Preparation of uranium-bearing stock for extraction

FIELD: metallurgy.

SUBSTANCE: proposed process comprises leaching of uranium by nitric acid and separation of water phase from undissolved precipitate. Then, undissolved precipitate is mixed with fluorine-bearing agent, dissolution of produced charge and/or charge as a suspension in nitric acid solution. Produced solution is returned to production process for extraction of uranium. Nitric acid concentration in solution makes at least 2 mol/l. Dilution is carried out at fluorine-ion concentration at, at least, 15 g/l. Dilution is performed at 60-100°C.

EFFECT: decreased losses of uranium, minimised wastes.

4 cl, 1 dwg, 1 tbl

 

The invention relates to methods of processing of uranium raw materials, and in particular to methods of preparation of raw material to solvent extraction processing.

Leaching of uranium-bearing material leads to the formation of slurries consisting of aqueous solutions of uranium and impurities and undissolved particles. In the known methods for the preparation of uranium raw material for the extraction processing after leaching hold office productive solution from the solid phase.

For example, in the method for processing chemical concentrate of natural uranium [RF Patent №2398036, IPC C22 In 60/02, publ. 27.08.2010] a solution of uranyl nitrate is obtained by dissolution of NUC in a solution of nitric acid and separating the resulting undissolved residue by decantation.

The method of processing of concentrated natural uranium oxides [RF Patent №2323883, IPC C01G 43/01, publ. 10.05.2008] includes leaching of uranium with concentrated nitric acid at elevated temperature and separating the precipitate from the aqueous phase by filtration through a polyester cloth, PE-100 after settling for several hours or by centrifugation.

Depending on the method of separation of the separated undissolved residue retains a certain amount of uranium-containing solution.

In the method of processing of uranium ores (prototype) [Turaev NS, Gerin I.I. Chemistry and technology of uranium. - M.:Publishing house "Ore and metals", 2006, p.40] phase separation of solid and liquid phases after leaching of metals from ores includes the steps of thickening, filtration, washing of the solid phase obtained from the leaching production solution. In order to reduce losses of uranium for washing the solid phase used repeated dilution in filtration repulation cycle or counter-current decantation [Turaev NS, Gerin I.I. Chemistry and technology of uranium. - M.: Publishing house "Ore and metals", 2006, s-182].

The disadvantages of this method are complex instrumentation and a multi-stage process undissolved residue; the formation of a significant amount of washing solutions, leading to poor performance of the scheme as a whole. The application of the above method does not allow for complete extraction of uranium from undissolved residue (residual uranium content reaches 2% wt.), which leads to the loss of uranium and increased costs for disposal of these wastes. Also the high content of total moisture in the undissolved residue (20-30%.) increases capital and operating costs to comply with the norm NP-020-2000 on the content of the liquid in the waste sent for disposal (not more than 3% wt.). All this, ultimately, leads to increased cost pererabotki whole.

The objective of the invention is to develop a method of preparation of the uranium raw material for the extraction processing that reduce losses of uranium, minimization of waste volumes, the simplification of the technological scheme and as a result increase its performance.

The solution of this problem is achieved in that in the method of preparing uranium raw material extraction and processing, including the leaching of uranium with nitric acid and separating the aqueous phase from the undissolved residue, the undissolved residue is mixed with the fluorine-containing reagent, dissolve the resulting mixture and/or suspension in a solution of nitric acid and the resulting solution is returned to the production process. The concentration of nitric acid in the solution is not less than 2 mol/L. Dissolution is carried out at the concentration of fluoride ion is not less than 15 g/L. the Process is conducted at a temperature of 60-100°C.

Figure 1 presents the dependence of the amount of undissolved residue from concentration of fluoride and nitric acid in the system.

As source material for testing the proposed method used a NUC in the form of uranium peroxide UO4·H2On (piroxicamnova acid (H2UC5·H2O). The chemical composition of this raw material is characterized by a high content (up to 30 wt.%, by weight of the sample) such is problematic impurities, as iron, aluminum, calcium, sulfur, molybdenum.

Solid waste generated in the process of dissolution of any uranium-containing raw materials consist of two main components:

- undissolved residue (his number is determined by the impurity composition of the feedstock and does not depend on the concentration of nitric acid);

remnants caused by hydrolysis of the ballast impurities (these residues are susceptible to dissolution in nitric acid solution).

Therefore, the maximum amount of undissolved residue is formed with a minimum amount of free acid and the maximum amount of uranium in solution. Therefore, experiments were performed with the waste isolated from the suspension obtained taking into account the concentration of uranyl nitrate in terms of uranium 450-470 g/l of nitric acid of 0.1-0.5 mol/L.

