JPH0722699B2 - Collection material for heavy metals such as complex radionuclides - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heavy metal scavenger, particularly a scavenger suitable for collecting heavy metals such as radionuclides in a complex state with non-radioactive salts. Is.

[Conventional technology]

Radioactive waste liquid generated from nuclear power plants, radioisotope handling sites, etc. has various problems such as radiation exposure of workers, release of radioactivity to the surrounding environment, and storage of radioactive waste on site.

Conventionally, radioactive waste has been stored by processing such as drum packing. However, as the total amount of waste drums has increased, storage site problems have arisen, and reducing the volume of radioactive waste is becoming a major issue in the future.

When radioactive heavy metal ions contained in the primary cooling water of a nuclear power plant are adsorbed and removed, since the salt concentration in the water is low, it can be easily adsorbed and removed by an ion exchange resin having a sulfonic acid group, etc. In regeneration of the exchange resin, radioactive heavy metal ions are eluted from the ion exchange resin with an acid or alkali such as NaOH or H ₂ SO ₄ . Therefore, the ion-exchange resin recycling waste liquid contains radioactive heavy metal ions and non-radioactive salts such as Na ₂ SO ₄ , and these are released and stored in large amounts as radioactive waste.

If the radioactive heavy metal ions in this can be completely adsorbed and separated by using a small amount of an adsorbent, it will greatly contribute to the volume reduction of radioactive waste.

Recently, the Japan Atomic Energy Society, "Sho 62nd Annual Meeting", publication number J-
It has been reported in 60, J-61 and J-62 that the total amount of radioactive waste can be significantly reduced by adsorbing a waste liquid containing a radioactive heavy metal ion.

That is, the insoluble suspension in the waste liquid was removed by a non-auxiliary type microfiltration device, and among the residual ionic radionuclides, C
Metal ions such as o, Mn, and Zn nuclides are adsorbed and removed by the chelate resin first tower, and Sr and Cs nuclides are adsorbed and removed by the chelate resin second tower and the natural mordenite adsorbent, respectively. Books / year needed
We have reported an epoch-making adsorption removal system with 49 bottles / year.

However, Co, Mn, Zn and Sr can be easily adsorbed by the chelate resin tower, but it is difficult to remove Cs by adsorption, and the amount of natural mordenite adsorbent used is 49 waste drums generated from the treatment system. This is a result of occupying about 1/3 of the total, 16 per year, and it must be said that this is a problem considering that the chelating resin used for the adsorption treatment can be burned to almost zero capacity. Absent.

[Problems to be solved by the invention]

Therefore, an object of the present invention is to reduce the amount of radioactive waste extremely by completely adsorbing and removing radioactive heavy metal ions contained in wastewater containing non-radioactive salts in nuclear power plants and the like with a very small amount of adsorbent. It is to provide the technology to obtain.

[Means for solving problems]

The present inventors have conducted extensive studies to achieve the above object, and as a result, by combining an acrylic fiber carrying a ferrocyanate compound and a granular or fibrous chelate resin, the amount of radioactive waste can be extremely reduced. The inventors have reached the present invention by finding that they can be reduced.

That is, in the present invention, the acrylic fiber has the general formula K ₂ M (II) [FeCN) ₆ ] [wherein M (II) represents a divalent metal. ] The present invention relates to a heavy metal scavenger such as a radionuclide, which is composed of a combination of an adsorbent carrying a ferrocyanate compound represented by:

Hereinafter, the present invention will be described in detail.

The acrylic fiber used in the present invention may be a fiber made of a binary or ternary copolymer or acrylonitrile homopolymer containing 40% by weight or more of acrylonitrile. Here, the copolymer component, acrylic acid, sodium methallyl sulfonate, sodium allyl sulfonate, sodium p-styrene sulfonate, acrylamide, methacrylamide, vinyl chloride, vinylidene chloride, vinyl acetate,
Examples thereof include, but are not limited to, methyl acrylate, N, N′-dimethylaminoethyl acrylate, N, N′-diethylaminoethyl methacrylate and the like.

The acrylic fiber may be used as the acrylic fiber of the present invention after the surface is hydrolyzed with a base such as sodium hydroxide or an acid such as sulfuric acid.

Furthermore, a carboxyl group and / or a sulfonic acid group is added in an amount of 0.1 to 5
Acrylic fibers containing mmol / g are more preferred. Since the ferrocyanate compound of the present invention (hereinafter referred to as insoluble ferrocyanide) is adsorbed on the acrylic fiber by ionic interaction via the carboxyl group and / or sulfonic acid group, This is because the adhesion amount increases. However, the total content of carboxyl group and / or sulfonic acid group is 0.1 mmol / g
When the amount is less than the above, the amount of the insoluble ferrocyanide attached hardly increases, and when it exceeds 5 mmol / g, the physical properties of the single yarn when used as a heavy metal scavenger such as a radionuclide are remarkably deteriorated. Results in being limited.

