JPH0262032B2 - - Google Patents

Description

[Detailed description of the invention]

A. Field of industrial application of the invention The present invention is a collection material for radionuclides, heavy metals, etc. The present invention relates to the separation and removal of radionuclides contained in radioactive waste liquid generated from nuclear facilities such as nuclear power plants and radioisotope handling facilities, and the radionuclides and heavy metals contained in marine rivers or industrial wastewater. It is used for separation and removal of etc. BACKGROUND ART Radioactive waste fluids generated from various nuclear facilities, such as nuclear power plants (water type) and offices that handle radioactive isotopes, contain various radionuclides. In the treatment of these radioactive waste liquids, it is necessary to separate and remove the radionuclides contained in the waste liquids to reduce the radiation level from the perspective of reducing exposure. or,
⁶⁰ CO, ⁹⁰ Sr, ¹³⁷ Cs are present in marine rivers, although in trace amounts.
The existence of various artificial nuclides such as
Accumulating data on the concentration and distribution of these radionuclides over a long period of time is important from the viewpoints of oceanography, marine ecology, and ocean dumping of medium- and low-level radioactive waste. Conventionally, coagulation-sedimentation methods and ion exchange methods have been mainly used to separate and remove radionuclides from radioactive waste liquids or to recover radionuclides and heavy metals from marine rivers. The coagulation-sedimentation method is a treatment method in which a flocculant is mixed with the waste liquid to neutralize the electric charge of the radioactive substance, and this is flocculated to produce a group of large molecules, or flocs, and the flocs are sedimented and separated.
Al ₂ (SO ₄ ) ₃ +Ca(OH) ₂ , clay (+polymer flocculant),
FeCl ₃ +Na ₂ S, Na ₃ PO ₄ +Ca(OH) ₂ , etc. are used as flocculants. Although this method is time-consuming for processing small volumes or complex waste liquids, the decontamination coefficient is not large, but it is cheap and simple, and is suitable for processing large quantities of simple liquid waste liquids, so it is widely used. ing. Ion exchange methods include various synthetic cation exchangers, synthetic anion exchangers, mixed bed ion exchange resins,
Alternatively, there is a method of treating waste liquid using a natural organic exchanger based on coal, lignite, peat, etc., or an inorganic exchanger based on greenside, kaolinite, zeolite, etc. When wastewater is treated by such coagulation-sedimentation and ion exchange methods, radioactivity is concentrated in the sludge and regenerated wastewater, respectively. In the case of non-radioactive waste liquids, these concentrated liquids are generally disposed of as long as purified water is obtained, but in the case of radioactive waste liquids, secondary treatment is required to retain and fix the concentrated radioactivity without re-diffusion. is necessary. Currently, such sludge and recycled waste liquid are processed through sedimentation, sand bed filtration, pressure filtration, vacuum filtration, centrifugation,
Solidification is performed after dehydration and volume reduction using secondary treatment methods such as autoclaving, but the volume reduction ratios due to these secondary treatments are <1, 4, 5 to 10, respectively.
The actual situation is 10-15, 25-35 and 2-4. For the reasons mentioned above, a collection material with a high volume reduction ratio that can efficiently separate and remove radionuclides contained in radioactive waste fluids generated from various nuclear power plants, radionuclides or heavy metals contained in marine rivers or industrial wastewater, etc. is needed. It was desired in this world. Problems to be Solved by the Invention The present invention provides a radionuclide and heavy metal trapping material with high trapping efficiency and volume reduction ratio. According to the present invention, radionuclides contained in radioactive liquid waste, marine rivers or industrial wastewater, in particular, ⁵⁹ Fe,
A collection material is provided that can collect ⁶⁰ CO, ⁶⁵ Zn, ^103+106 Rn, ^134+137 Cs, ¹⁴⁴ Ce, etc. with high efficiency and reduce the volume at a high rate. The present invention provides a collection material capable of collecting trace amounts of radionuclides in deep seawater at a water sampling site. The problems solved by the present invention will be successively clarified below. (b) Means for solving the structural problems of the invention The above-mentioned problems are solved by the general formula
A collection material that supports and fixes a ferrocyanate compound represented by K ₂ M〓 [Fe(CN) ₆ ] (where M〓 is a type selected from divalent metals such as Co, Zn, Ni, and Zr) is used. This is solved by The present inventors have discovered that ultra-low concentrations contained in deep seawater
Efficiently collects radionuclides such as ^134+137 Cs and ⁶⁵ Zn,
In addition, we have been developing a collection material with a high volume reduction ratio.
As a result, acrylic fibers have the formula _K2Co [Fe(CN) ₆ ]
The collection material supporting and fixing cobalt and potassium ferrocyanide expressed as ^134+137 Cs is almost 100%
I discovered that I could collect it. Further research has shown that in addition to ^134+137 Cs, the collection material contains ³⁹ Fe, ⁶⁰ Co,
We discovered that ⁶⁵ Zn, ^103+106 Ru, and ¹⁴⁴ Ce can also be collected. Furthermore, as a result of repeated studies, we found that depending on the form of the radioactive waste liquid, acrylic fibers such as nickel/potassium ferrocyanide (K ₂ Ni [Fe (CN) ₆ )] or zinc/potassium ferrocyanide (K ₂ Zn [Fe (CN) ) ₆ 〕)
Alternatively, we discovered that a collection material supported and fixed with zirconium/potassium ferrocyanide (K ₂ Zr [Fe(CN) ₆ ]) is more effective than a collection material supported/fixed with cobalt/potassium ferrocyanide. . Below, we will explain the method for producing a collection material in which cobalt and potassium ferrocyanide are supported and fixed on acrylic fibers. 100g of acrylic fiber was immersed in a 10% potassium ferrocyanide aqueous solution, heated at 60 to 70℃ for 3 hours, taken out, and immersed in a 10% cobalt nitrate aqueous solution.
