured. It was measured by Atomic Absorption Spectrometry (AAS) and is shown in FIG. 1 .

Referring to FIG. 1 , in Comparative Example 1, the adsorption efficiency for strontium was only 85.7%, but in the case of the hydroxyapatite nanoparticles of Examples 4 and 3 in which the surface was modified with sodium and barium cations, 89.7%, respectively. and 91.4%. Furthermore, the hydroxyapatite nanoparticles of Example 2, whose surface was modified with iron cations, had an adsorption capacity of 95.5%. It can be seen that it has the best adsorption capacity.

[Experimental Example 2]

In order to confirm the adsorption efficiency according to the concentration of magnesium, the hydroxyapatine nanoparticles prepared according to Examples 5 to 9 were tested as in Experimental Example 1 using a 250 ppm strontium solution, and this is shown in FIG. 2 . .

Referring to FIG. 2 , the adsorption capacity of Comparative Example 1 was only 11.47 mg/g, but in the case of Example 1, it increased by about two times to 24 mg/g, and the amount of Mg ²⁺ in Example 1 was 10.82 μg/g/g. g was detected. In the case of Example 5, the adsorption capacity was slightly increased to 27 mg/g, and the Mg ²⁺ content was also 15.22 μg/g.

In the case of Example 9, in which the surface was modified with a maximum of 4M magnesium, the adsorption capacity was 30.01 mg/g, and the Mg ²⁺ content was measured to be 18.21 μg/g. From this, it can be seen that when the surface is modified with 0.1M magnesium, the adsorption capacity is increased by about two times compared to before the modification, and the adsorption capacity also increases as the concentration of magnesium is increased, but 30 mg/g is expected to be the maximum value. In addition, it can be seen that the Mg ²⁺ content of the surface-modified hydroxyapatite examples increased as the concentration of magnesium used during the modification increased, indicating that the higher the adsorption capacity, the greater the Mg ²⁺ content.

[Experimental Example 3]

In order to confirm the degree of surface modification of the metal cations, the hydroxyapatite nanoparticles prepared in Examples 1 to 4 were analyzed through X-ray diffraction (XRD), and the results are shown in Table 1 and FIG. 3 below. It was.

Exchanged cation Ca ²⁺ (mol) Cation (mol) P (mol) (Ca ²⁺ +cation)/P Exchange efficiency (%) Comparative Example 1 41 - 26 1.56 0 Example 1 30 0.91 20 1.55 2.96 Example 2 25 5.48 20 1.52 17.87 Example 3 33 1.21 23 1.49 3.52 Example 4 34 0.25 22 1.56 0.73

Referring to Table 1, as a result of surface-modifying the amorphous hydroxyapatite nanoparticles according to the present invention with each metal cation, as shown in Relation 1 above, the sum of calcium cations and substituted metal cations (Cation) and the ratio of phosphorus (Phosphorus) It can be seen that this represents 1.48 to 1.56. From this, it can be seen that the crystal structure of hydroxyapatite is maintained as a hexagonal structure even after surface modification.

Next, referring to FIG. 3, as shown in FIG. 3a, most of the peak positions were confirmed to have slightly different values for each type of cation used for surface modification. In order to find a more accurate peak position, the corresponding spectra were fitted with a Voight function (FIG. 3b).

The peak of Comparative Example 1 was derived to be 25.868 °, the peaks of Examples 3 and 4 were the same as before surface modification, but in Examples 1 and 2, the peak increased to the right by approximately 0.02-0.05 °. The unit lattice value of the measured characteristic peak is (a,b,c=0,0,2), which means d-space in the height direction. From this, Examples 3 and 4 showed little change in the surface structure of the modified hydroxyapatite nanoparticles, but in Examples 1 and 2, the corresponding cations were partially substituted with Ca ²⁺ on the surface of the hydroxyapatite nanoparticles. It can be seen that the height of the apatite nanoparticle unit cell was slightly decreased.

[Experimental Example 4]

In order to measure the adsorption capacity of the hydroxyapatite nanoparticles prepared according to Example 1 and Comparative Example 1, an adsorption isotherm experiment was performed, and the result is a Langmuir-model expressed by the following Relational Equation 2 4 and Table 3 below.

[Relational Expression 2]

Adsorbent Q _Ca1 (mg/g) k _Ca1 Q _Ca2 (mg/g) k _Ca2 Comparative Example 1 4.33 0.202 32.46 0.005 Example 1 15.22 0.327 49.47 0.002

4 and Table 2,

As shown in FIG. 4 , it can be seen that the isothermal adsorption line of Comparative Example 1 and Example 1 behaves according to the Bi-Langmuir model.

