RU2501603C1 - Method of producing fly grit microsphere-based sorbent for removal of radioactive wastes (versions) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to sorbents produced on the basis of fly grit microspheres of thermal electric power stations and can be used for removal of radio nuclides from liquid wastes. Synthesis of sorbent comprises deposition of active component on the surface of microspheres by mixing the latter with alkaline metal ferrocyanide solution (arrester), removal of excess arrester solution whereby arrester volume retained by microspheres is defined. Transition metal salt solution is added to the mix of microspheres and arrester to hold the mix to phase separation. Thereafter liquid phase is removed while obtained sorbent is dried. In compliance with second version, sorbent synthesis comprises processing of microspheres with the solution of vanadium, or zirconium or tungsten salts and removal of excess solution whereby salt solution volume retained by microspheres is defined. Thereafter, alkaline metal ferrocyanide solution (arrester) is added thereto, excess arrester solution is removed to hold the mix to phase separation. Thereafter liquid phase is removed while obtained sorbent is dried. In compliance with both versions, sorbent is dried at 60-80°C for 1-2 hours or at a room temperature for 15-20 hours.

EFFECT: efficient removal of cesium, cobalt, cerium, europium, etc.

11 cl, 6 dwg, 6 ex, 1 tbl

Description

The invention relates to sorbents, in particular sorbents based on fly ash microspheres, and can be used in the field of sorption purification of low and medium activity liquid radioactive solutions from radionuclides, for example, Cs ¹³⁷ , Co ⁶⁰ , Ce ¹⁴⁴ , Eu ¹⁵⁵ , etc.

Inorganic sorbents are widely used for the treatment of liquid radioactive waste (LRW) of low and medium activity.

Their circle is very wide: these are phosphates, molybdates, and tungstates of zirconium; heavy metal ferrocyanides; oxides of tin, zirconium, manganese and lanthanides. (Inorganic ion-exchange metals. Edited by B.P. Nikolsky, ed. LGU, 1974.)

In order to improve technological and hydrodynamic characteristics, inorganic sorbents are often applied to various inert materials: cement, silica gels, zeolites, clays, etc.

A promising carrier of an ion-exchange substance may be microspheres from fly ash of thermal power plants. This is a light ash fraction in the form of a fine granular powder, consisting of hollow thin-walled particles of a spherical shape and having an average chemical composition: SiO ₂ ~ 60%; Al ₂ O ₃ ~ 26%; Fe ₂ O ₃ ~ 3%; K ₂ O, Na ₂ O, TiO ₂ , MnO, CaO - the rest. Microspheres have a density <1 g / cm ³ .

Given the large industrial reserves of ash microspheres, as a by-product of the operation of power plants, the comparative simplicity of the modification process, good kinetic and sorption characteristics, this class of ion exchangers can be considered quite promising in solving the problems of LRW purification at various pollution levels. A unique feature of sorbents is their high buoyancy.

For selective extraction of Cs ¹³⁷ , ferrocyanide sorbents NZHA, FEZHEL, antimony ferrocyanide on clinoptelolite were proposed (A.I. Ratko, A.S. Panasyugin. Radiochemistry, Vol. 38, issue 1, pp. 66-68, 1996), iron ferrocyanide on zeolite (ZF) or fiber tin (FF). (VISergienno, VA Avramenko, VYGemschenko. J. Ecotechnology Res, 1995, v.1, No. 2. P.152).

A large group of inorganic sorbents called “Thermoxide” was synthesized by L.M. Sharygin and employees using sol-gel technology. So, zirconium (IV) ferrocyanide, these authors obtained by treating wet particles of zirconium hydroxide with a hydrochloric acid solution of yellow blood salt, followed by washing and drying the obtained ion exchanger (L.M. Sharygin, V.E. Moiseev, R.V. Kuzmina and others. Radiochemistry No. 3, p. 361-367, 1986).

The sorbent based on clinoptilolite modified with titanium hydroxide to absorb Cs ¹³⁷ , Sr ⁹⁰ from fresh water was studied by A.N. Vorontsov, N.V. Betenkov, S.V. Pranchuk (Radiochemistry, vol. 37, issue 2, p. 182-186, 1995).

A high degree of purification of LRW from Cs, Sr radionuclides was achieved by passing the latter through two sorbents, one of which is industrial ferrocyanide, for example, SelexUVN, and the second is zirconium hydroxide deposited on an inert material (patent RU 2050027, publ. 10.12.1995, G21F 9 /12).

