Method of purifying uranium from natural uranium concentrate

FIELD: physics, atomic power.

SUBSTANCE: invention relates to a method with which uranium from a natural uranium concentrate may be purified. The method includes extracting uranium present as uranyl nitrate in an aqueous phase A1 resulting from the dissolution of the natural uranium concentrate in nitric acid using an organic phase which contains an extractant in an organic diluent; washing the organic phase obtained at the end of step a), with an aqueous phase A2, and extracting the uranyl nitrate from the organic phase obtained at the end of step b), by circulating said organic phase in an apparatus as a counter-current of an aqueous phase A3. The extractant is an N,N-dialkylamide and the ratio between the flow rate at which the organic phase obtained at the end of step b) and the aqueous phase A3 circulate in the apparatus where step c) occurs, is greater than 1.

EFFECT: high efficiency of purifying uranium by preventing loss of uranium in the organic phase.

15 cl, 2 tbl, 4 ex

 

The technical field to which the invention relates.

The present invention relates to a method for purification of uranium from natural uranium concentrate.

The method finds application in the field of purification of natural uranium concentrates that produce uranium mines and contained uranium after extraction is intended, in particular, for turning or uranium metal or uranium compounds, such as, for example, uranium hexafluoride (or UF6), tetraploid uranium (or UF4), uranium dioxide (or UO2or truran-octoxide (U3O8) which are intermediate products in the production of nuclear fuel.

The level of technology

The plants for the purification of natural uranium concentrates in order to bring the uranium contained in the concentrates, the so-called "nuclear" purity, the apply method, which after dissolution of these concentrates in nitric acid to obtain an aqueous solution of the crude uranyl nitrate includes:

extraction of the nitrate organic phase containing the extracting agent, having a high affinity for this nitrate in an organic solvent, and then

- washing of the organic phase obtained after the extraction, the aqueous phase for removal from the organic phase unwanted chemically the compounds which can be extracted together with uranyl nitrate, and

- extraction of uranyl nitrate from washed so the organic phase for the conversion of uranyl nitrate to the aqueous phase.

These three operations are performed in the apparatus for liquid-liquid extraction, for example, in the columns of a with stirring.

Used extracting means is a tri-n-butyl phosphate (or TBP), which is also used as extracting agent for reprocessing of irradiated nuclear fuel and which was selected for all sewage treatment plants as the most suitable in relation to the limitations imposed by this method in terms of selectivity, solubility in water, chemical stability, density, corrosion degradation, toxicity and safety.

However, this cleaning method has several shortcomings, which involve extracting means.

The first of these disadvantages is that in the apparatus in which the operation is carried out extraction, there is an accumulation of thorium (impurities present in uranium ores) that is associated with the cycle extraction/extraction of this element in this unit. Indeed, since the thorium can be extracted with TBP, it is extracted in the region of the device where the organic phase is discountestrace of uranyl nitrate, and then removed from this phase in the region of the device where the organic phase is saturated with uranyl nitrate.

This accumulation of thorium causes a maximum dose in the radiation generated by metastable protactinium 234 (234mRA) after decay of thorium 234 present in the solution of the crude uranyl nitrate, which is a direct product of uranium 238.

It is known that in order to avoid the appearance of such a peak dose rate, to a solution of the crude uranyl nitrate can be added means during the process of extraction to form complexes with thorium, which can be a fluorides or phosphates. However, the presence of complexing agents in the receiving water effluent imposes additional restrictions upon the use of the method and these effluents caused by factors such as: contamination of the regenerated nitric acid and distillates, corrosion of the equipment used, sediment, etc.

Another disadvantage is that the extraction operation is relatively difficult to perform because of the TBP extraction of uranium, which cannot be neglected even at low pH. Therefore, for the quantitative extraction of uranyl nitrate is necessary to heat the aqueous phase, which is used to perform this Opera is AI (usually distilled water), at least up to 50°C and use a high velocity flow of fluids.

In addition to the fact that the use of aqueous phase having a temperature equal to at least 50°C, leads to a reduction of security due to the risk of ignition of the organic phase, the use of significant flows of liquids leads to a significant dilution of uranyl nitrate. Thus, if the concentration of uranyl nitrate source was equal to the value of about 400 g/l in the untreated solution of uranyl nitrate, the aqueous phase resulting after the extraction operation, it is in the best case is 130 g/L. Rich uranium in the organic phase contains about 150 g/l of uranium at the exit from the extraction step. In order to avoid losses of uranium in this organic phase, the maximum ratio O/A (organic to aqueous) flow velocity at the extraction should be less than 1 (0.8) even at 60°C.

If the extract concentration was insufficient, then, as a consequence, before further processing by generirovaniya need to expose this aqueous phase operation concentration, which requires a large power consumption.

Finally, because the solubility of TBP in an acidic aqueous phase, which cannot be neglected, it may be necessary to flush water effluents obtained when extrac the AI, organic solvent for extraction of TBP present in these effluent, so as to avoid wasting extracting means.

Therefore, given the above, the inventors have set themselves the goal is to create a method, which allows for highly efficient purification of uranium contained in natural uranium concentrate, at the same time would be deprived of the above-mentioned disadvantages.

