CN100460057C - An adsorbent for simultaneously separating exothermic elements Cs and Sr and its preparation method and application - Google Patents

Abstract

The invention discloses an adsorbent for separating exothermic elements Cs and Sr and its preparation method and application. The adsorbent is made by loading crown ether and calixaryl ether on the macroporous _SiO2 of the coated polymer; calixaryl ether The mol ratio with crown ether is 0.3-2.0; The quality of _the macroporous SiO of coated polymer is 2～40 times of the sum of calixaryl ether and crown ether quality; Described calixaryl ether has general structural formula (I) ; The macroporous SiO ₂ of the coating polymer is SiO ₂ -styrene-divinylbenzene polymer; the crown ether is 4,4', (5')-bis(tert-butylcyclohexyl)- 18-crown-6. The adsorbent of the present invention does not need to be diluted or dissolved with a diluent with special properties during the adsorption process, which not only overcomes the shortcomings of the solvent extraction method, but also retains the characteristics of its high extraction capacity, which is helpful for realizing safe and effective treatment and disposal of HLLW There's important meaning.

Description

An adsorbent for simultaneously separating exothermic elements Cs and Sr and its preparation method and application

technical field

The invention relates to the field of post-treatment of high-level radioactive waste in the nuclear industry, in particular to an adsorbent for simultaneously separating heat-generating elements Cs and Sr in high-level radioactive waste and its preparation method and application.

Background technique

As the high-level radioactive waste (HLLW) produced by spent fuel (SF) reprocessing, its safe treatment and disposal is one of the key links in nuclear fuel cycle technology.

Spent fuel contains fragmentation products (FP) such as exothermic elements and long-lived (millions of years) minor actinides (MA). and almost all FP elements went into HLLW. For long-lived MA, separation/transmutation technology has been proposed and some extraction and separation processes developed for this purpose (such as the TRUEX process using CMPO in the United States and the DIAMEX process using ammonia compounds in France, etc.), but the heat generation There are not many theoretical and technical studies on the separation and recovery of elements Cs/Sr.

Cs/Sr in HLLW is a highly exothermic element, and the half-lives of its main nuclides Cs-137 and Sr-90 are 30 years and 28 years, respectively. The physical and chemical instability that may be caused by their exothermic properties is considered to affect HLLW glass One of the most dangerous harmful elements for solidification and safe disposal; another major nuclide, Cs-135, has a half-life of up to 2×10 ⁶ years, causing a long-term burden on the safety of the earth's ecological environment, for which it is required to be effectively separated and safely disposed of . In addition, the separated and recovered Cs/Sr can be used as both a line source and a heat source in the medical and health care system. This enables the separation and recovery of Cs/Sr from HLLW, leading to the following favorable technical elements: a significant reduction in the number of vitrified solidified bodies; a significant shortening of the SF cooling period; from the viewpoint of improved economics of HLLW treatment and disposal, reduced ecological and environmental burdens, and efficient use of resources It is also of great significance to build an innovative nuclear fuel cycle system.

The earliest Cs/Sr separation research started from the United States, France and Japan. As far as its separation technology is concerned, there are mainly adsorption method and solvent extraction method. The current research on Cs/Sr adsorption method mainly focuses on inorganic adsorbents such as aluminosilicate, titanate and insoluble ferricyanide. However, in order to reduce the adsorption of Cs and Sr, which is seriously hindered by the competitive adsorption of H+ in strongly acidic solution, neutralization and denitrification are necessary as pretreatments, resulting in a significant increase in treatment costs and secondary waste, and its slow adsorption rate makes it difficult to Effective separation of Cs/Sr is achieved. The adsorption and separation of Sr by crown ether adsorbents has also been studied. The representative one is the Sr-Resin resin in the United States. Its saturated adsorption capacity is too low, coupled with poor acid resistance, high temperature resistance and radiation resistance, it is not yet suitable for separating Sr from HLLW.

 L萃取体系中。The separation technology of Cs in HLLW is currently focused on liquid-liquid solvent extraction. The representative process is the CSSX (or CSEX) (Caustic-SideSolvent Extraction) process of ORNL and INL in the United States. The extraction agent used is BOBCalixC6 (Calix[4]arene-bis-(tert-octylbenzo-crown-6). To eliminate extractant in hydrocarbon diluent The third phase that appears in L, the alkyd molecular modifier Cs-7SB (1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol) or Cs-3 (1-(1,1,2,2-tetrafluoroethoxyl)-3-[4-(tert-octyl)phenoxyl]-2-propanol) and tri-n-octylamine (TOA) were added in BOBCalixC6-

L extraction system.