Closest to the claimed invention is a method for producing a microspherical sorbent based on fly ash microspheres, which are treated with various chemical solutions that allow regular through pores with a diameter of 2-20 μm to be obtained in the cenosphere shell, making the internal volume accessible for filling with active components, such as molybdophosphate ammonium (AMP), transition metal ferrocyanides and sulfides (Cu, Ni, Zr, etc.), magnesium and ammonium phosphates, as well as organic extractants (tributylphosphine lphide (TIBFS), trioctylphosphine oxide (TOFO), etc. (A.G. Anshits, T.A. Vereshchagin, E.R. Fomenko. Patent RU 2262383, publ. 10/20/2005, B01J 20/30). The obtained sorbent is effective for the extraction of radionuclides, non-ferrous and heavy metals and platinum group metals.

The disadvantage of this invention is the complexity of the technological process of perforation and filling of the microspheres with the active component, the loss due to this buoyancy, which limits the scope of these sorbents.

The objective of the present invention is to simplify the method of producing a sorbent based on fly ash microspheres while increasing sorption capacity, improving kinetic characteristics and maintaining high buoyancy, expanding functionality.

When using the claimed method, the following technical result is achieved:

- high selectivity with respect to the radionuclide Cs ¹³⁷ .

- good kinetic characteristics;

- sorption capacity in terms of gram of modifier - 430 mg Cs ¹³⁷ ; 20 mg Co ⁶⁰ ; 30 mg Ce ¹⁴⁴ ; 30 mg Eu ¹⁵⁵ ;

- high buoyancy of the sorbent;

- the possibility of using sorbents in static and dynamic modes;

- simplicity of the technological cycle and reduction of synthesis time.

To solve this problem and achieve a technical result in a method for producing a sorbent based on fly ash microspheres for purifying liquid radioactive waste, comprising introducing an active component, according to the invention, the active component is introduced by precipitation on the surface of the microspheres by mixing them with a precipitant, which is an alkaline ferrocyanide solution metal, followed by removal of the excess precipitant solution, which determines the amount of precipitant used by the microspheres, and then to cm B, consisting of microspheres and the precipitant is added a transition metal salt solution, the mixture was allowed to stand until phase separation of components, the liquid phase was removed and the resulting dried sorbent.

The concentration of the precipitant solution is 0.1-0.25 mol / L, and the concentration of the transition metal salt is 0.2-0.5 mol / L.

A flocculant, for example polyacrylamide in the form of an aqueous solution, is added to suppress peptization.

The drying of the solid phase is carried out at a temperature of 60-80 ° C for 1-2 hours or at room temperature for 15-20 hours to an air-dry state.

In another embodiment, to solve this problem and achieve a technical result in a method for producing a sorbent based on fly ash microspheres for cleaning liquid radioactive waste, comprising introducing an active component, which according to the invention is carried out by depositing it on the surface of microspheres by treating them with a solution of vanadium or zirconium salt or tungsten followed by removal of excess solution, which determines the volume of salt solution held by the microspheres, and then precipitate is added to the resulting mixture b, which is an acidic solution of an alkali metal ferrocyanide, the mixture of components is kept to phase separation, whereupon the liquid phase is removed and the resulting dried sorbent.

The acidification of the precipitating solution is carried out with a 1M hydrochloric acid solution.

The concentration of the precipitant solution is 0.1-0.2 mol / L, and the concentration of the metal salt solution is 0.3-0.6 mol / L.

A flocculant is added to suppress peptization. An aqueous solution of polyacrylamide is used as a flocculant. The drying of the solid phase is carried out at a temperature of 60-80 ° C for 1-2 hours or at room temperature for 15-20 hours to an air-dry state.

In the first embodiment of the proposed method, the microspheres are treated with an alkali metal ferrocyanide solution, removing its excess and subsequent processing with a transition metal salt at a ratio of [Fe (CN) ₆ ] ^4- / Me ^{n +} ≤0.5. In order to suppress the peptization of the formed ferrocyanide, a flocculant, in particular polyacrylamide, is introduced in the form of an aqueous solution.

