Method of extracting uranium from phosphate solutions

FIELD: metallurgy.

SUBSTANCE: invention relates to hydraulic metallurgy, particularly to extraction of uranium from used phosphate solutions. This process consists in adding the solvent to initial solution, said solvent being selected from the series: KMnO4, K2Cr2O7, HNO3, H2O2, KClO3. Then, uranium-bearing sediment is precipitated by acidity correction by ammonia to pH 2.8-4.0 at 20-35°C. Filtered precipitate is treated by 20-35% solution of NaOH at 80-85°C for 1.5-2.0 hours.

EFFECT: higher yield of uranium, return of high-enriched uranium to fuel cycle, lower costs of higher safety at long-term storage, accounting and control.

2 cl, 1 tbl, 4 ex

 

The invention relates to the field of hydrometallurgy, in particular to a method of extracting uranium from phosphate waste solutions resulting from the chemical analysis conducted by a standardized titrimetric method Davis-gray, on the uranium content in its various derivatives (oxides, nitrides, carbides and other).

The method for extracting uranium from solutions using ion-exchange resins that selectively sorbing uranium with subsequent elution (leaching) in desorbed (RF Patent No. 2159741, IPC C01G 43/00, B01D 15/04, publ. 27.11.2000).

The drawback of this method is low specific capacity of the resin and therefore no need for a bulky nuclear-safe equipment.

There is also known a method of extracting uranium from phosphoric acid solutions by multistage countercurrent extraction using as the organic phase of the mixture dialkylphosphorous acid and trialkylphosphine in inert diluent (Patent USSR No. 858572, IPC C22B 60/02, publ. 23.08.81).

A large number of equipment, and high capital costs required to create a closed extraction cycle, limit the application of this method.

The closest in technical essence and the tasks of the claimed invention prototype one is by the method of extraction of uranium from phosphate solutions, the resulting acidic opening monazite concentrates. The method is almost complete neutralization of the free acid with ammonia (pH~6,0) and subsequent separation of the uranium-containing precipitate by filtering (I. N. Beckman, Lectures MSU "Thorium", 2010,, 136 S.).

The disadvantage is the low rate of deposition of uranium, due to the fact that man-made solutions, resulting from the application of techniques of Davis-gray, at least part of the uranium has a valence U4+and does not form a deposited ammonia chemical complex. Furthermore, formed in the more alkaline environment of the ammonium phosphate has a substantially lower solubility compared to its di - and hydro-phosphate, which really complicates further processing due to the inclination of the system to spontaneous crystallization.

The present invention is directed to the achievement of the technical result consists in increasing the degree of extraction of uranium from concentrated on the phosphate ion solutions, obtaining the processed uranium concentrate and low uterine solutions.

The technical result is achieved in that in the method of extracting uranium from phosphoric acid solutions, including the introduction in the original precipitant solution, adjusting pH, filtering and processing of the resulting sludge, coz the ACLs to the invention in the original phosphate solution pre-enter the oxidizer, carry out the adjustment of the pH with ammonia to pH (2.8÷4,0) at a temperature of (20÷35°C, as obtained after filtration the precipitate is treated (20÷35)% solution of NaOH at a temperature of (80÷85)°C for (1,5÷2,0) hours.

This oxidizing agent may be selected from the range: KMnO4, K2Cr2O7, HNO3H2O2, KClO3.

The inventive method differs from the known fact that in the original solution is injected oxidant, for example a saturated aqueous solution of potassium permanganate to get a stable purple color, indicating the completion of the transition U4+=>U6+. Next, the free acid is neutralized with an aqueous solution of ammonia to a pH of 2.8÷4,0, while maintaining a temperature in the range 20÷35°C.

The need to maintain the indicated temperature range due to the fact that at temperatures over 35°C is thermal decomposition of potassium permanganate and, accordingly, its wasteful consumption, while lowering the temperature below 20°C significantly slows down the flow of liquid-phase oxidation-reduction reactions. The choice of the interval of pH values is determined by the fact that at a pH of less than 2.8 increasing uranium concentration in the mother solution and at pH 4.0, the formation of ammonium phosphate, considerably less soluble than hydrophosphate form.

D is stijene technical result contributes to the fact, that is obtained after filtration, the residue treated with 20÷35% sodium hydroxide solution at a temperature of 80÷85°C for 1,5÷2,0 hours. This is done in order to reduce the phosphorus content in selected from the original solution of uranium concentrate, thereby ensuring its absolute suitability for further refinery processing.

The essence of the proposed technical solution is illustrated by examples of specific implementation.

The table shows the typical chemical composition of spent uranium phosphate solutions as a result of chemical analysis by standardized titrimetric method Davis-gray, on the uranium content in its various derivatives (oxides, nitrides, carbides and other). (Branch instruction. Procedure for potentiometric determination of uranium, 2000, 33 S. AOI 001.493-00).

Table
ChemicalConcentration
Uranium total(a 2.0 to 4.6) g/l
Phosphoric acid384 g/l; 4M; 12N
Sulfamic acid5.7 g/l
The bichromate is Aliya 1.2 g/l
Nitric acid43,4 g/l; 0,7 N
Molybdate ammonium0.36 g/l
Ferric sulfate6,72 g/l
Sulfuric acid2.16 g/l
Ammonium Vanadate0,044 g/l

Example 1. The original solution of the above composition, taken in an amount of 1.0 l, was treated with 25% ammonia to obtain a pH=6,8. After filtering received 1,66 l stock solution containing 0.6 g/l of uranium. Thus, its degree of deposition did not exceed 80%.

