JPH05264415A - Radioactive-gas capturing filter - Google Patents

Abstract

PURPOSE:To enhance the capturing property of radioactive gas and to make it possible to achieve the compact size of a filter by using active carbon, wherein the reaction product of polyethyleneimine and carbon disulfide or the quarternary product of the reaction product is added. CONSTITUTION:This filter is constituted of an adsorbent, wherein the reaction product of polyethyleneimine and carbon sulfide is added tinto fibrous active carbon. The adsorbent is made to be the quarternary product with a compound, which is expressed by a general formula RX (R indicates an alkyl group or benzyl group, whose carbon number is 1-5, and X indicates halogen). The radioactive-gas capturing filter is constituted of this adsorbent. This filter adsorbs not only general radioactive gas but also the radioactive gas, whose main materials are iodine and organic iodine compound, at high adsorbing efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter for collecting radioactive gas generated in nuclear facilities, medical facilities, etc., and particularly suitable for collecting and removing radioactive iodine and methyl iodide. is there.

[0002]

2. Description of the Related Art In recent years, the amount of energy consumption has increased sharply, and many nuclear power plants have been constructed accordingly.
In these nuclear facilities, etc., nuclear fission of nuclear fuel produces gaseous radioactive waste, but the gaseous radioactive waste cannot be discharged directly out of the facility for safety reasons. It is completely processed and discharged outside the facility. Further, since radioisotopes have come to be used in many places such as universities, various research institutes, medical facilities, etc., exhaust treatment thereof has become important.

Activated carbon has been used as a filter for collecting and removing radioactive gas. Activated carbon has a collecting performance for simple iodine, but is very effective for collecting organic iodine compounds. is not. Therefore, for the collection of organic iodine compounds, it has been proposed to impregnate activated carbon with iodine or an inorganic iodine compound or a strongly basic substance such as piperazine, morpholine or triethylenediamine.

[0004]

However, in the conventional filter as described above, the radioactive gas collection performance is not sufficient, and it is necessary to increase the capacity of the collection material in order to prevent leakage. Therefore, there is a problem that the device becomes large, and there has been a demand for the development of an adsorbent having a large collection amount.

The present invention solves the above problems and provides a filter for collecting radioactive gas, which is excellent in collecting radioactive gas, allows the filter to be made compact, and makes the adsorption device compact. It is a specific subject.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have surprisingly found that the reaction product of polyethyleneimine and carbon disulfide and the reaction product of 4 The present invention was reached by finding that activated carbon impregnated with a grade effectively adsorbs not only general radioactive gas but also organic iodine compounds.

That is, the present invention has the following configuration. (1) A filter for collecting radioactive gas, comprising an adsorbent in which a reaction product of polyethyleneimine and carbon disulfide is impregnated on activated carbon.

(2) The adsorbent of the above (1) is treated with a compound represented by the general formula RX (wherein R represents an alkyl group having 1 to 5 carbon atoms or a benzyl group, and X represents halogen).
A filter for collecting radioactive gas, which is composed of a graded adsorbent.

The present invention will be described in detail below.

In the present invention, the activated carbon to which the reaction product of polyethyleneimine and carbon disulfide is impregnated may be any of those obtained from wood, coconut shell, coal pitch, etc. It is preferable that the specific surface area is 300 m ² / g or more, particularly 600 m ² / g or more, because the amount of impregnation increases and the ability to collect radioactive gas also improves.
If the specific surface area is less than 300 m ² / g, the pore volume and specific surface area of the activated carbon become small when the reaction product is impregnated in a sufficient amount, and the adsorption effect of the activated carbon by the micropores is remarkably reduced, which is not preferable. The specific surface area is determined by the BET theoretical formula from the adsorption amount of nitrogen gas.