In the second embodiment of the proposed method, the microspheres are treated with a solution of a salt of vanadium or zirconium or tungsten, followed by removal of excess salt solution, adding a precipitant to the resulting mixture, which is an acid solution of an alkali metal ferrocyanide. In order to suppress the peptization of the formed ferrocyanide, a flocculant, in particular polyacrylamide, is introduced into the metal salt solution in the form of an aqueous solution.

A very important point in this case is the procedure for processing microspheres with solutions. In the first embodiment, with an excess of alkali metal ferrocyanide, a mixed salt forms, to which a chain structure is attributed, i.e. crosslinking of individual polymolecular molecules occurs, i.e. system structuring. (Chemistry of ferrocyanides. Ed. By I.V. Tananaev. Moscow: Nauka, 1971). In the second variant, when reagents are re-merged, the negative charges of the Fe (CN) ₆ ion are instantly bound by ^4– excess metal ions, which complicates the formation of polymer structures.

Figure 1 shows the sorption isotherm of cesium. The experiment was carried out in a static mode, with a total solution volume of 750 ml. 9 mg of stable cesium and 818 Bq of the radioactive label Cs ¹³⁷ were introduced into the solution. As the sorbent, microspheres modified with copper ferrocyanide in an amount of 0.75 g were used, the mass of the modifier was 15 mg / (g ash microspheres).

Figure 2 shows the kinetic absorption curves of cesium. The experiment was carried out in a static mode, at a solution pH of 4.01 (phthalate buffer), a solution volume of 25 ml. Cesium stable in the amount of 15.7 mg and 900 Bq of the radioactive label Cs ¹³⁷ was introduced into the solution. The sorbent mass was 1.0 g. The following were used as sorbents:

- curve 1, K ₂ Cu ₃ [Fe (CN) ₆ ] ₂ , the mass of the modifier is 49.1 mg / (g ash microspheres);

- curve 2, K _0.34 Cu _1.83 [Fe (CN) ₆ ], the mass of the modifier is 30.1 mg / (g ash microspheres);

- curve 3, K _1.8 Co _1.1 [Fe (CN) ₆ ], the mass of the modifier is 38.4 mg / (g ash microspheres);

- curve 4, ash microspheres modified with vanadium ferrocyanide, the mass of the modifier was not determined;

- curve 5, ash microspheres modified with tungsten ferrocyanide, the mass of the modifier was not determined.

Figure 3 shows the sorption isotherms of cobalt:

- curve 1, the experiment was carried out in a static mode, at a solution pH of 4.01 (phthalate buffer), in a total solution volume of 25 ml. Stable cobalt in an amount of 1 to 4.2 mg and 205 Bq of a radioactive label Co ⁶⁰ , sorbent-ash microspheres modified with cobalt ferrocyanide was introduced into the solution. The mass of the sorbent was 1.0 g, the mass of the modifier was 30 mg / (g ash microspheres). The contact time of the sorbent with the solution is 24 hours;

- curve 2, the experiment was carried out in a static mode, at a solution pH of 4.01 (phthalate buffer), in a total solution volume of 25 ml. Stable cobalt from 1 to 3.2 mg and 205 Bq of a radioactive label Co ⁶⁰ , sorbent ash microspheres modified with tungsten ferrocyanide were introduced into the solution. The mass of the sorbent was 1.0 g, the mass of the modifier was not determined. The contact time of the sorbent with the solution is 48 hours.

Figure 4 shows the kinetic absorption curves of milligram amounts of cesium ash microspheres modified with copper ferrocyanide:

- curve 1, studies were conducted in static mode. The total volume of the solution is 770 ml. 100.3 mg of stable cesium and 4520 Bq of Cs ¹³⁷ radioactive label were introduced into the solution. The mass of the sorbent was 4.0 g;

- curve 2, studies were carried out when passing through a solution of air (mixing with air). The total volume of the solution is 770 ml. 100.3 mg of stable cesium and 4520 Bq of Cs ¹³⁷ radioactive label were introduced into the solution. The mass of the sorbent was 4.0 g;

- curve 3, the studies were carried out while passing through a solution of air (mixing with air), in addition, 50 g of MgSO ₄ · 7H ₂ O was introduced into the solution. The total solution volume was 4000 ml. 100.3 mg of stable cesium and 4520 Bq of Cs ¹³⁷ radioactive label were introduced into the solution. The mass of the sorbent was 5.0 g.

