KR20180032337A - Titanosilicates absorbants substituted tetravalance cation - Google Patents

Abstract

The present invention provides a titanosilicate-based absorbent, which comprises niobium (Nb) and having a structure into which a tetravalent cation is introduced. The titanosilicate into which the tetravalent cation is introduced according to the present invention is capable of efficiently adsorbing strontium including Nb, and replaces a part of silicon (Si) contained in the skeleton of the titanosilicate with the tetravalent cation such as germanium (Ge) or tin (Sn) to increase the number of bonds to cesium. As compared with the known titanosilicate, the titanosilicate-based absorbent of the present invention has high selectivity and adsorptivity to cesium and has a high thermal and chemical stability due to reduced structural distortion, thereby being effectively used as an adsorbent for removing radionuclides.

Description

TECHNICAL FIELD [0001] The present invention relates to a titanosilicate-based adsorbent to which tetravalent cations are introduced {Titanosilicates absorbants substituted tetravalance cation}

The present invention relates to titanosilicates capable of effectively removing strontium, cesium and the like by introducing tetravalent cations and thus being used as an adsorbent for removing radionuclides.

In recent years, due to the excellent economics of nuclear energy around the world, a large number of nuclear power plants have been constructed and used for power generation, and the number is increasing.

However, human life and safety are threatened by radioactive pollutants that can be released due to a large amount of radioactive waste inevitably generated during the operation of a nuclear power plant and accidents occurring accidentally.

For example, a recent major earthquake and tsunami triggered a major nuclear accident in Fukushima, Japan, where a large number of radioactive materials were generated and leaked to nearby areas. A large amount of seawater used to cool the exploded nuclear reactors Radioactive nuclides containing radioactive nuclides are generated and polluted the surrounding soil and the sea to cause serious environmental problems.

Since Korea is also highly dependent on nuclear energy and nuclear power plants are concentrated in the East Sea coast, it is impossible to exclude the possibility of nuclear accidents caused by natural disasters such as earthquakes and tsunamis. There is a growing demand for a method for treating cooling water containing radionuclides. In particular, it is urgently required to develop a technique for efficiently separating and removing radionuclides from a liquid radioactive waste solution.

In general, most of the low- and mid-level radioactive wastes generated in the nuclear industry are composed of heavy and long-term radionuclides such as ⁶⁰ Cs, ¹³⁷ Cs or ⁹⁰ Sr and large non-radioactive species such as Na, K and B, .

In particular, ¹³⁷ Cs is one of the most abundant radionuclides present in radioactive liquid wastes. Its half-life is very long, about 30 years, and its solubility is very high. It is one of the most important nuclides in radioactive waste disposal. It has chemically similar properties to potassium (K) and is known to cause serious damage to human health and the environment because it is readily absorbed by living organisms. Treatment issues such as separation or removal of Cs exhibiting such properties have been of constant interest.

At present, the treatment of medium- and low-level radioactive liquid wastes generated in the nuclear power industry in Korea is different not only in different power plants but also in different treatment processes depending on the characteristics of the wastes. Basically, it is evaporated and concentrated using a waste liquid evaporator, Is used as a solidifying agent to solidify and treat waste.

However, this method is very effective for concentration of waste, but it is required to consume all the solids without discrimination between the nuclides and non-nuclides, thereby lowering the weight loss effect and requiring a lot of operation cost due to heat treatment. In the evaporator, The performance of the evaporator is deteriorated and the operation cost is increased due to frequent maintenance. In addition, there is a problem in that the continuous operation is hindered. Therefore, a study on a method of treating a radioactive waste solution that can solve such problems is actively conducted .

Recently, a variety of inorganic ion exchangers, such as zeolite, titanosilicate, metal oxide, hexacyanoferrate, modified or synthetic clays, The present invention relates to a treatment agent for a radionuclide contained in a radioactive waste solution.

