RU2741909C1 - Selenium-derivative of n-hydroxyamidine aminofurazan for extraction of uranium from liquid media - Google Patents

Abstract

FIELD: organic chemistry.SUBSTANCE: invention relates specifically to selenium-containing polymer based on N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide, obtained by a method comprising boiling mixture of 4-amino-N-hydroxy-1,2,5-oxadiazole-3-carboximidamide and Se(IV) oxide in solvent to obtain precipitate, which, after cooling to room temperature, is filtered, successively washed with cold distilled water and organic solvents, and then dried to constant weight.EFFECT: proposed selenium-containing polymer is used as sorption material for extraction of uranium from liquid media.1 cl, 1 dwg, 9 ex

Description

The invention relates to the field of organic chemistry, specifically to the production of a selenium-containing polymer based on N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide and its use as a sorbent for the extraction of U (VI) from liquid media, including technological and sea water.

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 spread 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, sorption methods are used in practice using various natural and synthetic sorption materials, for example, titanosilicates, phosphorsilicates, 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 also prone to destruction followed by desorption of the radionuclide. When using these materials, special conditions are required, which complicates the technological process.

In contrast to the above, promising polymer sorption materials are known that contain amidoxime functional groups in their structure and are highly selective for U (VI) compounds in a wide pH range from 6 to 9. A feature of such sorbents is the fact that amino groups in the amidoxime provide extraction of uranyl ions both by the ion exchange mechanism and as a result of complexation.

One of the first studies to extract uranium from seawater using amidoxime polymers was carried out in Japan in the late 1970s and early 1980s. So, in [Sugasaka K. et al. "Recovery of Uranium from Seawater" // Journal Separation Science and Technology, 1982, V.16, No. 9, P. 971] describes the preparation of chelating resins and fibers based on polyacrylamidoxime from various copolymers of acrylonitrile and crosslinking agents. The resulting resins with a chelated amidoxime group showed selective adsorption of uranium in seawater. The amount of uranium adsorbed from seawater at room temperature reached 3.2 mg / g resin after 180 days. Polyacrylamidoxime fiber, which was made from polyacrylonitrile fiber and hydroxylamine, showed a high adsorption rate for uranium. The known fiber, conditioned with 1 Μ HC1 and 1 Μ NaOH, adsorbed uranium from seawater in an amount of 4 mg / g of fiber during 10 days of exposure.

The disadvantage of the described sorbent is the use of highly toxic copolymers of acrylonitrile for its production. In addition, the time to reach the maximum uranium adsorption values is rather long, which complicates the process of uranium extraction in industrial conditions.

Also known [Seko N. et al. "Fine Fibrous Amidoxime Adsorbent Synthesized by Grafting and Uranium Adsorption-Elution Cyclic Test with Seawater" // Journal Separation Science and Technology, 2004, V. 39, No. 16, P. 3753] amidoxime fibrous adsorbents synthesized by radiation-induced polymerization of acrylonitrile and methacrylic acid and subsequent amidoximation. Uranium adsorption in seawater was evaluated by pumping seawater into a column with an adsorbent. The best ratio of acrylonitrile monomers to methacrylic acid was 7: 3. Tartaric acid was used as an effective eluting agent. After each elution, the sorption properties of the adsorbents were restored using alkaline treatment.

A significant drawback of the known material is the use of toxic substances, as well as a complex synthesis that requires special expensive equipment.

In [US Pat. CN No. 108404888, publ. 17.08.2018] to obtain a polymer amidoxime sorbent by radiation-induced polymerization at a radiation dose of 15-100 kGy, macromolecular fibers or non-woven materials, namely ultra-high molecular weight polyethylene fibers, polyethylene / polypropylene fibers, high-density polyethylene fibers, polyethylene in the form of non-woven webs, polyethylene / polyethylene terephthalate fiber, polyamide fiber, polyethylene / polypropylene nonwoven fabric, polypropylene fiber, polyethylene terephthalate fiber to form a fiber or nonwoven fabric grafted with a polyacrylonitrile group. Then, the grafted material was immersed in an aqueous solution containing hydroxylamine hydrochloride to form a base fiber or nonwoven fabric with amidoxime groups.

The disadvantages of this method are also the complexity of the process, since it requires special equipment.

