Method of processing chemical concentrate of natural uranium

FIELD: chemistry.

SUBSTANCE: invention relates to the technology of processing chemical concentrates of natural uranium, involving leaching (dissolving) the concentrate and extracting uranium using tributyl phosphate in a hydrocarbon diluent. The method involves dissolving the concentrate using aqueous nitric acid solution, feeding the obtained aqueous uranyl nitrate solution to the extract outputting step of a stepped extraction unit and extracting uranium with tributyl phosphate in a hydrocarbon diluent. Extraction is carried out by counterflow interaction of the aqueous and organic phases. Concentrate containing thorium impurities in ratio of 1 wt % to uranium is used. During extraction at the extract outputting step, the step for saturating the extractant with uranium is kept at least 87% of the maximum saturation of the extractant with uranium, and a portion of the aqueous phase, which is not more than 60 vol. % of the uranyl nitrate solution fed to the extract outputting step, after one of the extraction steps is removed from the extraction process and fed for dissolving the uranium concentrate.

EFFECT: high extraction of uranium and nitric acid from the raffinate.

1 tbl

 

The invention relates to the technology of chemical processing of natural uranium concentrates (NUC), including leaching (dissolution) of the concentrate refining and extraction of uranium using tributyl phosphate (TBP) in a hydrocarbon diluent.

Known methods of processing NUC, in which the concentrate is dissolved in a solution of nitric acid, and then carry out the extraction of uranium as uranyl nitrate from an aqueous phase (nitrate uranyl nitrate solution) in the organic phase (TBP solution in the hydrocarbon diluent) by counter-current interaction of aqueous and organic phases. The extract containing uranium, mostly cleared of impurities, and the raffinate, containing residual amounts of uranium (wasteway uranium content), impurities and nitric acid (patent RF №2323883, IPC C01G 43/01, publ. 10.05.2008 (2006.01), RF patent №2398036, IPC C22B 60/02, C22B 3/06, C22B 3/38 (2006.01), publ. 27.08.2010, Harrington H, Ruelle A. production Technology of uranium. - M.: gosatomizdat, 1961. - SS-186 - prototype). The refined are liquid radioactive waste, and prepare them for burial in the deep reservoir.

The concentration of nitric acid in the raffinate usually exceeds the value of the concentration with which liquid radioactive waste may be disposed of (buried) in the deep reservoir. Typically, the concentration of nitric acid in UD is mined waste should not exceed 10 g/L. To bring the concentration of nitric acid in accordance with the concentration required to remove waste, you can use one of two methods: either by dilution refined, either by neutralizing the acid in refined or partially removing nitric acid from refined, for example, by evaporation and subsequent concentration of nitric acid from the vapor phase by distillation. Retrieved nitric acid can be reused for dissolving a new portion of the concentrate.

However, dilution of refined will lead to a significant increase in the volume of waste and the irretrievable loss of valuable component is nitric acid, the neutralization of the refined would also lead to the loss of valuable component and will require additional costs for alkaline reagent, and removing the acid from refined evaporation is a time - consuming and energy-consuming operation.

The invention is more rational use of nitric acid, the reduction of nitric acid, waste sent to landfill by ensuring the necessary quality of purification of uranium extraction refining and reducing the concentration of uranium in the raffinate.

The set task is solved by the fact that in the method for processing chemical concentrate of natural uranium, including the dissolution of the concentrate using an aqueous solution of isotonicity, feeding the resulting aqueous nitric acid solution of uranyl nitrate on the extraction to the stage of issue of the extract and solvent extraction refining uranium tributyl phosphate in a hydrocarbon diluent by counter-current interaction of aqueous and organic phases, the processing is subjected to a concentrate containing a mixture of thorium is not more than 1.0 wt.% the uranium in the extraction process at the stage of issuing an extract of the degree of saturation of uranium extractant support at least 87% of the saturation of the extractant uranium, with a part of the aqueous phase, not exceeding 60% vol. from the fed to the step of issuing extract uranyl nitrate solution, after one stage of extraction is removed from the extraction process and direct the dissolution of uranium concentrate.

Part of the aqueous phase is withdrawn from the extraction process after the stage at which the concentration of nitric acid in the aqueous phase does not exceed the concentration of nitric acid in the feed to the degree-granting extract aqueous nitric acid solution of uranyl nitrate.

From the extraction process deduce a part of the aqueous phase, comprising 50 wt.% from the fed to the step of issuing an extract of the aqueous nitric acid solution of uranyl nitrate.

The method is as follows.