Manufactured by heating and fixing cobalt and potassium ferrocyanide on acrylic fibers by heating to 60-70℃ for an hour, washing with water, drying at 60-70℃ for 10 hours, and repeating this operation three times. be done.
In addition, in another embodiment, 100g of acrylic fiber is
% cobalt nitrate aqueous solution and heated at 60 to 70°C for 3 hours, then taken out, immersed in a 10% potassium ferrocyanide aqueous solution and heated at 60 to 70°C for 3 hours, then washed with water and heated at 60 to 70°C for 10 hours. By drying and repeating this operation three times, cobalt/potassium ferrocyanide can be supported and fixed on the acrylic fiber. The color of the collecting material of the present invention produced in this manner is reddish brown and remains flocculent even after supporting and fixing cobalt/potassium ferrocyanide. The exchange capacity was determined to be 0.13 meq/g of collection material. Results of quantifying potassium, iron, and cobalt to investigate the components in the collection material (K:Fe:Co) = (9.8:12:35)
mg/g/collection material. The acrylic fiber used to produce the collection material of the present invention has a fiber diameter of 18 μm and is copolymerized with 8 wt% methyl acrylate, and has anionic groups.
Contains 0.05 meq/g of fiber SO ₃ ^- . 30%
It has very strong resistance to acids such as hydrochloric acid, nitric acid, and sulfuric acid, but has weak alkali resistance and can be denatured even with a 1% sodium hydroxide solution. The collection material of the present invention can collect 90% or more of ⁶⁵ Zn, ¹⁰⁶ Ru, and ¹⁴⁴ Ce using the batch method in the pH range of 7 to 9.
Part of ⁵⁴ Mn, ⁶⁰ Co, and ⁵⁹ Fe was collected and 59 Fe, ⁵⁹ Fe,
Captures over 90% of ⁶⁰ Co, ⁶⁵ Zn, ^134+137 Cs, and ¹⁴⁴ Ce.
More importantly, even in the presence of large amounts of Na ⁺
It has the characteristic of being able to collect ¹³⁷ Cs. In the production of the above-mentioned collection material of the present invention, zinc ferrocyanide and potassium ferrocyanide can be added to the acrylic fiber by using zinc nitrate instead of cobalt nitrate, and ferrocyanide can be added to the acrylic fiber by using nickel nitrate instead of cobalt nitrate. By using zirconium nitrate instead of potassium nickel chloride or cobalt nitrate, zirconium ferrocyanide
It can support and fix potassium. It is preferable to use the collection material of the present invention depending on the type of radioactive waste liquid.For example, to separate and remove radionuclides from a light water primary cooling water system, nickel/potassium ferrocyanide is supported and fixed rather than cobalt/potassium ferrocyanide. It is preferable to use a collection material that is The effects of the present invention will be specifically explained below using Examples and Reference Examples. Example - Manufacture of collection material Fiber diameter 18μm, 8wt% methyl acrylate copolymerized as an anion group 0.05meq/g fiber
100 g of acrylic fiber containing SO ₃ ^- was immersed in a 10% potassium ferrocyanide solution and heated at 60 to 70° C. for 3 hours. After taking it out, it was immersed in a 10% cobalt nitrate solution and heated at 60 to 70°C for 3 hours. 60~ after washing with water
It was dried at 70°C for 10 hours. Repeat this operation three times to coat the acrylic fiber with cobalt ferrocyanide.
A reddish-brown collection material supporting and fixing potassium was produced. The exchange capacity of this collection material is 0.13meq/g・
It was a collection material. The results of quantifying potassium, iron and cobalt in the collection material (K:Fe:Co) = (9.8:
12:35) mg/g/collection material. Next, the results obtained by performing a collection test of various radionuclides from seawater using the collection material manufactured in the example will be described as Reference Examples 1, 2, and 3. Reference example 1 Collection test using batch method 1.1 Experimental materials 1.1.1 Seawater Seawater (collected in Katsuura City, Chiba Prefecture) was filtered with a microfilter (0.45μm) manufactured by Fujifilm, and various tracers were used. After adding the radionuclide, it was added with hydrochloric acid and sodium hydroxide solution.
The pH was adjusted to 8.0±0.5. The salinity of the seawater used was 33.7%. 1.1.2 Nuclides used ⁵⁴ Mn (MnCl ₂ , 0.5NHCl) No carrier ⁵⁹ Fe (FeCl ₃ , 0.5NHCl) 11 mCi/mgFe ⁶⁰ Co (CoCl ₂ , 0.1NHCl) 136 mCi/mgCo ⁶⁵ Zn (ZnCl ₂ , 0.5NHCl) 2.8 mCi/mgZn ⁸⁵ Sr (SrCl ₂ , 0.5NHCl) 7.4mCi/mgSr ¹⁰⁶ Ru (chloride, 4NHCl) 7.7mCi/mgRu ¹³⁷ Cs (CsCl, 0.5NHCl) 9.0mCi/mgCs ¹⁴⁴ Ce (CeCl ₃ , 1NHCl) 250mCi/ mgCe The radioactive concentration of these nuclides is approximately 100nCi/
After diluting to ml, it was added to seawater. 1.1.3 Measuring device Nal (Tl) scintillation spectrometer: Measurement was performed by connecting a 44φ x 51 mm well type Nal (Tl) detector to a universal scaler (model TDC-501) manufactured by Aloka. 1.2 Experimental procedures 1.2.1 Stirring time and collection rate by batch method Add various tracers to every 200 ml of seawater.
Add collection material to this and stir for 2, 5, 10, 20
I changed it to minutes. After each stirring period, a certain amount of seawater is transferred into the measuring polyethylene tube.
The collection rate was determined by measurement using a Nal (Tl) detector. The collection rate A was defined as in the following equation. A (%) = {(R ₁ − R ₂ )/R ₁ }×100 A: Collection rate of fiber (KCFC) R ₁ : Count rate of tracer-added seawater R ₂ : Count rate of seawater after stirring 1.3 Results 1.3.1 Stirring time and collection rate Table 1 shows the experimental conditions of the batch method and changes in pH. There was no difference in the pH of seawater between the beginning of the experiment and after stirring for 20 minutes. The experimental results using the batch method are shown in Table 2 and Figure 1. As is clear from the figure and table, ⁶⁵ Zn, ¹⁰⁶ Ru, and ¹⁴⁴ Ce were added to the collection material after stirring for 20 minutes.
In addition to being well collected at over 90%, ⁵⁴ Mn, ⁶⁰ Co, and ⁵⁹ Fe were also partially collected. However, it became clear that ⁸⁵ Sr was not collected at all.