Disclosure of inventions

This objective and other objectives achieved through the present invention, in which is disclosed a method for purification of uranium from natural uranium concentrate containing at least one of the following impurities: thorium, molybdenum, zirconium, iron, calcium and vanadium, including:

a) extraction of uranium that is present in the form of uranyl nitrate in the aqueous phase A1, the resulting dissolution of the specified natural uranium concentrate in nitric acid, by bringing this aqueous phase into contact with an organic phase that is immiscible with water, which comprises extracting agent in an organic solvent, and the subsequent separation of the water and organic phases;

b) washing the organic phase obtained after stage a), by bringing this organic phase into contact with an aqueous phase A2 and the last is the total separation of these organic and aqueous phases; and

c) extraction of uranyl nitrate from the organic phase obtained after stage b) is performed by circulating this organic phase in the apparatus in countercurrent with respect to the aqueous phase A3, and separation of these organic and aqueous phases;

and characterized in that, on the one hand, extracting tool contained in the organic phase, is represented by N,N-dialkylamide, and, on the other hand, the ratio between the flow rates at which the organic phase obtained at the end of stage B), and the aqueous phase A3 circulate in the apparatus, the operator is to stage C), is greater than 1, so that the extraction of uranyl nitrate is accompanied by the concentration of nitrate.

Thus, in the method according to the invention is repeated three basic operations (extraction, washing, extraction) are known from the prior art method of extraction, but use N,N-dialkylamide as extracting means, instead of TBP.

It should be noted that the use of the organic phase containing N,N-dialkylamide, for the extraction of uranium from the aqueous phase, in which it was discovered, is not a new application per se. So, for example, such an application was proposed for the extraction of uranium and/or plutonium present in the aqueous solution resulting from the dissolution of irradiated nuclear fuel (French is avca patent published under the number 2 642 562), as well as for the extraction of uranium present in aqueous solutions with concentrated thorium, because it is produced by irradiation of thorium (French patent application published under the number 2 642 561).

On the other hand, what is new is the application of the organic phase containing N,N-dialkylamide for the purification of uranium from uranium concentrate, and is unexpected that this application at the same time allows for:

- in order to avoid accumulation of thorium when the extraction operation is performed with the use of containing TBP organic phase, which reduces the need to use complexing agents with all the ensuing advantages, particularly from the point of view of simplification of the method of application and processing of the resulting aqueous effluent;

- implementation of the extraction operation at temperatures lower than those used in known from the prior art method of cleaning out, even if such removal, however, can be performed at temperatures from 50 to 60°C, and use a lower flow rate of the aqueous phase, compared to the speeds that are required when the organic phase contains TBP that, as a consequence, facilitates the subsequent operation of concentrating also with all the attendant benefits, is osobennosti, from the point of view of energy savings;

- loss extracting means in the aqueous phase due to the low solubility of N,N-dialkylamides in the aqueous phase, and facilitate the processing of extracted refined for re-use of nitric acid in the method.

As for N,N-dialkylamides, it is possible in particular to apply those which correspond to formula (I) below:

in which:

- R1represents an alkyl group, a branched in the alpha or beta position from the carbonyl group and containing from 3 to 12 carbon atoms;

- R2and R4that may be the same or different, represent a linear or branched alkyl group containing from 2 to 4 carbon atoms;

- R3and R5that may be the same or different, represent a linear or branched alkyl group comprising from 1 to 6 carbon atoms; and

- a and b, which may be the same or different, are integers ranging from 1 to 6.

Among these, N,N-dialkylamides it is preferable to use those in which both a and b equal to 1 and in which both R2and R4represent ethyl groups, such N,N-di (2-ethylhexyl) isobutyramide (or DEHiBA, where R1=-CH(CH3)2and R3=R5=-(CH2 )3CH3), N,N-di(2-ethylhexyl)-2,2-di-methylpropanamide (or DEHDMPA, where R1=-C(CH3)3and R3=R5=-(CH2)3CH3or optionally N,N-di(2-ethylhexyl)-3,3-Dimethylbutane (or DEHDMBA, where R1=-CH2C(CH3)3and R3=R5=-(CH2)3CH3), where DEHiBA most preferred.

As for the organic solvent, it is preferred isoparaffin or a mixture isoparaffins, the carbon chain of which contains from 9 to 13 carbon atoms, such as those supplies on the market, the company "TOTAL" under the trade name of Isane IP 185.

However, it is also possible to use other aliphatic organic solvents, such as kerosene or a linear or branched dodecane, such as n-dodecane and hydrogenated tetrapropylene (or TPH).

In all cases, the concentration of N,N-dialkylamide in an organic solvent, preferably equal to from 1 to 2 mol/L.

The aqueous phase A1 preferably contains from 0.5 to 4 mol/l of nitric acid.

The aqueous phase A2 preferably represents water, mostly distilled water, or an aqueous solution containing from 0.01 to 1.5 mol/l nitric acid, or another part of the aqueous phase obtained after the completion of stage C).

With respect to the water phase A3, it can be either water, etc the property of distilled water, or an aqueous solution of nitric acid of low concentration, i.e., preferably containing not more than 0.01 mol/l of nitric acid.

In accordance with the invention, this aqueous phase A3 can be applied at room temperature, i.e. at temperatures typically ranging from 20 to 25°C, but it can also be heated to a temperature equal to from 50 to 60°C., as known in the prior art method of retrieval.

