XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1739
The relationships seen in Figure 10 indicate that the
O/A ratio has a marked effect on the extraction and dis-
tribution coefficients of Ta and Nb. It is apparent that
increasing the O/A ratio leads to an increase in the extrac-
tion efficiencies and distribution coefficient of both metals.
Based on the data shown in Figure 10, the correspond-
ing equilibrium isotherms indicate for the case of Ta, a
maximum Ta loading achieved in the organic phase (14%
Aliquat 336) of about 2645 mg/L. For Nb, the respective
loading was 8760 mg/L. These results showcase the ability
of Aliquat 336 to serve as a promising extractant for separa-
tion of Ta and Nb from oxalic-based solutions. However,
defining the theorical number of stripping/extraction stages
in view process upscaling would require further study on
the effect of accompanying metals presence and the role of
Ta and Nb repartitioning in the aqueous phase.
Ta and Nb Stripping
The co-extraction of Ta and Nb with Aliquat ® 336 requires
a selective back extraction for their separation and recov-
ery. Stripping experiments were carried out in parallel with
extraction experiments, where the loaded organic phase was
obtained by equilibrating the organic and aqueous phase
under the optimal found conditions, namely: 14% Aliquat ®
336, 4 minutes of contact time, O/A phase ratio of 2, tem-
perature of 20°C. Stripping experiments were conducted
using an O/A phase ratio of 1:1 and employing different
acid solutions, the results being summarized in Figure 11.
From Figure 11, it can be deduced that 0.5 M HNO3
media (3) secures the highest separation factor of Nb against
Ta (SF
Nb/Ta =6). However, the obtained Nb stripping effi-
ciency is relatively low, being close to 32% and around 7%
for Ta. This low stripping efficiency shows that the stripping
and separation steps for Nb from the Ta-loaded organic
phase requires more stages to enable complete stripping of
Nb.
CONCLUSIONS
A fluoride-free extraction and separation process of Ta and
Nb has been investigated. The operational process condi-
tions of solvent extraction were optimized to purify Nb
and Ta from oxalic-based productive solutions. Almost
complete extraction of Ta and Nb can be achieved using
an O/A ratio of 2, aqueous phase pH of 1.1, Aliquat ®336
concentration of 14% and an extraction temperature of
20°C. Stripping and separation of Nb using 0.5 M nitric
acid solution, yield a separation factor of about 6 for Nb
against Ta.
Ultimately, the obtained results are suggesting that an
oxalic acid based process could be an economically feasible
and environmentally responsible extractive metallurgical
approach for sourcing Ta and Nb from primary resources.
REFERENCES
Ayanda, O.S., Adekola, F.A., 2011. A Review of Niobium-
Tantalum Separation in Hydrometallurgy. J Miner
Mater Charact Eng 10, 245–256. doi: 10.4236
/jmmce.2011.103016
Bhattacharyya, S.N., (Nandi) Ganguly, B., 1986. Solvent
extraction separation of tantalum from niobium on
macro scale using di(2-ethylhexyl) phosphoric acid as
extractant. J Radioanal Nucl Chem Artic 98, 247–253.
doi: 10.1007/BF02037087
0
10
20
30
40
50
60
70
(8) (7) (6) (5) (4) (3) (2)
Nb
Ta
(1)
(a)
0
1
2
3
4
5
6
(8) (7) (6) (5) (4) (3) (2) (1)
(b)
Figure 11. Stripping efficiency (a) with respective separation factor of Nb/Ta (b) from the loaded organic phase for different
acidic solutions: (1) H
2 SO
4 (2M), (2) HNO
3 (0.7M) +H
2 C
2 O
4 (0.5M), (3) HNO
3 (0.5 M), (4) NH
4 F (1 M), (5) HCl (1 M),
(6) H
2 O, (7) H
2 C
2 O
4 (1 M), (8) H
2 C
2 O
4 (0.5 M) +HNO
3 (0.3 M) +NaNO
3 (0.15 M)
Strippi
efficiency,
%
Separati
factor
(SF
Nb/Ta
)
The relationships seen in Figure 10 indicate that the
O/A ratio has a marked effect on the extraction and dis-
tribution coefficients of Ta and Nb. It is apparent that
increasing the O/A ratio leads to an increase in the extrac-
tion efficiencies and distribution coefficient of both metals.
