Journal of Minerals & Materials Characterization & Engineering, Vol. 4, No. 2, pp 85-93, 2005
jmmce.org Printed in the USA. All rights reserved
85
Assessment Of Beneficiation Routes Of Tantalite Ores
From Key Locations In Nigeria
1
Adetunji, A. R
*
;
2
Siyanbola, W.O.;
3
Funtua, I. I;
1
Olusunle, S. O. O.;
1
Afonja A.A and
1
Adewoye, O.O.
1
Metallurgical and Materials Engineering Department, Obafemi Awolowo University, Ile-Ife
2
Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife
3
Centre for Energy Research and Training, Ahmadu Bello University, Zaria
*Correspondence Author; e-mail: aadetunj@oauife.edu.ng or aderade2004@yahoo.com
Abstract:
The beneficiation methods for some tantalite ores from selected deposits in
Nigeria have been assessed through mineralogical and compositional analyses of the
ores. Tantalite ores obtained from eight different well-known locations of the mineral in
the country were analyzed with
109
Cd excitation source Energy Dispersive X-ray
spectrometry using the emission-transmission method of quantification. The major
minerals detected and quantified include TiO
2
, MnO, Fe
2
O
3
, Ta
2
O
5
, Nb
2
O
5,
WO
3,
Th and
U. Impurity elements such as Hf, Zn, Zr, Co, Pb, Rb, and Y were also observed and
evaluated. Our analyses further show that Ta
2
O
5
in the ores ranged from a minimum
concentration of about 8% in Otu to about 60% in the Egbe deposits, while the Nb
2
O
5
concentrations in the ores ranged from about 20% to 37.5% with the highest coming
from the Ofiki deposit. Based on these results and the work of other authors, we deduced
that clean-up operations might be adequate for Ta extraction from most of the tantalite
deposits in Nigeria. The consideration of simplicity and cost of process favours the direct
dissolution of the ores in HF for the clean-up operations.
Keywords: Tantalite ores, Elemental Composition, EDXRF
INTRODUCTION
Nigeria is blessed with abundant mineral resources. These include vast deposits of
coal, cassiterite, columbite, marble, limestone, clay, bitumen and tantalite. While some of
these minerals are currently mined, several others have been identified to have huge
potentials of being exploited in commercial scale. The Federal Government of Nigeria is
paying renewed attention to the solid m ineral sector; therefore, development activities in
the sub-sector are expected to increase many-fold. Recent studies conducted by the Raw
Materials Research and Development Council (RMRDC) have shown that the need to
develop capacity for processing of these minerals into intermediate products is the most
important requirement of the solid mineral sector in the country [1].
The recovery of tantalite in Nigeria dates back to the 1940’s as a by-product of
cassiterite mining [2, 3]. Later, large tonnages of granite containing about 0.26% Nb
2
O
5
in urania pyrochlore (3.1% U
3
O
8
, 3.3% ThO
2
, 37.5% Nb
2
O
5
and 3.5% Ta
2
O
5
) were
86Adetunji, A. R
*
; Siyanbola, W.O.; Funtua, I. I; Olusunle, S. O. O.;Vol. 4, No. 2
Afonja A.A and Adewoye, O.O
identified. The reserves were however not confirmed. Primary deposits of huge economic
value of the ore have now been reported in various parts of the country [4, 5, 6]. Indeed,
Nigeria is currently rated to be the 7
th
largest producer of tantalum resources in the world
[7]. The production in 2004 was estimated at 25 metric tons.
Tantalite is the most important mineral form of tantalum, a specialty metal used
mainly in the electronics industry for the manufacture of capacitors and in several
specialty alloy applications. The beneficiation of tantalite ores usually involves pre-
concentration, primary concentration and concentrate clean up. The choice of any or all
of these processes would depend on the nature of the ore, particularly the content of
Ta
2
O
5
in the ore relative to its associated minerals and impurities. Typically,
mechanically mined ores contain less than 0.1%Ta
2
O
5
, and would therefore essentially
require enrichment through the three processes stated above. The concentration processes
may be carried out by wet gravity, magnetic or electrostatic methods or by flotation to
produce concentrates containing up to 70% combined Ta
2
O
5
and Nb
2
O
5
to meet
extraction requirements. However, the universally employed method for the
concentration of tantalite ores is gravity separation – the separation of two or more
minerals as a result of differences in specific gravity and their movement in response to
the force of gravity and one or more other forces [8, 9]. Other m ethods, when used, are
employed in the final cleanup of gravity concentrates.
