RU2746214C1 - Sulfur-derivative of n-hydroxyamidine aminofurazan for extraction of uranium from liquid media - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a sulfur derivative of N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide of the formula

.

The invention also relates to a method for producing the compound.

EFFECT: new compound that can be used as a sorption material for the extraction of uranyl ions from liquid media is proposed.

3 cl, 11 ex, 1 dwg

Description

The invention relates to the field of organic chemistry, specifically to the production of a new sulfur-containing polymer based on N-hydroxyamidine aminofurazan, which can be used as a sorbent of uranyl ions from liquid media, including from technological or sea solutions.

In the processes of mining and processing of mineral uranium raw materials necessary for the development of nuclear power, solid and liquid radioactive waste is accumulated, containing natural uranium and uranium radionuclides. This leads to the proliferation of uranium as a chemical element with a high migration ability into environmental objects. The high chemical hazard of uranium, which has a wide range of water-soluble forms in the biosphere, as well as its radiotoxicity, dictates the search for effective methods for its concentration and isolation from polluted natural and technological waters.

For the quantitative extraction of uranium from aqueous media, in practice, sorption methods are used with the use of various natural and synthetic sorption materials, for example, titanosilicates, phosphorosilicates, synthetic cation exchange resins, etc. However, sorbents known and widely used in practice are effective only in an acidic medium in the pH range = 2.0–4.5, and are also prone to destruction followed by desorption of the radionuclide. When using these materials, special conditions are required, which complicates the technological process.

Known promising polymeric sorption materials containing amidoxime functional groups in their structure and possessing high selectivity to U (VI) compounds in a wide pH range from 6 to 9. A feature of such sorbents is the presence of amino groups in the amidoxime, which ensures the extraction of uranyl ions as mechanism of ion exchange, and as a result of complexation.

To date, the preparation of adsorbents based on amidoxime has been described, such as resins from polymer granules, chemically prepared amidoxime fibers and fibers obtained by radiation-induced graft polymerization, porous materials and polymer fibers modified with amidoxime groups.

So, in the work [Astheimer L. et al. Development of Sorbers for the Recovery of Uranium from Seawater. Part 2. The Accumulation of Uranium from Seawater by Resins Containing Amidoxime and Imidoxime Functional Groups "// J. Separation Science and Technology, 1983, V.18, No. 4, P.307] developed hydroxylamine derivatives of crosslinked polyacrylonitriles, the so-called polyacrylamidoxime resins suitable for accumulation of uranium from natural seawater with pH = 8.1–8.3. The absorption rate of uranium, which is 5-30 ppm per day at room temperature, increases with increasing seawater temperature. Uranium can be eluted with 1M HCl with over 90% efficiency. The obtained polyacrylamidoxime resins simultaneously contain at least two types of functional groups: open chain amidoxime groups, which are stable, and cyclic imidoxime groups, which are unstable in 1 M HCl, which leads to the destruction of the sorbent. This feature of the material is a disadvantage in industrial use. In addition, the narrow range of operating pH values severely limits the use of the known material.

Known [Omichi H. et al. “A New Type of Amidoxime-Group-Containing Adsorbent for the Recovery of Uranium from Seawater. III. Recycle Use of Adsorbent "// J. Separation Science and Technology, 1986, V.21, No. 6-7, P.563] an adsorbent containing an amidoxime group for extracting uranium from seawater, made by radiation-induced graft polymerization of acrylonitrile on polymer fiber followed by amidoximation. Conditioning the adsorbent with an alkaline KOH solution at a temperature of 80 ° C after acid desorption restores the adsorption capacity to its original level, which allows the adsorbent to be reused.

The disadvantages of the known material include the complex synthesis and use of a highly toxic compound of acrylonitrile.