The resulting leaching NUC suspension was subjected to filtration. The separated residue was dried to constant weight (to eliminate the effect of residual moisture on the change in sample mass), then mixed it with the fluorine-containing reagent. The fluoride ion can be introduced into the system in the form of any water-soluble reagent. In the described experience as a fluorine-containing reagent used sodium fluoride.

When mixing undissolved residue with fluorine-containing reagent were obtained from samples of suspense the end concentration of the fluoride ion 15, 30, 60, 80, 120 g/l

The samples were dissolved in nitric acid from the calculation of its concentration of 0.5-8 mol/L.

Figure 1 presents the results of the experiment, which suggests that a significant part of undissolved formed after leaching residue (in the form of a laminated mass (suspension)) is dissolved in a solution of 2 molar nitric acid at a concentration of fluoride ion 15 g/l and above.

To determine the dependence of the mass of undissolved residue from the solution temperature and concentration of fluoride experiments were conducted, the results of which are presented in table 1.

Table 1
The dependence of the mass of undissolved residue from the fluoride concentration and solution temperature
The solution temperature, °CMass balance, g
The concentration of fluoride in solution, g/l
06080120
250,920,590,430,38
500,900,370,310,26
600,860,130,100,10
800,840,110,090,10
1000,820,090,080,09

When determining the optimal temperature conditions it was found that the minimum concentration of fluoride ion (at 15 g/l) and nitric acid (2 mol/l) the best performance is achieved at a temperature of 60-100°C.

The result of dissolution of the residue separated from the productive solution is to obtain the solution suitable for subsequent extraction, providing product that meets the requirements of ASTM With 788-03.

Thus, the proposed method of preparing uranium raw material for the extraction processing reduces the losses of uranium, minimization of waste volumes.

The lack of branches filtering, occupying up to one-third of production space, or is istemi 3-7 serially connected thickeners for counter-current decantation (prototype) provides a simplified process flow diagram and, as a consequence, increase of its performance.

1. The method of preparing uranium raw material extraction and processing, including the leaching of uranium concentrated nitric acid and separating the aqueous phase from the undissolved residue, wherein the undissolved residue is mixed with the fluorine-containing reagent, dissolve the resulting mixture and/or the charge in the form of a suspension in a solution of nitric acid and the resulting solution is directed into the production process for the extraction of uranium.

2. The method according to claim 1, wherein the dissolution is carried out at the concentration of fluoride ion is not less than 15 g/L.

3. The method according to claim 1, characterized in that the concentration of nitric acid in the solution is not less than 2 mol/L.

4. The method according to claim 1, characterized in that the dissolution process is carried out at a temperature of 60-100°C.



 

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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.

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1 tbl

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3 cl, 1 dwg, 1 tbl

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4 tbl, 4 ex

FIELD: chemistry.

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1 tbl

FIELD: chemistry.

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4 cl, 5 tbl, 3 ex

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1 tbl

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SUBSTANCE: method involves leaching the concentrate with aqueous nitric acid solution at high temperature to obtain a pulp consisting a solid and an aqueous phase. The aqueous phase is then separated by filtration from the solid phase in form of uranium nitrate solution. Uranium is then extracted from the nitrate solution using tributyl phosphate in a hydrocarbon solvent. The extract is washed and uranium is re-extracted. Leaching is carried out by adding nitric acid and water in an amount which enables to obtain a nitrate solution in the aqueous phase of the pulp, said nitrate solution containing dissolved silicon in concentration of 2.5-3.7 g/l. The solid phase, which consists of insoluble concentrate residues, is separated by filtration from the solution which contains dissolved silicon, uranium in concentration of 170-250 g/l and nitric acid in concentration of 80-120 g/l. Filtration is carried out not more than 24 hours after leaching, preferably not more than 5 hours after leaching.

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2 tbl, 2 ex

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SUBSTANCE: method involves leaching in order to dissolve uranium when the concentrate reacts with nitric acid solution to obtain pulp from the concentrate. Uranium is then extracted from the pulp using tributyl phosphate in a hydrocarbon solvent. The extract is washed and uranium is re-extracted. Extraction is carried out from freshly prepared pulp which is obtained through direct-flow reaction at temperature 20-65°C of a stream of a suspension of the concentrate in water which is prepared beforehand and a stream of nitric acid solution with flow rate ratio which ensures nitric acid concentration in the pulp of 25-120 g/l. The period from the beginning of leaching to the beginning of extraction is not more than 10 minutes.

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2 tbl, 1 ex

FIELD: metallurgy.