Leached (dissolved) chemical concentrate of natural uranium, the content of impurities which corresponds to the international standard With ASTM 967-08 for uranium ore concentrates (thorium impurities not more than 1 wt.% with respect to U), in an aqueous solution of nitric acid. Got the uranyl nitrate solution composition: [U]=456,5 g/l, [HNO3]=68 g/l and impurities total concentration of ~10 g/l (in terms of metal), of which the thorium is an element limiting the cleanup of uranium, i.e. is an element, which is the hardest to clean up uranium; thorium is present in a concentration of 4,56 g/L. In further dissolution of the concentrate is carried out in an aqueous nitric acid solution, which was a nitric acid solution of uranium is extracted from the extraction process and adjusted the amount of water and nitric acid required to dissolve the concentrate.

Spent extraction refining of uranium extraction stage mixer-settlers, including extraction unit consisting of 4 stages, and the Stripping unit.

In experiments at the first stage solvent extraction unit (the stage of issue of the extract stage extraction unit numbered in the course of the aqueous phase) was applied obtained by dissolving the concentrate aqueous nitric acid solution of uranyl nitrate. On the last fourth stage, considering in the course of the aqueous phase, was filed extractant (tributyl phosphate in a hydrocarbon diluent) countercurrent aqueous phase. With the last step taken raffinate allocated for preparation for burial. In all experiments, the saturation of the uranium from the extractant article the penalties of issue of the extract (the first stage) was maintained equal to at least 87% of the saturation of the extractant uranium. When extraction using 30%TBP in the hydrocarbon diluent saturation of uranium extractant in the first stage was maintained equal to ~107 g/l, and using 55%TBP ~191 g/l For 30%TBP limit the saturation of the extractant uranium is ~120 g/l, 55% ~220 g/L. the Degree of saturation of uranium extractant supported by the ratio of organic and aqueous phases Of:(in experiments 1-4 with 30%TBP a:=3,4÷4,3, and in experiments 5-8 with 55%TBP a:=1,8÷2,3), feeding the extractant on the last stage and feeding the aqueous solution in the first step with predetermined costs.

In experiments 2-4 and 6-8 half of the aqueous phase after one extraction speed unit was removed and sent to the chemical dissolution of uranium concentrate. Another part of the aqueous phase continued movement by the extraction unit. Accordingly, the scope of the raffinate leaving the last (fourth in the course of the aqueous phase) level decreased in two times. In experiments 1 and 5 extraction of uranium held without output extraction portion of the aqueous phase. Analyzed the concentration of nitric acid and uranium refined allocated for preparation for burial.

The results of the experiments are shown in the table.

55
Table
no experience[The Foundation], vol.%Stage selection (output) of the aqueous phaseThe saturation of the extractant Uranus at 1 degree, %Concentrations of U and HNO3in the aqueous phase, g/l, on the steps of extractionLoss of U and HNO3with raffinate %
No.-speed1234
130Without selection89,8[U]89,82,20,210,030100
[HNO3]107674429100
230Selection 1 speed89,7[U]95,61,60,100018 30
[HNO3]8254282034
330Selection 2 speed88,7[U]93,92,70,090,01220
[HNO3]9663322238
430Selection with 3-speed90,1[U]91,82,50,220,02033
[HNO3]9966402543
5Without selectionof 89.1[U]41,81,40,190,040100
[HNO3]124673523100
655Selection 1 speed89,4[U]to 70.21,80,080,01721
[HNO3]91,553241635
755Selection 2 speed87,4[U]47,82,00,080,015 19
[HNO3]10465271839
855Selection with 3-speedto 89.9[U]45,21,80,190,02228
[HNO3]11067311941

It should be clear that when the extraction takes place the transfer of the acid, which acid, partially extractable organic phase from the aqueous phase on the extraction speed of the block is transferred extract back to the first stage, where due to the high concentration of uranium in the aqueous and organic phases is her reextracted (the displacement of the uranium from the organic phase).

The table shows that in all experiments there was a decrease of the concentration of HNO3in the aqueous phase in the direction of travel of the aqueous phase, which is explained by the extraction of HNO3the extractant, this is but the first steps in this cascade - only the first stage), the concentration of nitric acid in the aqueous phase exceeds the concentration of nitric acid in the feed solution of uranyl nitrate due to the transfer of acid extractant and Stripping in the first stages (stages with a high content of uranium in the aqueous and organic phases). The concentration of HNO3in the aqueous phase of the first stage is equal to 82-124 g/l in experiments 1-8, exceeds its concentration in the feed (initial) solution of uranyl nitrate (68 g/l).