Figure 5 shows the dependence of the sorption of the indicator amounts of Cs ¹³⁷ , Ce ¹⁴⁴ , Eu ¹⁵⁵ and Co ⁶⁰ zirconium ferrocyanide. Sorption of radionuclides was carried out in a static mode, the volume of the solution was 25 ml, the pH of the solution was ~ 2-3, the exposure time of the sorbent in the solution was 16 hours. The activity of radionuclides, Bq: Cs ¹³⁷ - 216.8; Ce ¹⁴⁴ - 264.4; Eu ¹⁵⁵ - 149.8 and Co ⁶⁰ - 184.4.

Figure 6 shows the dependence of the sorption of the indicator amounts of Cs ¹³⁷ , Ce ¹⁴⁴ , Eu ¹⁵⁵ and Co ⁶⁰ tungsten ferrocyanide. The sorption of radionuclides was carried out in static mode, the volume of the solution was 25 ml, the pH of the solution was ~ 2-3, the exposure time of the sorbent in the solution was 1 hour. The activity of radionuclides, Bq: Cs ¹³⁷ - 216.8; Ce ¹⁴⁴ - 264.4; Eu ¹⁵⁵ - 149.8 and Co ⁶⁰ - 184.4.

The technological approach to the implementation of this invention is as follows.

Air-dry ash microspheres are poured into a clean separatory funnel without any additional treatment with a volume of V ₀ ml and a mass of m g. Microspheres are compacted by tapping. Then, the volume of the alkali metal ferrocyanide Me ₄ Fe (CN) ₆ , equal to the volume of the microspheres, with a concentration of C ₁ mol / L, is introduced into the column. The contents of the funnel are shaken vigorously until a homogeneous mass is formed and left until the phases are completely separated. The liquid phase merges and its volume V _{zh.f. is measured} . The difference between the volume V ₀ and V _zh.f. represents the volume of ferrocyanide with a concentration of C ₁ held by ash microspheres. Therefore, the amount of ferrocyanide is:

m = (V ₀ -V _gf ) · С ₁ , mol.

Typically, the precipitation of metal ferrocyanides is carried out at a ratio of the concentration of ferrocyanide to the metal salt, i.e. [Fe (CN) ₆ ] ^4- / Me ^{n +} equal to "n", where n - takes a different value. So, in the case of deposition of Cu ₂ [Fe (CN) ₆ ], n≤0.5; the same ratio is also characteristic for Co ₂ [Fe (CN) ₆ ]. In the case of Ni ^{2+, the} preparation of a normal salt is difficult due to the absorption of excess alkali metal ferrocyanide. It should be noted that many normal ferrocyanides are characterized by the formation of mixed ferrocyanides according to the general scheme:

Me ₂ [Fe (CN) ₆ ] + M ₄ [Fe (CN) ₆ ] → M ₂ Me [Fe (CN) ₆ ].

Since the equilibrium of this reaction is slowly established, various mixed ferrocyanides are obtained (Chemistry of Ferrocyanides. Edited by I.V. Tananaev. Moscow: Nauka, 1971).

To precipitate a ferrocyanide, for example copper ferrocyanide, a solution of a metal salt is prepared containing in the volume V ₀ twice the amount of the latter, i.e. 2 m, mol. To suppress peptization, ≈100 mg of a flocculant is introduced into the solution, which is used as polyacrylamide (PAA).

The contents of the separatory funnel are thoroughly mixed and left to separate phases. The liquid phase is discharged, and the solid phase is washed twice with distilled water. After the second washing, the solid phase, together with the aqueous phase, is transferred to the funnel and is aspirated by a foreline pump.

Then it is washed once (under discharge) with distilled water with a volume of V ₀ ml. The contents of the funnel are extracted and dried in air to an air-dry state. The chemical form of the modifier is determined and its mass is calculated.

According to the second variant, a weighed portion of ash microspheres is treated with a solution of vanadium or zirconium or tungsten salts, followed by removal of excess salt solution and the addition of a precipitant to the resulting mixture, which is an acid solution of alkali metal ferrocyanide. In order to suppress the peptization of the formed ferrocyanide, a flocculant is introduced into the metal salt solution, in particular, polyacrylamide in the form of an aqueous solution.

The invention is demonstrated by the following examples.

