A method of obtaining a weakly acidic cation exchanger based on polyacrylonitrile fiber

 

(57) Abstract:

Use: nuclear power for the control and treatment of water coolant of the primary and secondary circuits of nuclear power plants. The inventive polyacrylonitrile fiber is treated with a mixture of ethylsilicate sodium and hydrazine. Then subjected to additional irradiation with ionizing radiation with a dose of 4104-7105in an aqueous solution of hydrazine with a concentration of 0.1 - 0.5 g/l 2 Il., table 4.

The invention relates to the field of chemical technology of fibrous ion-exchange materials and can be used in nuclear power to control and clean water coolant of the primary and secondary circuits of nuclear power plants.

A method of obtaining an ion-exchange fibers based on polyacrylonitrile fibers (PAN-fibers) methods polymeranalogous transformations, for example by saponification (processing) sodium hydroxide [1]

This method is quite labor intensive, time consuming and the value of the static exchange capacity (SOY), the main characteristics of the resin, small.

It is known that radiation exposure can lead to the evident stability of ion-exchange materials can be concluded, when the irradiation of the majority of the ion is reduced exchange capacity and the deterioration of their performance properties.

Closest to the invention is a method for ion-exchange polyacrylonitrile fiber, conclude himself in the saponification source suzeormanshow fiber processing in aqueous solution with a mixture of ethylsilicate sodium (GGC-10) with hydrazine hydrate in a ratio of components(4:1)-(19:1) within 20-40 minutes at a temperature of 96-98aboutWith, washing and drying. This method allows to reduce processing time and increase the static exchange capacity of the ion exchanger [4]

The disadvantage of this method is that the surface of the fibrous materials is a strong heterogeneity, therefore, the ion-exchange groups formed on the surface of polyacrylonitrile fibers by hydrolysis of the ester and nitrile groups, have a more distorted structure than ion-exchange groups of the matrix resin (type RL-2, AV-17 and others) the Use of hydrazine with a strong reducing properties, contributes to the structuring of ion-exchange fibers, but the resulting material has a lower selectivity than the matrix ion.

The technology is from polyacrylonitrile fibers. This technical problem is solved due to the fact that acrylic fiber, after processing them in a mixture of ethylsilicate sodium (NGL-10) and hydrazine, are subjected to additional irradiation with ionizing radiation to the absorbed dose 4104-7105G in an aqueous solution of hydrazine with a concentration of 0.1-0.5 g/L.

Under the action of ionizing radiation in water and aqueous solutions formed by the radiolysis products of water chemically highly active particles: N-radicals and solvated electrons, which is a very strong reducing agents. Oh-radicals and hydrogen peroxide having oxidizing properties. Fibrous materials have sellersville surface, so radiolysis products, when exposed fibers in water with high efficiency can interact with the surface of the ion exchanger, producing a variety of chemical transformations.

The restorative properties of H-radicals and solvated electrons is significantly superior to the properties of hydrazine-hydrate, so the irradiation PAN-fibrous ion exchanger in the water leads to additional structuring of the fibers and, consequently, to increase the selectivity of the resin.

When irradiated in aqueous solution added acceptor QA is e, to interact with rehabilitation particles of the products of radiolysis of water and, therefore, reduce the effectiveness of radiation exposure.

The invention consists in the following.

The original freshly formed saponified POLYACRYLONITRILE fiber is treated with a mixture of ethylsilicate sodium (NGL-10) and hydrazine at a ratio of components(4: 1)-(19: 1). The treatment is carried out within 20-40 minutes at a temperature of 96-98aboutC. Upon completion of the reaction, the fiber is rinsed from impurities. Fiber is subjected to the radiation ionizing radiation to the absorbed dose (4104)-(7105) Gr. Irradiation is carried out in a solution of hydrazine with a concentration of 0.1-0.5 g/L.

The invention is illustrated by the following examples.

Experimentally under laboratory conditions was studied the influence of radiation on the PAN fibres treated with a mixture of ethylsilicate sodium (NGL-10) and hydrazine. The experiment was performed by the method in accordance with [4], followed by the radiation of the obtained resin.

P R I m e R 1. Freshly formed not stretched fiber (PAN) is treated with 4% NaOH solution for 4 min at a temperature of 98-100aboutWith and dried on who is igrata in the ratio of 90:10. The resulting fiber has the following properties:

SOY 4,5 mg EQ/g (mmol/g)

Fiber strength 26,03 HS/Tex

Elongation 48,6%

Selective viviremos copper 3.25 mgex/g (mmol/g)

Further samples of PAN fibers, washed and dried, the weight of 2.0 g placed in glass vials with a volume of 100 ml and irradiated at the facility RKHM - -20 gamma-quanta60With, a capacity of 2.4 G/C. the Selectivity of the ion exchanger is determined by the following method. Washed and dried after irradiation the samples placed in plastic cups with 50 ml of solution. Selectivity was calculated from the ratio of the amount adsorbed and the remaining solution of the substance after a long (over 100 hours) of contact of the resin and solution [5]

For research were selected solutions of radioactive isotope137Cs with specific activity 1,27106Bq/l High sensitivity radiometric measurement methods allowed us to work with solutions of low concentration, which is especially important in determining the selectivity of the resin.