In [Frizon T.E. et al. “Selenides and diselenides containing oxadiazoles: a new class of functionalised materials)) // Liquid Crystals, 2012, V. 39, No. 6, P.769] provides a method for the synthesis of organoselenium compounds. The binding of aryl bromides with elemental selenium was catalyzed by copper oxide nanopowder in the presence of potassium hydroxide using dimethyl sulfoxide as a solvent. As a result of the synthesis, derivatives of 1,2,4 and 1,3,4-oxadiazole diselenides were obtained. The known compounds are not polymeric sorbents, but belong to liquid crystals of the smectic Α-phase. They also demonstrate weak blue fluorescence in solution at λ = 350-405 nm and a Stokes shift of about 90 nm.

The disadvantages, first of all, include the inapplicability of the known compounds for the extraction of uranium ions due to the absence of amidoxime functional groups, since it is their presence that provides the sorption capacity.

Thus, despite significant advances in the preparation of sorbents based on amidoximes and oximes, the methods of preparation and properties of polymers with an inorganic component of the Se type as polymer-forming components are not known.

Closest to the claimed invention according to the method of production and use is the invention US Pat. CN No. 106749883 (publ. 05/31/2017), describing the synthesis of an ion exchange resin with amidoxime functional groups. The composition of the reaction mixture for preparing the resin includes an organic phase and an aqueous phase. The organic phase includes the following starting materials in mass fractions: 5-10 - hydroxyethyl acrylate, 5-10 - glycidyl acrylate, 30-40 - acrylonitrile, 30-35 - divinylbenzene, 50-80 - xylene, 30-40 - isoamyl alcohol, 20- 30 - isooctyl alcohol and 3-5 - azodiisobutyronitrile. The aqueous phase includes the following starting materials in mass fractions: 3-5 - 10% aqueous polyvinyl alcohol, 3-5 - gelatin, 10-20 - sodium chloride, 10-15 - calcium carbonate, 3-5 - 0.1% methylene blue solution and 1500-2000 - deionized water.

A matrix of divinylbenzene-acrylonitrile resin was prepared by suspension copolymerization by alternately adding monomers and adding foaming agents, then an oximation reaction was carried out to functionalize the polymer matrix with amidoxime groups.

The disadvantages of the known invention include the duration and multistage nature of the process, the use of a large number of components, including highly toxic ones, and the lack of data on the efficiency of sorption of uranium from liquid media.

In this regard, the technical result of the claimed invention is the development of a simple method for the synthesis of a selenium derivative of N-hydroxyamidine aminofurazan by polycondensation of SeO ₂ and 4-amino-N-hydroxy-1,2,5-oxadiazole-3-carboxyimidamide. The advantage of the present invention lies in the one-step production of a polymeric amidoxime sorbent highly selective to uranyl ions by introducing a heteroelement selenium with a high coordination capacity. This made it possible, firstly, to simplify the synthesis of the amidoxime-containing sorbent by using a smaller amount of starting materials, carrying out the synthesis in one stage, and secondly, to obtain a polymer with a developed structure and a high content of ion-exchange groups (amino and hydroxyl groups), suitable for use as a sorbent for the extraction of uranium from liquid media.

The technical result of the invention is achieved by a method of obtaining a Se-derivative of N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide by boiling a mixture of 4-amino-N-hydroxy-1,2,5-oxadiazole-3-carboxyimidamide and oxide Se (Iv) in a suitable solvent to obtain a precipitate, which, after cooling to room temperature, is filtered, washed with cold distilled water and successively with organic solvents, and then dried to constant weight in a vacuum desiccator.

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

The synthesis of the Se-derivative of N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide is carried out in one stage according to the scheme:

As a solvating solvent, for example, 1,4-dioxane, acetonitrile, dimethyl sulfoxide, pyridine is used, preferably acetic acid.

Compounds from two groups are sequentially used as organic solvents. The first solvent is selected from a number of substances, for example, ethyl alcohol, methanol, isopropanol, acetone, preferably ethyl alcohol is used. The second is from a series, for example, dichloromethane, chloroform, petroleum ether, preferably dichloromethane is used.

The synthesis of the Se-derivative of N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide is carried out as follows:

A mixture of 1.43 g, 10 mmol of 4-amino-N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide and 1.11 g, 10 mmol of Se (IV) oxide was boiled in acetic acid (30 ml) with reflux, for 80-100 minutes with vigorous stirring. This forms a dark purple precipitate. At the end of the reaction, the mixture is cooled to room temperature, followed by precipitation by filtration. The resulting precipitate is sequentially washed with cold distilled water (three times), ethyl alcohol and methylene chloride to remove unreacted components of the initial mixture. Then the precipitate is dried to constant weight in a vacuum desiccator at 5-10 mm Hg. over P ₂ O ₅ at 20-25 ° C for 24 hours. The resulting material with a yield of 45% is dark purple irregularly shaped granules with a grain size of 0.05-0.2 mm.

