RU2697447C1 - Boron isotope separation method - Google Patents

Abstract

FIELD: physics.SUBSTANCE: invention relates to production of stable boron isotopes. Method of separating boron isotopes is carried out by chemical exchange in a two-phase liquid-liquid system using an aqueous solution of boric acid as an aqueous phase and an organic phase consisting of a complex compound of boric acid with an organic substance, which is represented by tributyl phosphoric acid ester, wherein re-extraction of boric acid with water is carried out, followed by evaporation of the aqueous solution under conditions of cross-current of the organic phase and water.EFFECT: invention reduces the number of components of the organic phase, increases the single separation coefficient, reduces the number of theoretical separation steps required to achieve the required concentration of the boron isotope, high efficiency of the extraction process of boric acid, low water consumption and low power consumption.1 cl, 4 tbl, 4 ex

Description

The invention relates to a technology for the production of stable boron isotopes ( ¹⁰ V and ¹¹ V).

Known methods for the separation of boron isotopes by the rectification of boron compounds with a total composition of BX ₃ , where X is a halogen atom: Cl (Sevryugova NN, Uvarov OV, Zhavoronkov N.M. Separation of stable boron isotopes // Atomic energy, 1960 t. 9, No. 2, pp. 110-125; Andriets S.P., Gushchin A.A., Kalashnikov A.L., Kozyrev A.S. et al. Design and testing of a pilot plant for the separation of boron isotopes by BCl distillation ₃ // Promising materials. - Special issue (8). - Feb. 2010, p. 193-198) or F (Nettley R.T., Cartwright DK, Kronberger N. The production of ¹⁰ Boron by low-temperature distillation of boron trifluoride // In: Proc. of the Intern. Symp. on isotope separa tion. Amsterdam: North Holl Pub. Co., 1958, p. 385-407; Amirkhanova IB, Asatiani P.Ya., Borisov AB, Gverdtsiteli I.G. et al. Effect of pressure on the separation of boron isotopes / / Atomic Energy, 1967, vol. 23, No. 4, pp. 336-339).

A known method of separating boron isotopes by the method of chemical exchange distillation of a complex compound of boron halide (boron trifluoride) with dimethyl ether (CH ₃ ) ₂ O⋅BF ₃ (Kaminsky V.A., Karamyan A.T., Giorgadze I.A. et al. Concentration isotope B ¹⁰ by the method of chemical exchange distillation (CH ₃ ) ₂ O⋅BF ₃ at atmospheric pressure // In the book: Production of isotopes. Collection of articles, Moscow: Atomizdat, 1973, p. 466-468).

There are also known methods for the separation of boron isotopes by chemical isotopic exchange between gaseous boron trifluoride and its complex compounds with methylphenyl (anisole) or ethyl phenyl (phenethol) ethers, that is, in two-phase systems “BF _{3, gas} - BF ₃ ⋅CH ₃ OC ₆ H _{5, fluid} "Or" BF _{3 gas} - BF ₃ ⋅C ₂ H ₅ OC ₆ H _{5 liquid} "Respectively (Voloshchuk AM, Dzhidzhiyshvili Sh.I., Katalnikov SG, etc. Separation of boron isotopes in a pilot plant using complex compounds BF ₃ with anisole and phenethol // In: Isotope production. Collection of articles, M. : Atomizdat, 1973, pp. 443-450; Katalnikov SG Physico-chemical and Engineering Principles of Boron Isotopes Separation by Using BF ₃ -Anisole⋅BF ₃ System // Separation Science and Technology, 2001, Vol. 36, No. 8 & 9, p . 1737-1768) or nitromethane in the system "BF _{3 gas} - BF ₃ ⋅ CH ₃ NO _{2, liquid.} "(Patent US No. 5419887 A, publ. 05/30/1995; Khoroshilov AV, Lizunov AV, Stepanov AV, Cherednichenko SA Thermal dissociation of the complex BF ₃ ⋅ D and boron isotope separation in the system BF ₃ -BF ₃ ⋅CH ₃ NO ₂ // Radiochemistry, 2009, Vol. 51, No. 4, p. 400-402; Khoroshilov AB, Stepanov AB, Lizunov AB, Zernova EV The first separation of boron isotopes by chemical exchange at low temperature in the system of boron trifluoride - its complex compound with nitromethane // Promising materials. - Special issue (8). - Feb. 2010, p. 258-262).