The amount of the reaction product of polyethyleneimine and carbon disulfide impregnated on the activated carbon is preferably 7 to 50% by weight, more preferably 10 to 40% by weight, based on the activated carbon. Deposition amount is 7% by weight
When it is less than the above, the adsorption effect by the functional group is small and the collection rate of the radioactive gas is small. On the other hand, when the content is 50% by weight or more, the impregnated substance blocks the pores of the activated carbon and the collection effect is reduced, which is not preferable.

In order to obtain the adsorbent constituting the collecting filter of the present invention, first, activated carbon is added to an aqueous solution of polyethyleneimine, preferably an aqueous solution of 0.5 to 25% by weight.
Polyethyleneimine is impregnated on the activated carbon by reacting at ~ 90 ° C for 30 minutes to 5 hours. Next, this polyethyleneimine-impregnated activated carbon is reacted with carbon disulfide at a reaction temperature of 30-
The reaction time at 100 ° C. is preferably 1 to 5 hours. The amount of carbon disulfide added here was 0. 1 with respect to 1 equivalent of the primary and secondary amino groups of polyethyleneimine impregnated on the activated carbon.
3 to 1.1 equivalents are preferred. If it is less than 0.3 equivalent, the collection rate of radioactive gas will be reduced, and if it exceeds 1.1 equivalent, excess carbon disulfide will be adsorbed on the activated carbon to give offensive odor and not only the collection of radioactive gas will occur. It is not preferable because the yield is lowered. The polyethyleneimine used here preferably has a molecular weight of 140 to 6000. When the molecular weight exceeds 6000, it becomes difficult to enter the pores of the activated carbon and it becomes difficult to impregnate it.

In the present invention, an adsorbent obtained by impregnating activated carbon with a reaction product of polyethyleneimine and carbon disulfide,
A filter for collecting radioactive gas is composed of an adsorbent quaternized with a compound represented by the general formula RX (wherein R represents an alkyl group or a benzyl group having 1 to 5 carbon atoms, and X represents halogen). You may.

The introduction of the quaternary ammonium group into the reaction product of polyethyleneimine and carbon disulfide is carried out by introducing a moiety of the tertiary amino group in the reaction product and the general formula RX (where R is a group having 1 to 5 carbon atoms). An alkyl group or a benzyl group is reacted with a compound represented by X is halogen.
As the compound, benzyl chloride, methyl chloride, methyl bromide, ethyl chloride and the like are preferably used. The quaternization is carried out by immersing the impregnated activated carbon in an aqueous solution or alcohol solution of the quaternization compound,
It can be obtained by reacting at -80 ° C for 1 to 5 hours. The amount of the quaternized compound is preferably 0.7 to 1.1 equivalents relative to the tertiary amino group.

In the present invention, it is preferable to use fibrous activated carbon to which a reaction product of polyethyleneimine and carbon disulfide or a quaternary product thereof is impregnated. An adsorbent that uses fibrous activated carbon has a significantly faster adsorption rate of radioactive gas than an adsorbent that uses granular activated carbon, and can exert a sufficient trapping effect even with a small amount, making the trapping filter smaller. Can be made lighter. Further, it has an advantage that it can be molded into various shapes and a filter suitable for the apparatus can be manufactured.

The fibrous activated carbon is a material in which pitch-based, polyacrylonitrile-based, cellulosic-based or phenol-based fibers are used as a raw material to infusibilize it by a conventional method and activate it to provide fine pores, and its specific surface area is 500 m ^2. / G or more,
It is particularly preferably 900 m ² / g or more. Since the fibrous activated carbon has pores smaller than those of the granular activated carbon, those having a specific surface area larger than that of the granular activated carbon are preferable. The fibrous activated carbon can be made to have a larger specific surface area than the granular activated carbon, the amount of the impregnated carbon can be increased, and the filter having excellent adsorption performance due to the synergistic effect of the functional groups and pores It is preferable because it is obtained and the collection effect is also increased.

The filter for collecting radioactive gas according to the present invention is obtained by molding into a filter by a method of filling the cartridge with activated carbon impregnated with these functional groups, a method of sandwiching it between a woven fabric or a non-woven fabric, and the like. be able to.