Example No. 1

1. 250 ml (106 g) of air-dried ash microspheres without any preliminary treatment were placed in a separatory funnel with a capacity of 1000-1500 ml and slightly tamped.

2. 250 ml of a 0.1 mol / L solution of yellow blood salt were added and the contents of the funnel were thoroughly mixed until a homogeneous mass was formed, after which they were left until the phases were completely separated.

3. The liquid phase was drained and its volume was fixed. He amounted to 164 ml. By the difference between the initial volume introduced and the filtrate (164 ml), the volume of yellow blood salt held by the microspheres was found. It amounted to 86 ml, which is 8.6 mmol of precipitant. Usually, to obtain normal ferrocyanides, the ratio of the amount of precipitant to the amount of transition metal is taken to be equal to or less than 0.5

4. To precipitate copper ferrocyanide, 250 ml of Cu (II) salt containing 17.2 mmol of metal and a small amount of flocculant polyacrylamide were introduced into a separatory funnel. The contents of the funnel were thoroughly mixed and left until the phases were completely separated. Solid phase i.e. the resulting sorbent was washed with 250 ml of distilled water and, together with the liquid phase, was transferred to a Buchner funnel and the liquid phase was removed. The solid phase was washed once again with 250 ml of water, aspirated and dried on paper in air, and then weighed.

5. In the exact weight of the air-dry sample, the chemical composition of the modifier was determined. It was found that it corresponds to the formula K _0.2 Cu _1.9 [Fe (CN) ₆ ]. The modifier content is 27 mg / (gram ash microspheres). Sorption properties with respect to Cs ions in a 0.1 mol / L hydrochloric acid medium under static conditions were 386.7 mg / (g modifier) or 2.82 mg equiv Cs ¹³⁷ / g modifier.

Example No. 2

1. 400 ml (173 g) of air-dried ash microspheres were added to a 1500 ml separatory funnel without preliminary treatment.

2. 400 ml of a 0.117 mol / L solution of yellow blood salt were poured, thoroughly mixed and left until complete separation, after which the volume held by the ash microspheres was determined, it amounted to 125 ml, which corresponds to the amount of yellow blood salt of 14.6 mmol.

3. When the ratio of [Fe (CN) ₆ ] ^4- / Me ^{n +} ≤0.5, we find that the content of Cu ²⁺ in the solution should be equal to 29.2 mmol. The total volume of the copper-containing solution was taken equal to 250 ml plus 10 ml of a solution of polyacrylamide (80-100 mg).

4. After settling, the liquid phase was discharged and the precipitate was washed once with 250 ml of distilled water. Together with the liquid, the sorbent was transferred to a Buchner funnel, aspirated and washed with water, the sorbent was dried on paper at room temperature. The analysis showed that the chemical composition of the modifier corresponds to the formula K _1.2 Cu _1.36 [Fe (CN) ₆ ]. The modifier mass is -34 mg / (gram ash microspheres). Sorption properties with respect to Cs ions in a 0.1 mol / L hydrochloric acid medium under static conditions were 430 mg / (g modifier) or 3.14 mg equiv Cs ¹³⁷ / g modifier.

Example No. 3

1. 250 ml (190 g) of air-dried fly ash microspheres were added to a 1000 ml dry separation funnel and slightly tamped.

2. 250 ml of a 0.1 mol / L solution of Li ₄ [Fe (CN) ₆ ] were added and the contents of the funnel were thoroughly mixed. Left until complete phase separation.

3. The liquid phase was discharged and the amount of precipitant retained by the ash microspheres was determined. He was equal to 90 ml, which corresponded to 9 mmol of Li ₄ [Fe (CN) ₆ ].

4. Then, 250 ml of an aqueous solution containing 18 mmol of Co ²⁺ salt and 10 ml of polyacrylamide solution (80-100 mg.) Was introduced into the funnel, thoroughly mixed, and after settling, the aqueous phase was drained.

5. The emerald green solid phase was shaken with 200 ml of distilled water and transferred to a Buchner funnel. Pumped out, washed 2 times with 250 ml of distilled water during pumping.

6. The microspheres were removed and dried in air.

7. Chemical analysis showed that the modifier corresponds to the formula Li ₂ Co ₃ [Fe (CN) ₆ ] ₂ . The modifier mass is 28.9 mg / (gram ash microspheres). Sorption properties with respect to Cs ions in a 0.1 mol / L hydrochloric acid medium under static conditions were 342.7 mg / (g modifier) or 2.5 mg equiv Cs ¹³⁷ / g modifier.