The insoluble ferrocyanide is a substance which has a solubility in water of 0.1 g / 100 cc or less at 25 ° C. and is composed of [Fe (CN) ₆ ] and a metal. For example, K ₂ Co [Fe (CN) ₆ ],
Na ₂ Ni [Fe (CN) ₆ ], K ₂ Zn ₃ [Fe (CN) ₆ ] 2, Cu ₂ [F
e (CN) ₆ ], Zn ₂ [Fe (CN) ₆ ], Cd ₂ [Fe (C
N) ₆ ], Ni ₂ [Fe (CN) ₆ ], Fe ₄ [Fe (CN) ₆ ] ₃ , T
i [Fe (CN) _6] and the like can be mentioned, as the metal, Li, K, Na, Ag , Zn, Cd, Cu, Co, Ni, Mn, Fe, T
One or more metals such as i, Zr, V, Mo, W, and U can be used in combination, but not limited thereto.

For supporting and fixing the insoluble ferrocyanide on the acrylic fiber, the acrylic fiber itself takes in the insoluble ferrocyanide, or the carboxyl group in the acrylic fiber and / or
Alternatively, the sulfonic acid group and the insoluble ferrocyanide are adsorbed by an ionic interaction, or by a synergistic effect thereof.

The amount of the insoluble ferrocyanide supported on the acrylic fiber should be 0.001 g or more per 1 g of the fiber, and 0.001 g
When the amount is less than the above, the amount of acrylic fiber required for adsorbing heavy metals such as radionuclides increases, which is a practical problem.

A method for supporting and fixing the insoluble ferrocyanide on the acrylic fiber is, for example, a method in which the insoluble ferrocyanide is mixed with a spinning stock solution at the time of spinning the acrylic fiber and then spun by a conventional method using a wet method or a dry method, Examples of the spinning solvent include dimethylformamide, dimethylacetamide, dimethylsulfoxide, nitric acid, and an aqueous solution of rhodanate. Also, for example, when spinning acrylic fibers,
K ₄ [Fe (CN) ₆ ], which is a water-soluble ferrocyanide, Na ₄
[Fe (CN) ₆ ] and the like are dissolved in water having a saturated solubility or higher and mixed with a spinning dope, and then spinning is carried out by a conventional method using a wet method. The ferrocyanide becomes an insoluble ferrocyanide. One or more of Ag, Zn, Cd, Cu, Co,
A method of adding a metal ion or metal complex of Ni, Mn, Fe, Ti, Zr, V, Mo, W, U, etc. to a coagulation bath and spinning it can be mentioned. Furthermore, for example, at least one kind of Ag, Zn, Cd, such that the ferrocyanide becomes an insoluble ferrocyanide in the spinning dope when the acrylic fiber is spun,
Metal ions or metal complexes of Cu, Co, Ni, Mn, Fe, Ti, Zr, V, Mo, W, U, etc. are dissolved in water having a saturation solubility or higher and mixed with a spinning dope, followed by a wet method. Spinning is carried out by the method, which is a water-soluble ferrocyanide such as K ₄ [Fe (CN)
₆ ], Na ₄ [Fe (CN) ₆ ] and the like are added to the coagulation bath and spinning is performed. In addition, for example, acrylic fiber K ₄ [Fe (CN) ₆ ] which is a water-soluble ferrocyanide,
Treatment temperature 10 ℃ ～ 1 with Na ₄ [Fe (CN) ₆ ]
The treatment is performed at 40 ° C. for a treatment time of 30 seconds to 3 hours, and then one or more of Ag, Zn, Cd, Cu, Co, Ni, and Mn are used so that the ferrocyanide becomes an insoluble ferrocyanide. ,
A method of performing treatment with an aqueous solution of a metal ion or a metal complex such as Fe, Ti, Zr, V, Mo, W and U at a treatment temperature of 10 ° C. to 140 ° C. and a treatment time of 30 seconds to 3 hours can be mentioned. or,
For example, an acrylic fiber may be prepared by combining one or more kinds of A with which the ferrocyanide becomes an insoluble ferrocyanide.
g, Zn, Cd, Cu, Co, Ni, Mn, Fe, Ti, Zr, V, Mo,
Treatment with an aqueous solution of a metal ion such as W or U or a metal complex at a treatment temperature of 10 ° C. to 140 ° C. for a treatment time of 30 seconds to 3 hours is performed, and then K ₄ [Fe (C (Fe (C
N) ₆ ], Na ₄ [Fe (CN) ₆ ] or the like may be used at a treatment temperature of 10 ° C. to 140 ° C. for a treatment time of 30 seconds to 3 hours. The above methods are examples,
It is not limited to these.

