RU2259412C1 - Method for ion-exchange recovery of uranium from sulfuric acid solutions and pulps - Google Patents

Abstract

FIELD: uranium technologies.

SUBSTANCE: method comprises sorption of uranium on low-basicity anionites, desorption of uranium, and recovery of finished product. In particular, uranium-saturated low-basicity anionite is converted into OH^- form and uranium into soluble stable complex [UO₂(CO₃)₃]^-4 by treating sorbents with alkali metal and ammonium carbonate solutions.

EFFECT: achieved complete desorption of uranium and simultaneously sorbent is freed from poisons and other sorption components.

2 dwg

Description

The invention relates to the field of ion exchange technology for the extraction of uranium from solutions and pulps obtained as a result of sulphate leaching of uranium ores.

Known ion-exchange method for the extraction of uranium from solutions and pulps obtained as a result of sulphate leaching of uranium ores. The method includes uranium sorption processes on strongly basic anion exchangers, uranium desorption processes on strongly basic anion exchangers with solutions:

- sulfuric acid (~ 150 g / l)

- nitric acid mixed with sulfuric acid

- sodium nitrate acidified with sulfuric acid

and processes for processing commodity desorbates either by extraction or precipitation.

/ B.V. Gromov. Introduction to uranium technology. Moscow: Atomizdat. 1978, pp. 140-150 /.

The known method has several disadvantages associated with the difficulties in the implementation of the processes of desorption of uranium and the subsequent operations of processing commodity desorbate.

During desorption with sulfuric acid, commodity uranium desorbates are obtained, the volume of which is significant - more than 5 volumes with 1 resin (respectively, the concentration of uranium in them is low). The sulfuric acid content in the commercial desorbate is not much different from the concentration of sulfuric acid in the initial stripping solution; therefore, precipitation of sodium diuranate (or ammonium) from these solutions is impossible for technological reasons. Extraction is used to extract uranium from such solutions, which is unprofitable in conditions of underground or heap leaching.

When solutions containing nitrates or chlorides are used in the desorption process, these ions fall into the process of sorption of uranium, where they significantly depress sorption of uranium, reducing the completeness of extraction to the ion exchanger.

Closest to the proposed method is a method for extracting uranium on weakly basic anion exchangers. [H. Gardner, R. Kunin. The use of a weakly basic anion-exchange resin for the extraction of uranium from the deposits of Uravan, Colorado, USA. In the collection "Theory and practice of ion exchange." Proceedings of the International Conference. Cambridge, London. 1976]

For the experiments, weakly basic anion exchangers Amberlite XE-270 and Amberlite XE-299 were used. The experiments showed that the processes of sorption of uranium on these anion exchangers proceed quite intensively, not much different from the indicators of sorption on strongly basic anion exchangers. For uranium desorption, traditional desorption solutions were used:

- sulfuric acid;

- a mixture of sulfuric acid and sulfates of alkali metals and ammonium;

- a mixture of sulfuric acid with chlorides of alkali metals and ammonium;

- solutions of alkali metal and ammonium chlorides.

All of the above desorption processes on weakly basic anion exchangers proceed similarly to processes on strongly basic anion exchangers. It was indicated that after the accumulation of poisons on the resins (silicates, polythionates, etc.), the resin must be treated with sodium hydroxide.

Thus, uranium extraction processes on weakly basic anion exchangers retain all the drawbacks of uranium extraction processes on strongly basic anion exchangers. In this regard, weakly basic anionites were not found for industrial use for sorption extraction of uranium.

The technical result of the invention is the complete desorption of uranium on weakly basic anion exchangers with the simultaneous purification of sorbents from "poisons" and other components of sorption.

The technical result is achieved by the fact that in the method of ion-exchange extraction of uranium from sulfuric acid solutions and pulps, including sorption of uranium on weakly basic anion exchangers, desorption of uranium, production of finished products from desorbate, desorption with saturated uranium weakly basic anion exchange resin is carried out by treating the sorbent with a solution of alkali metal carbonate or ammonium carbonate with the conversion of anion exchange resin to the OH ^- form, and uranium to the soluble stable complex [UO ₂ (CO ₃ ) ₃ ] ^-4 .

When anionite is converted to the OH ^- form, all sorbed components are removed together with uranium together with uranium, including those components that are “poisons” for the ion exchanger in an acidic environment. At the same time, other components that are depressants in the process of sorption of uranium, for example, nitrate or chloride ions, are not introduced into the sorption-desorption system.

At the same time, the carbonate content used for desorption in the commercial solution is minimal.

Weakly basic anion exchangers in the OH ^- form are undissociated and do not absorb any other anions and, therefore, are not ion exchangers in an alkaline medium. In the process of alkaline treatment, they completely transfer to the OH ^- form, giving into the desorption solution all sorbed ions, including all "poisons" that got into the resin during sorption. The use of hydroxides for the desorption of uranium is impossible due to the formation of insoluble uranyl hydrates, which precipitate in the resin phase. Therefore, for the desorption of uranium, water-soluble alkali metal and ammonium carbonates should be used. In this case, uranium binds to the stable uranyl tricarbonate complex, which is highly soluble in water.

The uranium desorption reaction proceeds in accordance with the equation:

R + UO ₂ (SO ₄ ) ₃ + Me ₂ CO ₃ → R-OH + Me ₄ [UO ₂ (CO ₃ ) ₃ ] + Me ₂ SO ₄

From the obtained solution (commercial desorbate) containing the minimum amount of the initial alkali metal carbonate, it is easy to isolate the precipitate of alkali metal or ammonium diuranate by traditional methods, which is very important when using the proposed method especially in heap or underground leaching sites.