The calix[4]arene developed by the French Atomic Energy Commission (CEA) is shown in the structural formula, and it has excellent performance in the selective separation of Cs in the CCCEX extraction process.

1,3-[(2,4-diethyl-heptylethoxy)oxy]-2,4-crown-6-calix[4]arene

Controlling and selecting the appropriate pore size of Calix[4]arene-crown can selectively separate Cs in HNO ₃ solution. Its main disadvantage is that the solubility of these macrocyclic organic compounds in common hydrocarbon diluents such as n-dodecane and kerosene is very low, and some very special ones such as nitrobenzene, tetrapropyl hydrogen, and nitrophenyl octyl ether must be used. Even so, its saturation concentration is only 0.001-0.1M; in order to suppress the appearance of the third phase, a large amount of organic phase regulator must be added, such as methyl octyl-2-dimethylbutanamide, 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol (Cs-7SB), 1-(1,1, 2,2-Tetrafluoropropoxy)-3-[4-(tert-octyl)phenoxy]-2-propanol (Cs-3) and 2,3-(4-tert-octylbenzene Oxygen)-propanol (Cs-4), etc., so that the separation process must use large-capacity multi-stage extraction equipment, a large amount of liquid waste and difficult-to-handle secondary radioactive organic waste are generated in the post-treatment process, and the resulting solvent chemistry is disturbed. Qualitatively lead to concerns about the safety of the reprocessing cycle.

 L中出现的第三相，磷酸三丁酯(TBP)被添加在DtBuCH18C6-

 L萃取体系中。The current research work on the separation technology of Sr in HLLW is also mainly focused on the liquid-liquid solvent extraction method. The representative process is the SREX (Strontium Extraction) process developed by ORNL in the United States. The extraction agent used is DtBuCH18C6(4,4′, (5')-di-(tert-butylcyclohexano)-18-crown-6). To eliminate extractant in hydrocarbon diluent

The third phase appearing in L, tributyl phosphate (TBP) was added in DtBuCH18C6-

L extraction system.

The ORNL National Laboratory of the United States has also developed the Sr resin (Sr-resin) with the porous polymer XAD-7 as the carrier. It dissolves DtBuCH18C6 in n-octanol, and then pours the liquid DtBuCH18C6-n-octanol mixture into the Porous XAD-7. The experimental results show that the Sr resin has a good adsorption performance for Sr, but there is serious tailing phenomenon and the adsorption capacity is not high.

The chromatographic research and process flow of the simultaneous separation and recovery of exothermic elements Cs and Sr from HLLW by macroporous silicon-based supramolecular recognition materials with a silicon-based background have not been reported yet.

Contents of the invention

The invention provides an adsorbent with good separation effect and environmental protection for simultaneously separating heat-generating elements Cs and Sr, as well as a preparation method and application thereof.

An adsorbent for simultaneously separating exothermic elements Cs and Sr, which is made of crown ether and calixaryl ether supported on macroporous SiO ₂ coated with polymer;

The molar ratio of calixaryl ether to crown ether is 0.1-2.0; preferably 1:1.

The mass of the macroporous _SiO2 of the coated polymer is 0.5 to 40 times the sum of the mass of calixaryl ether and crown ether; preferably 2 times.

Described calixaryl ether has structural general formula (I)

In the general structural formula (I), R is an unsubstituted or substituted alkyl, alkoxy, haloalkyl or cycloalkyl of C ₁ to C ₂₀ ; a substituted alkyl, alkoxy, haloalkyl or cycloalkyl Have at least one of the following substituents: C ₁ -C ₈ haloalkyl, C ₁ -C ₁₈ alkoxy, C ₃ -C ₈ cycloalkyl;

The macroporous SiO ₂ of the coating polymer is SiO ₂ -styrene-divinylbenzene polymer;

The crown ether is 4,4',-bis(tert-butylcyclohexyl)-18-crown-6 or 4,5'-bis(tert-butylcyclohexyl)-18-crown-6.

As a preference, in the general formula (I) of the calixaryl ether structure, R is an unsubstituted or substituted alkyl or alkoxy group of C ₁ to C ₂₀ ; the substituted alkyl or alkoxy group has at least one substitution as follows: Group: C ₁ -C ₈ haloalkyl or C ₁ -C ₈ alkoxy.