In particular, studies have been conducted on titanosilicate inorganic adsorbents composed of titanium and silica skeleton having excellent performance for cesium removal under various conditions, and they are known to be the most excellent substances for removing cesium, a radioactive species, until now .

Also, a description has been given of a method for improving the adsorption performance of the titanosilicate-based inorganic adsorbent through post-treatment such as acid treatment or base treatment of the titanosilicate inorganic adsorbent.

However, in order to increase the efficiency of the titanosilicate-based inorganic adsorbent, the technical contents of titanosilicate-based adsorbents having improved performance and high selectivity and adsorptivity to radionuclides due to the introduction of new cations, especially tetravalent cations into the skeleton, No research is needed.

Korean Patent Laid-Open No. 10-2012-0003319 (published on Jan. 10, 2012) Korean Patent Publication No. 10-2010-0110997 (published on October 14, 2010)

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made in order to solve the problems of the prior art as described above, and it is an object of the present invention to provide a titanosilicate-based adsorbent capable of effectively adsorbing radioactive nuclides by introducing tetravalent cations into the skeleton of titanosilicate, Technology contents.

Technical Solution In order to accomplish the above object, the present invention provides a titanosilicate-based adsorbent having niobium-incorporated tetravalent cations.

The tetravalent cation is characterized by being at least one selected from germanium tetravalent cation and tin tetravalent cation.

The titanosilicate-based adsorbent having the tetravalent cation introduced therein is characterized in that the tetravalent cation is introduced at a substitution rate of 5 to 30%.

The present invention also provides a method for preparing a titanosilicate having a tetravalent cation introduced therein, comprising the steps of: (a) mixing titanium isopropoxide (TTIP) with tetraethyl orthosilicate (TEOS ) And a second mixed solution containing sodium hydroxide (NaOH), niobium oxide and tetravalent cation oxide to prepare a third mixed solution; And (b) heating the third mixed solution to prepare a crystallized titanosilicate. The present invention also provides a method for producing a titanosilicate having a tetravalent cation introduced therein.

The titanosilicate introduced with the quadrivalent cation of the present invention can efficiently absorb strontium including niobium (Nb), and a part of silicon (Si) contained in the skeleton of titanosilicate can be substituted with germanium (Ge) or tin Sn), the number of bonds to cesium is increased. As compared with the titanosilicate known in the art, not only the selectivity and adsorption ability to cesium are high but also the structural distortion is reduced and the thermal and chemical stability is high It can be effectively used as an adsorbent for removing radionuclides.

1 is a process diagram showing a process for producing a titanosilicate into which a tetravalent cation is introduced by the method according to the first embodiment.
Fig. 2 shows X-ray diffraction analysis results of titanosilicates prepared by the method according to Example 1 and Example 2 and having tetravalent cations introduced therein.
FIG. 3 shows the results of measurement of cesium removal rates of titanosilicates prepared by the method according to Example 1 and Example 2 and titanosilicate introduced with tetravalent cations and titanosilicate prepared according to the method according to Comparative Example.

Hereinafter, the present invention will be described in detail.

The present invention provides a titanosilicate-based adsorbent comprising niobium and having a structure in which a tetravalent cation is introduced.

The quaternary cation-introduced titanosilicate has a structure containing niobium and contains titanium and silicon. The quaternary cation has a structure in which a part of silicon (Si) contained in the titanosilicate is replaced with a tetravalent cation, The adsorbing ability is high and cesium can be effectively adsorbed. The niobium can absorb high activity of the radioactive nuclear species strontium, and the titanosilicate having the tetravalent cation structure of the present invention can effectively adsorb strontium and niobium.

The tetravalent cation to be introduced into the structure of the titanosilicate is preferably a tetravalent cation which is stable at four coordinates and is larger in ionic radius than the silicon (Si) contained in the titanosilicate structure. The tetravalent cation is preferably a germanium tetravalent cation, Tin tetravalent cations are representative examples of the titanosilicate, which may contain tetravalent cations or contain germanium tetravalent cations or tin tetravalent cations, respectively, at the same time.