The table shows that the reduction of the aqueous phase by half (i.e. output 50% vol. the aqueous phase from the extraction process) after one step of extraction (experiments 2-4, 6-8) resulted in reducing the concentration of HNO3and uranium refined compared to experiments 1 and 5, in which the selection of the aqueous phase from the extraction speed is not produced. For example, in experiment 3, the concentration of acid in the raffinate decreased from 29 g/l to 22 g/l, i.e. by 1.3 times, and uranium - from 0.030 g/l to 0,012 g/l, i.e. 2.5 times. On an industrial scale is very significant. Taking also into account the reduction of the volume of raffinate in experiments 2-4 in the experiments 6-7 twice compared with experiments 1 and 5, the combined losses of HNO3with raffinate decreased to 34-43%, and the total loss U fell to 20-33% in experiments 2-4, compared with experiment 1; the total loss of HNO3with raffinate decreased to 35-41%, while the losses U fell to 19-28% in experiments 6-7 compared with the experience of 5. For 100% loss vatacricith U or HNO 3lost with the raffinate in experiments 1 and 5. In this case, loss of nitric acid and uranium is reduced when the output part of the aqueous phase from the extraction process after every level. (Under "derived from the extraction process part of the aqueous phase" refers to the part of the phase, which was not all steps of the extraction). For comparison: if half of the raffinate (aqueous phase with the last stage of the extraction, i.e. the phase that has passed all stages of extraction) from experiments 1 or 5, i.e. the aqueous phase obtained at the end of the extraction process, aiming at the dissolution of the concentrate, loss of uranium and acid waste in this case is 50%.

Part of the aqueous phase, derived from the extraction process and containing nitric acid, is directed to the dissolution of uranium concentrate. In it add the nitric acid solution with a given concentration and water (if necessary) to ensure the required for dissolution of the concentrate, the amount of solution and the concentration of acid in it.

Conclusion part of the aqueous phase after the stage at which the concentration of uranium in the aqueous phase is still very significant, and the direction of this part of the aqueous phase in the head of the process, the dissolution of the concentrate, leads to the fact that a large number of uranium is rotated during processing of the concentrate "idle". Thus, in experiment 2 conclusion half of the aqueous phase from the extraction process after 1 is tupeni extraction is accompanied by the conclusion of the extraction cascade 10.5% of uranium in the aqueous phase 1 stage contains uranium is 95.6 g/l, this amounted to 20.9%. from 456,5 g/l - concentration of uranium in spent on the extraction of the uranyl nitrate solution, half from 20.9 percent 10.5%). This recycling of uranium significantly reduces the performance of the processing of the concentrate as a whole.

During the experiments it was established that if at the stage of extraction, the concentration of nitric acid in the aqueous phase decreased to values not exceeding the concentration of acid in the solution supplied to the stage of issue of the extract (experiments 3, 4 and 7, 8), the concentration of uranium in the aqueous phase is not large and is a few grams. Part of the aqueous phase containing the concentration of uranium can be selected and directed to the dissolution of the concentrate without significant reduction in performance of the process as a whole. If the selection of the aqueous phase lead from the steps, in which the uranium content does not exceed 3 g/l (in experiments 3, 4 and 7, 8 is 2 or stage 3), then the activities will include (return) uranium will not exceed 0.3% of the introduced with the initial solution. Part of the aqueous phase should be derived from the extraction process after the stage at which the concentration of nitric acid in the aqueous phase does not exceed the concentration of nitric acid in the feed to the degree-granting extract aqueous nitric acid solution of uranyl nitrate.

Results concentrations of nitric acid and uranium in the raffinate better (i.e. lower concentration) in which Petah 3 and 7, than in experiments 4 and 8, respectively. It is advisable to withdraw a portion of the aqueous phase from the first stage, in which the concentration of nitric acid in the aqueous phase decreased to a concentration not exceeding its concentration in the feeding solution of uranyl nitrate (in this example, the second stage of extraction).

As can be seen from the table, the decrease in the concentration of uranium and nitric acid refined in the inventive method is using 30%TBP, and 55%TBP.

Conclusion part of the aqueous phase from the extraction process and the direction of its dissolution concentrate is accompanied also because of the impurities, as part of Uranus rotates on a circle, the content of impurities in the feed to the extraction of aqueous uranyl nitrate solution gradually increases, but to a certain limit.

