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Elution of uranium from an anion-exchange resin by extraction with an organic extractant in the presence of an aqueous phase
JourrraC of Chromatography, 102 t 1974) 42943 1 0 Elscvier Scientific Publishing Company, Amsterdam
-
Printed
in The Netherlands I
CHROM.
7740
ELUTION OF URANIUM EXTRACTION WITH AN OF AN AQUEOUS PHASE
FROM ORGANIC
M. ERDGLYI and B. CZEGLGDI Mccseki Z%cbdrry&zati Vciffalat (Mccsek and M. VIGVARI Fdmipari
Kutatd ZtrtEzct (Research
AN ANION-EXCHANGE EXTRACTANT IN THE
Ore Mitting Enterprise), _
Zrrstitrrte for NowFerrous
RESIN BY PRESENCE
P&s (Hungary)
Metals),
Budapest
(Htmgary)
SUMMARY
The elution of uranium from anion-exchange resins by dilute sulphuric acid has many advantages, but as a consequence of unfavourable distribution values it has limited value. However, if the sulphuric acid phase serves only as a medium phase, and elution is carried out by organic extraction, the advantages of both elution and extraction are combined, while the undesirable factors can be eliminated.
The concentration of uranium from leach liquor or pulp by using an anionexchange resin is a well known process. Uranium is extracted from the solution obtained by elution of the saturated resin with an organic solvent. The overall recovery is improved by the combination of these two processes. Elution of uranium from an anion-exchange resin can be carried out with dilute hydrochloric, nitric or sulphuric acid. The eluting qualities of hydrochloric and nitric acids are satisfactory, while the application of sulphuric acid, which is desirable in many respects, has certain disadvantages. Of the elution and extraction processes the former takes more time in the first place because of the slow diffusion. Fig. 1 shows the isotherm of elution by dilute sulphuric acid and it can be seen that the unfavourable conditions of equilibrium also contribute to the long time required for elution. The distribution ratio of uranium between the resin and the aqueous phase is about 10 when dilute sulphuric acid is used as the eluent. Hence the elution should be carried out with a large volume of solution or the number of theoretical plates should be increased, although even at an infinite number of plates the uranium concentration in the eluate is limited by the convex character of the isotherm. One of the techniques for solving the problem is the so-called Eluex method, which makes the application of a large volume of eluting solution possible. Another method is to perform the elution directly with an organic solvent (for example, di-2-ethylhexylphosphoric acid) in the presence of the aqueous phase which
M. ERDkYI,
Y
I
I
1
2
B. CZEGLBDI,
M. VIGV,&RI
ca(g/l)
Fig.
1.
Isotherm
of uranium
in the system resin-dilute
sulphuric
acid.
mediates in the mass transfer. In this case, the distribution ratio of uranium between the resin phase and the organic solvent is given by the proportion of those of elution and extraction :
D,,=-=
C"WSlll
co”rIl
D
clucion
D
CXI
.
The line of the isotherm of uranium distribution between the resin and organic solvent differs from that between the resin and aqueous phase, as shown in Fig. 2, being concave on the side of the work-line of elution; this is highly favourable for the required number of theoretical plates. Its concave character permits the efficient utilization of the uranium capacity of the organic phase, and thus the number of plates can be significantly reduced by carrying out elution in countercurrent reactors, as shown by the scheme in Fig. 3.
Fig. 2. Isotherm
of uranium
Fig. 3. Three-phase
elution
in the system resin-organic in a line of reactors.
solvent,
ELUTION
OF URANIUi4
FROM
AN ANION-E.XCNANGE
RESIN
431
The purpose of the aqueous phase, as the mediating phase, is to restrain the organic solvent from being absorbed into the resin by hindering the direct connection between the resin and organic phases. This is important in order to decrease both the loss of solvent and the corrosion of the resin. This technique of elution can also be carried out in a pulsing column.
-
Printed
in The Netherlands I
CHROM.
7740
ELUTION OF URANIUM EXTRACTION WITH AN OF AN AQUEOUS PHASE
FROM ORGANIC
M. ERDGLYI and B. CZEGLGDI Mccseki Z%cbdrry&zati Vciffalat (Mccsek and M. VIGVARI Fdmipari
Kutatd ZtrtEzct (Research
AN ANION-EXCHANGE EXTRACTANT IN THE
Ore Mitting Enterprise), _
Zrrstitrrte for NowFerrous
RESIN BY PRESENCE
P&s (Hungary)
Metals),
Budapest
(Htmgary)
SUMMARY
The elution of uranium from anion-exchange resins by dilute sulphuric acid has many advantages, but as a consequence of unfavourable distribution values it has limited value. However, if the sulphuric acid phase serves only as a medium phase, and elution is carried out by organic extraction, the advantages of both elution and extraction are combined, while the undesirable factors can be eliminated.
The concentration of uranium from leach liquor or pulp by using an anionexchange resin is a well known process. Uranium is extracted from the solution obtained by elution of the saturated resin with an organic solvent. The overall recovery is improved by the combination of these two processes. Elution of uranium from an anion-exchange resin can be carried out with dilute hydrochloric, nitric or sulphuric acid. The eluting qualities of hydrochloric and nitric acids are satisfactory, while the application of sulphuric acid, which is desirable in many respects, has certain disadvantages. Of the elution and extraction processes the former takes more time in the first place because of the slow diffusion. Fig. 1 shows the isotherm of elution by dilute sulphuric acid and it can be seen that the unfavourable conditions of equilibrium also contribute to the long time required for elution. The distribution ratio of uranium between the resin and the aqueous phase is about 10 when dilute sulphuric acid is used as the eluent. Hence the elution should be carried out with a large volume of solution or the number of theoretical plates should be increased, although even at an infinite number of plates the uranium concentration in the eluate is limited by the convex character of the isotherm. One of the techniques for solving the problem is the so-called Eluex method, which makes the application of a large volume of eluting solution possible. Another method is to perform the elution directly with an organic solvent (for example, di-2-ethylhexylphosphoric acid) in the presence of the aqueous phase which
M. ERDkYI,
Y
I
I
1
2
B. CZEGLBDI,
M. VIGV,&RI
ca(g/l)
Fig.
1.
Isotherm
of uranium
in the system resin-dilute
sulphuric
acid.
mediates in the mass transfer. In this case, the distribution ratio of uranium between the resin phase and the organic solvent is given by the proportion of those of elution and extraction :
D,,=-=
C"WSlll
co”rIl
D
clucion
D
CXI
.
The line of the isotherm of uranium distribution between the resin and organic solvent differs from that between the resin and aqueous phase, as shown in Fig. 2, being concave on the side of the work-line of elution; this is highly favourable for the required number of theoretical plates. Its concave character permits the efficient utilization of the uranium capacity of the organic phase, and thus the number of plates can be significantly reduced by carrying out elution in countercurrent reactors, as shown by the scheme in Fig. 3.
Fig. 2. Isotherm
of uranium
Fig. 3. Three-phase
elution
in the system resin-organic in a line of reactors.
solvent,
ELUTION
OF URANIUi4
FROM
AN ANION-E.XCNANGE
RESIN
431
The purpose of the aqueous phase, as the mediating phase, is to restrain the organic solvent from being absorbed into the resin by hindering the direct connection between the resin and organic phases. This is important in order to decrease both the loss of solvent and the corrosion of the resin. This technique of elution can also be carried out in a pulsing column.