More specifically, the titanosilicate-based adsorbent to which the tetravalent cation is introduced is a tetonisilicate-based adsorbent that introduces quadrivalent cations having a large ion radius into the titanosilicate having a structure including titanium and silicon, instead of silicon, When the cesium having a large ionic radius is ion-exchanged, the number of bonds to cesium increases, and at the same time, structural torsion is reduced, and thus, it is thermally and chemically stable.

Accordingly, the titanosilicate-based adsorbent of the present invention having tetravalent cations as described above can efficiently adsorb strontium including niobium (Nb), and can adsorb a part of silicon (Si) contained in the skeleton of titanosilicate Is substituted with tetravalent cations such as germanium (Ge) or tin (Sn), the number of bonds to cesium contained in the radioactive waste solution is increased, and the selectivity and adsorptivity to cesium are high as compared with the titanosilicate known in the art , It is possible to effectively use it as an adsorbent for removing radionuclides because of its high thermal and chemical stability due to reduced structural distortion.

In addition, the titanosilicate into which the tetravalent cation is introduced can introduce tetravalent cation at a substitution rate of 5 to 30% and exhibit high selectivity and adsorptivity for cesium contained in the radioactive waste solution.

The tetravalent cation-introduced titanosilicate is prepared by (a) mixing a first mixed solution containing titanium isopropoxide (TTIP) and tetraethyl orthosilicate (TEOS) and a first mixed solution containing sodium hydroxide (NaOH), a niobium oxide and a tetravalent cation oxide to prepare a third mixed solution; And (b) heating the third mixed solution to prepare a crystallized titanosilicate.

In the step (a), mixing a precursor for producing titanosilicate having a tetravalent cation introduced therein is a step of mixing a first mixed solution containing titanium isopropoxide and tetraethyl orthosilicate, a first mixed solution containing sodium hydroxide, And the second mixed solution containing the tetravalent cation oxide may be mixed to prepare the third mixed solution.

The tetravalent cation oxide can be constituted by adding a tetravalent cation oxide including germanium (Ge) or tin (Sn) to produce a titanosilicate into which tetravalent cation is introduced in a step to be described later.

Titanium isopropoxide and tetraethyl orthosilicate contained in the first mixed solution may be mixed in a ratio of 10: 1 to 1:10, and a crystallization reaction may be induced in a step to form a titanosilicate skeleton And preferably in a ratio of 5: 1 to 1: 5.

In the case of the second mixed solution, niobium oxide and tetravalent cation oxide, which are added to an aqueous solution of sodium hydroxide, are mixed in a ratio of 1: 1 to 1:10 to prepare titanosilicate containing niobium (Nb) having high strontium adsorption capacity (Si) contained in the skeleton of the carbon nanotubes is replaced with tetravalent cations and the titanosilicate having improved cesium adsorption ability can be produced according to an increase in the number of bond coordination to cesium contained in the radioactive waste solution, 1: 2 to 1: 5.

At this time, the addition amount of the tetravalent cation oxide is set to be in the range of 1 to 20 wt% based on the total weight of the second mixed solution, thereby improving the adsorption capacity of the titanosilicate introduced with the tetravalent cation introduced in the subsequent step And preferably 1 to 10% by weight, based on the total weight of the composition.

The reason for limiting the addition amount in this way is that when the substitution amount of the tetravalent cation in the titanosilicate skeleton is too large, the titanosilicate may not be synthesized or an undesired impurity may be synthesized. When the substitution amount of the tetravalent cation in the titanosilicate skeleton is too small The selectivity to radioactive cesium is lowered, so that the adsorption capacity of the titanosilicate introduced with the tetravalent cation introduced by regulating the addition amount can be improved.