When the output from the extraction of 50% of the aqueous phase and the direction of the out part of the aqueous phase by dissolving concentrate the impurities in the feed to the extraction solution increases eventually in 2 times in comparison with the value obtained by dissolving a first portion of the concentrate. For example, the content of impurities in the volume V of a solution obtained by dissolving the concentrate is 10, supplied to the extraction solution in the volume V, first impurities contained also 10, When returning 50% of the aqueous phase is the stage of extraction to the stage of dissolution of the concentrate, this returns and half of impurities, i.e 5 g, the content of impurities in the feed to the extraction of the volume V of the solution is increased to 15 g, and then to 17.5 g, etc. up to 20, In the raffinate goes first, 5 g, and then 7.5 g, etc. up to 10, In the end, the solution supplied to the extraction, with each portion of the concentrate comes impurities 10 g, and with the return part of the aqueous phase comes impurities 10 g, (i.e. in the feeding solution comes 20 g), and in the raffinate leaves 10,

Studies have shown that saturation of uranium extractant at the stage of issuance of an extract of at least 87% of the saturation of the extractant uranium and used for dilution of the concentrate selected from the second or third stage of the aqueous phase in the amount of 50 vol.% is sufficient purification of uranium from thorium and other impurities by extraction. On Stripping it turns out the reextract uranium, conditioned on the content of impurities (meets ASTM With 788-03 on a solution or crystals of uranyl nitrate nuclear purity).

When increasing part of the aqueous phase output from the extraction and directed to the dissolution of the concentrate, up to 60% (the content of impurities in the feed solution increases in total 2.5 times) just get conditioned reextract. The increase of the withdrawal of part of the aqueous phase over 60% already leads to substandard to reextract the thorium. The selection of the aqueous phases of the extraction of a block must not exceed 60% of the fed to extraction of the aqueous solution of uranyl nitrate.

Thus, the return of part of the aqueous phase from the extraction on the dissolution of uranium concentrate allows you to increase the extraction of uranium and nitric acid from the raffinate allocated for preparation for burial, to reduce its volume and to save nitric acid dissolution concentrates uranium.

1. Method for processing chemical concentrate of natural uranium, including the dissolution of the concentrate in an aqueous nitric acid solution, feeding the resulting aqueous nitric acid solution of uranyl nitrate on the stage of issue of the extract step extraction unit and the extraction of uranium by tributyl phosphate in a hydrocarbon diluent by countercurrent flow of aqueous and organic phases, characterized in that the processing is subjected to a concentrate containing a mixture of thorium is not more than 1 wt.% the uranium in the extraction process at the stage of issuing an extract of the degree of saturation of uranium extractant support at least 87% of the saturation of the extractant uranium, with a part of the aqueous phase, not exceeding 60% vol. from the fed to the step of issuing extract uranyl nitrate solution, after one stage of extraction is removed from the extraction process and direct the dissolution of uranium concentrate.

2. The method according to claim 1, characterized in that the aqueous phase is withdrawn from the extraction process after level con who entrace nitric acid in the aqueous phase does not exceed the concentration of nitric acid in the feed to the degree-granting extract aqueous nitric acid solution of uranyl nitrate.

3. The method according to claim 1, characterized in that the extraction process deduce a part of the aqueous phase, comprising 50 wt.% from the fed to the step of issuing an extract of the aqueous nitric acid solution of uranyl nitrate.



 

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2 tbl, 2 ex

FIELD: inorganic chemistry, chemical technology.

SUBSTANCE: invention relates to technology for producing rare and scattered elements. Invention proposes using a mixture of isododecylphosphetanic and dialkylphosphinic acid in organic solvent as an extractant. Invention provides enhancing selectivity of extraction by metal-impurities and separation of indium from gallium, and possibility for carrying out re-extraction of metals from organic phase with sulfuric acid solutions in the concentration 200-350 g/dm3. Invention can be used in extraction and separation of gallium and indium from acid sulfate solution of the complex composition.

EFFECT: improved separating method.

4 tbl, 4 ex

FIELD: technology of non-ferrous, rare and trace rare metals.

SUBSTANCE: proposed method includes extraction and separation of arsenic by organic extracting agent. Extracting agent is prepared from mixture of dialkyl methyl phosphonate in the amount of 40-70% with trialkyl amine in the amount of 20-30 vol-% and inert diluting agent in the amount of 10-30%. At extraction, arsenic changes to organic phase.

EFFECT: increased degree of extraction of arsenic (+5); enhanced selectivity and economical efficiency.

5 tbl, 6 ex

FIELD: chemistry.

SUBSTANCE: extractant has bi-phosphorus acid and additionally has tri-phosphate with relation of said components (0,5-1,25):1. Method for producing extractant includes adding to 2-ethylhexanole of chlorine oxide of phosphorus with their relation (4,5-5,1):2,0, and with parameters determined by reaching fullness of passing of reaction, after that reaction mixture is exposed until full removal of formed chlorine hydrogen, then to received mixture 1 mole of water is added, mixture is exposed to full hydrolysis. Then mixture is washed ad water layer is separated from organic remainder, containing said bi-phosphoric acid and tri-phosphate.

EFFECT: higher efficiency.

2 cl, 1 dwg, 2 tbl, 4 ex

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