As a further preference, the calixaryl ether has structural formula (II):

The 4,4',-bis(tert-butylcyclohexyl)-18-crown-6 English name is: 4,4',-di-tert-butylcyclohexano)-18-crown-6, referred to as (4, 4'-DC18C6), see structural formula (III).

The 4,5'-bis(tert-butylcyclohexyl)-18-crown-6 English name described therein is: 4,5',-di-(tert-butylcyclohexano)-18-crown-6, referred to as (4, 5'-DC18C6), see structural formula (IV).

Structural formula (III)

Structural formula (IV)

The macroporous SiO ₂ of the coating polymer is SiO ₂ -styrene-divinylbenzene polymer (SiO ₂ -P), which is a new type of inorganic/organic carrier, and the coating polymer is disclosed in US Patent No. 6,843,921 Macroporous SiO ₂ , SiO ₂ -P is an organic high polymer complex carrier containing porous silica carrier particles, and its preparation method is:

(1) Wash the macroporous SiO ₂ with concentrated nitric acid, suction filter, and deionized water to neutrality, repeat more than 10 times, and dry.

(2) Under the condition of vacuum and argon protection, with 1,2,3-trichloropropane and m-xylene as solvent, add 48.7g of m/p-formyl styrene in macroporous _SiO2 , 8.9 g of m/p-divinylbenzene, 72.2g dioctylphthalate, 54.0g sodium methylbenzoate, 0.56g α,α-diisobutyronitrile and 0.57g 1,1′- Dicyclohexylamine-1-carbonitrile was gradually heated from room temperature to 90°C and kept for 13 hours, and then gradually cooled to room temperature.

(3) Wash and filter the above product with acetone and methanol respectively, repeat more than 10 times, and dry.

Described adsorbent is prepared by following method:

Dissolve crown ether and calixaryl ether in dichloromethane, mix well, then add polymer-coated macroporous _SiO2 , stir well, and dry in vacuum.

Due to the high content of dichloromethane in the initial stage during drying, in order to reduce the load of the vacuum pump in the later stage of vacuum drying, you can first stir at about 45°C under normal pressure to volatilize most of the dichloromethane until the material is nearly dry, and then nearly dry The material in this state was dried under vacuum at 45 °C for 24 h.

The invention also provides a method for simultaneously separating exothermic elements Cs and Sr from high-level radioactive waste.

A method for simultaneously separating exothermic elements Cs and Sr from high-level radioactive wastes. After the adsorbent of the present invention is filled into a chromatographic separation column, liquid chromatography is used to conduct the separation of exothermic elements Cs and Sr in high-level radioactive wastes (HLLW). Separation, the separation conditions are: mix high-level radioactive waste with nitric acid to make a nitrate solution, the concentration of _HNO3 in the nitrate solution is 3-5 mol/liter, and the total concentration of metal ions in the nitrate solution is 5.0×10 ^-3 mol/liter liters, the size of the separation column is 10mm x 200mm, the flow rate of the nitrate solution is 1.0cm ³ /min, and it is operated at room temperature.

Based on the excellent extraction performance of calixaryl ether for Cs and crown ether for Sr, the present invention uses crown ether and calixaryl ether to support macroporous SiO ₂ (SiO ₂ -P) coated polymer to synthesize a novel macroporous silicon-based supramolecular recognition adsorption Agent [Calix[4]arene+DtBuCH18C6]/SiO ₂ -P.

The adsorbent of the present invention adopts the macrocyclic silicon-based supramolecular recognition material calixaryl ether, which has good recognition ability for Cs and crown ether for Sr, high adsorption capacity, and high recovery rate, and can realize simultaneous high-selective separation and recovery of Cs and Sr from HLLW .

If calixaryl ether is supported on SiO ₂ -P alone, it is difficult to support it on SiO ₂ -P due to the poor water solubility of calixaryl ether, and it must be supplemented with other additives. ₂ -P, because the water solubility of the crown ether is too good, it is easy to lose during use. The present invention loads the calixaryl ether and the crown ether on SiO ₂ -P at the same time, which not only saves other additives, but also makes the calixaryl ether The properties of ethers and crown ethers complement each other.