SUBSTANCE: processing method of nitric-acid solution of regenerated uranium involves uranium (VI) extraction with tributyl phosphate in organic diluter; flushing of extract with nitric-acid solution and re-extraction of uranium. At that, removal of technetium from uranium is performed by shifting technetium (VII) to non-extracted quadrivalent state in flushing zone of extraction cascade with the use of flushing solution containing 0.1-0.2 mol/l of carbohydrazide and 0.05-0.15 mol/l of nitric acid. Extract is flushed at the ratio of flows of organic and water phases, which is equal to 10-15. Method can be implemented in two versions. As per the first version, used flushing solution is supplied to feed stage of extraction cascade and technetium is removed to raffinate. As per the second version, used flushing solution is a separate flow from which uranium is extracted by contact with flow of fresh extractant; organic phase is connected to initial uranium extract prior to supply to flushing zone, and technetium is removed to separate product the volume of which is 5 times less than the raffinate volume.

EFFECT: increasing separation efficiency of uranium and technetium.

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SUBSTANCE: conversion method of non-ferrous metal salt involves counterflow extraction of metal from solution of its converted salt with the use as cation-exchange extractant in salt form of solution of organophosphorus acid in inert diluter and re-extraction of non-ferrous metal with converting acid so that re-extract containing converted salt of non-ferrous metal is obtained. As non-ferrous metal there used is cobalt or nickel; extraction is performed from solution of converted salt of cobalt or nickel at concentration of cobalt or nickel in solution 65-80 g/l and pH 4-7 with the use as cation-exchange extractant of 20-50% solution of organophosphorus acid in sodium, potassium or ammonia form. Re-extraction is performed with 0.5-2.0 M solution of converting acid. Number of non-ferrous metals to which the proposed method is applied can also include copper and zinc.

EFFECT: increasing conversion degree at minimum content of impurities and enlarging the range of obtained salts of non-ferrous metals.

5 cl, 8 ex

FIELD: metallurgy.

SUBSTANCE: invention refers to procedures for processing chemical concentrate of natural uranium. The procedure consists in dissolving natural uranium in solution of nitric acid, in directing solution to uranium extraction with tri-butyl-phosphate and hydrocarbon thinner, in washing extract with re-extract and in uranium re-extracting. There is dissolved chemical concentrate of natural uranium with increased content of phosphorus and sulphur. Uranium is extracted from solutions with increased concentration of phosphorus and sulphur and with concentration of nitric acid 30÷80 g/l to 60÷75% saturation of extractant with uranium. Also this level of extractant saturation with uranium in the said range in % is maintained not exceeding value equal to (0.3×[HNO3]+51), where [HNO3] is concentration of nitric acid in solution directed to extraction, in g/l.

EFFECT: purification of uranium at minimal uranium losses with raffinate.

2 tbl

FIELD: metallurgy.

SUBSTANCE: method includes leaching of uranium concentrate by solution of nitric acid, uranium extraction by tributyl phosphate in hydrocarbon solvent. Uranium extraction is implemented up to 85-92% saturation of extragent by uranium. Then it is implemented washing of extract by part of evapoarted reextract, containing 450-500 g/l of uranium, which is implemented in the mode of ultimate (up to 119-120 g/l of uranium) of saturation of extragent by uranium. After washing it is implemented uranium re-extraction. Washing solution, received after washing of uranium extraction is combined with uranium solution from concentrates leaching and after correction by content of nitric acid and uranium mixed solution is directed to extraction. Extract washing is implemented at correlation of flows O:B=(15-20):1. Content of nitric acid in uranium solutions directed to extraction is 0.5-0.8 mole/l.

EFFECT: increasing of uranium purification efficiency from molybdenum.

4 cl, 4 tbl, 1 ex

FIELD: chemistry.

SUBSTANCE: invention refers to extraction methods for metal ion extraction and concentration from aqueous solutions and can be used for zirconium separation from compound ion solutions with hydrogen chlorine acid. Invention rests on zirconium ion ability to be extracted in layer system water - ammonium sulphate - potassium bis-(alkylpolyoxyethylene) phosphate (oxyphos-B), [CnH2n+1+1O(C2H4O)m]POOK, where n=8-10, m=6 in ratio as follows, wt %: ammonium chloride - 10-15; oxyphos-B - 10-15; water - to 100.

EFFECT: possibility for quantitative zirconium ion separation from aqueous solutions thus avoiding application of expensive, fire-hazardous and toxic substances.

2 tbl, 1 dwg, 9 ex

FIELD: process engineering.

SUBSTANCE: invention relates to cleaning of silver-bearing materials by hydrometallurgy processes, for example, scrap and wastes of microelectronics. Proposed method comprises dilution of silver-bearing material in nitric acid, addition of sodium nitrate to nitrate solution at mixing, extraction of silver salt precipitate and pits treatment to get metal silver. Note here that after addition of sodium nitrate the reaction mix is held for 1 hour to add sodium carbonate or bicarbonate to pulp pH of 8-10. Free silver salt precipitate as silver carbonate is separated from the solution by filtration. Sodium nitrite and carbonate or bicarbonate is added in the dry form. Note here that sodium nitrite is taken with 25% excess of stoichiometry.

EFFECT: higher purity and yield, simplified process.

2 cl, 2 ex

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