Example 2. In 1.0 l of the starting solution introduced ≈20 ml of a saturated solution of KMnO4to get a stable weakly-violet color. Then, avoiding overheating of the solution, introduced a 25% ammonia to pH=3,5. After filtration, the residual uranium content in the mother solution was 0.03 g/l Specific activity such solutions at a ratio of isotopes 235/238≈9 does not exceed 3.7·105Bq/kg of This can be attributed to the category of low and greatly simplifies and reduces the cost of disposal.

Example 3. In 1.0 l of the starting solution was added ≈25 ml of potassium permanganate solution until obtaining the SLA is on-violet color, and then, gradually adding ammonia, brought the pH to a value of 4.5. The precipitation was filtered, and the solution was analyzed for uranium content, which was 0.07 g/L. Therefore, further reduction of the acidity of the system does not contribute to the completeness of precipitation.

Example 4. 30 l of the starting solution was treated with ammonia according to the proposed procedure, the precipitate was filtered and treated with 25% sodium hydroxide solution at a temperature of 85°C for 1.5 hours. The weight of the resulting chemical concentrate amounted to 422 g when the uranium content of 25.0 wt.%, which corresponds to the degree of extraction of >96%.

Thus, as seen from the above examples, the claimed technical solution in the form of a set of proposed operations and parameters, novel, technically feasible and is cost effective.

Economic efficiency from the use of the invention due to the high degree of extraction of uranium, the return of highly enriched uranium in the fuel cycle, the elimination of a significant amount of intermediate level liquid waste by transferring them into the category of low, reduce costs associated with maintaining their safe long-term storage, accounting and control.

1. The method of extraction of uranium from phosphoric acid solutions, including the store the precipitation of the uranium-containing precipitate from the original solution by adjusting the pH, filtering and processing of the resulting sludge, characterized in that in the original phosphate solution pre-enter the oxidizer, the adjustment of the acidity spend ammonia up to pH values of 2.8÷4,0 at a temperature of 20÷35°C, and obtained after filtration, the residue treated with 20÷35% NaOH solution at a temperature of 80÷85°C for 1,5÷2,0 hours.

2. The method according to p. 1, characterized in that the oxidizing agent is chosen from the series: KMnO4, K2Cr2O7, HNO3H2O2, KClO3.



 

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4 cl, 1 dwg, 1 tbl

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1 ex

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4 tbl, 1 ex

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9 cl, 3 dwg, 1 tbl, 1 ex

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4 cl, 2 tbl, 2 ex

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1 tbl, 1 ex

FIELD: nanotechnology.

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3 ex

FIELD: process engineering.

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EFFECT: lower processing costs.

3 cl, 1 dwg, 1 tbl

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EFFECT: practically complete separation of mercury without negative impact at gold sorption.

4 cl, 1 dwg, 1 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing bismuth potassium citrate. Bismuth potassium citrate is obtained by treating bismuth citrate with aqueous potassium hydroxide solution. The method is carried out with molar ratio of potassium hydroxide to bismuth citrate of 1.0-1.5, and with weight ratio of potassium hydroxide solution to bismuth citrate of 0.5-2.0. The product is obtained in form a paste.

EFFECT: simple process and reduced consumption of reactants.

1 tbl, 3 ex

FIELD: metallurgy.

SUBSTANCE: method of noble metal extraction from solid stock comprises dissolving of noble metal and base metals in acid. Noble metal is extracted with the help of substituted quaternary ammonium salts (SQAS). Noble metal can be oxidised and reduced. Said substituted quaternary ammonium salts represent the following form H0-3R4-1NX, where H= hydrogen, R= organic group, N= nitrogen and X= halogen. This method uses, for example, tetramethyl ammonium chloride. Au-SQAS is separated by flushing with solvent. Rh-SQAS is dissolved in acid and oxidised to precipitate the salts, and separated. SQAS is added to filtrate and cooled to precipitate Rh-AQAS to be separated. Rh-SQAS is cleaned before formation of final product. Other metals are separated by boiling the initial acid solution with precipitation of metal salts, cooling and separation. The pulp is separated by dissolution and separation.

EFFECT: simplified extraction.

20 cl, 4 dwg, 4 tbl, 2 ex

FIELD: powder metallurgy, namely processes for producing silver powder used in electrical engineering industry branches, possibly for making electrodes of chemical electric current sources, electric contacts and so on.

SUBSTANCE: method comprises steps of depositing silver chloride from solution of silver nitrate with use of water soluble chloride at temperature 20 - 50°C and pH 1 - 5; decanting mother liquor; treating suspension with solution of alkali metal hydroxide at concentration in reaction medium 12 - 200 g/l; reducing silver from suspension by means of Formalin or formate at temperature 40 - 90 c for 10 -60 min; washing out successively in hot deionized water, in ammonium solution and in cold deionized water; filtering and drying deposit of silver powder at 70 - 120°C.; sifting dried powder through sieve with mesh 250 micrometers.

EFFECT: improved electrochemical, chemical and physical properties of silver powders.

2 cl, 1 tbl, 1 ex

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