【table】

[Table] Reference Example 2 Collection test using column method 2.1 Experimental materials The same seawater, nuclides, and measurement equipment as in Reference Example 1 were used. 2.2 Experimental operations 2.2.1 Flow rate and collection rate by column method A glass with an inner diameter of 15 mmφ and a length of 20 cm was filled with a collection material, and 200 ml of seawater added with a tracer was passed through it at varying flow rates. A fixed amount of the passing liquid was transferred to a polyethylene tube for measurement, and the collection rate was determined by equipping it with a Nal (Tl) detector. The collection rate A was defined as follows. A (%) = {(R ₁ − R ₃ )/R ₁ }×100 A: Collection rate of the collection material R ₁ : Count rate of tracer-added seawater R ₃ : Count rate of the liquid passing through the collection material column 2.3 Results and discussion 2.3.1 Flow rate and collection rate The experimental conditions and results are shown in Table 3 and Figure 2. ⁵⁹ Fe, ⁶⁰ Co, ⁶⁵ Zn, ¹³⁷ Cs at a flow rate of 20 ml/min.
The collection rate of ¹⁴⁴ Ce was over 90%, and even when the flow rate was increased to 180ml/min, the collection rate of these nuclides was as high as 80%. No decrease in collection rate was observed for ⁶⁵ Zn, ¹³⁷ Cs, and ¹⁴⁴ Ce, but a decrease of 5% for ⁵⁹ Fe and 10% for ⁶⁰ Co was observed. ¹⁰⁶ Ru is 20ml/min and 180ml/min
At min, it showed a significant decrease of 55%. These results revealed that ⁶⁵ Zn, ¹³⁷ Cs, and ¹⁴⁴ Ce can be sufficiently applied to large columns. However, ¹⁰⁶ Ru, which had a high collection rate in the batch method (91% in the batch method), was surprisingly low in the column method, and the collection rate decreased rapidly as the flow rate increased. The cause of this is thought to be the ¹⁰⁶ Ru tracer (hydrochloric acid type) used in the column method.

