Ozah Blessing N, Shittu Samuel A, John Ade Ajayi,AlabiOladunni O, Akoja Ayo

1. International Journal of Engineering and Techniques - Volume 5 Issue 6 ,December 2019
ISSN: 2395-1303 http://www.ijetjournal.org Page 1
Determination of Liberation Size of Iperindo -
Ilesha (Nigeria) Lode Gold Ore and Amenability
to Froth Flotation.
Ozah Blessing N.1
, Shittu Samuel A.2
, John Ade Ajayi.3
,AlabiOladunni O.4
, Akoja Ayo5
12345
(Federal University of Technology, Akure, Ondo State, Nigeria)
Corresponding Author:
Ozah Blessing N.
Email Address: ozah_blessing@yahoo.com, GSM: +234 (0) 8130633220
zzz
RESEACH ARTICLE OPEN ACCESS
Abstract:
This research determined the liberation size of Iperindo lode gold ore, Osun State, Nigeria and assessed
its amenability to froth flotation technique. 50 kg crude sample of the ore was sourced, crushed, and
sampled for chemical analysis using atomic absorption spectrometer (AAS). The crushed sample was
subjected to fractional sieve size analysis using root 2 series sieve sets ranging from 500 – 45 µm to
determine the liberation size. The size /assay analyses carried out established that the actual and
economic liberation sizes of the ore were 45µm and 250 µm respectively.Thereafter, froth flotation
technique was carried out at 45 µm while varying the collector dosage between 0.2 – 0.3 mol/dm3
. The
chemical analysis result revealed that the ore assayed 4.10 ppm Au. Recovery was observed to increase
with increasing collector dosage while optimum recovery of 78.93 % at concentrate grade of 115 ppm Au
was obtained at 0.3 mol/dm3
PAX, 1200 rpm stirring speed,and pH 9. These paramters will be adopted in
subsequent processing to extract gold from Iperindo Ilesha lode gold deposit.
Keywords — Iperindo lode gold ore, Beneficiation, Froth flotation, Liberation size and Atomic Absorption
Spectrometer (AAS)

2. International Journal of Engineering and Techniques - Volume 5 Issue 6 ,December 2019
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I. INTRODUCTION
Gold ores are found in alluvial and lode deposits
as free milling ores from which gold is recoverable
by amalgamation. Also, refractories ores such
astellurides and auriferous sulphides yield gold by
complex processing routes. More so, chemically
bondedgold ores are relatively rare, some of which
include calaverite, sylvanite, petzite, nagyagite, and
krennerite [1]. Gold ores containing carbonaceous
materials are, however, difficult to process because
gold present in the ores gets easily absorbed on the
carbon which subsequently reports in the tailings
[2]. Therefore, to foster effective separation, it is
pertinent that the gold must be liberated from
associative gangue minerals at a size where these
minerals are distinct and finely distributed within
the ore matrix.The process adopted to effect
liberation is termed comminution; which
encompasses operations undertaken towards
reducing ore to a size where the mineral
assemblages therein are distinct and subsequently,
separated via beneficiation processes [3]. The
earliest stage of comminution is often referred to as
blasting a process carried out to make the excavated
material easier to handle by scrapers, conveyors,
and ore carriers, and to produce material of
controlled particle sizes [4]. Generally, placer
deposits require no comminution but lode deposits
do priorto particle size analysis which is done to
establish the size where optimum separation occurs.
In order to effect effective and efficient separation,
it is highly pertinentto determine the quality of
grinding as well as the degree of liberation of the
valuable mineral from the gangue at various particle
sizes. This would make known the size where the
grains exhibit a high degree of liberation so as to
prevent under-grinding and over-grinding while
increasing the recovery of the gold from the ore [5].
The determination of the liberation size of an ore
is paramount in any process design. Therefore, this
research establishes the size where optimum
liberation of the gold from the associated gangue
minerals is towards maximizingrecovery.
Consequently, this will facilitate efficient
grindability of the ore, reduce the amount of fines
produced and also decrease the operating cost
associated with comminution of the ore.
A. Froth Flotation
Beneficiation of gold ore has mainly been
carried out via processes such as amalgamation and
cyanidation [6]. The later processes employ the use
of chemicals which pose extensive detrimental
effects on the ecosystem ([7], [8], [9]). Hence, the
need to explore alternatives such as froth flotation
which will yield increased gold recovery while
enhancing environmental sustainability.Froth
flotation is a physicochemical process that involves
selectively separating hydrophobic materials from
hydrophilic. It utilizes the differences in the surface
properties of the material through the use of
chemical conditioning agents [10].Gold grain
surfaces are often coated with a hydrophobic
organic layer or iron oxides coating and some are
leached free of impurities (such as silver) leaving a
rim of pure gold, all of these render the surface
hydrophobic. Froth flotation has the potential to be
used for the recovery of fine gold [11].
II. GEOLOGICAL SETTING OF STUDY
AREA
Gold occurs in placers (alluvial and eluvial) and
primary veins from different parts of the schist belts
in the northwest and southwest of Nigeria [6].
Though smaller occurrences exist beyond these
major areas, more predominant regions are shown
in Fig. 1. The Ilesha schist belt occurs in
Southwestern Nigeria and is famous for its
alluvial and lode gold mineralization. This belt is
separated into two different lithological
groupings by the Ifewara-Zuugeru major fault. In
the western half of the belt, the lithology
includes amphibolites, hornblende gneiss, biotite
schist, talc,tremolite schist, quartzmuscovite,
Pan-African granite, and pegmatite.Alluvial gold
deposits occur at Igun and Itagunmodi in this
section of Ilesha schist belt within the
amphibolite terrain. In the eastern section of