The disadvantage of the above methods based on the method of distillation, chemical exchange distillation and chemical isotope exchange in a gas-liquid system is the need to use toxic boron halides, as in the form of a liquid (BCl _{3, liquid} , BF _{3, liquid} , BF ₃ ⋅CH ₃ OS ₆ H _{5, liquid} , BF ₃ ⋅C ₂ H ₅ OC ₆ H _{5, liquid} , BF ₃ ⋅ CH ₃ NO _{2, liquid} ), and in the form of gas (BCl _{3, gas} , BF _{3, gas} ) when the maximum permissible concentration in the air of the working zone _(RZ MPC), for example, BCl ₃ and BF ₃ is 1 mg / m ^3, hazard class 2, and occupational exposure levels of pollutant tmosferu substance (TSEL _ai) is 0.03 mg / ^m3 and 0.005 mg / m ^3, respectively (boron trichloride [Electronic Resource] - Access mode:. http: /toxi.dyndns.org/base/nonorganic/Borum4 /Trihloridboran.htm (accessed: 12/01/2017); Boron trifluoride [Electronic resource]. - Access mode: http://toxi.dyndns.org/base/nonorganic/Borum4/Bora_triftorid.htm (accessed: 12/01/2017 ) and Harmful substances in industry. Handbook for engineers, chemists and doctors. In 3 t. / Ed. N.V. Lazareva and E.N. Levina / - L., Chemistry, 1977. T. 3. Inorganic and organoelement compounds, p. 312-313).

To reduce the toxicity of the working systems used in the separation of boron isotopes and based on the use of its halides of general composition BX ₃ , where X is the halogen atom (Cl, F), a chemical exchange in the extraction liquid-liquid system “aqueous solution of boric acid - N ₃ VO ₃ in isoamyl alcohol "or in the system" N ₃ VO ₃ / H ₂ O // N ₃ VO ₃ / (CH ₃ ) ₂ CHCH ₂ CH ₂ OH "with a single boron isotope separation coefficient α = 1,0027 and, accordingly, the enrichment coefficient ε = α-1 = 2.7⋅10 ^-3 (Kuznetsova E.M., Panchenkov G.M., Filippova R.S., Malakhov V.F. On a new method for the separation of boron isotopes // ZhFKh, 1960, v. 34, No. 10, pp. 2370-2371).

The main disadvantage of this method is the relatively small value of a single separation coefficient (enrichment).

The closest in technical essence to the claimed invention (prototype) can be considered a method for the separation of boron isotopes by chemical exchange in an extraction two-phase liquid-liquid system "a solution of boric acid H ₃ BO ₃ in water - a complex compound of boron with a nitrogen-containing phenol-formaldehyde resol oligomer (brand" Yarresin B ") Obtained by polycondensation of p-tert-butylphenol with formaldehyde in the presence of ammonia, having an average molecular weight of 450-500 atomic units and dissolved in a mixture of organic solvent - octanol and tridecane "or, more appropriately," aqueous solution of H ₃ BO ₃ - H ₃ BO ₃ Yarrezinom B in octanol and tridecane solution "or more briefly" H ₃ BO ₃ / H ₂ O // H ₃ BO ₃ ⋅ Yarrezin B / C ₈ H ₁₇ OH + C ₁₃ H ₂₈ ". In this case, the reversal of phase flows according to the ¹⁰ V isotope, as indicated in the prototype, can be carried out by reextraction of boric acid with water, followed by evaporation of the resulting solution (RF Patent No. 2311949 dated 12/10/2007, Bull. No. 34) - prototype.

The values of the single boron isotope separation coefficient α in the prototype (Table 2) are designated as R _i (change in the ratio of the concentration of isotopes ¹¹ V to ¹⁰ V, that is, [ ¹¹ V] / [ ¹⁰ V]) and found as

where R ₀ and R - [ ¹¹ B] / [ ¹⁰ B] in the aqueous phase before and after contacts, respectively; n is the total number of contacts.

The numerical values of α at a ratio of phase volumes O: B = 1: 1 for n = 3 (example 1) and n = 4 (example 2), as indicated in table. 2, amounted to 1.00274 and 1.00316, respectively, and at O: B = 2: 1 and n = 2 (example 3) - 1.00856. According to these data, the average value of a single isotope effect for a series of three experiments is α = 1.005 ± 0.003, and ε = (5 ± 3) ⋅ 10 ^-3 and this value is almost two times higher than ε in the system with isoamyl alcohol: (5 / 2.7) ⋅10 ^-3 ≈1.9.