Example No. 4

1. 310 ml of air-dried ash microspheres (134 g) were introduced into a dry separatory funnel and slightly tamped.

2. Then, 300 ml of a 0.1 mol / L solution of Li ₄ [Fe (CN) ₆ ] was added to the funnel; the contents were thoroughly mixed and left until the phases were completely separated.

3. The volume of the filtrate was 204 ml, which corresponds to the retention of 96 ml or 9.6 mmol of Li ₄ [Fe (CN) ₆ ] with ash microspheres.

4. To precipitate Ni (II) ferrocyanide, 300 ml of a solution containing 22 mmol of metal and 10 ml of an aqueous solution of polyacrylamide with a titer of 8–10 mg / ml were added to the separatory funnel. Thoroughly mixed. After settling, the aqueous phase was removed, and the sorbent was washed with 250 ml of distilled water containing 5.0 ml of polyacrylamide solution. Stirred, after which the aqueous phase was removed.

5. 100 ml of distilled water was added to the funnel and the suspension was transferred to a Buchner funnel. The aqueous phase was removed. The sorbent was washed 2 times with 100 ml of distilled water. The product was air dried. Light green loose powder was analyzed. It was found that the composition of the modifier corresponds to the formula: Li _0.54 Ni _3.73 [Fe (CN) ₆ ] ₂ . The mass of the modifier is 29.1 mg / (gram ash microspheres). Sorption properties with respect to Cs ions in a 0.1 mol / L hydrochloric acid medium under static conditions were 313.1 mg / (g modifier) or 2.3 mg equiv Cs ¹³⁷ / g modifier.

Example No. 5

1. 160 ml (47 g) of air-dry microspheres were introduced into a 1000 ml separatory funnel and treated with 100 ml of a 1 mol / L solution of Ni (II) salt containing ≈80 mg of polyacrylamide. Thoroughly mixed and left until complete phase separation.

2. The solution of Ni (II) salt held by microspheres was 10 ml, i.e. 10 mmol for metal.

3. To precipitate Ni (II) ferrocyanide, 70 ml of a 0.15 mol / L solution of Li ₄ [Fe (CN) ₆ ] in 200 ml of distilled water was introduced into a separatory funnel. The contents of the funnel were thoroughly mixed and left to separate phases.

4. After removal of the liquid phase, the light green sorbent was washed with 250 ml of distilled water containing 10 ml of a solution of polyacrylamide with a titer of 8-10 mg / ml, stirred and the suspension was transferred to a Buchner funnel. The liquid phase was aspirated, and the precipitate was washed twice with distilled water, 200 ml each.

5. The sorbent was removed from the funnel and dried on paper. Chemical analysis showed that the modifier has a composition of Li _2.46 Ni _2.77 [Fe (CN) ₆ ] ₂ , and the mass of the modifier is 80.5 mg / (gram ash microspheres). Sorption properties with respect to Cs ions in a 0.1 mol / L hydrochloric acid medium under static conditions were 329.9 mg / (g modifier) or 2.4 mg equiv Cs ¹³⁷ / g modifier.

Example No. 6.

1.400 ml (160 g) of air-dried ash microspheres were introduced into a 1000 ml separatory funnel and treated with 300 ml of 0.2 mol / L sodium tungstate solution with vigorous shaking.

2. After phase separation, the liquid phase was discharged and its volume was determined. The difference between the initial and final volumes was used to determine the amount of liquid held by ash microspheres. The amount of sodium tungstate (in mmol) was determined by the ratio:

Q = C _WNa · V _CB.

In this case, it was equal to 32 mmol. 3. Modification of the microspheres with tungsten ferrocyanide was carried out by treating the microspheres with 160 ml of a 0.1 mol / L solution of yellow blood salt in 1.0 mol / L hydrochloric acid.

4. After phase separation, the liquid phase was drained and the solid phase was washed twice with distilled water containing flocculant (~ 100 mg polyacrylamide). After the second washing, the sorbent was transferred to a Buchner funnel and carefully aspirated. The wet product was dried either in air or at 80 ° C to constant weight.

5. According to the chemical analysis, the W / Fe ratio was determined and the ion exchange ability was studied for various radionuclides. In this experiment, it was equal to ~ 5.0.