Known [US Pat. CN No. 106902747, publ. 13.09.2019] microspherical adsorbent of amidoxime-mesoporous silicon dioxide with sodium metasilicate as primary raw material. Mesoporous silicon dioxide in the form of microspheres is obtained by microwave hydrothermal synthesis; functionalization with amidoxime groups is carried out by copolycondensation. The resulting adsorbent has an ordered structure of branched mesopores, good mechanical strength and chemical stability, can be used for separation and extraction of uranium, purification of uranium-containing wastewater. The molecular structure is described by the formula SiO ₂ [O ₃ SiCH ₂ CH ₂ C (NH ₂ ) NOH] _x (x = 0.06 ~ 0.13). The variant of obtaining a microsphere sorbent from amidoxime mesoporous silicon dioxide includes the following stages. Triethoxysilane with 3-cyanogenpropyl groups is dissolved in a mixture of ethyl alcohol and water, and then azanol and Na ₂ CO ₃ are added. The reaction mixture is heated at 70 ° C for 12 hours, extracted to obtain functionalized amidoxyorganosilane. Next, a mixture of ethyl alcohol, deionized water, acetate is prepared and, with stirring, a sodium silicate solution with a functionalized amine oximate and a functionalized silane is added. The resulting mixture is again placed in a reactor at 40 ° C for 2 ~ 3 hours with stirring, then a hydrothermal microwave treatment is carried out for 10 hours under the conditions of heating to 90 ° C and intermediate I is obtained, which is cooled, separated by filtration to obtain a solid product, washed in turn deionized water and ethanol. Then, a solution of ethanol with compound I is heated to 60 ° C for 12 hours with a triblock copolymer of the PEO-PPOX-PEO type (P123) and intermediate II is obtained. After separation by filtration, compound II at 60 ° C is repeatedly washed with water and ethanol for final purification. From the obtained material, after 48 hours of vacuum drying, an adsorbent is obtained from microspheres of silicon dioxide with amidoxime with a particle diameter of 90-150 μm.

The disadvantages of the invention include the multistage, duration of the synthesis and the use of expensive reagents.

The invention described in US Pat. KR No. 101718052, publ. 03/20/2017, concerns the amidoxime polymer and its thin film, which has its own microporosity and the efficiency of sorption of uranium in seawater equal to 95%, and with the possibility of regeneration and reuse. In one embodiment of the invention, a solution of the amidocyclic microporous polymer in dimethylformamide is uniformly distributed over the wafer and cured at 150 ° C. to form a thin film of the amidocyclic microporous polymer. The efficiency of uranium adsorption and the rate of sorption in synthetic seawater with a concentration of 5 ppm uranium were the highest at pH = 6 and amounted to 95%.

The disadvantage of the obtained amidoxime polymer, first of all, is the low degree of uranium extraction.

CN patent No. 109954483, publ. 07/02/2019 describes a method for producing a modified polyacrylonitrile porous material for the sorption of uranium containing amidoxime. The method of obtaining includes the following stages: dissolving acrylonitrile in a suitable solvent at room temperature, cryofreezing to obtain a porous matrix, drying it and adding hydroxylamine hydrochloride solution. After the amidoximation reaction, the solid content is recovered, washed several times and dried at room temperature to constant weight. The known material has uniformly distributed pores, providing a large specific surface area, satisfactory mechanical properties and has a larger number of uranium adsorption centers. The adsorption capacity of the material was 211.9 mg / g.

The significant disadvantages of the method for obtaining a highly selective material include the use of toxic solvents such as methanol or tetrahydrofuran, or chloroform, dimethyl sulfoxide or dimethylformamide, as well as the duration of the synthesis, as the process takes 2-7 days.

The prototype of the claimed invention, in essence, is a polymer gel based on amidoxime for extracting uranium from seawater [Wongjaikham W. et al. "Synthesis of amidoxime polymer gel to extract uranium compound from seawater by UV radiation curing" // J. Nuclear Science and Technology, 2019, V.56, No. 6, P.541]. The paper describes an alternative to gamma radiation in the method of radiation-induced graft polymerization, a synthesis route. The material was obtained by the method of photoinitiated crosslinking polymerization, including UV-induced radical polymerization of acrylonitrile and methacrylic acid monomers with a crosslinking agent and a photoinitiator. UV curing at 60 W was carried out for 8 hours to form a polymer gel. The characteristic peaks of IR spectroscopy confirm the conversion of the nitrile group to the amidoxime group. When uranium was sorbed from seawater in an amount of 10 ppm, the adsorption capacity of the resulting gel was 17.02 mg / g. For a seawater sample with an addition of 2.245 ppm uranium, the adsorption capacity reached 432.41 mg / g. The amidoxime polymer gel was tested in sorption-elution cycles at least eight times, while retaining about 50% of the ability to absorb uranium. Thus, the present amidoxime polymer adsorbent is a highly efficient material for uranium recovery in seawater for both high and low uranium concentrations.

Nevertheless, the disadvantages include the energy consumption and the duration of the method for its production, as well as the need to use a photoinitiator and the toxicity of acrylonitrile.