It should be noted that boric acid is re-extracted from the organic phase into water by balancing the organic phase with a significantly larger volume of water, followed by evaporation of an aqueous solution of boric acid to its equilibrium concentration in the aqueous phase.

The disadvantages of the prototype, as a method of separation of boron isotopes, are:

- multicomponent organic phase (actually Yarrezin B, octanol and tridecane), requiring at least four operations for its preparation: measuring the mass of solid Yarresin B; measurement of the volume of each of the solvents (octanol, tridecane); formation of a common solution;

- low values of a single coefficient of separation (enrichment) of boron isotopes and, accordingly, a large number of theoretical stages of separation necessary to achieve a given concentration of the isotope ¹⁰ V (or ¹¹ V);

- low productivity of the process of extraction of boric acid;

- high water consumption and, consequently, high energy costs during the circulation of phase flows along the ¹⁰ V isotope due to the reextraction of boric acid with water.

The objective of the present invention is to reduce the number of components of the organic phase and, accordingly, reduce the cost of its preparation, increase the single separation coefficient (enrichment) of boron isotopes and, as a result, reduce the number of theoretical separation stages necessary to achieve the required concentration of ¹⁰ V isotope (or ¹¹ C), increasing the productivity of the process of extraction of boric acid, reducing the flow of water and energy costs for the circulation of phase flows along the isotope ¹⁰ V.

The problem is solved by the method of separation of boron isotopes by chemical exchange in a two-phase liquid-liquid system using an aqueous solution of boric acid as an aqueous phase and an organic phase consisting of a complex compound of boric acid with an organic substance, and reversing the streams by reextraction of boric acid with water, followed by evaporation in this case, tributyl ether of phosphoric acid is used as an organic substance, and re-extraction is carried out under conditions of cross organic phase current and water.

Example 1

A two-phase liquid-liquid system was prepared at room temperature (295 ± 2) by dissolving boric acid in water to prepare a 0.80 M solution and contacting the resulting solution with phosphoric acid tributyl ester (tributyl phosphate) as an organic phase with a phase volume ratio of 1: 1 . Comparative data on the composition of the phases for the prototype and the present invention, when the working system "aqueous solution of N ₃ VO ₃ - a complex compound of N ₃ VO ₃ with TBP) has the form" N ₃ VO ₃ / N ₂ O // N ₃ VO ₃ ⋅ TBP / TBP "are given in table. one.

From the table. 1 it follows that the solution to the problem of preparing a two-phase system differs significantly from the prototype in the number of components used for its formation: instead of the three components of the prototype, the use of a single substance is proposed, which leads to a significant reduction in the number of technological operations at the stage of its preparation: instead of four prototype operations, only one is the measurement of TBP volume, and this comparison is given without taking into account the quality control of each component.

Example 2

After balancing an aqueous solution of boric acid with an initial concentration of C ⁰ = 0.80 M with tributyl phosphate (TBP) at a temperature of (295 ± 2) K, water samples were taken for 24 hours and isotope analysis was performed by inductively coupled argon plasma mass spectrometry , as well as an isotopic analysis of the initial solution of H ₃ VO ₃ , with the determination of the values of the isotopic ratio according to the equation:

The obtained R values were used to determine a single boron isotope separation coefficient α in the system “N ₃ VO ₃ / N ₂ O // N ₃ VO ₃ / TBP”:

where R ⁰ and R ^* are the isotope ratios for boric acid boron in the aqueous phase before (R ⁰ ) and after (R ^* ) equilibration with TBP.

The results of three measurements in the form of average values are given in table. 2, whence it follows that the single coefficient of boron isotope separation in the extraction system “N ₃ VO ₃ / H ₂ O // N ₃ VO ₃ ⋅ TBP / TBP” at room temperature is α = 1.006 ₇ ± 0.003 ₄ or α = 1.007 ± 0.003. Comparison of the measured value of the separation coefficient with the average α of the prototype (α = 1.005 ± 0.003) shows that a single isotopic effect, expressed by the enrichment coefficient ε, in the present method is 1.4 times higher compared to the prototype (7⋅10 ^-3 / 5 ⋅10 ^-3 = 1.4).