3. International Journal of Engineering and Techniques - Volume 5 Issue 6 ,December 2019
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Ilesha schist belt, the terrain consists of granite
gneisses, migmatite gneiss, quartz-muscovite
schist, and PanAfrican granite. A system of
auriferous quartz veins occurs in the biotite
granite gneiss between Odo and Iperindo villages
in this section of the schist belt [12].
III. RESEARCH METHODOLOGY
A. Sample Collection and Preparation
Samples of the ore were sourced from Iperindo-
Ilesha, Osun State goldfield deposit site which is
about 23 square kilometers having latitude
7ᵒ
35’0’’E and longitude 4ᵒ
30’0’’N.The samples
were randomly collected from different pits
ofdimension 3 m x3 m x 5 m so as to have a true
representation of the entire bulk ore within the
study area. Samples collected were crushed using
a sledgehammer to size range of 2–4 cm,
followed by further reduction to 1 mm using a
Denver Laboratory Jaw Crusher (Model –
D12).The resulting pulverized ore sample was
homogenized properly and sampled towards
particle size analysis.
B. Liberation Size Determination
In view of ascertaining the liberation size of
Iperindo-Ilesha gold ore, fractional sieve size
analysis technique was adopted. The sieves were
properly cleaned to avoid contamination of the
mineral sample and stacked in conformity with √2
seriesfrom 500 – 45m [6]. 100 g crude sample was
charged into the upper sieve (500m), tightly lidded
and agitated for 30 minutes using an Automated
Sieve Shaker (Model: Endecott AS400 control).
Consequently, stratification of the ore particles into
different fractions occurs as they fall through the
sieves.The analysis was done for three consecutive
times; the weights retained on the sieves were
measured and averaged. Samples were randomly
selected for chemical analysis.
C. Chemical Analysis of Sieve Fractions
Atomic Absorption Spectrometer (Model: Nov 300)
was employed to chemically analyze the sieve
fractions. The machine was operated at 40 kV and
18 mA. The samples were pulverized and a
representative sample each of weight 2 g was taken
and properly digested in aqua regia (solution of
concentrated HNO3HCl) in the ratio 3:1to ensure
the removal of organic impurities which may
interfere with the analysis. The digested samples
were heated and then filtered. The filtrates were
transferred to 100 ml volumetric flasks, diluted to
the mark with distilled water and then analyzed for
the presence of gold and other elements such as
manganese, iron, and copper.
D. Froth Flotation of Iperindo Lode Gold Ore
Froth flotation experiment was carried out using
Denver flotation machine. 100g of Iperindo lode
gold ore of particle size -65µm was measured
separately into the Denver flotation cell. The ore
was mixed with 2.5L of distilled water and agitated
to form a pulp. The pH of the pulp was determined
using pH meter and the pulp wasconditioned by
adding drops of lime solution to a pH of 9, to
depress pyrite. 0.2ml of methyliso-butyl carbinol
was added to the pulp in the flotation cell. The pulp
was agitated by an impeller in the flotation cell at
an impeller speed of 1200rpm for 3 minutes.
0.20mol/dmpotassium amyl xanthate (PAX) was
added to the pulp and it was agitated by the
flotation cellimpeller for another 3 minutes. Drops
Figure 1: Gold Mineralization in Nigeria and Study Area Location [13]