In the filter using the fibrous activated carbon, the fibrous activated carbon having functional groups attached thereto may be used alone, but it is preferably used in the following various forms. That is, a synthetic fiber, a non-woven fabric such as natural fiber, a woven fabric, a knitted fabric, or the like laminated on at least one surface of a sheet-like product consisting of a fibrous activated carbon alone impregnated with a functional group, or these are entangled by a needle punch or heat-sealed. Or a fibrous activated carbon impregnated with a functional group and a certain amount of thermoplastic synthetic fiber mixed dry or wet to form a sheet, and one of the thermoplastic synthetic fibers obtained by heat-treating the sheet. A part or all is heat-melted, and a fibrous activated carbon and a thermoplastic synthetic fiber or a thermoplastic synthetic fiber are fused and integrated into a sheet-like material, and further, a synthetic fiber on at least one surface of these sheet-like materials, Nonwoven fabrics such as natural fibers, woven fabrics, knitted fabrics and the like are used.

Examples of the thermoplastic synthetic fibers used above include polyester, nylon, polyethylene,
Examples thereof include core-sheath composite fibers using polypropylene, copolyester or polyester for the core and polyethylene, polypropylene or copolyester for the sheath. When fibrous activated carbon having functional groups attached thereto and thermoplastic synthetic fiber are mixed, the mixing ratio is 98: 2 to 40:60, preferably 95: 5 to 50:50. When the ratio of the fibrous activated carbon is 98% or more, the moldability of the filter is deteriorated, and when the ratio is less than 40%, the radioactive gas collecting performance is deteriorated.

The fibrous activated carbon and the thermoplastic synthetic fiber are mixed by, for example, introducing the fibrous activated carbon and the thermoplastic synthetic fiber into a card machine at a predetermined ratio, mixing them while applying the card, and then integrating them by needle punching. It is possible to employ a method of forming a sheet-like product by a wet process by a papermaking method while mixing fibrous activated carbon and a thermoplastic synthetic fiber. Furthermore, when the fibrous activated carbon and the thermoplastic synthetic fiber are mixed, natural fibers such as hemp and cotton may be mixed.

Since the reaction product of polyethyleneimine and carbon disulfide and the quaternary product thereof are impregnated on the activated carbon in the filter for collecting radioactive gas of the present invention, not only general radioactive gas but also iodine and Even a radioactive gas mainly composed of an organic iodine compound can be collected satisfactorily and with high adsorption efficiency.

[0022]

EXAMPLES Next, the present invention will be specifically described by way of examples.

Example 1 Polyethyleneimine having a molecular weight of 1200 (Epomin SP-012;
10 g of Nippon Shokubai Co., Ltd. was dissolved in 90 g of ion-exchanged water, and coconut shell activated carbon (20 to 50 mesh; specific surface area 950 m ² /
g) 30 g was added, and the mixture was stirred at 30 ° C. for 2 hours, filtered, and thoroughly washed with ion-exchanged water. From the increase in weight after drying, the impregnation rate of polyethyleneimine was 15% by weight. next,
34 g of the obtained polyethyleneimine-impregnated activated carbon was gently stirred together with 5.3 g of carbon disulfide and 100 g of ion-exchanged water, heated and stirred at 40 ° C. for 1 hour and further at 75 ° C. for 4 hours, and then filtered to obtain ion-exchanged water. It was thoroughly washed with to obtain an adsorbent. The total adsorbing rate of the obtained adsorbent was 23% by weight, and the specific surface area was 570 m ² / g.

36 g of the adsorbent was uniformly filled in a casing having a diameter of 104 mm, and both ends thereof were sandwiched with a polyester non-woven fabric having a basis weight of 30 g / m ² to prepare a filter. About 450Bq (auto well gamma system
Using the Aloka ARC-301B device, the radioactive gas mainly composed of methyl iodide of 125-I radioactivity was counted.
The adsorption efficiency was calculated by counting the radioactivity before and after the passage at 1.0 m / s and showing an adsorption efficiency of 86%.