In this regard, the technical result of the claimed invention is to obtain an S-derivative of N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide with a developed structure and a high content of ion-exchange groups (amino and hydroxyl groups), suitable for use as sorbent for the purpose of extracting uranium from liquid media. The method for its preparation consists in fusing thiourea with 4-amino-N-hydroxy-1,2,5-oxadiazole-3-carboximidamide. The advantage of the present invention is based on the use of a highly coordinated sulfur heteroelement for the synthesis of a sulfur derivative of N-hydroxyamidine aminofurazan. This made it possible, firstly, to simplify the synthesis of the amidoxime-containing sorbent by refusing to use the long-term and energy-consuming method of UV-induced radical polymerization, and, secondly, to exclude the presence of a photoinitiator and toxic acrylonitrile in the synthesis.

The technical result is achieved by the method of obtaining the S-derivative of N-hydroxyamidine aminofurazan by fusing 4-amino-N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide with thiourea, followed by cooling the melt to room temperature, grinding the product, and sequential washing with distilled water and organic solvents, and drying to constant weight in a vacuum desiccator. Two compounds are alternately used as organic solvents for washing the synthesis product. The first solvent is selected from a number of substances, for example ethyl alcohol, methanol, isopropanol, acetone, preferably ethyl alcohol. The second is from a series of, for example, dichloromethane, chloroform, petroleum ether, preferably methylene chloride.

The resulting substance is used in the static sorption mode to extract uranyl ions from liquid media.

The synthesis of the S-derivative of N-hydroxyamidine aminofurazan is carried out in one stage as follows.

Example 1

The dry compound 4-amino-N-hydroxy-1,2,5-oxadiazole-3-carboximidamide is mixed with thiourea (1.5 mol) in a molar ratio of 1: 3, followed by fusion at 220-250 ° C for 60-80 minutes. After the formation of a homogeneous melt and the cessation of active gas evolution, the melt is cooled to room temperature, crushed and sequentially washed with distilled water (three times), ethyl alcohol (twice) and methylene chloride (once). Dry to constant weight in a vacuum desiccator at 5-10 mm Hg. over P ₂ O ₅ at 20-25 ° C during the day. The resulting material with a yield of 36% is an irregularly shaped, yellowish-brown granules with a grain size of 0.05-0.2 mm.

Example 2

4-amino-N-hydroxy-1,2,5-oxadiazole-3-carboximidamide is mixed with thiourea (1.5 mol) in a molar ratio of 1: 1. Further, the synthesis is carried out in accordance with example 1. The yield of the target product was 26%.

The elementary link of the proposed compound is a nonlinear disulfide containing two furazan and two triazine rings and corresponds to the formula:

.

...

The structure of the obtained polymer was established based on the results of IR spectroscopy, X-ray photoelectron spectroscopy (XPS). The IR spectra revealed the following bands: 3323 cm ^-1 (NH), 2056 cm ^-1 (SN), 1537 cm ^-1 (S = CN), 1623 cm ^-1 (C = N), 3163 cm ^-1 (HOH ), 532 cm ^-1 (SS), 810 cm ^-1 (S-H), 476 cm ^-1 (NS), 1369 cm ^-1 (CN). The XPS spectrum has the following form: 533.5 eV and 530.5 eV (O 1s); 399.7 eV and 388.3 eV (N 1s); 288.4 eV, 286.9 eV and 285.0 eV (C 1s); 165.0 eV and 163.0 eV (S 2p).

The inventive material has mechanical strength and chemical stability. It is abrasion resistant and does not dissolve in the most common organic and inorganic solvents. The resulting sorbent has a high affinity for uranyl ions in the pH range 6-9 with a high extraction efficiency. Using the Sips equation, the value of the limiting adsorption was calculated, which in the presence of nitrate ions (100 mg / L) and pH 8 was 460 mg / g. The obtained value indicates a high sorption capacity, which is explained by the presence of a large number of sorption centers formed in the process of polymer formation as a result of polycondensation of cyclic molecules through the –S – S– bond.