As noted earlier stage C), the ratio between the flow rates at which the organic phase obtained at the end of stage B), and the aqueous phase A3 circulate in the apparatus, the operator is to stage C), is greater than 1 and, preferably, equal to or greater than 1.5.

The method according to the invention can be used in vehicles of all types, traditionally used in the field of liquid-liquid extraction, such as the battery of mixers-decantation, pulse columns or columns with mixing, dewatering centrifuges, etc.

In addition to the above advantages, the method of the invention additionally has other advantages, such as the fact that, on the one hand, the degradation products of N,N-dialkylamides much less harmful than the TBP degradation products, and, in particular, di-n-butyl phosphate, which forms stable complexes with certain metal cations, and, on the other hand, N,N-dialkylamide can be full of the flesh burned, because they consist only of carbon atoms, oxygen, nitrogen and hydrogen, which is not the case TVR.

Other characteristics and advantages of the invention will become clear from the subsequent description, which refers to experimental tests and by means of which the method of the invention can be confirmed.

Obviously, this additional description is given only as an illustration of the purpose of the invention and in any way, should not be interpreted as limiting this purpose.

Brief description of drawings

Fig.1 schematically illustrates a first test of the method according to the invention in powered mixers-decantation.

Fig.2 shows the values of the distribution coefficient of thorium 234, denoted as DTh observed during the test tubes, which consists in the extraction of uranium from aqueous solution containing 2 mol/l nitric acid, with five organic phases containing or DEHiBA, or TVR at Isane IP 185.

Fig.3 schematically illustrates another test of the application of the method of the invention in powered mixers-decantation.

Fig.4 shows the profiles of the concentrations of uranium in the aqueous and organic phases obtained experimentally and by calculations at different stages in the mixer-decanter applied in the test illustrated in Fig.3.

The implementation of izaberete the Oia Example 1

First of all, consider Fig.1, which schematically illustrates a first application of the method according to the invention in powered mixers-decantation. This test is carried out in the plant 10, including:

- the first battery, designated as 11, which consists of 16 mixer-decantation designed for the extraction of uranyl nitrate from an aqueous phase A1;

- a second battery, designated as 12, consisting of 8 mixers-decantation intended for washing the organic phase obtained after the extraction; and

third battery, designated as 13, consisting of 16 mixer-decantation designed for the extraction of uranyl nitrate from the organic phase obtained after washing in this phase.

Were applied:

as the organic phases are: phase containing 1 mol/l DEHiBA in TRN and circulating a flow rate of 100 ml/hour, three batteries mixers-decantation;

as the aqueous phase A1: a solution of 4 mol/l nitric acid and 120 g/l of uranium (in the form of uranyl nitrate) circulating a flow rate of 45 ml/hour in the battery 11;

as the aqueous phase A2: a solution of nitric acid in a concentration of 0.5 mol/l, circulating a flow rate of 10 ml/HR battery 12, which is added with the same flow rate to the aqueous phase A1 in the battery 11; and

as the aqueous phase is A3: a solution of nitric acid at a concentration of 0.01 mol/l, circulating a flow rate of equal to 31.5 ml/h, in the battery 13.

Relations O/A (organic relative to water) flow rates in the batteries 11,12 and 13 is equal to 1,8,10 and 3, respectively.

All phases, including the aqueous phase A3, used at 25°C.

After 700 hours of operation test showed that in the aqueous phase coming from the battery 13, it is possible to remove more than 99.9% of uranyl nitrate, present in the original aqueous phase A1 in a concentration exceeding the concentration in which it was in the aqueous phase A1, i.e., 160 g/l compared to 120 g/l, i.e., the concentration coefficient equal to 1.3.

The organic phase coming from the battery 12, contains about 54 g/l of uranium, which quantitatively remove the battery 13, using the relation O/And velocities of flows equal to 3, to obtain a solution of 160 g/l of uranium.

Low extractibility of uranium DEHiBA at low concentrations of nitric acid, thus, allows the extraction of the "concentration" of uranyl nitrate at a temperature of 25°C, whereas this cannot be achieved if the organic phase contains TBP, and that even if this extraction is applied to the heated water phase.

Example 2

The solubility of DEHiBA in the aqueous phase was evaluated by testing in mixers-decantation similar to that described above in example 1, iutam measure total organic carbon or TOC), present in the output from the battery 11 to the water phase (referred to further in this document, the purified product after extraction"), on the one hand, and in the aqueous phase coming from the battery 13 and containing the extracted uranium nitrate (referred to in this document as "output U"), on the other hand.

The total amount of organic carbon measured by thermal TOC meter in the water phase obtained after decanting, i.e., without subjecting these phases any centrifugation.

Table 1 below shows both the tested aqueous phase, their acidity, the obtained value of TOC and converting this value into the equivalent of DEHiBA, this translation is performed on the assumption that all organic carbon is present in the streams of the aqueous phase from this extracting means.

Table 1
The aqueous phaseThe purified product after extractionOutput U
HNO3(mol/l)3,10,34
TOC (mg/l)3146
The equivalent of DEHiBA (mol/l) 1.3 to 10-41,9-10-4

This table shows that approximately 40 to 60 mg/l DEHiBA can be dissolved in the aqueous phase in the test conditions.