Furthermore, Burt [10] had noted that concentrates suitable for further processing
to recover Ta are generally required to exceed 25% Ta
2
O
5
, with 50% combined Ta
2
O
5
and Nb
2
O
5.
Primary ores with these Ta
2
O
5
and Nb
2
O
5
contents would only need clean-up
operations for Ta extraction processes. The clean-up operation results in the removal of
associated minerals and im purity elements to a tolerable extent. Typical associated
minerals include zircon, rutile, monazite, cassiterite, ilmenite, garnet, uranium and
thorium minerals, beryl, spodumene, tourmaline and, in some cases, aquamarines and
gold: light minerals such as quartz and feldspar may also be present due to inefficient
primary concentration.
A number of reports [11, 12] have given the mineralogical composition of Ta-Nb
ores obtained from a few locations in the middle belt region of Nigeria. However, the
limitation of these previous works is the failure to relate the results to an upgrading
process for a value-added Nigerian tantalite.
The main objective of this work is to assess the appropriate beneficiation schemes
by identifying the associated elements and impurity elements in samples obtained from
notable tantalite deposits across Nigeria. The associated elements are known to contribute
to the physical characteristics of the Ta mineral and thes e characteristics dictate the
beneficiation methods. The outcome of the work reported here would therefore provide
critical information about the appropriate routes for the beneficiation processes needed
for value addition to the Nigerian tantalum industry.
Vol. 4, No. 2. Assessment Of Beneficiation Routes Of Tantalite Ores From Key Locations In Nigeria87
MATERIALS AND METHODS
Eight samples were collected from different notable deposits in Nigeria. The
sources are Egbe, Komu, Nassarawa, Agunrege, Baba Ode, Ofiki, Igbo Ijaye and Otu. Six
of the locations are in Oyo State in the South Western Nigeria; one location is in Kogi
State while one is in Nassarawa State, both deposits located within the middle belt region
of the country. The samples were obtained from miners in the study areas. The miners
employ manual methods of mining, in which the samples would have been upgraded to
some extent by hand sorting. Measurements of the major constituents and trace elements
were carried out using a radioisotope source Energy Dispersive X-Ray Fluorescence
(EDXRF) Spectrometer at the Centre for Energy Research and Training, Ahm adu Bello
University, Zaria, Nigeria.
The samples were ground manually to powder with an agate m ortar and pestle to
grain size of less than 125 µm. Pellets of 19 mm diameter were prepared from 0.3 – 0.5g
powder mixed with three drops of organic liquid binder and then pressed at 10 tons with a
hydraulic press. Measurements were performed using an annular 25 mCi
109
Cd as the
excitation source, which emits Ag-K X-rays (22.1 keV) in which case all elements with
lower characteristic excitation energies were accessible for detection in the samples. The
system further consists of a Si(Li) detector, with a resolution of 170 eV for the 5.90 keV
line, coupled to a computer controlled ADC-card. Further details about the system have
been given elsewhere [11, 13,14].
Quantitative analysis of the samples was carried out using the Emission-
Transmission (E-T) method, for which a number of quantification methods has been
developed and applied [13 – 18]. These quantification methods provide different
approaches to correct the matrix absorption as well as enhancement effects. In this work
quantification was carried out using a modified version of E-T method [11, 19, 20],
which involves the use of pure target material (Mo) to measure the absorption factors in
the sample. The Mo target serves as a source of m onochromatic X-rays, which are
excited through the sample by primary radiation and then penetrate the sample on the
way to the detector. In this way, the absorption factor is experimentally determined. The
program then uses th is factor in the quantification of concentration of the elements. In
addition, the contribution to the Mo-K peak intensity by the Zr-K is subtracted for each
sample. The spectra for the samples were collected for 3000s with the
109
Cd and the
spectra were then evaluated using the AXIL- QXAS program [21]. It was noted that very
light mineral associations of the Ta ores could not be determined due to the absence of an
55
Fe excitation source.