Further, the second mixed solution is added to the first mixed solution and stirred for a sufficient time to form the precursor contained in the first mixed solution and the second mixed solution sufficiently to be dispersed, and the titanosilicate The purity of the solution can be further improved.

In the step (b), the third mixed solution is heated to induce a crystallization reaction to produce a titanosilicate crystal. The third mixed solution is heated to induce hydrothermal synthesis to form a crystallized titanosilicate .

In this step, the hydrothermal synthesis is preferably carried out at a temperature of 100 to 300 ° C for 24 to 150 hours, more preferably at a temperature of 150 to 220 ° C for 48 to 120 hours, And the reaction is carried out at a temperature of 170 ° C to 220 ° C for 72 hours or more, and the titanosilicate crystals can be prepared through hydrothermal synthesis as described above.

In this step, the titanosilicate crystals prepared may be further washed to prepare titanosilicate crystals having improved selectivity. The titanosilicate crystals may be prepared by adding distilled water, hydrochloric acid (HCl), nitric acid (HNO ₃ ), sulfuric acid ₂ SO ₄ ), phosphoric acid (H ₃ PO ₄ ), or sodium hydroxide (NaOH).

For example, the titanosilicate can be prepared by cooling the titanosilicate to room temperature, washing with distilled water, and washing with 1 M hydrochloric acid and 1 M sodium hydroxide, respectively.

The method may further include drying the washed titanosilicate crystals. The drying may be performed using various known drying methods, and preferably at a temperature of 50 ° C.

The use of the tetanusilicate-containing process for preparing tetanusilides as described above allows introduction of tetravalent cations to increase the number of bonds to cesium contained in the radioactive waste solution and reduce the structural distortion, It is possible to produce titanosilicate particles having high selectivity to cesium and excellent adsorptivity.

The present invention also provides a titanosilicate-based adsorbent for removing radionuclides, which comprises a titanosilicate having a tetravalent cation introduced therein.

The adsorbent may be in the form of a powder, a foam, a film, etc. The adsorbent may be packed in a column with a filler and the waste solution may be passed through a column to easily remove the radionuclide contained in the waste solution. It is possible to fix the adsorbent and effectively utilize it to remove radionuclides.

Hereinafter, preferred embodiments of the present invention will be described in more detail. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Embodiments in accordance with the concepts of the present invention can make various changes and have various forms, so that specific embodiments are illustrated in the drawings and described in detail in this specification or application. It is to be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms of disclosure, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Also, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise.

≪ Example 1 >

The titanosilicate with the tetravalent cation introduced according to the example was prepared by the method shown in Fig. 1, and each step is described in detail below.

To a first mixed solution of 4 g of titanium isopropoxide (TTIP) and 4 g of tetraethyl orthosilicate (TEOS) in a 100 mL Teflon vessel was added 0.5 g of niobium oxide and 2 g of germanium oxide in a sodium hydroxide solution 50 mL, and the mixture was stirred to prepare a third mixed solution.

The Teflon container carrying the third mixed solution thus prepared was placed in a hot water synthesizer, and the lid was closed. Then, the titanosilicate having tetravalent cation introduced into the skeleton was synthesized by heating in an electric furnace at 200 ± 5 ° C for 3 days.

The thus-synthesized titanosilicate was washed with distilled water, washed with 1 M hydrochloric acid solution for about 3 hours and then with 1 M sodium hydroxide solution for 3 hours at 40 ° C., washed with distilled water, and dried in an oven at 50 ° C. . The dried samples were analyzed for diffraction pattern using an X-ray diffractometer, and the results are shown in FIG. 2 (a).

As shown in FIG. 2 (a), the titanosilicate exhibits distinct diffraction pattern of titanosilicate, which indicates that titanosilicate has been synthesized.

In order to analyze the composition of the titanosilicate prepared as described above, the amount of germanium and tin introduced into the skeleton was confirmed by using an X-ray fluorescence analyzer for the composition of the titanosilicate prepared in Example 1, Table 1 shows the results.