These values of solubility is greater than the solubility of DEHiBA in the aqueous phase, according to the results of the work of Al-Jallo et al. (J. Chem. Eng. Data 1984, 29, 479-481) and work Gasparini and Grossi (Separation Science and Technology 1980, 15(4), 825-844), but they include the solubility of the extracting means, the solubility of the organic solvent (TRN), and the phenomenon of making the organic phase in the aqueous solutions at the output of the battery of mixers-decantation, which cannot be ignored.

These values of solubility, however, remain less than full TVR solubility under the same conditions, which is equal to 200 to 300 mg/l, and confirm the fact that the loss of the extracting means in the aqueous phase is significantly less than in the case where the organic phase contains the DEHiBA.

Example 3

Selectivity DEHiBA for uranium with respect to the impurities, which are mainly present in natural concentrates of uranium or which lead to the cost of subsequent stages of processing and enrichment of uranium, was also evaluated by conducting two series of tests.

The first series of tests consisted of determining the distribution coefficients of thorium (IV), mo (VI), zirconium (IV), W is found in (III), calcium (II) and vanadium (V) at the end of a single contact in the pipes between the phase solvent containing 1.5 mol/l in DEHiBA Isane IP 185, and solutions of nitric acid, containing these cations, as in the presence of 30 g/l of uranium, and without it, and with different acidity (from 0.5 to 4 M).

For each test water and the organic phase is introduced into the contact volume to volume, and left to mix for 1 hour at a constant temperature of 25°C. Then, after decantation and separation of these phases in the aqueous phase and the organic phase determine the concentration of cations with atomic emission spectrometry (or ICP-AES).

This first set of tests showed that uranium or without him in the studied range of concentrations of nitric acid, the distribution coefficients of molybdenum, zirconium, iron, calcium and vanadium were less than 10-3and led to the separation factors U/impurities, equal to more than 10,000, i.e. largely adequate to meet the technical requirements in accordance with ASTM With 788, from the point of view of extraction of uranyl nitrate.

The distribution coefficient of thorium (IV) was also very small (less than 5·10-3for the concentration of nitric acid, 4 mol/l, and this, regardless of the concentration of uranium in the aqueous phase, confirms the high selectivity of DEHiBA for uranium relative to thorium (IV).

The second series of ispycameltoe from the depleted aqueous solution, containing 360 g/l of uranium and 2 mol/l nitric acid, by introducing this aqueous solution in the tubes into contact with successive five organic phase containing 1.5 mol/l DEHiBA, or 36% (volume/volume) TBP in Isane IP 185, and following each contact determination of distribution coefficient of thorium 234, resulting from the decay of uranium 238.

For the first two contacts of water and the organic phase was used in the amount of one volume of the aqueous phase on the two volumes of the organic phase, whereas for the last three contacts water and the organic phase was applied in a volume ratio of 1 to 1. In all cases water and the organic phase was left to stir for 10 minutes at a constant temperature of 25°C.

After decantation and separation of aqueous and organic phases was determined activity of thorium 234 in each of these phases by using γ-spectrometry.

The results of this second series of tests is illustrated in Fig.2, which shows the magnitude of the distribution coefficient of thorium 234, denoted as DThobtained after each contact for both types of organic phases.

This figure shows that in the case of organic phase containing TEV, DThbecomes greater than 1 after 3rd contact, i.e., after the depletion of uranium in the aqueous phase, whereas, in the case where the organic phase is going to win DEHiBA, DThis maintained at a level less than 10" even after depletion of uranium in the phase.

Thus, the accumulation of thorium, which occurs in the extraction apparatus known in the prior art method of extraction and simulation which has been made possible thanks to the above tests should not occur in the method according to the invention.

Example 4

Now let us turn to Fig.3, which schematically illustrates another test of the application of the method according to the invention in powered mixers-decantation. This test is carried out in the installation of 20, including:

- the first battery, designated as 21, which consists of 8 mixers-decantation designed for the extraction of uranyl nitrate from an aqueous phase A1;

- a second battery, designated as 22, consisting of 8 mixers decantation intended for washing the organic phase obtained after the extraction; and

third battery, designated as 23, is heated to 50°C. and consisting of 8 mixers-decantation designed for the extraction of uranyl nitrate from the organic phase obtained after washing this phase.

Used:

as the organic phases are: phase containing 1.5 mol/l DEHiBA in TRN and circulating a flow rate of 145 ml/h in the three-powered mixers-decantation;

as the aqueous phase A1: a solution containing 5 mol/l of nitric acid, 435 g/l of uranium (as uranyl nitrate), approximately 5400 kBq/l (i.e., 6 ng/l) thorium 234, resulting from the decay of uranium 238, and typical impurities (736 mg/l iron, 359 mg/l molybdenum, 258 mg/l zirconium, 34 mg/l vanadium and 106 mg/l of calcium), and circulating a flow rate of 50 ml/h in the battery 21; and

as the aqueous phase A2: part of the solution coming out of the battery 23, circulating a flow rate of 6 ml/h in the battery 22 and is added with the same flow rate to the aqueous phase A1 in the battery 21;

as the aqueous phase A3: the solution heated distilled water, circulating a flow rate of 75 ml/h in the battery 23.