Further, the granular or fibrous chelate resin used in the present invention is not limited in its resin composition and shape as long as it contains a functional group having a chelate-forming ability. Examples of the functional group having chelating ability, e.g., an amino carboxylic acid group [-N = (CH ₂ COONa) _2],
Polyamine group [-NHC ₂ N ₄ NHnH], thiourea group Aminophosphoric acid group (-NHCH ₂ PO ₃ Na), amidoxime group Glucamine group However, the present invention is not limited to these.

In addition, granular or fibrous chelate resin (hereinafter simply referred to as
(Referred to as “resin”)
Registered trademark name (hereinafter referred to as) Diaion CR10 , Dowex
 A-1 , Uniselec UR-10 , Uniselec UR-20
, Uniselec UR-30 , With polyamine group
Diaion CR20 , Hokuetsu carbon M containing thiourea group
A , Duolite ES469 as aminophosphate-containing compound , A
Diaion CR50 as a body containing a midoxime group , Duolite C
S346 , Diaion CRB02 as glucamine group containing body , Am
berlite IRA743 can be mentioned.

The chelating resin preferably contains 0.01 mmol / g or more of a functional group having a chelate-forming ability. When the content of the functional group having a chelate-forming ability is less than 0.01 mmol / g in the chelate resin, the necessary amount of the chelate resin required for removing the radionuclide in the waste liquid becomes large, and the radioactive waste which is the object of the present invention. It becomes difficult to reduce the volume.

As a combination of these adsorbents, an acrylic fiber adsorbent is packed in the lower column and a chelate resin is packed in the upper column. The lower column of the column is filled with the chelate resin, and the upper column of the column is filled with the acrylic fiber adsorbent. Acrylic fiber adsorbent and chelate resin are mixed and packed in the column. Also, a combination of alternately filling the acrylic fiber adsorbent and the chelate fiber from the lower column is used.

Radioactive metal ions that can be adsorbed and removed by the combination of these adsorbents are Cs, Sr, Mn, Co, Fe, Ni, Zn, Cu, Ce,
It is a metal element such as Ru except Li, K, and Na.

By using the heavy metal scavenger for radioactive nuclides of the present invention, radioactive heavy metal ions are selectively adsorbed from radioactive heavy metal ion-containing wastewater containing non-radioactive salts, and the volume of radioactive waste is reduced. This is different from the ion exchange resin, because the granular or fibrous chelate resin and the acrylic fiber adsorbent each have a stable coordination structure with each radioactive heavy metal ion regardless of the presence or absence of non-radioactive salts. It is thought that it has become possible to remove by adsorption.

In addition, the method for treating heavy metal wastewater such as radioactive nuclides may introduce the treated water from any direction above or below the column of the chelate resin and / or the acrylic fiber adsorbent, and the liquid passing coefficient is 1 It is possible to process from a small treated water flow rate of ~ 2000 to a large treated water flow rate.

[Examples] Examples are shown below.

[Preparation of heavy metal waste liquid such as radionuclide]

Radionuclides generated from nuclear power plants, etc., and radionuclides in heavy metal wastewater have the same chemical properties as the corresponding stable elements, so the radionuclide and heavy metal wastewater used in Examples and Comparative Examples are A wastewater containing a heavy metal that does not contain a radionuclide represented by the composition of (hereinafter abbreviated as model wastewater) is used.

Model wastewater composition Model wastewater Na ₂ SO ₄ 2 wt% Sr 1ppm Cs 1ppm Cu 1ppm Co 1ppm Ni 1ppm Nn 1ppm pH 7.0 Each heavy metal ion solution was used by diluting a metal aqueous solution for atomic absorption spectrometry.

Example 1 (1) Production of Acrylic Fiber Adsorbent The copolymer composition was 91.5% by weight acrylonitrile, 8% by weight methyl acrylate, and 0.5% sodium methallyl sulfonate.
To 4 kg of 3 denier acrylic fiber (weight%), 3N aqueous sodium hydroxide solution 40 is added, and the reaction temperature is 50 ° C.
And react for 1 hour using an Overmeier dyeing machine. After the reaction, the washing is repeated until the washing water has a pH of 7.0 (the content of carboxyl group and sulfonic acid group of the obtained fiber was 2.3 mmol / g). Further, 40% of a 10 wt% cobalt nitrate aqueous solution is added, and the treatment is carried out at a treatment temperature of 60 ° C. for 1 hour using an Overmeier type dyeing machine. After treatment,
The washing is repeated until the color of the washing water disappears.

Then, 10 wt% potassium ferrocyanate aqueous solution 40 is added, and the treatment is carried out at a treatment temperature of 60 ° C. for 1 hour using an Overmeier type dyeing machine. After the treatment, the washing is repeated until the coloring of the washing water disappears. Then, the treated acrylic fiber is dehydrated and dried at 70 ° C. for 10 hours.