Comparative Example 1 A filter was prepared in the same manner as in Example 1 except that only activated carbon was impregnated with polyethyleneimine, and the adsorption efficiency of radioactivity was measured in the same manner as in Example 1. As a result, the adsorption was as low as 48%. It was efficient.

Example 2 Polyethyleneimine having a molecular weight of 600 (Epomin SP-006;
16 g of Nippon Shokubai Co., Ltd. was dissolved in 3000 g of ion-exchanged water and fibrous activated carbon (A-15, Unitika Co., specific surface area 1530) was added to this.
m ² / g) 100 g was added, and it was immersed at 28 ° C. for 4 hours. To this, 8.4 g of carbon disulfide was added and gently stirred for 1 hour, then heated and stirred at 85 ° C. for 4 hours, then filtered and sufficiently washed with warm water to obtain a fibrous adsorbent. .. The total adsorbed amount of the obtained adsorbent was 11% by weight, and the specific surface area was 1130 m ² / g.

This fibrous adsorbent was molded into a non-woven fabric having a basis weight of 300 g / m ² , and both surfaces thereof were sandwiched with a polyester non-woven fabric having a basis weight of 15 g / m ² to prepare a cylindrical filter having a diameter of 104 mm. A radioactive gas was passed through this filter in the same manner as in Example 1, and the adsorption efficiency was calculated by counting the radioactivity before and after that, and the adsorption efficiency was 82%.

Example 3 40 g of the fibrous adsorbent obtained in Example 2 was mixed with 10 parts of ethanol.
It was immersed in a solution of 5.6 g of benzyl chloride dissolved in 00 g, stirred at 50 ° C. for 3 hours, filtered, and sufficiently washed with a 50% by volume aqueous ethanol solution to obtain a quaternized adsorbent. The total adsorbed amount of the adsorbent thus obtained was 15% by weight, and its specific surface area was 980 m ² / g.

This fibrous adsorbent was formed into a non-woven fabric having a basis weight of 300 g / m ^{2 in} the same manner as in Example 2, and both sides of the basis weight 15
It was sandwiched between g / m ² polyester non-woven fabrics to form a cylindrical filter with a diameter of 104 mm. A radioactive gas was passed through this filter in the same manner as in Example 2, and the adsorption efficiency was calculated by counting the radioactivity before and after that, and the adsorption efficiency was 92%.

Comparative Example 2 A filter was prepared in the same manner as in Example 2 except that only polyethyleneimine was attached. As a result of measuring the adsorption efficiency of radioactivity using this filter in the same manner as in Example 2, the adsorption efficiency was as low as 42%.

[0031]

EFFECTS OF THE INVENTION The filter for collecting radioactive gas according to the present invention has a reaction product of polyethyleneimine and carbon disulfide and its quaternary compound attached to activated carbon. Even a radioactive gas mainly containing iodine or an organic iodine compound can be satisfactorily collected with high adsorption efficiency. INDUSTRIAL APPLICABILITY The filter of the present invention is suitable as a filter for collecting radioactive gas, which is incorporated in an adsorption device in combination with a dust filter or used alone as a mask.

Claims (4)

[Claims] 1. A filter for collecting radioactive gas, which comprises an adsorbent in which a reaction product of polyethyleneimine and carbon disulfide is impregnated on activated carbon. 2. The filter for collecting radioactive gas according to claim 1, wherein the activated carbon is fibrous. 3. The adsorbent according to claim 1 is quaternized with a compound represented by the general formula RX (wherein R represents an alkyl group having 1 to 5 carbon atoms or a benzyl group, and X represents halogen). A filter for collecting radioactive gas, which is composed of an adsorbent. 4. The filter for collecting radioactive gas according to claim 3, wherein the activated carbon is fibrous.