When the anion exchange resin returns to the sorption process, the OH ^- neutralization reaction proceeds

R-OH + H ₂ SO ₄ → R-SO ₄ + H ₂ O

after which the anion exchange resin acquires the ability to ion exchange reactions.

Example:

The study of sorption of uranium was carried out using real, industrial solutions of heap leaching. For work, weakly basic anion exchangers were used:

- Lewatit

- Purolite A500

- AM-3

- AM-7

- Purolite A100

- VP-1p.

and strongly basic AMP anion exchange resin having the best uranium sorption indicators - for comparison.

Figure 1 shows the dependence of the capacity of the resin samples on uranium on the concentration of uranium in an equilibrium solution. Sorption isotherms from heap leaching solutions:

T = 6 hours C _H2SO4 = 7.8 g / l pH = 1.3 SO ₄ = 34 g / l t = 32 ° C Fe ³⁺ = 2.04 g / l

U = Var

1 - Lewatit

2 - Purolite A500

3 - AM-3

4 - Purolite A 100

5 - VP-1p

6 - AMP

It can be seen from the figure that the capacities of weakly basic anion exchangers differ slightly from the capacities of strongly basic anion exchangers of AMP and can be used to extract uranium from sulfuric acid media.

When dynamic sorption of uranium was carried out from heap leaching solutions with a uranium content of about 200 mg / L, capacities for strongly basic AMP anion exchange resin were 33 g / L, and for weakly basic VP-1p and Purolite A 100 anion exchangers, about 30 g / l.

Currently, new samples of weakly basic ANS and AMN anion exchangers with a uranium capacity 5–10% higher than the AMP capacity have been synthesized on an industrial scale.

Uranium desorption on weakly basic anion exchangers was carried out with 100 g / L soda solutions.

For preliminary experiments, weakly basic anion exchangers AM-3 and AM-7 were used. Their uranium capacity from standard solutions was 40 g / l and 45 g / l, respectively.

After treatment with a soda solution in static mode, the residual capacity of the ion exchangers was 0.034 g / l and 0.008 g / l, respectively. This indicator ensures the completeness of the extraction of uranium from sulfate environments.

The residual capacity of the AMP ion exchanger after treatment with sulfuric acid (a stronger desorbent than a soda solution) is at least 2 g / l.

Figure 2 shows the results of desorption of weakly basic anion exchangers with a solution of soda in a column in a dynamic mode.

On figa:

1. Purolite A 100

Desorption solution of 5% Na ₂ CO ₃

2. AM - 7D

Desorption solution of 5% Na ₂ CO ₃

3. Purolite A 100

Desorption solution of 20% Na ₂ CO ₃

E _Ref = 43.6 g / l

E _Desorb = 0.1

The yield of a commercial desorbate having a pH of 7.2 was 1 volume from the volume of the resin. Soda is almost completely consumed in transferring the resin to the OH ^- form.

Thus, the volume of commodity desorbate is determined only by the total exchange capacity of the resin and the concentration of the stripping solution of soda.

Figv confirms the correctness of the mechanism of the process of desorption of uranium on weakly basic anion exchangers. E _ref = 34.9. For desorption, a soda solution (20%) with an initial uranium content of 49 g / L was used. Despite the very high uranium content, the residual uranium resin capacity was 0.255 g / l, i.e. the formation of an undissociated OH ^- form occurs regardless of what other anions are in the system.

The uranium concentration in the product desorbate is calculated according to the material balance and is about 20 g / l.

Uranium desorption using potassium carbonate showed similar results.

The experiments on the desorption of uranium on an AM-7 resin with solutions (~ 100 g / l) of ammonium carbonate showed that the process proceeds intensively, and the residual uranium capacity after desorption was about 0.3 g / l.

The process of extracting uranium from sulfuric acid media onto a weakly basic anion exchange resin proceeds only from the solution phase. The presence of inert solid particles in the initial sulfate uranium solution does not affect the course of the ion-exchange reaction, but only determines the hardware design of the process.

Thus, the use of weakly basic anion exchangers for the extraction of uranium from sulfate media in the processing of uranium ores allows you to:

- increase the degree of extraction of uranium from ore due to the low residual uranium content in the resin supplied to the sorption process;

- reduce the cost of the desorption process;

- get concentrated on uranium commodity desorbates in an amount equal to the ratio

where E _total - total exchange capacity of the resin;

With _r-ra - the concentration of carbonate of an alkali metal or ammonium in a stripping solution;

- eliminate the negative effect of "poisons" that accumulate on the resin during the sorption of uranium (silicates, etc.), since weakly basic resins in the OH ^- form are not sorbents;

- eliminate ingress into the ore processing system of undesirable components in the sorption and environmental aspect, for example, nitrate or chloride ions.

Developed on the basis of sorption of uranium on weakly basic anion exchangers for one of the heap leaching sites, the method is notable for the simplicity of technology and equipment design.

Claims (1)

The method of ion-exchange extraction of uranium from sulfuric acid solutions and pulps, including sorption of uranium on weakly basic anion exchangers, desorption of uranium, production of finished products from desorbate, characterized in that the desorption from saturated with uranium weakly basic anion exchangers is carried out by treating the sorbent with a solution of alkali metal carbonate or ammonium carbonate with by transferring anion exchange resin to the OH ^- form, and uranium to the soluble stable complex [UO ₂ (CO ₃ ) ₃ ] ^-4 .

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