As shown in Table 1, it was confirmed that the titanosilicate prepared according to Example 1 contained germanium in an amount of 12.47%, and the titanosilicate prepared according to Example 1 had a structure in which a portion of the titanium skeleton was substituted with germanium Was confirmed to be titanosilicate (NGTS) into which a cation was introduced.

≪ Example 2 >

A titanosilicate was prepared in the same manner as in Example 1, except that 1 g of tin oxide was added instead of 2 g of germanium oxide as the second mixed solution.

The titanosilicate thus prepared was analyzed for diffraction pattern using an X-ray diffractometer, and the result is shown in FIG. 2 (b).

As shown in FIG. 2 (b), it was confirmed that the titanosilicate was synthesized because the characteristic diffraction pattern of the titanosilicate was apparent.

In order to analyze the composition of the titanosilicate prepared as described above, the amount of germanium and tin introduced into the skeleton was confirmed by using an X-ray fluorescence analyzer for the composition of the titanosilicate prepared in Example 2, Shown in Table 1 above.

As shown in Table 1, the titanosilicate prepared according to Example 2 was found to contain tin in an amount of 18.98%, and the titanosilicate prepared according to Example 2 was found to have a structure in which a portion of the titanium skeleton was replaced with tin Was titanosilicate (NSTS) introduced with cations.

<Comparative Example>

Titanosilicate (TS) was prepared by crystallizing only the first mixed solution containing TTIP and TEOS in the same manner as in Example 1.

&Lt; Experimental Example > Evaluation of ability to remove aqueous cesium

In order to evaluate the removal ability of cesium contained in the aqueous solution of titanosilicate introduced with tetravalent cations according to the above Example 1 and Example 2, the cesium removal ability in an aqueous solution was evaluated using NGTS, NSTS and TS Respectively.

To this end, 0.1 g of NGTS, NSTS and TS were added to 15 mL of a solution having a cesium concentration of 100 ppm. After stirring for 24 hours, the supernatant was collected. The collected supernatant was filtered to remove impurities, and the content of cesium remaining in the solution was measured using an induction defect plasma spectrometer. The measurement results are shown in FIG.

As shown in FIG. 3, in the case of NGTS and NSTS, the cesium concentration remaining in the solution after the adsorption was 0 ppm and the removal rate was 100%, whereas in the case of TS, the cesium concentration remaining in the solution after the adsorption was 2.5 ppm, Was 97.5%, indicating that the cesium-removing ability of the titanosilicate substituted with tetravalent cations according to Example 1 and Example 2 was superior to that of the titanosilicate prepared according to the Comparative Example.

Accordingly, it has been confirmed that the titanosilicate according to the present invention substituted with tetravalent cations can be effectively used for the removal of cesium contained in radioactive contaminants, particularly water.

Claims (4)

A titanosilicate-based adsorbent having a structure containing niobium and having a tetravalent cation introduced therein. The method according to claim 1,
Wherein the tetravalent cation is at least one selected from germanium tetravalent cation and tin tetravalent cation. 2. The titanosilicate sorbent according to claim 1, wherein the tetravalent cation is at least one selected from germanium tetravalent cation and tin tetravalent cation. The method according to claim 1,
Wherein the titanosilicate into which the tetravalent cation is introduced has a tetravalent cation introduced at a substitution rate of 5 to 30%. A method for producing a tetradentate-introduced titanosilicate according to any one of claims 1 to 3,
(a) a first mixed solution comprising titanium isopropoxide (TTIP) and tetraethyl orthosilicate (TEOS), and a first mixed solution comprising sodium hydroxide (NaOH), niobium oxide and tetraethyl orthosilicate Mixing a second mixed solution containing a cationic oxide to prepare a third mixed solution; And
and (b) heating the third mixed solution to prepare crystallized titanosilicate. The method for producing titanosilicate according to claim 1,

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