RESULTS AND DISCUSSION
The results of the mineralogical analysis including a number of impurities/trace
elements are shown in Table 1. The results show that the Egbe sample contains the
highest Ta
2
O
5
content at 59.58%. The Ta
2
O
5
contents of Komu, Nassarawa, Agunrege,
88Adetunji, A. R
*
; Siyanbola, W.O.; Funtua, I. I; Olusunle, S. O. O.;Vol. 4, No. 2
Afonja A.A and Adewoye, O.O
Baba Ode, Ofiki, Igbo Ijaye and Otu ore samples are respectively 49.57%, 46.15%,
45.42%, 42.00%, 36.63%, 23.64% and 8.00%. The results further showed that the
samples also contain appreciable amounts of Nb
2
O
5
and TiO
2
. Other mineral ores/phases
identified and quantified include MnO, Fe
2
O
3
, WO
3
, Th and U. Impurities/trace elements
such as Hf, Zn, Zr, Co, Pb, Rb, and Y were also determined.
Table 1: Mineralogical Analysis of Tantalum Ore Samples From 8 Different Locations in Nigeria.
OxideEgbeKomuNassara
wa
Agunreg
e
Baba
Ode
OfikiIgbo
Ijaye
Otu
TiO
2
%--3.81
±0.42
1.64
±0.37
2.34
±0.42
1.05
±0.33
20.36
±0.58
33.38
±0.67
MnO%4.15
±0.10
9.03
±0.17
5.80
±0.13
6.69
±0.14
8.62
±0.17
10.10
±0.18
3.46
±0.12
0.74
±0.09
Fe
2
O
3
%7.76
±0.18
3.51
±0.14
10.69
±0.23
7.37
±0.18
4.69
±0.16
2.86
±0.13
9.66
±0.21
9.70
±0.20
Ta
2
O
5
%59.58
±0.62
49.57
±0.54
46.15
±0.52
45.42
±0.49
42.00
±0.46
36.63
±0.42
23.64
±0.40
8.00
±0.17
Nb
2
O
5
%19.74
±0.17
29.18
±0.23
24.86
±0.20
31.18
±0.26
32.90
±0.26
37.48
±0.29
28.90
±0.29
22.43
±0.17
WO
3
%-0.38
±0.13
1.80
±0.14
---0.32
±0.09
0.17
±0.05
SnO
2
%--8.43
±1.97
-----
Hf%0.22
±0.05
0.26
±0.05
0.31
±0.05
0.18
±0.05
0.17
±0.05
0.11
±0.04
0.13
±0.04
-
Zn%-0.22
±0.03
0.09
±0.03
-0.09
±0.03
0.07
±0.02
--
Zr%0.31
±0.01
0.12
±0.01
0.26
±0.01
0.15
±0.01
0.22
±0.01
0.17
±0.01
0.06
±0.01
0.06
±0.01
Pb (ppm)489
±146
570
±146
1720
±195
-1010
±168
720
±146
--
Rb ppm)-120 ±47------
Y (ppm)--333 ±51-----
ThO
2
%0.340.030.150.020.020.050.030.01
U
3
O
8
%0.170.370.650.420.941.570.280.27
The elemental Ta content in the respective ore samples are 48.79%, 40.59%,
37.79%, 37.19%, 34.39%, 30%, 19.36% and 6.55% respectively for Egbe, Komu,
Nassarawa, Agunrege Baba Ode, Ofiki, Igbo Ijaye and Otu. An earlier work by Funtua
[11] put the Ta content in the central pegmatite region around Jos, Nassarawa and Jama’a
areas of central Nigeria at between 21 and about 30%. We note that this figure is
somehow less than the Nassarawa ore found to be about 38% in the current investigation.
The difference could probably be explained in terms of the diversity in the ore contents
from site to site and from ore vein to ore vein.
In terms of beneficiation, the density of Ta-Nb minerals allows concentration with
other heavy minerals by gravity methods; sluices, jigs, spirals and shaking tables are used
in conjunction with screen sizing; other processes, when used, are employed in the final
cleanup of gravity concentrates. Ta-Nb is separated from other heavy minerals by a
combination of high-tension electrostatic and high-intensity electromagnetic means.
Vol. 4, No. 2. Assessment Of Beneficiation Routes Of Tantalite Ores From Key Locations In Nigeria89
Concentrates from Nigerian placer deposits, which are worked primarily for cassiterite,
are dried and treated by magnetic separators to remove the magnetic constituents:
magnetite, ilmenite, columbite, monazite and magnetic cassiterite. The magnetic fraction
is then re-treated to separate the different minerals. Columbite, monazite and magnetic
cassiterite are weakly magnetic. Columbite and magnetic cassiterite are separated on air
flotation tables, whereas columbite and monazite are separated electrostatically [2].