Relations O/A (organic to aqueous) velocities of flows in the batteries 21, 22 and 23 are, therefore, equal to 2, 6, 24 and 1.9, respectively.

After 24 hours of the installation, the test showed that in the aqueous phase coming from the battery 23, it is possible to extract more than 99% of uranyl nitrate, present in the original aqueous phase A1 in a concentration equal to 281,5 g/l, i.e. much greater than the concentration of the extracted uranium is known from the prior art method of extraction (130 g/l). Estimated loss of uranium in the aqueous phase coming from the battery 21, is equal to 0.2 mg/L.

Thorium 234, tracked γ-spectrometry, again was quantitatively detected in the aqueous phase coming from the battery 21 (i.e., at the end of the test have removed 100% of the original thorium), and not NAC which they drank in the battery, and this without the use of specific complexing substances that, therefore, confirms the selectivity of DEHiBA for uranium than thorium.

The organic phase coming from the battery 22, contains about 156 g/l of uranium, which quantitatively remove the battery 23 by applying the ratio of speeds of threads On/A 1,9 to obtain a solution with 281,5 g/l of uranium.

In addition, testing showed that the uranyl nitrate was largely cleared from the major impurities present in the ore concentrates. The results showed the presence in the extracted solution of uranyl nitrate traces of iron, molybdenum, zirconium and calcium in amounts of less than 1 mg/l and the presence of vanadium discover completely failed. The presence of thorium concentration in the extracted uranium nitrate according to the measurements was equal to 8-10-14g/l, probably due to the regeneration of thorium in the sample of uranium in the decay of uranium, which is confirmed by the very low distribution coefficients thorium obtained organic phase containing DEHiBA.

These values are given in the following table 2 in comparison with the technical requirements of the ASTM standard With 788.

Table 2
Impurities in the extracted nitrate solution ur of the sludge MoVZrCAFe
Technical requirements for ASTM standard With 788, (µg/g of uranium)1,41,4The amount of <500
Test mixers-decantation (µg/g of uranium)1,1<13,62,73

In addition, in Fig.4 shows expressed in g/l profiles of the concentrations of uranium in water and the organic phase obtained experimentally and by calculation, at different stages in the mixer-decanter.

This figure [U(VI)]AQexp. corresponds to the experimental concentrations of uranium in the aqueous phase; [U(VI)]org. exp. corresponds to the experimental concentrations of uranium in the organic phase; [U(VI)]AQthe calculation corresponds to the calculated concentrations of uranium in the aqueous phase, whereas [U(VI)]org. the calculation corresponds to the calculated concentrations of uranium in the organic phase.

Good agreement between experimental and calculated values confirms the validity of the model extraction of uranium using EHiBA, developed for the simulation method of the invention.

Consequently, the use of DEHiBA allows you to extract all of the uranium present in the solution, with a concentration two times higher compared to that which currently receive in industrial production with TBP, and in sufficient amount to clear it from the main impurity cations present in the ore concentrates and represents an obstacle for subsequent operations, enrichment, and at the same time to prevent the accumulation of thorium in the extraction step.

1. The method of purification of uranium from natural uranium concentrate containing at least one impurity selected from thorium, molybdenum, zirconium, iron, calcium and vanadium, comprising the following stages, which are:
a) extracted with the uranium present in the form of uranyl nitrate from aqueous phase A1, the resulting dissolution of natural uranium concentrate in nitric acid, and extraction comprises bringing the aqueous phase A1 in contact with immiscible with water, the organic phase, which contains the extracting agent in an organic solvent, and subsequent separation of the water and organic phases;
b) wash the organic phase obtained after stage a), and the washing includes the conversion obtained after stage a), the content of inorganic fillers phase into contact with an aqueous phase A2 and the subsequent separation of the water and organic phases; and
c) extract the uranyl nitrate from the obtained at the end of stage b) of the organic phase and extract includes circulation obtained after stage b) of the organic phase in the apparatus in countercurrent with the aqueous phase A3 and subsequent separation of these organic and aqueous phases;
in which the extracting means, contained in the organic phase, is represented by N,N-dialkylamide and the relationship between flow velocity, which is obtained at the end of stage b) of the organic phase and the aqueous phase A3 circulate in the apparatus of stage C), is greater than 1.

2. The method according to p. 1, in which N,N-dialkylamide selected from N,N-dialkylamides corresponding to the following formula (I)

in which:
- R1represents an alkyl group which is branched in the alpha or beta position from the carbonyl group and which includes from 3 to 12 carbon atoms;
- R2and R4that may be the same or different, represent a linear or branched alkyl group containing from 2 to 4 carbon atoms;
- R3and R5that may be the same or different, represent a linear or branched alkyl group comprising from 1 to 6 carbon atoms; and
- a and b, which may be the same or different, are integers ranging from 1 to.

3. The method according to p. 2, in which N,N-dialkylamide corresponds to the formula (I), in which both a and b equal to 1 and both R2and R4represent an ethyl group.

4. The method according to p. 3, in which N,N-dialkylamide represents N,N-di(2-ethylhexyl)-isobutyramide.

5. The method according to p. 1, in which the organic solvent is a C9-C13-isoparaffin or mixture With9-C13-paraffins.

6. The method according to p. 1, in which the concentration of N,N-dialkylamides in an organic solvent is equal to from 1 to 2 mol/L.