This means that, for example, the minimum number of theoretical stages of separation for changing the concentration of the ¹⁰ V (or ¹¹ V) isotope from the natural level to a given value will be 1.4 times less. In addition, it can be noted that, in comparison with the system based on isoamyl alcohol, the value of the enrichment coefficient is more than two and a half times greater: 7⋅10 ^-3 / 2.7⋅10 ^-3 ≈2.6 with all the ensuing consequences.

Example 3

Under conditions similar to those indicated in the prototype (initial concentration of H ₃ BO ₃ , two phase volume ratios O: B = 1 and 2; different number of phase contacts or equilibria n), experiments were performed on the extraction of boric acid from its aqueous solution with tributyl phosphate. In this case, the time of a single contact in experiments with TBP is taken equal to τ = 5 min, since the equilibrium in the system “H ₃ BO ₃ / H ₂ O // H ₃ BO ₃ ⋅ TBP / TBP” is achieved, as studies have shown, in less than 5 minutes. At the end of n equilibrations, the equilibrium concentration of boric acid in the aqueous phase C ^{* was} determined, and the amount of H ₃ BO ₃ extracted with tributyl phosphate was calculated

where V _in - the volume of the aqueous phase,

and the productivity of the boric acid extraction process as a change in the concentration of H ₃ BO ₃ per unit time, that is, as

The results obtained in comparison with the data of the prototype are given in table. 3.

Notes to the table:

C ⁰ is the concentration of H ₃ BO ₃ in the initial aqueous solution;

O: B is the ratio of the volumes of phases in the organic (O) and aqueous phase (B);

τ is the time of one phase contact (time of a single balancing);

n is the number of contacts (balances);

τ _Σ is the total time n of contacts (balances);

C ^* is the concentration of H ₃ BO ₃ in the aqueous phase after n contacts (equilibrations);

ΔС is the amount of extracted H ₃ VO ₃ , and ΔС = (С ⁰ -С ^* ) × V _c , where V _c is the volume of the aqueous phase;

P is the productivity of the process of extraction of boric acid (boron), and P = ΔC / τ _Σ .

According to the table. 3 under the same conditions for the extraction of H ₃ BO ₃ (series of experiments 4-6 in comparison with experiments 1-3 of the prototype) using TBP as an extractant can increase the productivity of the process of extraction of boric acid in (22.6 / 5.6) × 10 ^{- 3} = 4.0; (20.6 / 4.6) × 10 ^-3 = 4.5 and (39.3 / 5.6) × 10 ^-3 = 7.0 times, respectively, that is, 4-7 times.

Example 4

20 ml of 20% aqueous solution of H ₃ BO ₃ - complex compound H ₃ BO ₃ with TBP or “H ₃ BO ₃ / H ₂ O // H ₃ BO ₃ ⋅ TBP / TBP” were taken from an equilibrium state at room temperature organic phase, that is, containing boric acid tributyl phosphate. In the first series of experiments (“1” in Table 4), this volume was balanced for approximately 10 min with different volumes of distilled water (direct back extraction), varying the O: B ratio from 1: 1 to 1: 3 and determining the values of H ₃ concentrations BO ₃ in each of the phases (C ^* _water and C ^* _org ), as well as calculating the degree of extraction (G _p ) of boric acid:

In the second series (“2” in Table 4), the same volume of the organic phase was initially balanced for 10 minutes with the same volume of water (O: B = 1; 1), but after phase separation, C ^* concentrations were not only determined _water, C ^* _org and T _p, and the organic phase is decanted and re-equilibrated with its original water conducting overall balancing operation three times and a total consuming the same amount of water (cross reextraction).

A comparison of the results presented in the table. 4 shows that with an equal volume of water spent on the re-extraction of boric acid from tributyl phosphate, when the ratio of volumes is O: B = 1: 3, in the case of cross-extraction, the degree of extraction of boric acid was 98.30% against 95.47% for direct re-extraction that at given values of the residual concentration of boric acid in TBP (C ^* _org ) and the degree of extraction of G _p will lead to a decrease in water consumption by at least 3% rel.

Claims (1)

A method for separating boron isotopes by chemical exchange in a two-phase liquid-liquid system using an aqueous solution of boric acid as an aqueous phase and an organic phase consisting of a complex compound of boric acid with an organic substance, and reversing the streams by reextraction of boric acid with water, followed by evaporation of the aqueous solution, characterized in that as an organic substance, tributyl ether of phosphoric acid is used, and re-extraction is carried out under conditions of a cross flow of organic phase and water.