The structure of the obtained compound has the form of a nonlinear diselenide and contains two furazan rings. The structure of the obtained polymer was established on the basis of the results of IR spectroscopy, X-ray photoelectron spectroscopy (XPS), and solid-state NMR. The IR spectra revealed the following bands: 3454 cm ^-1 (O-H at the oxime group), 3311 cm ^-1 (NH), 412 cm ^-1 (Se-Se), 489 cm ^-1 (N-Se), 1623 cm ^-1 (C = N), 1357 cm ^-1 (CN), 1540 cm ^-1 (Se-CN), 1150 cm ^-1 (C-NO). The XPS spectrum has the following form: 533.6 eV and 531.2 eV (O Is); 400.4 eV and 399.2 eV (N Is); 288.5 eV, 286.9 eV and 285.0 eV (C Is); 164.0 eV and 169.3 eV (Se 3p). 13C NMR: 138 ppm. (> C = NOH), 146 ppm (-HN-C = N-) 154 ppm. (= C-C =). NMR 1 H: 1.5 ppm. (HN-C) 7.1 ppm. (HN (C) -Se).

The claimed material has mechanical strength and chemical stability. It is resistant to abrasion 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 370 mg / g. The obtained value indicates a high sorption capacity, which is determined by the presence of a large number of sorption centers that are formed in the process of polymer formation due to the polycondensation of cyclic molecules through the -Se-Se- bond.

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

Example 1.

The study of sorption depending on the pH of the solution was carried out under static conditions in the presence of a macroquantity of UO ₂ ²⁺ (40 mg / L) from solutions with a pH of 2-10. The experiment was carried out at a ratio of the solution volume to the sorbent weight of 1000 ml / g, the stirring time was 48 hours. We used a fraction of sorbents with a size of 0.05-0.2 mm. Before the start of the experiment, the weighed portions of the sorbents 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 in the form of a diagram of the dependence of the efficiency of adsorption of UO ₂ ²⁺ on the pH of the medium, which demonstrates the efficiency in the range of pH 6-9. In this case, the maximum Kp values range from 5 × 10 ^-3 ml / g.

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 2-9:

Example 2.

Sorption of macroquantities of U (VI) was carried out under static conditions at a ratio of the solution volume to the sorbent weight of 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 spectrophotometrically in the presence of Arsenazo III. The sorption efficiency was 98%, the static exchange capacity was 73 mg / g, the distribution coefficient of uranyl ions was 39.5 × 10 ^-3 ml / g.

Example 3.

Sorption was carried out analogously to example 2 with the difference that 0.1 mol / L HCO _{3 was} used as a competing ion ^- at pH 6. The sorption efficiency was 91%, the static exchange capacity was 31 mg / g, the distribution coefficient of uranyl ions was is equal to 9.6 × 10 ^-3 ml / g.

Example 4.

Sorption was carried out analogously to example 3 with the difference that 0.1 mol / l NO ₃ ^{- was} used as a competing ion. The sorption efficiency was 98%, the static exchange capacity was 75 mg / g, the distribution coefficient of uranyl ions was 46.7 × 10 ^-3 ml / g.

Example 5.

Sorption was carried out analogously to example 2 with the difference that 0.1 mol / L SO ₄ ^{2- was} used as an interfering inorganic ion, and the pH value was maintained equal to 8. The sorption efficiency was 86%, the static exchange capacity was 38 mg / g, the distribution coefficient of uranyl ions is 7.7 × 10 ^-3 ml / g.

Example 6.

Sorption was carried out analogously to example 3 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 36 mg / g, the distribution coefficient of uranyl ions was 1.9 × 10 ^-3 ml / g.

Example 7.

Sorption was carried out analogously to example 3 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 41 mg / g, the distribution coefficient of uranyl ions was 2.0 × 10 ^-3 ml / g.

Example 8.

Sorption was carried out analogously to example 3 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 24 mg / g, the distribution coefficient of uranyl ions was 4.0 × 10 ^-3 ml / g.

Example 9.

Sorption was carried out analogously to example 3 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 23 mg / g, the distribution coefficient of uranyl ions was 1.3 × 10 ^-3 ml / g.

Claims (1)

Selenium-containing polymer based on N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide, used as a sorption material for the extraction of uranium from liquid media, obtained by a method including boiling a mixture of 4-amino-N-hydroxy-1,2 , 5-oxadiazole-3-carboximidamide and Se (IV) oxide in a solvent to obtain a precipitate, which, after cooling to room temperature, is filtered, successively washed with cold distilled water and organic solvents, and then dried to constant weight.

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