In addition, referring to Table 2, it can be seen that compared to Comparative Example 1, the hydroxyapatite nanoparticles according to Example 1 have relatively excellent adsorption capacity at both the first adsorption site (Ca-1) and the second adsorption site (Ca-2). In particular, it can be seen that the adsorption capacity at the first adsorption position (Ca-1) is measured at 15.22 mg/g, which is about 3.5 times higher than that of Comparative Example 1. Also, in the second adsorption position (Ca-2), the adsorption capacity was increased by 17.01 mg/g compared to Comparative Example 1.

[Experimental Example 5]

In order to confirm the adsorption capacity of the hydroxyapatite nanoparticles prepared according to Example 1 and the hydroxyapatite nanoparticles prepared according to Comparative Example 1, respectively, non-radioactive 1 ppm strontium and 9,500 Bq/L radioactive strontium were added to each of the competing ions. After evaluation according to Experimental Example 1 under the existing groundwater conditions (Na ⁺ :125 ppm, Ca ^2+: 25 ppm, Mg ²⁺ : 10 ppm, K ⁺ : 5 ppm), it is shown in FIG. 5 .

Referring to FIG. 5 , in the case of Example 1 in which the surface was modified, the non-radioactive strontium showed a strontium removal rate of 86.8% based on a solid to liquid ratio (S/L ratio) of 5 g/L, 10 When increasing to g/L, the removal rate was 93.6%. However, in Comparative Example 1, where the surface was not modified, a removal rate of 45% based on 5 g/L was exhibited, and when it was increased to 10 g/L, a removal rate of 51% was exhibited. It was confirmed that the hydroxyapatite nanoparticles according to Example 1 could effectively remove strontium.

In addition, the initial radioactivity of the radioactive strontium removal experiment was measured to be 9,500 Bq/L, and in Comparative Example 1 where the surface was not modified, the radioactivity after 1 hour of reaction was 3,316 Bq/L at high/liquid ratio 5g/L, and 2,277 at 10g/L. On the other hand, it decreased to 699 Bq/L and 283 Bq/L, respectively, in the case of Example 1 in which the surface was modified. If this is calculated as the decontamination efficiency, it reached only 66 ~ 77% before surface modification, whereas it reached 93 ~ 97% after surface modification. Confirmed.

Claims (10)

(1) preparing amorphous hydroxyapatite nanoparticles that are not modified inside; and
(2) A metal cation solution containing any one of a sodium cation (Na ⁺ ), a magnesium cation (Mg ²⁺ ), an iron cation (Fe ³⁺ ), and a barium cation (Ba ²⁺ ) in the amorphous hydroxyapatite nanoparticles A method for producing a strontium adsorbent comprising the step of modifying the surface of the amorphous hydroxyapatite nanoparticles by contacting the
According to claim 1,
The method for producing a strontium adsorbent, characterized in that the amorphous hydroxyapatite nanoparticles in step (1) do not contain metal cations therein.
According to claim 1,
Step (1) is a method for producing a strontium adsorbent, characterized in that it is carried out in a basic condition of pH 9 or higher.
According to claim 1,
The method for producing a strontium adsorbent, characterized in that the amorphous hydroxyapatite nanoparticles in step (1) are formed by reacting calcium nitride and ammonium phosphate.
According to claim 1,
In the step of modifying the surface of step (2), a portion of calcium of the amorphous hydroxyapatite nanoparticles is substituted with a metal cation,
The method for producing a strontium adsorbent, characterized in that the surface-modified hydroxyapatite nanoparticles in step (2) satisfy Relational Equation 1 below.
[Relational Expression 1]
1.48 ≤

≤ 1.56
According to claim 1,
In step (2), the metal cation is a magnesium cation (Mg ²⁺ ) or an iron cation (Fe ³⁺ ).
According to claim 1,
The method for producing a strontium adsorbent, characterized in that the concentration of the metal cation solution in step (2) is 0.05 M or more.
The surface of the non-modified hydroxyapatite nanoparticles is sodium cation (Na ⁺ ), magnesium cation (Mg ²⁺ ), iron cation (Fe ³⁺ ), barium cation (Ba ²⁺ ) A strontium adsorbent whose surface is modified by being partially or completely substituted with at least one metal cation.
9. The method of claim 8,
The surface-modified hydroxyapatite nanoparticles satisfy Relational Equation 1 below.
[Relational Expression 1]
1.48 ≤

≤ 1.56
9. The method of claim 8,
The surface-modified hydroxyapatite nanoparticles have a hexagonal structure,
The metal cation is a strontium adsorbent, characterized in that at least one of a magnesium cation (Mg ²⁺ ) and an iron cation (Fe ³⁺ ).

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