The heavy metal exchange capacity of the obtained fiber is 0 as Cs exchange capacity.
It was 030 meq / g (fiber).

(2) Manufacture of column Thickness at the bottom of a polypropylene cylinder with an inner diameter of 5 cm and a height of 30 cm
Liquid-made support made of polypropylene non-woven fabric with a thickness of 5 mm
(Abbreviated as “polypro support” below)
100 g of fiber adsorbent is cut into 10 mm fiber length and separated into single fibers.
And fill the cylinder. Furthermore, on top of that, a polypro support
Laid, Uniselec Filled with 100 g of UR-10 chelating resin
And then there is no void in the cylinder with polypro support on it
So that it becomes a column.

Example 2 (1) Production of acrylic fiber adsorbent Same as in Example 1.

(2) Column production A polypropylene support with an inner diameter of 5 cm and a height of 20 cm is laid on the bottom of the polypropylene support, 100 g of the above acrylic fiber adsorbent is cut into a fiber length of 10 mm, and the fibers are separated into single fibers to form a cylinder. To fill. Column A is filled with a polypro support so that no void is formed in the cylinder.

At the bottom of a polypropylene cylinder with an inner diameter of 5 cm and a height of 10 cm,
Laying a repro support, Uniselec Charge 100 g of UR-10
Filled with polypro support on top of which there are no voids
And column B. Upper column A above
And the lower column B are connected with a pressure resistant tube.

Example 3 (1) Production of acrylic fiber adsorbent An acrylic fiber adsorbent was prepared in the same manner as in Example 1 except that copper sulfate was used instead of cobalt nitrate in the production of the acrylic fiber adsorbent of Example 1. To do.

The heavy metal exchange capacity of the obtained fiber is 0 as Cs exchange capacity.
It was 015 meq / g (fiber).

(2) Production of column A column was produced in the same manner as in Example 1 using the acrylic fiber adsorbent described above.

Example 4 (1) Production of acrylic fiber adsorbent The same as Example 3.

(2) Production of column A column was produced in the same manner as in Example 2 using the above acrylic fiber adsorbent.

Example 5 (1) Production of acrylic fiber adsorbent The same as in Example 1.

(2) Manufacture of column The bottom of a polypropylene cylinder with an inner diameter of 5 cm and a height of 30 cm is placed on the bottom.
Lay a repro support and add 100 g of the above acrylic fiber adsorbent.
Cut into fiber length of 5 mm, separate into single fibers, and uniselec
After uniformly mixing with 50 g of UR-10, fill the above cylinder.
It Further lay a polypro support on top of it
Ku After filling 50 g of UR-10, empty the polypropylene support into the cylinder.
Fill it so that there are no gaps, and use it as a column.

Comparative Example 1 Column A of Example 2 is a single column.

Comparative Example 2 The column B of Example 2 is a single column.

Example 6 The columns of Examples 1 to 5 and Comparative Examples 1 and 2 are put in a metal pressure-resistant cylindrical container, respectively, with a predetermined liquid permeability coefficient, from above or
Liquid is passed from below.

The results of the adsorption treatment are shown in Table 1.

In Examples 1 to 5, the treated water flow rate (displayed by the liquid permeability coefficient) is 100.
As much as ~ 300, and the breakthrough amount of heavy metal ions (the amount of treated water until the start of leakage of heavy metal ions ()) is 58 ~ regardless of the order of treatment of chelating resin and acrylic fiber adsorbent. It was possible to treat 62 and a large amount of water containing heavy metal ions. However, as shown in Comparative Examples 1 and 2, in Comparative Example 1, Co leaks out at 3, and in Comparative Example 2, Cs leaks out at 1. Therefore, the performance as a radionuclide and a heavy metal trapping material is high. Was insufficient.

Further, the polypropylene cylinder, resin and fiber after the adsorption treatment can be simply discarded, and the volume of waste can be further reduced by reducing the volume by incineration. The used adsorbent (resin, fiber) can be reused by regenerating with acid or alkali.

〔The invention's effect〕

By using the heavy metal scavenger such as the radioactive nuclide of the present invention, complete adsorption of metal ions except Li, Na and K can be carried out with or without non-radioactive salts, and is used as a compact device. Therefore, it is suitable for the waste treatment of radioactive isotope facilities such as nuclear power plants, nuclear fuel reprocessing plants, hospitals, and laboratories.

Claims (1)

[Claims] 1. An acrylic fiber having the general formula K ₂ M (II) [FeCN) ₆ ] [wherein M (II) represents a divalent metal. ] A heavy metal scavenger such as a radionuclide comprising a combination of an adsorbent carrying a ferrocyanate compound represented by and a granular or fibrous chelate resin.