RU2067328C1 - Method for removal of radionuclides from aqueous solutions - Google Patents

Abstract

FIELD: ecology, particular, removal from solutions, mainly, aqueous solutions of radionuclide impurities occurring in industrial wastes and as contaminants of environment. SUBSTANCE: method for removal of radionuclides from aqueous solutions includes subjection of aqueous solution contaminated with radionuclides to contacting (mechanical mixing, passing through column or filter) with biological sorbent prepared from raw materials of plant origin )phytosorbent) which is waste of food industry. Then, radioactive phytosorbent is separated from purified solution, burnt and radioactive ash is buried in soldered ampuls. EFFECT: available and low-cost raw materials used for preparation of sorbent, high capability of calcination at low energy consumption; nontoxic phytosorbent used for the purpose, and provision of purification of foodstuffs, high stability of phytosorbent, absence of contamination of purified solution with any byproducts; higher (practically 100%) efficiency of bonding the actinides (plutonium); higher efficiency of bonding of cesium and strontium, as compared with biological sorbents based on chitin and chitosan; higher efficiency as compared with inorganic sorbent of KLINOSORB type (Germany). 2 cl, 1 tbl

Description

 The invention relates to the field of ecology, namely to the purification of solutions (mainly aqueous) from impurities of radionuclides, and can be used to extract and dispose of radioactive elements found both in industrial waste and in the form of environmental pollution.

A known method of separation of strontium from water by contacting the purified water with a sorbent based on zeolite [1]
There is also known a method of extracting strontium from highly mineralized solutions, in which carboxyl cation exchange resin in mixed sodium-calcium form is used as a sorbent [2]
The disadvantage of these methods is the difficulty associated with the disposal of radioactive residues, since mineral sorbents are used in the extraction of radionuclides in these methods.

A known method of purification of aqueous solutions from radioactive isotopes by contacting these solutions with ground chitin, separation of chitin with associated radionuclides from the solution to be purified, its burning and disposal of radioactive ash [3]
The disadvantages of the method [3] are the low removal efficiency of strontium and cesium with a fairly good binding of actinides (plutonium), inaccessibility and the relative high cost of the used sorbent; relatively high energy costs when burning.

 Closest to the proposed method is the removal of heavy metals, including radioactive ones, from aqueous solutions, comprising contacting the solution to be cleaned with a tannin sorbent [4] previously obtained by a specific method, at pH of solutions from 3.5 to 10.0, and contacting the solution to be purified with the sorbent is carried out twice at different pHs: after the first contact, the sorbent is filtered off and the filtrate is contacted with a fresh portion of the sorbent. Sorbent can be regenerated.

 The disadvantages of this method [4] are the lack of efficiency in the removal of radioactive isotopes, inaccessibility and the relative high cost of the used sorbent.

 The objective of the invention is the development of a simple, cost-effective and efficient method for the extraction of radionuclides based on the use of a sorbent from cheap and affordable raw materials.

 This is achieved by the proposed method for removing radionuclides from aqueous solutions, including contacting the solution to be cleaned with phytosorbent at a pH of 3.0 to 9.0 and separating the sorbent from the solution, in which the crushed husk of sunflower seeds subjected to acid hydrolysis is used, separated the phytosorbent is burned and the radioactive ash is collected (for burial).

 In the proposed method, as a phytosorbent, non-hydrolyzed crushed husk of sunflower seeds is used.

 In the proposed method, in contrast to the known [4], another type of phytosorbent is used, namely, a sorbent obtained from cheap and affordable plant materials.

 The proposed method is as follows.

 Solutions containing radionuclides are either directly mixed with the sorbent (static mode) or passed through a column or filter containing the sorbent (dynamic mode). The initial concentration of radioactive elements in the solution ranged from 0.1 mg / L to 1000 mg / L. As phytosorbent in all examples (except 3b), crushed husk of sunflower seeds hydrolyzed in an acidic medium (3b unprocessed husk) was used. Three different phytosorbent concentrations were used: 1 g / l, 5 g / l and 10 g / l. To extract radionuclides, one can use both their aqueous solutions and their solutions in polar organic solvents or in mixtures thereof. The contact time of the sorbent with the solution covered both the minute and hour ranges, depending on the processing tasks.