7. The method according to p. 1 in which the aqueous phase A1 includes from 0.5 to 4 mol/l of nitric acid.

8. The method according to p. 1 in which the aqueous phase A2 represents water.

9. The method according to p. 8 in which the aqueous phase A2 represents distilled water.

10. The method according to p. 1 in which the aqueous phase A2 is an aqueous solution comprising from 0.01 to 1.5 mol/l of nitric acid.

11. The method according to p. 1 in which the aqueous phase A2 represents a portion of the aqueous phase obtained after the completion of stage C).

12. The method according to p. 1 in which the aqueous phase A3 represents water.

13. The method according to p. 12, in which the aqueous phase A3 represents distilled water.

14. The method according to p. 1 in which the aqueous phase A3 is an aqueous solution, containing at most 0.01 mol/l of nitric acid.

15. The method according to p. 1, in which respect the tion between flow rates, which obtained at the end of stage b) of the organic phase and the aqueous phase A3 circulate in the apparatus of stage C), is equal to or greater than 1.5.



 

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4 cl, 1 dwg, 1 tbl

FIELD: chemistry.

SUBSTANCE: method involves dissolving wastes in concentrated nitric acid, oxalate precipitation from the solution, drying and calcining the americium oxalate to americium dioxide. The solution obtained by dissolving wastes with high concentration of impurity cations, one of which is ferric iron, is mixed with a reducing agent for reducing ferric iron to ferrous iron. After reduction, the solution with acidity by nitric acid of 1-2.5 mol/l is taken for extraction of americium with a solid extractant based on different-radical phosphine oxide, followed by washing and re-extraction of americium. Oxalate precipitation is carried out from the re-extract with americium concentration of not less than 3 g/l and nitric acid concentration of not less than 3 mol/l, said precipitation being carried out in two steps: adding an oxalate ion to the americium-containing solution in weight ratio to americium of (2-7):1 and then adding water to the separated precipitate in volume ratio to the precipitate of (3-8):1 and the oxalate ion in weight ratio to americium of (1-4):1. The obtained reaction mixture is boiled and taken for separation of americium oxalate from the solution.

EFFECT: high output of the product and degree of purity thereof.

4 cl

FIELD: metallurgy.

SUBSTANCE: metallic uranium obtaining method involves electrolysis of uranium dioxide in the melt of lithium and potassium chlorides in an electrolysis unit with a graphite anode and a metal cathode and release of metallic uranium on the cathode and carbon dioxide on the anode. First, mixtures of uranium dioxide and carbon are prepared in molar ratio of 6:1 and 1:1 by crushing the corresponding powders; the obtained powders are briquetted into pellets. To the anode space of the electrolysis unit, which is formed with a vessel with porous walls, which is arranged in a ceramic melting pot, there loaded are pellets obtained from mixture of uranium dioxide and carbon, and melt of lithium and potassium chlorides. To the cathode space of the electrolysis unit, which is formed with the vessel walls with porous walls and the ceramic melting pot, there loaded is melt of lithium and potassium chlorides and uranium tetrachloride in the quantity of 5-15 wt % of lithium and potassium chlorides. Electrolysis is performed at the electrolyte temperature of 500-600°C, cathode density of current of 0.5-1.5 A/cm2, anode density of current of 0.05-1.5 A/cm2, in argon atmosphere with periodic loading to anode space of pellets of mixture of uranium dioxide and carbon.

EFFECT: current yield of metallic uranium is 80-90% of theoretical.

1 ex

FIELD: chemistry.

SUBSTANCE: method involves dissolving a chemical concentrate of natural uranium in nitric acid solution, extracting and re-extracting uranium. The dissolved concentrate contains 1.2-3.7 wt % iron to uranium, 1.4-4.0 wt % sulphur to uranuim and 0-0.7 wt % phosphorus to uranium in nitric acid solution. Nitric acid and water are taken in an amount which provides the following concentration in the solution fed for extraction: uranium 450-480 g/l, iron (III) ions 0.1-0.3 mol/l, sulphate ions 0.2-0.6 mol/l, phosphate ions 0-0.10 mol/l, and free nitric acid 0.8-2.4 mol/l, and saturation of extractant with uranium during extraction is maintained in accordance with the ratio: Y ≤90.691-34.316·[SO4]+7.611·([Fe]-[PO4])+5.887·[HNO3]-9.921·[SO4]·[HNO3]+19.841·[SO4]2+7.481·([Fe]-[PO4])·[HNO3]-64.728·([Fe]-[PO4])·[SO4]+92.701·[SO4]·[HNO3]·([Fe]-[PO4])-185.402·[SO4]2·([Fe]-[PO4]), where Y is saturation of the extractant with uranium, %, and concentration in the solution fed for extraction, mol/l: [SO4] - sulphate ions, [PO4] - phosphate ions, [HNO3] - nitric acid, [Fe] - iron (III) ions.

EFFECT: obtaining raffinates with low uranium content.

1 tbl

FIELD: metallurgy.