In table. 1 shows the results of experiments.

As can be seen from the presented results, exposure to ionizing radiation increases the selectivity of the resin is more than 5 times. , the effects of radiation due to the interaction of the resin with the products of water radiolysis.

P R I m m e R 2. Freshly formed stretched POLYACRYLONITRILE fiber treated according to example 1 10% solution of ethylsilicate sodium and 12% solution of hydrazine hydrate in a ratio of 90:10 for 25 minutes, the Obtained fiber has the following properties:

Total capacity 5.5 mgecw/g (mmol/g)

Fiber strength 20,03 HS/Tex

Elongation of 45.6%

Selective viviremos copper 3,9 mg EQ/g (mmol/g)

Then the samples PAN-fibers, washed and dried, the weight of 2.0 g placed in glass vials with a volume of 100 ml and irradiated at the facility RKHM - -20 gamma-quanta60With, a capacity of 2.4 G/S. Forth in example 1.

In table. 2 shows the experimental results obtained according to the description of example 2.

Comparing examples 1 and 2 it can be noted that changes in the concentration of the modifying agent has no significant effect on the coefficient of the selectivity of the ion exchanger that obtained by the subsequent radioactive irradiation. The selectivity coefficient is still high for the water environment, as in example 1. The impact of radiation is determined largely by the composition of the aqueous phase that horosheve selectivity of the ion exchanger, and in the highly alkaline environment, the impact is reduced and exposure to acid, even passivates the ion exchanger.

Thus, the positive effect of ionizing radiation is achieved only under certain conditions of exposure and is characterized by a specific composition of the solution and the dose of radiation.

P R I m e R 3. The rationale for the composition of the medium during irradiation of the resin.

On PAN-fibers, obtained as in example 1 treatment ethylsilicate sodium and hydrazine hydrate with SOY-4,5 mg EQ/g (mmol/g), was studied the influence of various substances, acceptors products of water radiolysis, the value of the selectivity of the resin upon irradiation. The results of the experiments are given in table. 3.

From the analysis of experimental data shows that the introduction of a solution of potassium nitrate, which is the acceptor recovery of the particles reduces the effectiveness of ionizing radiation in 1.6 times. Of acceptors oxidative particles were found the most effective hydrazine hydrate.

In Fig. 1 shows the dependence of the selectivity of the resin upon irradiation on the concentration of hydrazine in solution. It is seen that at a concentration of 0.3 g/l selectivity factor, which is riodic to decrease the selectivity of the resin after exposure.

Thus, the optimum concentration of hydrazine in solution should be considered as 0.3 g/l, and the boundary conditions adopted in the invention is 0.1-0.5 g/L.

P R I m e R 4. The rationale for the dose of ionizing radiation during irradiation.

On PAN-fibers, obtained as in example 1, determined the dependence of the coefficient of the selectivity of the ion exchanger from the exposure dose at the facility RKHM--20. The concentration of hydrazine in solution during irradiation was 0.3 g/l (see Fig. 2). It is seen that increasing the dose of ionizing radiation to 4104Gr naturally increases the coefficient of the selectivity of the resin. Further increase in the dose of radiation does not lead to a substantial increase in the selectivity of ion-exchange material. At doses of more than 7105Gray selectivity factor decreases, which, apparently, is connected with the beginning of the destruction of the fibers.

Thus, the optimum should take a dose of ionizing radiation 3,7105and the boundary values adopted in the claims -4104-7105Gr.

P R I m e R 5. Comparison of the effectiveness of water treatment with the PAN-fibrous ion exchangers obtained by the known and proposed methods.

Experimentalyou, obtained by a known method and the proposed method of example 1.

The tests were carried out on aqueous solutions of waste nuclear energy containing isotopes60With134Cs and137Cs.

The results are given in table. 4.

A method of OBTAINING a weakly acidic CATION exchanger BASED ON POLYACRYLONITRILE FIBERS by saponification of the original vegetariano fiber, treatment with an aqueous solution of a mixture of ethylsilicate sodium hydrazinehydrate, washing and drying, characterized in that after drying, the fiber is additionally irradiated with ionizing radiation to the absorbed dose 4 1047 of 105Gray in an aqueous solution of hydrazine with a concentration of 0.1 - 0.5 g/L.

 

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