The adsorbent of the present invention does not need to use a diluent with special properties to dilute or dissolve in the adsorption process, and does not need to add other organic compounds, which not only overcomes the shortcomings of the solvent extraction method, but also retains its high extraction capacity and other characteristics; Aromatic ethers and crown ethers are loaded on SiO ₂ -P carriers with a particle size of 40-60 μm. Compared with existing adsorbents, the ion diffusion, adsorption, and desorption rates are significantly improved, and the adsorption and desorption processes in the filled column are fast and almost stress-free. It can operate safely under high flow rate conditions. It retains the characteristics of simple operation, high efficiency and conciseness of the traditional adsorption separation method, and overcomes its inherent shortcomings. It can be expected to have sufficient safety, economy and high efficiency. Recycling technology process. This is of great significance to realize the safe and effective treatment and disposal of HLLW.

Description of drawings

Fig. 1 is the separation spectrogram of exothermic elements Cs and Sr in high-level radioactive waste (HLLW) by liquid chromatography after the adsorbent of the present invention is filled into the chromatographic separation column.

Abscissa: Indicates the quality of the effluent

Ordinate (left): Indicates the concentration of metal ions in the effluent

Detailed ways

The preparation of embodiment 1 adsorbent

100 grams of Calix[4]arene with structural formula (II) and 48 grams of 4,4',-bis(tert-butylcyclohexyl)-18-crown-6 were dissolved in 1000 mL of methylene chloride and mixed uniformly; 300 grams of The polymer-coated macroporous SiO ₂ (SiO ₂ -P) was evenly stirred to volatilize most of the methylene chloride until the material was in a nearly dry state, and then the nearly dry material was vacuum-dried at 45° C. for 24 hours. (1:2)

The preparation of embodiment 2 adsorbent

100 grams of Calix[4]arene with structural formula (II) and 24 grams of 4,5',-bis(tert-butylcyclohexyl)-18-crown-6 were dissolved in 1500 mL of dichloromethane and mixed uniformly; The polymer-coated macroporous SiO ₂ (SiO ₂ -P) was evenly stirred to volatilize most of the methylene chloride until the material was in a nearly dry state, and then the nearly dry material was vacuum-dried at 45° C. for 24 hours.

The preparation of embodiment 3 adsorbent

100 grams of Calix[4]arene with structural formula (II) and 100 grams of 4,4',-bis(tert-butylcyclohexyl)-18-crown-6 were dissolved in 3000mL of dichloromethane and mixed uniformly; The polymer-coated macroporous SiO ₂ (SiO ₂ -P) was evenly stirred to volatilize most of the methylene chloride until the material was in a nearly dry state, and then the nearly dry material was vacuum-dried at 45° C. for 24 hours.

Embodiment 4 Preparation of adsorbent

100 grams of Calix[4]arene with structural formula (II) and 50 grams of 4,4',-bis(tert-butylcyclohexyl)-18-crown-6 were dissolved in 4500 mL of dichloromethane and mixed uniformly; The polymer-coated macroporous SiO ₂ (SiO ₂ -P) was evenly stirred to volatilize most of the methylene chloride until the material was in a nearly dry state, and then the nearly dry material was vacuum-dried at 45° C. for 24 hours.

The preparation of embodiment 5 adsorbent

100 grams of Calix[4]arene (in general structural formula (I), R is CH ₃ CH ₂ OCH ₂ CH ₂ -) and 80 grams of 4,5',-bis(tert-butylcyclohexyl)-18-crown -6 was dissolved in 1000mL of dichloromethane, mixed evenly; added 300 grams of polymer-coated macroporous SiO ₂ (SiO ₂ -P) and stirred evenly to volatilize most of the dichloromethane until the material was nearly dry, and then nearly dry The material in this state was dried under vacuum at 45 °C for 24 h.

The preparation of embodiment 6 adsorbent

100 grams of Calix[4]arene (in the general structural formula (I), R is CH ₃ CH ₂ -) and 40 grams of 4,5',-bis(tert-butylcyclohexyl)-18-crown-6 are dissolved in In 600mL of dichloromethane, mix well; add 150 grams of macroporous SiO ₂ (SiO ₂ -P) coated with polymer and stir evenly to volatilize most of the dichloromethane until the material is in a nearly dry state, and then the nearly dry state of the material is Vacuum dry at 45°C for 24h.

Embodiment 7 The preparation of adsorbent

100 grams of Calix[4]arene (in the general structural formula (I), R is CH ₃ (CH ₂ ) ₅ OCH ₂ CH ₂ -) and 80 grams of 4,5',-bis(tert-butylcyclohexyl)- 18-crown-6 was dissolved in 800mL of dichloromethane, and mixed uniformly; adding 300 grams of polymer-coated macroporous SiO ₂ (SiO ₂ -P) and stirred evenly to volatilize most of the dichloromethane until the material was in a nearly dry state, and then The nearly dry material was dried under vacuum at 45° C. for 24 h.