[Table] Reference Example 3 Collection test using a large column In Reference Example 3, the collection material was packed into a large collection column,
We investigated the relationship between collection efficiency and flow velocity when a large amount of seawater (200) was flowing. 3.1 Experimental materials 3.1.1 Collection material Collection material of the present invention manufactured in the example 3.1.2 Column Specially made acrylic column inner diameter 50mmφ, 100mmφ,
A length of 40cm was used. 3.1.3 Seawater Seawater (sampled in Katsuura City, Chiba Prefecture) was filtered using a microfilter (0.45 μm) manufactured by Fujifilm, and after adding various radionuclides as tracers, hydrochloric acid and sodium hydroxide solution were used. in
The pH was adjusted to 8.0±0.5. The salinity of the seawater used was 33.7%. 3.1.4 Nuclide used ⁵⁴ Mu MnCl ₂ (MnCl ₂ 2μg/g in 0.1NHCl)
202.5pCi/ml ⁵⁹ Fe FeCl ₃ , (FeCl ₃ 2μg/g in 0.1NHCl)
337.6pCi/ml ⁶⁰ CoCoCl ₂ (CoCl ₂ 1μg/g in 0.1NHCl)
255.3pCi/ml ⁶⁵ Zn ZnCl ₂ (ZnCl ₂ 2μg/g in 0.1NHCl)
216.9pCi/ml ⁸⁵ Sr SrCl ₂ (SrCl ₂ 2μg/g in 0.1NHCl)
290.0pCi/ml ¹⁰⁶ RuRuCl ₃ (RuCl ₃ 10μg/g in 0.1NHCl)
248.0pCi/ml ¹³⁷ Cs CsCl (CsCl1μg/g in 0.1NHCl)
201.2pCi/ml ¹⁴⁴ Ce CeCl ₃ (CeCl ₃ 2μg/g in 0.1NHCl)
210.5pCi/ml 3.1.5 Measuring device Gamma ray spectrometer: Germanium detector is
The wave height analyzer is CANB- manufactured by ORTEC.
A product manufactured by ERRA was used. 3.2 Experimental operations 3.2.1 ⁵⁴ Mn, ⁵⁹ Fe, ⁶⁰ Co. ⁶⁵ Zn, ¹⁰⁶ Ru, ¹³⁷ Cs, ¹⁴⁴ Ce
Collection of ⁵⁴ Mn, ⁵⁹ Fe, ⁶⁰ Co, ⁶⁵ Zn, ¹⁰⁶ Ru, ¹⁴⁴ Ce, and ¹³⁷ Cs were packed in acrylic collection columns with inner diameters of 50 mmφ and 100 mmφ, and 200 mm of seawater added with tracer was collected. was passed through the column under the experimental conditions shown in Table 4. The collection material and ion exchange resin of the present invention were transferred to a measurement container, and then measured with a Ge semiconductor detector to determine the collection rate. The collection rate A was defined as follows. A (%) = R ₁₀ / R ₉ × 100 A: Collection rate of collection material R ₉ : Concentration of added tracer (pCi) R ₁₀ : Concentration of collected tracer (pCi)

【table】

[Table] 3.3 Results and Discussion As is clear from the experimental conditions and results in Tables 4 and 5, in the collection experiment using the collection material of the present invention,
It became clear that in addition to ¹³⁷ Cs, ⁶⁵ Zn was also collected at almost 100%. However, ⁵⁹ Fe, which is easily collected by the collection material of the present invention shown in Table 3,
Since ⁶⁰ Co and ¹⁴⁴ Ce showed a low capture rate of 32 to 69% in this experiment, it is thought that they are released during treatment of large amounts of seawater. Effects of the Invention By reviewing the above, (1) the collection material of the present invention: (1) ⁵⁹ Fe, ⁶⁰ Co, ⁶⁵ Zn, ^103+106 Ru, in the pH range of 7 to 9
⁽ 2) Captures ¹³⁷ Cs even in ^the presence of a large amount of ^Na (4) Since it is cotton-like, it is extremely easy to dispose of it as waste when burned. It can be seen that there are similar effects.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are graphs showing the results of a collection test using the collection material of the present invention in a batch method and a column method, respectively.

Claims (1)

[Claims] 1 General formula K ₂ M〓[Fe(CN) ₆ ] in acrylic fiber
A radionuclide and heavy metal collection material comprising a supported and fixed ferrocyanate compound represented by [M = divalent metal]. 2. The collection material according to claim 1, wherein M is cobalt. 3. The collection material according to claim 1, wherein M is zinc. 4. The collection material according to claim 1, wherein M is nickel. 5. The collection material according to claim 1, wherein M is zirconium.