The possibility of using the obtained compound for the sorption of uranium from liquid media is illustrated by the following examples:

Example 3

The study of the sorption properties of materials depending on the pH of the solution was carried out under static conditions in the presence of a macroquantity of UO ₂ ²⁺ from solutions with a pH of 2-10. The experiment was carried out at the ratio V / m = 1000 ml / g, uranium concentration 40 mg / l, stirring time 28 hours. A sorbent fraction 0.05-0.2 mm in size was used in the work. Before the beginning of sorption, the weighed portions of the sorbent were kept for 24 hours in working solutions that did not contain uranyl ions. At the end of stirring, the solution was separated from the sorbent on a "blue ribbon" filter and the residual content of UO ₂ ²⁺ in the filtrate was analyzed spectrophotometrically using Arsenazo III.

The test results of the claimed material are presented in Fig. 1 as a diagram of the dependence of the adsorption of UO ₂ ²⁺ on the pH of the medium. It can be seen from the diagram that the sorbent is effective in the pH range 6–9, with the maximum Kp values being from 4⋅10 ^–3 ml / g. In solutions with a pH above 9, a decrease in the extraction efficiency values is observed due to the adsorption of uranium on the walls of glassware or polypropylene, which was recorded in a control experiment without the addition of a sorbent. It was found that in acidic media (pH less than 6), no absorption of uranium occurs, which is associated with the predominant protonation reaction.

The possibility of using the obtained compound for the sorption of uranium from liquid media in the presence of competing ions is illustrated by the following examples:

Example 4

Sorption of macroquantities of U (VI) was carried out under static conditions at the ratio of the volume of the solution to the mass of the sorbent 1000 ml / g, in the presence of 0.1 mol / L NO ₃ ^- . The contact time of the phases was 48 hours, the initial uranium concentration was 50 mg / L, pH = 4. The content of U (VI) was determined by spectrophotometric analysis in the presence of Arsenazo III. The sorption efficiency was 91%, the static exchange capacity was 69 mg / g, the distribution coefficient of uranyl ions was 9.5⋅10 ^-3 ml / g.

Example 5

Sorption was carried out analogously to example 4 with the difference that 0.1 mol / L SO ₄ ^{2- was} used as a competing ion, and the pH value was maintained equal to 6. The sorption efficiency was 95%, the static exchange capacity was 40 mg / g, the coefficient distribution of uranyl ions is 15.310 ^-3 ml / g.

Example 6

Sorption was carried out analogously to example 4 with the difference that 0.1 mol / l HCO ₃ ^{- was} used as a competing anion. The sorption efficiency was 89%, the static exchange capacity was 32 mg / g, the distribution coefficient of uranyl ions was 10⋅10 ^-3 ml / g.

Example 7

Sorption was carried out analogously to example 4 with the difference that 0.1 mol / L NO ₃ ^{2- was} used as a competing anion, and the pH value was maintained equal to 8. The sorption efficiency was 93%, the static exchange capacity was 71 mg / g, the coefficient distribution of uranyl ions is 11.8⋅10 ^-3 ml / g.

Example 8

Sorption was carried out analogously to example 5 with the difference that 0.1 mol / L K + was used as a competing ion. The sorption efficiency was more than 95%, the static exchange capacity was 40 mg / g, the distribution coefficient of uranyl ions was 1.8⋅10 ^-3 ml / g.

Example 9

Sorption was carried out analogously to example 5 with the difference that 0.1 mol / L Na ^{+ was} used as a competing ion. The sorption efficiency was more than 95%, the static exchange capacity was 29 mg / g, the distribution coefficient of uranyl ions was 2.0⋅10 ^-3 ml / g.

Example 10

Sorption was carried out analogously to example 5 with the difference that 0.1 mol / L Ca ^{2+ was} used as a competing ion. The sorption efficiency was more than 95%, the static exchange capacity was 20 mg / g, the distribution coefficient of uranyl ions was 3.0⋅10 ^-3 ml / g.

Example 11

Sorption was carried out analogously to example 5 with the difference that 0.1 mol / L Mg ^{2+ was} used as a competing ion. The sorption efficiency was more than 95%, the static exchange capacity was 29 mg / g, the distribution coefficient of uranyl ions was 3.4⋅10 ^-3 ml / g.

Claims (4)

1. Sulfur derivative of N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide of the formula:

... 2. A method of obtaining a compound according to claim 1, which consists in fusing 4-amino-N'-hydroxy-1,2,5-oxadiazole-3-carboxyimidamide with thiourea, followed by cooling the melt to room temperature, grinding, sequential washing with distilled water and organic solvents, and drying to constant weight. 3. Use of a compound according to claim 1 as a sorption material for the extraction of uranyl ions from liquid media.

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