Embodiment 8 Preparation of adsorbent

100 grams of Calix[4]arene (in the general structural formula (I), R is CH ₃ (CH ₂ ) ₅ OCH ₂ CH ₂ -) and 50 grams of 4,5',-bis(tert-butylcyclohexyl)- 18-crown-6 was dissolved in 2000mL of dichloromethane, and mixed uniformly; adding 300 grams of polymer-coated macroporous SiO ₂ (SiO ₂ -P) and stirred evenly to volatilize most of the dichloromethane until the material was in a nearly dry state, and then The nearly dry material was dried under vacuum at 45° C. for 24 h.

Separation of exothermic elements Cs and Sr in high-level radioactive waste (HLLW)

After filling the chromatographic separation column with the adsorbent prepared in Example 1, the exothermic elements Cs and Sr in the high-level radioactive waste (HLLW) were separated by liquid chromatography.

Mix high-level radioactive waste with nitric acid to make nitrate solution. The concentration of HNO ₃ in the nitrate solution is 2.0 mol/liter, the total concentration of metal ions in the nitrate solution is 5.0×10 ^-3 mol/liter, and the size of the separation column is 10mm x 300mm , the flow rate of the nitrate solution is 1.0cm ³ /min, and it is operated at room temperature. After filling the chromatographic separation column with the adsorbent of the present invention, since the adsorbent has good selectivity to Cs and Sr, it can adsorb Cs and Sr and separate them from other metal elements, and has good separation effect. The separation effect spectrum is shown in Figure 1. In Figure 1, B is the absorption peak of Sr, C is the absorption peak of Cs, and many absorption peaks at A are the absorption peaks of other metal ions.

Claims (6)

1. An adsorbent for simultaneously separating exothermic elements Cs and Sr, characterized in that: it is loaded on the macroporous SiO of the coated polymer by crown ether and calixaryl ether ₂ and made; The molar ratio of calixaryl ether to crown ether is 0.1～2.0; The mass of the macroporous _SiO2 of the coated polymer is 0.5 to 40 times the sum of the mass of calixaryl ether and crown ether; Described calixaryl ether has structural general formula (I)

In the general structural formula (I), R is an unsubstituted or substituted alkyl, alkoxy, haloalkyl or cycloalkyl of C ₁ to C ₂₀ ; a substituted alkyl, alkoxy, haloalkyl or cycloalkyl Have at least one of the following substituents: C ₁ -C ₈ haloalkyl, C ₁ -C ₁₈ alkoxy, C ₃ -C ₈ cycloalkyl; The macroporous SiO ₂ of the coating polymer is SiO ₂ -styrene-divinylbenzene polymer; The crown ether is 4,4',-bis(tert-butylcyclohexyl)-18-crown-6 or 4,5'-bis(tert-butylcyclohexyl)-18-crown-6. 2. The adsorbent according to claim 1, characterized in that: in the general formula (I) of the calixaryl ether structure, R is an unsubstituted or substituted alkyl or alkoxy group of C ₁ to C ₂₀ ; The substituted alkyl or alkoxy group has at least one of the following substituents: a C ₁ -C ₈ haloalkyl group or a C ₁ -C ₈ alkoxy group. 3. Adsorbent as claimed in claim 1, characterized in that: described calixaryl ether has structural formula (II):

4. The preparation method of the adsorbent as claimed in claim 1, 2 or 3, characterized in that: crown ether and calixaryl ether are dissolved in methylene chloride, mixed uniformly, and then added _macroporous SiO coated polymer Stir well and dry under vacuum. 5. A method for simultaneously separating exothermic elements Cs and Sr from high-level radioactive waste, after the adsorbent described in claim 1, 2 or 3 is filled into a chromatographic separation column, liquid chromatography is used to carry out the determination of exothermic elements in high-level radioactive waste. Separation of Cs and Sr. 6. The method as claimed in claim 5, characterized in that: the separation condition is: the high-level radioactive waste is mixed with nitric acid to make a nitrate solution, the concentration _of HNO in the nitrate solution is 3 to 5 mol/liter, and the nitrate The total concentration of metal ions in the solution is 5.0×10 ^-3 mol/liter, the size of the separation column is 10mm×200mm, the flow rate of the nitrate solution is 1.0cm ³ /min, and it is operated at room temperature.

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