4. International Journal of Engineering and Techniques - Volume 5 Issue 6 ,December 2019
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of methyl iso-butyl carbinol were added, the pulp
was further agitated for 2 minutes and the air valve
of the flotation cell was opened to introduce air in
the pulp to produce froth. The froth was collected,
decanted and the residual filtrate was dried in an
oven. The process was repeated at various collector
dosages (0.2 mol/dm3
, 0.25 mol/dm3,
and 0.3
mol/dm3
). The respective froth produced in each
case was collected, dried in an oven and weighed.
The gold concentrates obtained from the froth
flotation experiments were analyzed to determine
the gold content using AAS located. The percentage
recovery and grade of gold concentrate from
Iperindolode gold ore is presented in Table 4 and
Fig. 4.
IV. RESULTS AND DISCUSSION
A. Results
Experimental results obtained are presented below.
Table 1: Chemical Composition of the As-mined Iperindo Lode Gold Ore
Sample Au
(ppm)
Mn
(ppm)
Fe
(ppm)
Cu
(ppm)
S(ppm)
Gold
Ore
4.100 29.970 4129.090 6.880 0.159
Table 2: Particle Size Analysis of Iperindo-Ilesha Gold Ore
Particle Size
Range
(µm)
Nominal Aperture
Size
(µm)
Weight
Retained
(g)
% Weight
Retained
Cumulative %
Weight Retained
Cumulative %
Weight
Passing
+500 500 19.23 19.56 19.56 80.44
-500+355 355 9.77 9.94 29.50 70.50
-355+250 250 11.13 11.32 40.82 59.18
-250+180 180 8.03 8.17 48.99 51.01
-180+125 125 14.87 15.11 64.10 45.90
-125+90 90 8.33 8.47 72.57 27.43
-90+63 63 16.97 17.26 89.83 10.17
-63+45 45 9.37 9.53 99.36 0.64
-45 - 0.63 0.64 100.00 0.00
98.33 100
Table 3: Chemical Analysis of Size Fractions of Iperindo-Ilesha Gold Ore
Nominal Aperture (µm) Au (ppm) Mn (ppm) Fe (ppm) Cu (ppm)
500 10.55 0.0750 4.0168 0.0050
355 15.10 0.2930 6.3300 0.0190
250 20.50 1.0600 7.4360 0.0250
180 30.40 1.2648 10.5860 0.0380
125 47.60 0.2010 38.8630 0.0090
90 30.50 0.0390 21.0140 0.3330
63 28.70 0.2180 41.0080 0.0990
45 103.00 0.2290 55.5666 1.0590

5. International Journal of Engineering and Techniques - Volume 5 Issue 6 ,December 2019
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Fig. 2: Log-Plot of Cumulative % Weight Passing and Retained against Sieve Size (µm)
Fig. 3: Predominant metals in Iperindo-Ilesha Gold Ore
Table 4: Percentage Recovery of Iperindo Lode Gold
S/N Parameter Used Feed Weight
(g)
Feed Assay
(ppm)
Wt. of conc (g) Conc Assay
(ppm)
Recovery (%)
1 0.2 mol/dm3
PAX
100 103 65.7 93.10 68.43
2 0.25mol/dm3
PAX
100 103 66.1 116.25 74.60
3 0.3mol/dm3
PAX
100 103 70.5 115.32 78.93
0
20
40
60
80
100
120
10 100 1000
WeightPercentage
Sieve Size (µm)
Cumulative % Weight Retained
Cumulative % Weight Passing
0
20
40
60
80
100
120
500 355 250 180 125 90 63 45
partspermillion
Sieve Size (µm)
Au (ppm) Mn (ppm) Fe (ppm) Cu (ppm)