SUBSTANCE: method includes sorption of rich components from production solutions by ion-exchange material counterflow under controlled pH of environment and oxidation-reduction potential Eh. Sorption is performed by ion-exchange materials in stages from production solutions containing uranium, molybdenum, vanadium and rare earth elements. At the first stage uranium and molybdenum are extracted by anion-exchange material sorption. At the second stage vanadium is extracted by anion-exchange material sorption with hydrogen dioxide available at Eh of 750-800 mV, pH of 1.8-2.0 and temperature of 60°C, at that vanadium sorption is performed till complete destruction of hydrogen dioxide and till Eh is below 400 mV. Then barren solutions are transferred to cationite at pH of 2.0-2.5 and Eh of 300-350 mV for extraction of rare earth elements.

EFFECT: sorption concentration and selective separation of uranium and molybdenum from vanadium, and vanadium from rare earth elements, and rare earth elements from iron and aluminium, intensification of sorption process, reduction of flow diagram and possibility of environmentally sound oxidants use.

1 dwg, 4 tbl, 1 ex

FIELD: metallurgy.

SUBSTANCE: processing method of black-shale ores includes crushing, counterflow two-stage leaching by sulfuric acid solution upon heating, separation of pulps formed after leaching at both stages by filtration. Then valuable soluble materials are washed from deposit at the second stage with strengthened and washing solutions being produced, marketable filtrate is clarified at the first stage for its further processing. Ore is crushed till the size of 0.2 mm, leaching at the first stage is performed by cycling acid solution with vanadium under atmospheric pressure, temperature of 65-95°C during 2-3 hours, till residual content of free sulphuric acid is equal to 5-15 g/l. Leaching at the second stage is performed at sulphuric acid rate of 9-12% from the quantity of initial hard material under pressure of 10-15 atm and temperature of 140-160°C during 2-3 hours. Cake filtered after the first stage is unpulped by part of strengthened solution which content is specified within 35-45% of total quantity.

EFFECT: high-efficiency extraction of rich components, possibility of pulps separation by filtration after leaching with high properties thus reducing costs for separation processes.

3 cl, 1 dwg, 1 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to hydrometallurgy of noble metals and can be used in extraction of gold (III) from hydrochloric acid solutions from leaching gold-containing intermediate products and concentrates. Extraction is carried out from a hydrochloric acid solution with concentration of 1-5 mol/l HCl. The extractant added to the solution is an undiluted secondary C7-C12 aliphatic alcohol with a normal structure. Extraction is carried out with a countercurrent at 2-4 steps with organic to aqueous ratio of 1:2-20 with transfer of gold (III) into the extract, and the main part of the acid and impurity elements into the raffinate. The process is carried out while ensuring equilibrium concentration of hydrochloric acid in the raffinate of 1-5 mol/l until achieving residual content of gold in the raffinate of less than 3 mg/l. The saturated extract is washed with water or hydrochloric acid solution with concentration of 0.1-0.5 mol/l at 1-4 steps with organic to aqueous ratio of 3-20:1. After washing the extract, gold (III) is re-extracted with ammonia solution or thiourea solution while recycling the purified extractant to the extraction step.

EFFECT: achieving extraction of gold of up to 99,40-99,99%, reduced combined extraction of impurities and reduced material flow.

6 cl, 8 ex

FIELD: metallurgy.

SUBSTANCE: method of extraction of ruthenium from nitrite water solutions includes the ruthenium extraction by the solution of 3-n-butyl phosphate, water washing of the extract, adding of a cleansing solution to the solution for extraction, and ruthenium re-extraction by a sodium carbonate solution.

EFFECT: improvement of efficiency of direct extraction of ruthenium and decrease of expenses.

1 tbl, 1 ex

FIELD: metallurgy.

SUBSTANCE: invention refers to liquid extraction processes, in particular to obtainment of rear-earth metals concentrates, in non-ferrous and ferrous metallurgy, during utilisation of chemical and metallurgical production waste and for purification of shaft, mine and industrial waste water. The method of rear-earth metals removal from diluted water acid solutions involves consecutive steps of liquid-phase extraction of rear-earth metals to organic phase and re-extraction of rear-earth metals from organic phase by settlement of rear-earth metals to solid phase in the form of slightly soluble salt of strong acid.

EFFECT: providing efficient removal of rear-earth metals without neutralising of acid containing in organic phase and use of cheap commercially available reagents.

7 cl, 6 ex

FIELD: chemistry.

SUBSTANCE: method of processing a rare-earth phosphate concentrate separated when neutralising a nitric-phosphoric acid solution obtained after breaking down apatite with nitric acid, includes treating rare-earth phosphate concentrate with nitric acid and separating the undissolved residue from the obtained rare-earth element nitrate-phosphate solution. After treatment, the undissolved residue is washed and rare-earth elements are extracted from the rare-earth element solution. The undissolved residue is washed with ammonium nitrate solution with concentration of 40-70 wt % in amount of 25 pts.wt per 1 pts.wt of the undissolved residue. The wash solution is combined with the rare-earth element solution fed for extraction, and the undissolved residue is taken for production of compound fertilisers.

EFFECT: high degree of extraction of rare-earth elements from the rare-earth phosphate concentrate while reducing consumption of ammonia at the step of neutralising the nitric-phosphoric acid solution, consumption of nitric acid and hydrogen peroxide when dissolving the rare-earth phosphate concentrate.

3 cl, 3 tbl, 4 ex

FIELD: chemistry.

