SusChemE 2015
International Conference on Sustainable Chemistry & Engineering
October 8-9, 2015, Hotel Lalit, Mumbai
Removal of Zr (IV) from Used Pickling Solution by Solvent Extraction
D.S.R.Theja1, Tessy Vincent2, S.SaiRam1, P.S.Dhami2, Poonam Jagasia2, J.N.Sharma2
Gourahari Das1, Meena Ravindran1
1
Nuclear Fuel Complex, Nuclear Fuel Complex, Hyderabad
Nuclear Recycle Group, Bhabha Atomic Research Centre, Mumbai
E-mail addresses: theja@nfc.gov.in, tessyv@barc.gov.in, sairam@nfc.gov.in
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1. Introduction:
Pickling is an important step during fabrication of various Zircaloy products. It removes the oxide layer & surface
contaminants by dissolving in HF & HNO3. Over a period of use, pickling solution gets depleted in HF and enriched
with salts of Zr and other alloying elements and is discarded as used pickling solution (UPS) when the Zr
concentration exceeds 35 g/l. UPS is a valuable reagent which needs to be recycled for making the process
environmental friendly. Extraction studies were taken up to remove the Zr from UPS
Literature available on extraction of Zr from UPS is very limited [1-3]. Various extractants were tried for
preliminary solvent extraction studies and the detailed study carried out with the chosen ligand is discussed.
2. Material and Methods:
Ligands like Tetra ethyl hexyl di-glycol amide (TEHDGA), Carbamoyl methyl phosphine oxide (CMPO) and Mono
glycol amide (MGA) used in the present study were available from Process Development Division, BARC,
Mumbai. Analytical grade HNO3, HF and oxalic acid were purchased from Ms. S.d.Fine-Chem Ltd, Mumbai. Zr
concentration in the feed as well as in the raffinate was analyzed using Inductively Coupled Plasma-Atomic
Emission Spectroscopy (ICP-AES).
3. Significant Results and Discussion:
Experiments were carried out for the UPS containing 35.5 g/l of Zr with TEHDGA, MGA and CMPO using 30%
Iso-Dodecyl Alcohol (IDA) as a phase modifier and 70% dodecane as diluent with an organic to aqueous (O/A) ratio
of 3. Highest extraction of 42% was found with 0.2 M MGA with a low distribution ratio (D Zr) of 0.24 as seen from
table-1. With an aim to improve DZr, one more run was performed with 1M MGA which resulted in a DZr,of 1.46
with 78.43% extraction. Stripping experiment was also carried out using 0.2 M oxalic acid and 0.5 M HNO3 for the
loaded organic containing 10g/l of Zr with an O/A ratio of 1. In two contacts, 80% separation was obtained.
Table 1: Comparison of Extraction Performance with Various Extractants
Sr.
No.
1
Ligand (0.2M) Raffinate
conc. g/l
TEHDGA
31.10
Distribution
Ratio (DZr)
0.05
% Extraction
2
3
CMPO
MGA
0.12
0.24
26.6
42
25.57
20.05
13.1
As the UPS contains about 4.2 M HNO3, experiments were carried out to study the uptake of nitric acid with 1 M
MGA by varying the concentrations of HNO3 in the range 0.5- 6.0M for an O/A ratio 1. Free acidity in both the phases
was calculated by titration method. Acid uptake equilibrium is depicted in Fig.1. It can be seen that the free acidity
increases as the nitric acid concentration increases. Further experiments have been performed in cross current mode to
study the efficiency of 1M MGA for the complete removal of Zr from UPS by maintaining an O/A ratio of 3 and the
results are summarized in table-2. Stripping behavior has also been studied for loaded organic in three contacts using
0.2M oxalic acid and 0.5 M HNO3. In three contacts 99.8% Zr could be transferred to aqueous phase.
1
SusChemE 2015
International Conference on Sustainable Chemistry & Engineering
October 8-9, 2015, Hotel Lalit, Mumbai
0.30
Free acidity M (Organic phase)
0.25
0.20
0.15
0.10
0.05
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
Free Acidity M (Aqueous)
Figure 1. Acid Uptake by MGA
Table 2: Extraction Performance with IM MGA in cross current mode
Contacts
C1
Zr in feed, g/l Zr in aq.
35
3.7
C2
C3
C4
3.7
0.9
0.23
g/l
0.9
0.22
0.05
Zr in org. g/l DZr
10.43
2.81
%Extraction
89.52
0.93
0.23
0.057
97.45
99.38
99.84
1.03
1.03
1.04
Conclusion:
The synthesized MGA is found to be a suitable ligand for the extraction of Zr from UPS and quantitative stripping
of the loaded Zr in MGA is also feasible by 0.2 M Oxalic acid and 0.5 M HNO3.
References
[1] Airy P. Lamaze, Process for recovering acids& zirconium contained in pickling solutions, U.S Patent: 4200612
filed on Nov, 7, 1978
[2] J. Rynasiewicz, Zircaloy pickle bath salts- chemical nature & thermal decomposition of a hydrated zirconium
fluoride, J. Nucl. Materials, 12 (2) 1964, 153-158
[3] Bang . M. Kim,, Process for recovery of zirconium from acid spent etching solutions. U.S Patent: 4572824 filed
on Nov, 1, 1984
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