Based on the data shown in Figure 10, the correspond-
ing equilibrium isotherms indicate for the case of Ta, a
maximum Ta loading achieved in the organic phase (14%
Aliquat 336) of about 2645 mg/L. For Nb, the respective
loading was 8760 mg/L. These results showcase the ability
of Aliquat 336 to serve as a promising extractant for separa-
tion of Ta and Nb from oxalic-based solutions. However,
defining the theorical number of stripping/extraction stages
in view process upscaling would require further study on
the effect of accompanying metals presence and the role of
Ta and Nb repartitioning in the aqueous phase.
Ta and Nb Stripping
The co-extraction of Ta and Nb with Aliquat ® 336 requires
a selective back extraction for their separation and recov-
ery. Stripping experiments were carried out in parallel with
extraction experiments, where the loaded organic phase was
obtained by equilibrating the organic and aqueous phase
under the optimal found conditions, namely: 14% Aliquat ®
336, 4 minutes of contact time, O/A phase ratio of 2, tem-
perature of 20°C. Stripping experiments were conducted
using an O/A phase ratio of 1:1 and employing different
acid solutions, the results being summarized in Figure 11.
From Figure 11, it can be deduced that 0.5 M HNO3
media (3) secures the highest separation factor of Nb against
Ta (SF
Nb/Ta =6). However, the obtained Nb stripping effi-
ciency is relatively low, being close to 32% and around 7%
for Ta. This low stripping efficiency shows that the stripping
and separation steps for Nb from the Ta-loaded organic
phase requires more stages to enable complete stripping of
Nb.
CONCLUSIONS
A fluoride-free extraction and separation process of Ta and
Nb has been investigated. The operational process condi-
tions of solvent extraction were optimized to purify Nb
and Ta from oxalic-based productive solutions. Almost
complete extraction of Ta and Nb can be achieved using
an O/A ratio of 2, aqueous phase pH of 1.1, Aliquat ®336
concentration of 14% and an extraction temperature of
20°C. Stripping and separation of Nb using 0.5 M nitric
acid solution, yield a separation factor of about 6 for Nb
against Ta.
Ultimately, the obtained results are suggesting that an
oxalic acid based process could be an economically feasible
and environmentally responsible extractive metallurgical
approach for sourcing Ta and Nb from primary resources.
REFERENCES
Ayanda, O.S., Adekola, F.A., 2011. A Review of Niobium-
Tantalum Separation in Hydrometallurgy. J Miner
Mater Charact Eng 10, 245–256. doi: 10.4236
/jmmce.2011.103016
Bhattacharyya, S.N., (Nandi) Ganguly, B., 1986. Solvent
extraction separation of tantalum from niobium on
macro scale using di(2-ethylhexyl) phosphoric acid as
extractant. J Radioanal Nucl Chem Artic 98, 247–253.
doi: 10.1007/BF02037087
0
10
20
30
40
50
60
70
(8) (7) (6) (5) (4) (3) (2)
Nb
Ta
(1)
(a)
0
1
2
3
4
5
6
(8) (7) (6) (5) (4) (3) (2) (1)
(b)
Figure 11. Stripping efficiency (a) with respective separation factor of Nb/Ta (b) from the loaded organic phase for different
acidic solutions: (1) H
2 SO
4 (2M), (2) HNO
3 (0.7M) +H
2 C
2 O
4 (0.5M), (3) HNO
3 (0.5 M), (4) NH
4 F (1 M), (5) HCl (1 M),
(6) H
2 O, (7) H
2 C
2 O
4 (1 M), (8) H
2 C
2 O
4 (0.5 M) +HNO
3 (0.3 M) +NaNO
3 (0.15 M)
Strippi
efficiency,
%
Separati
factor
(SF
Nb/Ta
)