Classification, screening, and desliming are employed as adjuncts, depending on the
composition of the ore. Treatment schemes vary from the most primitive hand methods to
extremely complex modern plants [22]. The liberation of values from waste must be
carried out with care, since all tantalum minerals are friable, and, according to Burt [10],
concentration efficiency decreases with decreasing particle size.
Gravity plant concentrate, grading approximately 25% Ta
2
O
5
is generally
upgraded to 50% in a clean-up plant. The Nb content in the ore is very important.
Concentrates suitable for further processing to recover Ta are generally required to
exceed 25% Ta
2
O
5
, with 50% combined Ta
2
O
5
and Nb
2
O
5
[10]. The ores below this level
of Ta
2
O
5
– Nb
2
O
5
content need to be enriched by methods discussed above. The tantalum
ores from Egbe, Komu, Nassarawa, Agunrege, Baba Ode and Ofiki all have Ta
2
O
5
-
Nb
2
O
5
combined content of about 70%, with the Ta
2
O
5
contents of over 25%. Thus these
ores can be subjected directly to clean-up operations, without pre-concentration or
primary concentration, for the removal of associated minerals. Many of the ores may
even be subjected to direct hydrometallurgical extraction processes without going
through clean-up operations. This is because their Ta
2
O
5
contents fall into categories for
which technologies have specifically been developed as raw materials of different origins
and grades [23], as shown in Table 2. The ore sample from Igbo Ijaye, which contains
23.64%Ta
2
O
5,
is rich enough for primary concentration, while the Otu ore sample, with
8%Ta
2
O
5
, would be enriched right from the pre-concentration stage (Table 3). These two
ore samples were however found to have a high TiO
2
content of 20.36% and 33.38%
respectively. Although the Otu figure is lower than that of a recently studied rutile sample
[24], it would be appropriate to treat the ore primarily for rutile r ecovery and then
secondary recovery for tantalite and niobite.
Table 2: Correlation between technology and raw material input [23]
The main associations of Ta
2
O
5
in the ores under investigation apart from Nb
2
O
5
and rutile are hematite, wolframite, uranium, cassiterite minerals as well as hafnium, zinc
and zirconium elements with other trace elements. We note that because T iO
2
and MnO
are paramagnetic and Fe
2
O
3
is ferromagnetic, they can be separated from the ore by
magnetic separation, whereas electrostatic separation can be employed to remove
cassiterite, hematite, ilmenite, tantalite, niobite and wolframite, which are electrically
TechnologyRaw Material Input%Ta/Ta
2
O
5
PyrometallurgyLow – Medium Grade Tin Slags2 – 10%Ta
2
O
5
ChlorinationAlloys, Scraps40 – 100%Ta
HydrometallurgyNatural Ores
Synthetic Concentrates
High Grade Tin Slags
20 – 40%Ta
2
O
5
20 – 40%Ta
2
O
5
>15%Ta
2
O
5
90Adetunji, A. R
*
; Siyanbola, W.O.; Funtua, I. I; Olusunle, S. O. O.;Vol. 4, No. 2
Afonja A.A and Adewoye, O.O
conducting, from the ore, leaving the non-conducting zirconium compounds in the
gangue. An earlier work by our group [25] had not been able to present the data shown in
this work on the impurity/trace element contents of the ores. Most of these elements
would go into the gangue during the elimination of the major constituents by the physical
and subsequent chemical methods.
