Method of separating gadolinium by extraction with phosphoroorganic compounds

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

 

The present invention relates to technology of rare earth elements (REE). Rare earth elements have similar sizes of the radii of the ions and the same configuration of the outer electron shell. In this regard, the difference in the properties of individual REE very little, and getting a clean connection of the individual element causes certain difficulties. In industry have been used ion-exchange methods [1, 2], and more recently the most widely used extraction methods [3, 4]. To separate the elements of the secondary group - samarium, europium, gadolinium, terbium known method of extraction alkylphosphonate acids [5-8]. There is a common characteristic dependence of the distribution coefficients of the serial number of the item. During extraction, all of organophosphorus acids the distribution coefficient of the element increases with increasing atomic number of the rare-earth elements, i.e., from lanthanum to lutetium. Assume that for a pure gadolinium must be separated first from the more extractable (terbium, dysprosium, and others), then from the less extractables (europium, samarium, and other). The selectivity of separation, usually characterized by the separation factor between neighboring REE, usually does not exceed 1.5 to 2.5. In these conditions the receipt of the gadolinium content of the basic substance more than 9.9% of difficult. The closest technical solution is the method described in the paper [9]. According to [9] gadolinium together with samarium separated by extraction with 15% solution D2EGFK on 8 stages with subsequent washing 2-4 levels and reextracting 1.5 mol/L. the Most difficult causes separation of gadolinium from europium, the separation factor from which R Gd|Eu does not exceed the value of 1.4 to 1.5. At the same time, the gadolinium used in the nuclear industry for the manufacture of uranium-gadolinium fuel must contain a minimum amount of europium (0.05% wt. or less, preferably of 0.01%). The purpose of the invention is to increase the separation efficiency of gadolinium and europium. This objective is achieved in that after the extraction of terbium, dysprosium and more heavy REE in the organic phase, washing and Stripping in the first stage, from the received ravintola solution in the second stage is extracted in the organic phase gadolinium, leaving the bulk of europium, samarium, neodymium and other lighter REE in the aqueous phase. From the resulting organic phase is extracted gadolinium in the reextract and all the reextract containing gadolinium, return to the step of leaching and lead the process to achieve the required content of samarium and europium gadolinium, derive the resulting solution of the gadolinium and the process is repeated again. As extraintestinal 20-40% (vol.) solutions of di-2-ethylhexyloxyphenol acid (D2EGFK) or bis((2,4,4)trimethylpentyl-phosphinic acid (Suape-272) or izodolasytonecyl acid (IDFC).

Example 1.

The original aqueous solution containing nitrates of rare-earth elements and nitric acid, in contact with the solution D2EGFK for 3 minutes. The correlation of phases A:B=1:1. From the organic phase rare-earth elements were transferred into the aqueous phase 3 times reextracting 4.0 mol/l nitric acid at a ratio of phase A:B=1:1. The reextractors and the aqueous phase (refined) were analyzed on an ICP spectrometer with an induction-coupled plasma. The results are shown in table 1 and table 2.

Table 1
The distribution of nitrate of rare earth elements during extraction D2EGFK (the content of REE in an aqueous solution of 110 g/l, nitric acid, 1.4 mol/l)
no PPConc. D2EGFK, orgf.,
%
Content. REE, orgf., g/lThe distribution coefficientThe separation factor
SmEuGdTbEu|SmGd|EuTb|Gd
1 155,20,0120,0250,0370,1971,831,483,70
22211,40,0400,0540,0800,2351,351,402,93
33016,80,0500,0800,120is 0.1351,401,502,87

Table 2
The distribution of nitrate REE extraction of 30% (about) solution D2EGFK in sentine (contents excess nitric acid in the aqueous phase of 0.7 mol/l)
no PPThe content of REE in aq. FG/lThe distribution coefficient The separation factor
SmEuGdTbEu SmGdEuTbGd
1240,1100,1600,2430,8321,451,513,42
2400,0950,1200,1800,5101,261,502,83
385to 0.0600,0700,0980,2911,161,402,96
41270,0520,0710,0930,2771,361,31 2,97

As can be seen from the obtained results, the coefficients of the separation of gadolinium and terbium very high, allowing to organize the effective separation of gadolinium from terbium and pravastatin elements in full countercurrent with getting gadolinium containing less than 0.01% (wt.) terbium and heavier REE. At the same time, the Department of gadolinium from the lighter elements, particularly from the EU, it is extremely difficult because of the low values of the separation factor of 1.4 to 1.5). The same low partition coefficients of gadolinium and europium are and extraction Sapeh-272 and IDCFC.

Example 2

The original aqueous solution containing nitrates of rare-earth elements (100 g/l) with a pH of 4-5, contacted with a solution Sapeh-272 for 3 minutes. Simultaneously in the aqueous phase was injected quantity of ammonium hydroxide equivalent to the amount of REE, transferred into the organic phase. The correlation of phases A:B=1:1. From the organic phase rare-earth elements were transferred into the aqueous phase 3 times reextracting 4.0 mol/l nitric acid at a ratio of phase A:B=1:1. The reextractors and the aqueous phase (refined) were analyzed on an ICP spectrometer with inductively coupled plasma. The results are shown in table 3.

Table 3
no PPConc. Sapeh-272, orgf., vol.%Content. REE, orgf., g/lThe distribution coefficientThe separation factor
SmEuGdTbEu|SmGd|EuTb|Gd
1154,80,0150,0220,0350,1101,661,593,14
2228,20,0330,0540,0830,2541,511,533,06
33012,30,040 0,0630,0950,3001,50.1,503,15

The results of the REE distribution in the extraction of 30%(vol.) solution izodolasytonecyl acid summarized in table 4. In the aqueous phase was injected quantity of ammonium hydroxide equivalent to the amount of REE, transferred into the organic phase. The correlation of phases A:B=1:1. From the organic phase rare-earth elements were transferred into the aqueous phase 3 times reextracting 4.0 mol/l nitric acid at a ratio of phases O:b=1:1. The reextractors and the aqueous phase (refined) were analyzed on an ICP spectrometer with an induction-coupled plasma.