SUBSTANCE: invention relates to methods of extracting cerium (IV) from sulphate solutions by extraction and can be used for concentration of cerium (IV) from ore, processing solutions with a complex salt composition and for analytical purposes. Extraction is carried out from 0.5-2.0 M sulphate solution with 0.32% 2-methyl-8,9-dihydro[1,2,4]triazolo[1,5-α]quinazolin-6(7H)-one solution, dissolved in methylene chloride. The phase contact time is 15 min. After demixing, the organic phase is separated and re-extraction is performed.

EFFECT: conducting the process in milder conditions without using concentrated acid solutions and high output of cerium.

1 dwg, 2 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of extracting rare-earth elements from nitrate-phosphate solutions from apatite processing. The method comprises dissolving apatite in nitric acid, freezing out calcium (strontium) nitrate, precipitating hydrate-phosphates of rare-earth elements and calcium (strontium), dissolving the precipitate in nitric acid, adding calcium (strontium) nitrate obtained from the freezing out step with concentration of 800-1000 g/l and heated to 40-50°C to the solution, wherein content of rare-earth elements (in terms of oxides) is kept at 40-60 g/l, and excess nitric acid 1-2 mol/l, followed by extraction of rare-earth elements with tributyl phosphate in the presence of calcium nitrate, washing and re-extraction, wherein the extract is washed with evaporated re-extraction product to rare-earth element concentration of 250-300 g/l. 70-90% of the obtained solution is removed in form of a finished product and the remaining solution is taken for washing, wherein the raffinate, which contains calcium nitrates and iron and aluminium impurities, is taken for recovering calcium (strontium) nitrate by freezing out or precipitating impurities with calcium oxide.

EFFECT: invention enables to avoid use of concentrated and explosive ammonium nitrate solutions, reduces consumption of nitric acid and improves efficiency of using apatite processing by-products.

2 cl, 6 tbl, 4 ex

FIELD: chemistry.

SUBSTANCE: invention relates to extraction of metals from water solution. Described are composition for extraction with solvent, which contains orthohydroxyaryloxime extractant, degradation-preventing agent and organic solvent which is not mixed with water. Also described is method of metal extraction from water solution with application of said composition. There exists method of reducing said composition degradation. Orthohydroxyaryloxime extractant is selected from: 5-(C8-C14 alkyl)-2-hydroxyacetophenonoximes, 5-(C8-C14 alkyl)-2-hydroxybenzaldoximes and their mixtures. Degradation-preventing agent represents element of the group, selected from: mono-, di- or tri-(1-phenylethyl)phenol, their mixtures and their isomers.

EFFECT: stabilisation of oximes, which are in contact with nitrate-containing raw material.

31 cl, 3 tbl, 4 ex

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical industry. At the first stage of gadolinium extraction terbium, dysprosium and heavier REM are extracted from mixture of rare earth metals in organic phase. At the second stage gadolinium is extracted from obtained raffinate solution in organic phase, with main mass if europium, samarium, neodymium and other lighter REM left in water phase. gadolinium is extracted into re-extract from obtained organic phase, with all gadolinium-containing re-extract being returned to stage of washing, and the process is carried out until required content of samarium and europium in gadolinium is achieved, obtained gadolinium solution is output and the process is repeated. As extractant used are 30-40% solutions of di-2-ethylhexylphosphoric acid or bis((2,4,4)trimethylpentylphosphinic acid (Cyanex-272), or isododecylphosphetanic acid.

EFFECT: invention ensures increased efficiency of gadolinium purification from europium.

2 cl, 5 tbl

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy of rare-earth metals, particularly to fine cleaning of bismuth of radioactive contaminants 210Po with the help of hydrochloric acid solutions. In compliance with this method, prior to bismuth electric refining in hydrochloric acid solution, the latter is brought in contact with organic phase containing hexane-1 and activated carbon. Then, obtained bismuth sponge is fused to bubble the melt with inert gas.

EFFECT: high-purity bismuth with low content of 210Po.

1 ex

FIELD: chemistry.

SUBSTANCE: method of determining tin (IV) in an aqueous solution involves extraction of tin (IV) ions. Extraction is carried out by adding antipyrine, sulphosalicylic acid and calcium chloride with concentration of 0.60, 0.35 and 2 mol/l, respectively, to the solution. After phase separation, morin solution is added to the extract to form a fluorescent tin and morin complex, followed by measurement of fluorescence of the obtained solution using liquid analyser Fluorat2-3M to determine concentration of tin (IV).

EFFECT: quantitative detection of tin ions and simple analysis.

1 dwg, 1 ex

FIELD: metallurgy of rare and dispersed metals, chemical technology.

SUBSTANCE: invention relates to a method for extraction separation of tantalum and niobium. Method involves extraction separation of tantalum from niobium with organic solvent. As an organic solvent method involves using a mixture of methyl isobutyl ketone taken in the amount 40-80 vol.% with aliphatic (C7-C9)-alcohol taken in the amount 20-60 vol.%. At the extraction process tantalum transfers into organic phase and niobium - into aqueous phase. Then organic and aqueous phases are separated. Invention provides enhancing the extraction degree of tantalum into organic phase and to enhance the separation degree of tantalum and niobium in extraction.

EFFECT: improved separating method.

5 tbl, 5 ex

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