Table 3: Recommended beneficiation routes for different grades of Ta
2
O
5
ores (Adapted from table
provided by Burt, [10])
Ta
2
O
5
Content (%)Sample Sources Content (%Ta
2
O
5
)Beneficiation Route
<10Out (8.00)Preconcentration (sizing, gravity
separation
10 – 25Igbo Ijaye (23.64)Primary concentration (jigs and sluices)
Hydraulic classification
Stage treatment (spirals, shaking tables)
>25Egbe (59.58), Komu (49.57,
Nassarawa (46.15), Agunrege
(45.42), Baba Ode (42.00), Ofiki
(36.63)
Concentrate clean-up (floatation,
leaching, magnetic or electrostatic
separation)
We note further that based on the characteristics of the ores analysed in this study,
a preliminary treatment for the samples would be fusion with K
2
CO
3
, which would
separate Sn, Fe, Mn and TiO
2
from the earth acids [26]. The approach in this case, is to
fuse at red heat with threefold excess of K
2
CO
3
, dissolve the fused mass in water, filter,
then precipitate the tantalum and niobium as the sodium salts. However, the number of
steps and amount of reagents required could make this process expensive. Gustion and
Pilloton [26] observed that direct dissolution of ores in HF as a clean-up operation would
not always produce adequate solution for separation by crystallization or liquid
extraction. Thus an alternative route to effect a rough purification is to fuse them with
caustic. The fused mass would then be leached with water to remove excess caustic, Sn
and W. The Ta and Nb, in the form of complex tantalates and niobates, are insoluble. An
acid leach would then dissolve Fe, Mn, Alkalies, and alkaline earths, leaving as a residue
a mixture of the acids, Ti, and traces of other contaminants. However, Gustion and
Pilloton [26] showed that six additional operations must be added to those required by
direct HF dissolution in order to accomplish this. These are caustic fusion, crushing of the
fusion mass, water leach, filtration of water-leach liquor, acid leach and filtration of acid-
leach liquor. The caustic fusion step is a high-labour operation. Furthermore, the labour
requirements for each filtration step are about the same as for direct dis solution, so that
filtration costs rise 100-200% over the direct dissolution operation. Leaching in water
requires about 50% as much labour as direct dissolution, but since leaching in acid is
comparable to direct dissolution the wet processing of the upgraded ores altogether
requires about 100-150% more labour than a direct dissolution operation. The
consideration of simplicity and cost of process therefore favours the direct dissolution of
the ores in HF to dissolve Ta, Nb, Fe, Ti, Mn and W. In practice, the advantages and
disadvantages of caustic fusion prior to the HF leach must be carefully evaluated. The
decision to use caustic fusion depends mainly on the type of ore that is treated and on the
method of separation used. If chemical and equilibria data were available for the
Vol. 4, No. 2. Assessment Of Beneficiation Routes Of Tantalite Ores From Key Locations In Nigeria91
dissolution process, it might be possible to maximize Ta and Nb dissolution with
minimum dissolution of the gangue material.
Finally, it is appropriate to m ention here that depending on the country or region
of exportation, some Ta/Nb minerals cannot be shipped out of their country of origin
because of their levels of radioactivity. The limits of allowed uranium and thorium oxide
contents are 0.1%U
3
O
8
and 0.1%ThO
2
[27]. All the ore samples under investigation
would not pass through such transportation regulation for their U
3
O
8
content while Egbe
and Nassarawa samples would not pa ss through as a result of their ThO
2
content. This
measure in principle could create a market problem for the tantalite ores originating from
these Nigerian deposits. Where there are ready buyers because of the strategic importance
of the end product, i.e. the tantalum metal/compounds, the crude ore is substantially
reduced in value because of their radioactive contents. However, Krismer and Hoppe [28]
have developed a process for the recovery of the non-radioactive metal compounds from
the ores containing complexes of U and Th. The gangue can now be treated to recover
uranium as an additional economic by-product [29].
CONCLUSION
The analysis of the tantalum ores from eight different notable deposits in Nigeria
using EDXRF spectrometry has shown that the Nigerian tantalum ores are of relatively
high quality and can therefore be subjected to direct processing for tantalum products
without the need for complex and costly preconcentration procedures. The consideration
of simplicity and cost of process favours the direct dissolution of the ores in HF. The
simultaneous evaluation of rutile and niobium in the ores allows for the assessment of the
suitability of the ores for primary/secondary recovery processes of rutile and niobium
products. In addition, the XRF technique offers the possibility of determining other major
constituents such as Fe, Mn, W, Th, U, Hf, Zn and Zr. The tantalite mineral can be
separated from the ore leaving the radioactive elements in the gangue, the secondary
recovery of which is an added economic advantage. The knowledge of the presence of
Co, Pb, Rb, and Y, as well as radioactive elements in the samples would assis t in
evaluating co-dissolved species as well as the development of appropriate beneficiation
routes for value-addition to the mineral in Nigeria.
ACKNOWLEDGEMENTS
The authors appreciate the support of the Engineering Materials Development
Institute, Akure, Nigeria for the part-sponsorship of this work. We are also grateful to the
Centre for Energy Research and Training, Ahmadu Bello University, Zaria, whose
facilities have been used in carrying out our analyses.
92Adetunji, A. R
*
; Siyanbola, W.O.; Funtua, I. I; Olusunle, S. O. O.;Vol. 4, No. 2
Afonja A.A and Adewoye, O.O
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