6. International Journal of Engineering and Techniques - Volume 5 Issue 6 ,December 2019
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Fig. 4: Effect of Collector Concentration on Recovery of Gold
B. Discussion
i. Chemical composition of the ore
The results of chemical analysis of crude Iperindo-
Ilesha lode gold ore usingatomic absorption
spectrophotometer (AAS) are presented inTable 1.
The analysis affirms the presence of gold in the ore
assaying 4.10 ppm. According to the U.S. DOI,
Bureau of Mines, the gold assay of Iperindo lode
gold ore deposit is above the minimum value (0.69-
1.37ppm) required for the deposit to be considered
economically worthwhile for mining and processing
[14]. In the same vein, the world gold council
defines a high-grade mine as a mine having a gold
grade between 8 and 10 ppm, while a low-grade
mine is such having a gold grade of 1 to 4 ppm but
both mines can be considered valuable [15]. On this
premise, Iperindo-Ilesha lode gold ore can be said
to be a low-grade ore assaying about 4.10 ppm.
Thus, there is a need for upgrading of the ore
deposit.
ii. Size/assay analysis of the ore
Result obtained from the fractional sieve size
analysis of Iperindo-Ilesha gold ore is presented in
Table 2. It can be deduced that considerable
retention in weight of the ore particles occurred at
sizes 500 µm, 125 µm and 63 µm at relative
percentages of 19.56 %, 15.11 % and 17.26 %
respectively. These sizes represent the mesh of
grind of Iperindo-Ilesha gold ore. However, the log-
chart of percentage cumulative weight retained and
passing against sieve size as shown in Fig.2
revealed that 50 % retention of the ore particles was
achieved at 250 µm, which also indicates the point
where the two curves intercept. As deduced from
the plot, the two curves are mirror-images of each
other which symbolizes a concurrent relationship
between weight retained and passing. According to
[1], the size at which 50 % retention or passing is
achieved for a specific ore is termed the economic
liberation size. Thus, it can be inferred that the
economic liberation size of Iperindo-Ilesha gold ore
is 250 µm. However, the economic liberation size is
insufficient to describe the size where optimal
66
68
70
72
74
76
78
80
0,1 0,2 0,3 0,4
%AuRecovery
collector dosage (mol/dm³)

7. International Journal of Engineering and Techniques - Volume 5 Issue 6 ,December 2019
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liberation of gold from associative gangue occurs
towards separation.
Table 3 presents the elemental composition in parts
per million (ppm) of the ensuing sieve fractions of
Iperindo-Ilesha gold ore. The major elemental
constituents of the fractions as shown in Fig. 3 were
Gold (Au) and Iron (Fe) while other elements exist
in trace amount. The predominance of gold and iron
in all the sieve fractions depict that the gold ore is
of auriferous deposit[12]. From Fig. 3, it is quite
evident that the optimal value of gold assay (103
ppm) was achieved at 45 µm. This depicts that high
degree of liberation of the gold mineral from other
minerals of Fe, Mn, and Cu was achieved at this
size. Thus, this size represents the actual liberation
size of Iperindo-Ilesha gold ore. Subsequent
processing of the gold ore at this size would yield
optimal recovery at a favorable assay.
iii. Effect of Collector Concentration on
Recovery of Gold
Fig. 4 illustrates the effect of collector
concentration variation on gold concentrate
recovery. The graph in Fig. 4 shows that gold
concentrate recovery increases with increasing
collector concentration. The plots reveal that PAX
as collector, at a concentration of 0.3mol/dmthe
highest recovery of 78.93 % while collector
concentration of 0.2mol/dm3
and 0.25 mol/dm3
gave
a recovery of 68.43 % and 74.60 % respectively.
This observation reinforces the opinion of [16] that
an increase in the collector concentration increases
recovery of gold
concentrate from Ilesha lode gold ore.
CONCLUSION
The chemical analysis of the crude ore affirms the
presence of gold in the ore assaying 4.10
ppm.Themesh of grind of Iperindo-Ilesha gold is
250 µm, this size depicts the size where 50 %
retention in weight of the ore particle was
achieved. Also, AAS analysis revealed the actual
liberation size of the ore to be 45 µm which is
the size having the optimal gold assay of 103
ppm. Furthermore, the gold ore was observed to
be of auriferous deposit due to the predominance
of elemental iron in the ore matrix. Subsequent
processing of Iperindo-lode gold at 45µm was
carried out using froth flotation process and a
recovery of 78.93 % was obtained at 0.3 mol/dm3
of PAX. The resulting grade and recovery shows
that the gold ore is amenable to beneficiation by
froth flotation.
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