Table 4
The distribution of nitrate REE extraction of 30%(vol.) solution IDFC in sentine

no PPThe content of REE in aq. F., g/lThe distribution coefficientThe separation factor
SmEuGd TbEu|SmGd|EuTb|Gd
120,00,1500,2100,3251,2001,401,543,69
240,00,1210,1830,2780,8671,541,523,11
388,00,0780,1130,1700,554the 1.441,503,25
4120,00,050,0800,120of 0.3371,451,502,81

Partition coefficients of gadolinium and terbium reach values of 3.5-3.7. In this regard, realizations separation from gadolinium, terbium, dysprosium and heavier REE is not difficult. Countercurrent cascade includes standard operations of extraction, washing and Stripping. Obtained in the raffinate solution of gadolinium directed to the second stage is to divide gadolinium-europium and europium, samarium and lighter REE remain in the aqueous phase, and gadolinium goes mainly in the organic phase. Received gadoliniumbased extract is treated in countercurrent proryvnym solution and the washed organic phase is extracted gadolinium in the reextract and all the reextract containing gadolinium, return to the step of leaching and lead the process to achieve the required content of samarium and europium gadolinium, derive the resulting solution of the gadolinium and the process is repeated again. Wash the part of the countercurrent cascade was examined in a counter 20 of the extraction steps of the method of Craig 10 funnels (1 funnel - 2 stages). The extractant - 30%(vol.) the solution D2EGFK, pre-saturated initial aqueous solution containing 103 g/l REE composition (% mass): samarium - 29,7; europium - 10,1; gadolinium - 60,4;, terbium <0,01; dysprosium <0,01; nitric acid 1 mol/L. Reextract was evaporated, corrected by nitric acid (0.8 to 1.2 mol/l) and concentration of total REE - 100-110 g/l and was introduced as the leaching solution. The correlation of phases a:podderjivayem 3:1. The distribution of REE on stages of the cascade are shown in table 5. In the first stage was introduced 30%(vol.) the solution D2EGFK, rich rare earth elements.

Table 5.
Distribution of rare earth elements in the organic phase by stage by flushing the reextract
no PPNo.-speedThe REE content, %
samariumeuropiumgadoliniumthe terbiumdysprosium
1223,38,765,2<0,01<0,01
2414,26,377,7<0,01<0,01
369,65,5838 <0,01<0,01
48a 4.93,791,4<0,01<0,01
510the 3.82,895,1<0,01<0,01
6121,02,196,4<0,01<0,01
7140,3U97,9<0,01<0,01
8160,080,399,5<0,01<0,01
918<0,030,0699,9<0,01 <0,01
1020<0,010,01of 99.97<0,01<0,01

As can be seen from the results of the last stage is output gadolinium containing less than 0.03% of the lighter elements. A positive effect is to increase the separation efficiency and the simplification of the process.

Literature

1. Andreeva SF and other "Trilon B in ion-exchange allocation more rare of rare earth elements". In Proc. of "Rare earth elements (production, analysis, application)", USSR Academy of Sciences. M.,1959, p.100-107.

2. Kharitonov O.V. and other "Influence diethylenetriaminepentaacetic acid separation REE chromatographic method for cationite KU-2" J. physical chem., 69, No. 7, 1995, str-1326.

3. Salnikova E.V. "Extraction processing technology sulfate solutions of rare earth elements mixtures of extractants". International Conf. in chemical engineering, XT 07. Abstr. M., 2007, so No. 4, p.81-84.

4. Val'kov AV and other "Industrial development of extraction technology of Didim high purity". International Conf. in chemical engineering, XT 07. Abstr. M. 2007, vol No. 4, p.78-80.

5. Peppard D.F. at all. "J. Inorg. Nucl. Chem." 4, No. 5-6, 334-343(1957).

6. Peppard D.F. at all "J. Inorg. Nucl. Chem" 5, No. 2, 141-146 (1957).

7. Ritchie G.M., Ashbrook AV "Extraction. Principles and applications in metallurgy. M.: metallurgy, 1983, p.90-93.

8. Carlos Antonio Morais and Marceio Borges Mansur "Equilibrium study of the gadolinium solvent extraction from concentrated metal solution using D2EHPA and NEWAR)". Proceedings of the international conference on .ISEC-2005. Beijing, 2005, str-465.

9. Preston J.S., du Preez A.S., Cole P.M., Fox, M.H. "The recovery of rare earth oxides from a phosphoric acid by-product. Part 3. The separation of the middle and light rare earth fractions and the preparation of pure europium oxide" "Hydrometallurgy", v.42, Issue 2, 1996, p.131-149.

1. The method of separation of gadolinium extraction from nitrate solutions of rare earth elements organophosphorus acid in countercurrent, including the extraction of terbium, dysprosium and more heavy REE in the organic phase, washing and reextraction in the first stage, wherein the received ravintola solution in the second stage is extracted in the organic phase gadolinium, leaving europium, samarium, neodymium and other REE cerium in the aqueous phase, the organic phase is extracted gadolinium in the reextract and all the reextract containing gadolinium, return to the step of leaching and lead the process to achieve the required content of samarium and europium gadolinium output obtained gadolinium solution and the process is repeated again.

2. The method according to claim 1, characterized in that the extractant used 20-40% vol.) solutions of di-2-ethylhexyloxyphenol acid, or bis((2,4,4)trimethylpentanediol acid, or izodolasytonecyl acid.



 

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