Annual Report 2009/2010 - JUWEL - Forschungszentrum Jülich

Single-centrifuge tests
A series of single-centrifuge tests were performed using TODGA + 1-octanol in TPH as the
solvent. The flow-sheets of the tests are shown in Fig. 45. The optimised conditions for
extraction, scrubbing and the An-stripping step were applied in these tests.
Solvent
TODGA 0.2 M
Octanol 5%vol
in TPH
60 mL/h
Loaded
organic phase
60 mL/h
Extraction
Loaded
organic phase
Raffinate
Scrubbing
Scrubbed
organic phase
Raffinate
Feed
Feed: HNO 3 4.6 M
Scrub1: HNO 3 3.0 M
Scrub2: HNO 3 0.5 M
0.05 M CDTA
210mL/h
Scrubbed
organic phase
60 mL/h
Scrub 2
HNO 3 0.5 M
Tracers: 152 Eu, 241 Am
60 mL/h
An(III) Stripping
Organic phase for
Ln(III) stripping
An(III) Product
An Strip
DTPA 0.05 M
Gycine 1.0 M
NO 3- 1.8 M
60 mL/h
Fig. 45: The flow-sheets for the single centrifugal contactor tests
The results of the single centrifugal contactor tests are summarised in the Tab. 15. The
lanthanides and Am(III) were quantitatively extracted in the first step (Extraction) with
distribution ratios over 200 and they remained in the loaded organic phase through the nitric
acid scrubbing step (Scrubbing). Three An-stripping solutions of different initial pHs were
tested, namely 1.7, 1.9 and 2.0. The solution with a pH of 2.0 appeared to be the best choice
for selective Am back-extraction (Stripping 2.0). The extraction of Pd and Zr was suppressed
by using CDTA in the feed. Strontium and molybdenum were partly extracted by TODGA.
However in the scrubbing step most of their content was removed from the organic phase.
The D Am and D Ln obtained in the An-stripping step (Stripping 2.0; see last column in Tab. 15)
of the single-centrifuge test were higher than in the batch tests (Fig. 44) with much lower
Ln/Am separation factors. This could be a result of inefficient nitric acid scrubbing from the
organic phase in the previous step (Scrubbing) and/or the low efficiency of a single contactor
in the stripping step. Therefore, these two steps must be further tested by increasing the
number of the centrifugal contactors, which should increase their efficiency.
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