Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Alkali metal
Patent
1999-01-27
2000-12-05
Griffin, Steven P.
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Alkali metal
423181, 549354, 540468, 540469, 540472, C01D 1500, B01D 1100, C22B 2610, C07D32100, C07D32110
Patent
active
061562823
DESCRIPTION:
BRIEF SUMMARY
TECHNOLOGICAL FIELD
The subject of this invention is crown calix[4]arenes, their method of preparation and their use for the selective extraction of caesium.
To put it more precisely, the invention relates to crown calix[4]arenes capable of selectively extracting caesium present in trace amounts in acid solutions, that may or may not have high concentrations of cations, such as the aqueous effluents arising from spent nuclear fuel reprocessing plants.
In these effluents, caesium 137 is one of the most noxious fission products due to its long half-life (30 years). It is therefore of interest to selectively remove it from liquid effluents coming from reprocessing plants, in particular from evaporator concentrates and acid solutions that may or may not have high salinity due, in particular to the presence of sodium nitrate.
Given the great similarity of the chemical properties of sodium and caesium, it is extremely difficult to selectively extract the caesium present in these effluents, at a concentration generally lower than 10.sup.-6 mol/l, while the concentration of sodium is about 4 mol/l.
In acid solutions of fission products, it is equally important to remove the .sup.135 Cs with a half life of 2.times.10.sup.6 years, with the intention either of transmuting it or incorporating it into a specified matrix, caesium being one of the most mobile elements in geological storage.
STATE OF THE PRIOR ART
In order to resolve this problem, it has been proposed to extract caesium using macrocyclic ligands such as the para tert-butyl-calixarenes described in U.S. Pat. No. 4,477,377. The para tert-butyl-calixarenes used are the tetramer, the hexamer and the octamer and the best results are obtained with the hexamer and the octamer, the tetramer not having very good selectivity for the separation of caesium from potassium. This technique for extracting caesium is interesting but its main disadvantage is that it is only applicable to aqueous basic solutions while most effluents arising from reprocessing are acid solutions.
More recently, for this separation the use of other calixarenes has been considered, in particular crown calixarenes as described in documents WO-A-94/12502 and WO-A-94/24138.
According to these documents, the one or two calixarene crowns are mainly made up of --C.sub.2 H.sub.4 --O-- chains which comprise from 4 to 7 atoms of oxygen.
The results obtained with crowns with 6 or 7 atoms of oxygen are satisfactory for the extraction of caesium from acid solutions which are not highly loaded with salts. On the other hand, when they are used with effluents highly loaded with sodium, containing, for example 4 mol.l.sup.-1 of NaNO.sub.3, their performance is clearly reduced. Also research has been pursued to find other extraction agents of the same type having improved performance in highly saline acid media.
The precise objective of this invention is new crown calixarenes which allow the selective extraction of caesium from acid solutions and the separation of it from sodium with better efficiency.
DESCRIPTION OF THE INVENTION
According to the invention, the calixarenes are crown calix[4]arenes of formula: ##STR2## in which: R.sup.1 represents a group of formula: --(YO).sub.r --(CH.sub.2 CH.sub.2 O).sub.s (II), cycloalkylene group, m, n, p, r and s are whole numbers such that: atoms, the two R.sup.2 groups can be identical or different, or the two R.sup.2 groups together form a group of formula: --(YO).sub.r --(CH.sub.2 CH.sub.2 C).sub.s (II), atoms, with the condition that, in the case where the two R.sup.2 groups together form a group of formula (III), p and r will not both be equal to 0 when n=1.
In the formula given above, the alkoxy groups used for R.sup.2 can be straight chain or branched chain and are not necessarily identical.
Generally, they comprise from 1 to 18 atoms of carbon, preferably from 1 to 12 atoms of carbon.
In the formula given above, by "cycloalkylene group" one understands a bivalent group derived from a cyclic hydrocarbon by the removal of a hydrogen atom from each of two car
REFERENCES:
patent: 4477377 (1984-10-01), Izatt et al.
patent: 5607591 (1997-03-01), Dozol et al.
Abstracts WO9424138 and EP695304.
Abstracts WO9412502, FR2698362 and EP670840.
Notification D'Un Rapport De Recherche Preliminaire Sans Reponse Obligatoire.
Asfari Zouhair
Bressot Christophe
Casnati Alessandro
Dozol Jean-Fran.cedilla.ois
Lamare Veronique
Commissariat a l''Energie Atomique
Griffin Steven P.
Strickland Jonas N.
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