The initial (C _out ) and final (C _con ) concentration of radionuclides were determined (mainly) on two types of installations:
1. On a Pripyat low-frequency gamma-coincidence spectrometer with a working volume of the measuring chamber of 5 l (cesium-137 sensitivity - 6 • 10 ^-12 Ci for a set time of 1 h or 1.2 • 10 ^-10 Ci for a set time of 10 s )

 2. At the Plasma-100 emission spectrometer (USA), which allows you to measure the concentration of elements in aqueous solutions with an error of several for most elements and allows you to simultaneously measure the concentrations of all elements present in the aqueous solution.

 We give specific examples of the method.

 PRI me R 1. Removal of europium (plutonium).

71 Отделенный фитосорбент сжигают и пепел собирают для захоронения.Plutonium as a radionuclide is especially dangerous due to the high degree of toxic effects on biological objects. It is known that the behavior of europium in aqueous solutions is very similar to plutonium. Therefore, methods for purifying plutonium from aqueous solutions are being developed (which is generally accepted) in less harmful europium:
a). To a solution containing 10 mg / l europium at pH 5, 100 mg of phytosorbent, which is a crushed husk of sunflower seeds, is added and the mixture is incubated for 1 h. The total volume of the solution is 10 ml. Then the sorbent is separated by filtration and the europium concentration is measured in the remaining solution. On average, it was 2.9 mg / L. The binding efficiency was

71 The separated phytosorbent is burnt and the ashes are collected for burial.

 b) To a solution containing 10 mg / l europium at pH 5, 100 mg of phytosorbent, which is a crushed husk of sunflower seeds, subjected to acid hydrolysis, is added and the mixture is incubated for 1 h. The total volume of the solution is 10 ml. Then the sorbent is separated by filtration and the europium concentration is measured in the remaining solution. On average, it was 0.42 mg / L. The binding efficiency was = 96 The separated phytosorbent was burned and the ash was collected for disposal.

 PRI me R 2. Removal of strontium.

To a solution containing 5 mg / L of strontium at pH 3, 100 mg of phytosorbent from a hydrolyzed husk of sunflower seeds is added and the mixture is incubated for 1 hour. On average, the concentration of strontium in the remaining solution was 2.3 mg / L. Binding Efficiency = 54
PRI me R 3. Removal of cesium:
a). To a solution containing 10 mg / ml cesium at pH 8.0, 100 mg of phytosorbent from unhydrolyzed husk of seeds was added and incubated for 60 minutes. The average concentration of cesium in the remaining solution was 4.63 mg / ml. The binding efficiency of 53.7
b) To a solution containing 10 mg / l of cesium at pH 9.0, 100 mg of phytosorbent from a hydrolyzed husk of sunflower seeds was added for 5 minutes. The average concentration of cesium in the remaining solution was 1.85 mg / L. Binding Efficiency = 81.5
The total results for the removal of radionuclides and heavy metals are shown in the table.

The amount of phytosorbent (m) in all samples was 100 mg; volume (v)
10 ml s% (C _ref C _con ) / C _ref % s (C _ref - C _con ) • v / m.

The proposed method for the removal of radionuclides has several advantages over the known [4]
a) the availability and low cost of raw materials used in the preparation of phytosorbent;
b) high ability to ashing at low energy costs;
c) non-toxicity of the phytosorbent used and the ability to clean food;
d) high stability;
e) the absence of contamination of the cleaned solution with any by-products;
f) higher (almost 100) actinide binding efficiency;
g) a high degree of removal during a single contact of the phytosorbent with the solution being cleaned. TTT1

Claims (2)

 1. A method of removing radionuclides from aqueous solutions, comprising contacting the solution to be cleaned with phytosorbent at pH 3 9 and separating the sorbent from the solution, characterized in that crushed sunflower seed husk is used as phytosorbent, the separated phytosorbent is burnt and the radioactive ash is collected for disposal.  2. The method according to claim 1, characterized in that as a phytosorbent use crushed husk of sunflower seeds, subjected to acid hydrolysis.

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