In a similar manner, sorbents modified with vanadium and zirconium ferrocyanides were synthesized.

Table 1 shows the effect of buffer media on the sorption of indicator amounts of Ce ¹⁴⁴ , Eu ¹⁵⁵ and Co ⁶⁰ sorbents based on fly ash microspheres modified with copper ferrocyanides (ZMFtsu), nickel (ZMPtsi), tungsten (ZMPtsW) and zirconium (ZMPtsZr).

Table 1 The effect of buffer media on the sorption of certain radionuclides No. p / p Sorbent % sorption (E) oxalate buffer pH 1.68 tartrate buffer pH 3.56 phosphate buffer pH 6.86 borate buffer
pH 9.18 Eu ¹⁵⁵ Ce ¹⁴⁴ From ⁶⁰ Eu ¹⁵⁵ Ce ¹⁴⁴ Co ⁶⁰ Eu ¹⁵⁵ Ce ¹⁴⁴ Co ⁶⁰ Eu ¹⁵⁵ Ce ¹⁴⁴ From ⁶⁰ one ZMFtsSu 97 97 53 13 26 fifteen 84 84 64 94 55 64 2 ZMFtsNi 61 59 53 25 23 36 49 39 48 32 40 66 3 ZMFtsW 28 32 64 12 22 fifty 33 39 56 21 31 thirty four ZMFtsZr 32 55 82 17 28 19 58 42 82 35 41 thirty

An analysis of the data in Table 1 indicates the influence of two factors: the chemical form of the modifier and the composition of the buffer solutions. The greatest decrease in the sorption of radionuclides is observed in the presence of tartrate buffer, which is possibly associated either with the formation of complex forms with the same charge, or with partial dissolution of the ferrocyanide complex. The obtained experimental data indicate the possibility of using synthesized sorbents for purification of LRW from Cs ¹³⁷ , Co ⁶⁰ , Ce ¹⁴⁴ , Eu ¹⁵⁵ , etc.

Claims (11)

1. A method of producing a sorbent based on fly ash microspheres for cleaning liquid radioactive waste, comprising introducing an active component, characterized in that the active component is introduced by depositing it on the surface of the microspheres by mixing them with a precipitant, which is an alkali metal ferrocyanide solution, followed by removing excess precipitant solution, which determines the amount of precipitant retained by the microspheres, and then a solution of a transition metal salt is added to the resulting mixture, the mixture is nents to withstand phase separation, whereupon the liquid phase is removed and the resulting dried sorbent. 2. The method according to claim 1, characterized in that the concentration of the precipitant solution is 0.1-0.25 mol / L, and the concentration of the transition metal salt solution is 0.2-0.5 mol / L. 3. The method according to claim 1, characterized in that a flocculant is added to suppress peptization. 4. The method according to claim 3, characterized in that as the flocculant use an aqueous solution of polyacrylamide. 5. The method according to claim 1, characterized in that the sorbent is dried at a temperature of 60-80 ° C for 1-2 hours or at room temperature for 15-20 hours to an air-dry state. 6. A method of producing a sorbent based on fly ash microspheres for cleaning liquid radioactive waste, comprising introducing an active component, characterized in that the active component is introduced by depositing it on the surface of the microspheres by treating them with a solution of vanadium or zirconium or tungsten salt, followed by removal excess salt solution, which is used to determine the volume of salt solution held by the microspheres, and then a precipitant is added to the resulting mixture, which is an acid solution of alkaline ferrocyanide thallium mixture of components is kept to phase separation, whereupon the liquid phase is removed and the resulting dried sorbent. 7. The method according to claim 6, characterized in that the acidification of the precipitating solution is carried out with a 1M hydrochloric acid solution. 8. The method according to claim 6, characterized in that the concentration of the precipitating solution is 0.1-0.2 mol / L, and the concentration of the solution of the vanadium salt, or zirconium, or tungsten is 0.3-0.6 mol / L. 9. The method according to claim 6, characterized in that a flocculant is added to the metal salt solution to suppress peptization. 10. The method according to claim 9, characterized in that as the flocculant use an aqueous solution of polyacrylamide. 11. The method according to claim 6, characterized in that the sorbent is dried at a temperature of 60-80 ° C for 1-2 hours or at room temperature for 15-20 hours to an air-dry state.

Images