1766 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
mineralogical and chemical analysis was conducted on the
sample. The chemical analysis revealed a gold content of
0.585g/t while XRD results revealed that more than 80%
of the sample was composed of quartz. A mineralogical
analysis conducted using QEMSCAN showed that 6.52%
of gold was present as free milling, 28.99% was associated
with pyrite while 6.52% was associated with quartz.
Leaching Studies
The leaching process involved studying the effect of ultra-
sound on the effect of physical and chemical parameters.
A comparative study using the conventional cyanide tech-
niques method represented by leaching in an agitated vessel
and bottle roll leaching were also applied.
Bottle Roll Leaching
Tests were conducted using ore slurries at 37% solids in
5 L bottles. The slurry was preconditioned using lime
(Ca(OH)2) to raise and maintain the pH between 10.5 and
11.5. Sodium cyanide was then added as the lixiviant at a
concentration of 5 kg/ton of ore. The bottles were then agi-
tated at a constant speed of 35 rpm on the rolling machine
at 25°C on all tests. The cyanidation process was carried out
for 24 hours and samples were collected after every 10 min-
utes for the first 2 hours and then at 4, 8, 12, 16, 20 and
24-hours. Dissolved oxygen (DO) levels were measured at
each and every interval. After a leaching period of 24 hours,
samples were collected then filtered using a filter press, to
separate the residue from the solution. The residues were
washed twice using distilled water then dried for 24 hours
in an oven at a temperature of 60°C. The gold content in
the leach residues and solution was analysed by fire assay
wet chemical analysis method using atomic absorption
spectrometry (AAS).
Cyanide Leaching in an Agitated Vessel
These cyanide leaching tests were conducted in a jacketed
5L agitated reactor at 25oC. The reactor was equipped with
pH, Eh and DO meters. The slurry was preconditioned
using lime (Ca(OH)2) to raise the pH and maintain it
between 10.5–11.5. Then sodium cyanide was added as
the main lixiviant at a concentration of 5 kg/ton of ore.
These tests were conducted in a continuous process and the
mixing speed maintained at 500 rpm. Pure oxygen gas was
provided directly into the leaching reactor at a flow rate of
10 ml/min.
Ultrasound Assisted Pre-Treatment and Leaching
Ultrasound leaching experiments were conducted in a jack-
eted reactor equipped with Hielscher UP400ST Ultrasonic
Processor with 400W maximum power rating and 24 kHz
frequency. The experimental setup consisted of an agitated
leaching vessel, equipped with pH, Eh, DO meter and an
ultrasonic probe. During these experiments, pure oxygen
gas was directly fed into the leaching vessel using a small
gas pipe. The pipe was connected to the oxygen bottle via a
regulator to control the oxygen flow rate. 400 ml of slurry
sample of gold leach tailings was added to the ultrasonic
reactor.
Before pre-treatment, the slurry was preconditioned
using lime (Ca(OH)2) to raise the pH and maintained
between 10.5–11.5. After preconditioning, the ultrasonic
generator was started and the air flow rate of air was main-
tained at10 ml/min. Ultrasound pre-treatment was hold for
30 minutes, 2 h, 5 h and 8h intervals. After every pre-treat-
ment interval, samples were collected then filtered using a
filter press, to separate the residue from the solution. The
residues were washed twice using distilled water then dried
for 24 hours in an oven at a temperature of 60°C. The gold
content in the leach residues and solution were analysed
by fire assay wet chemical analysis method using atomic
absorption spectrometry (AAS).
Sono-leaching process followed after pre-treatment
where sodium cyanide was added as the main lixiviant at a
concentration of 5 kg/ton of ore to the pre-treated samples.
Pure oxygen gas was injected directly into the sono-leach-
ing reactor at a flow rate of 10 ml/min. The sono-leaching
process was carried out for 24 hours and samples collected
after every 10 minutes for 2 hours and at 4, 8, 12, 16, 20
and 24-hours intervals.
Oxidation of Pyrite and Silicate Crystals Experiments
These tests were undertaken to verify the hypothesis that
the increased leaching efficiency of gold from the tailings in
the presence of the ultrasonic power were probably due to
physical impact on the pyrite and silicate minerals as most
of the gold in the sample was found associated with these
minerals. Pure pyrite and silicate crystals were however used
in the study instead of the gold tailings.
In pyrite and silicate oxidation experiments, the ultra-
sound power was set to 250 W, the distance between crystal
surface and ultrasound probe was 3 cm and the temperature
was controlled by thermostatic water bath. After 5 hours of
oxidation, the processed crystal was collected and analysed.
The surface morphology of pyrite and silicate slice before
and after sonication was characterized by scanning electron
microscope, SEM.
mineralogical and chemical analysis was conducted on the
sample. The chemical analysis revealed a gold content of
0.585g/t while XRD results revealed that more than 80%
of the sample was composed of quartz. A mineralogical
analysis conducted using QEMSCAN showed that 6.52%
of gold was present as free milling, 28.99% was associated
with pyrite while 6.52% was associated with quartz.
Leaching Studies
The leaching process involved studying the effect of ultra-
sound on the effect of physical and chemical parameters.
A comparative study using the conventional cyanide tech-
niques method represented by leaching in an agitated vessel
and bottle roll leaching were also applied.
Bottle Roll Leaching
Tests were conducted using ore slurries at 37% solids in
5 L bottles. The slurry was preconditioned using lime
(Ca(OH)2) to raise and maintain the pH between 10.5 and
11.5. Sodium cyanide was then added as the lixiviant at a
concentration of 5 kg/ton of ore. The bottles were then agi-
tated at a constant speed of 35 rpm on the rolling machine
at 25°C on all tests. The cyanidation process was carried out
for 24 hours and samples were collected after every 10 min-
utes for the first 2 hours and then at 4, 8, 12, 16, 20 and
24-hours. Dissolved oxygen (DO) levels were measured at
each and every interval. After a leaching period of 24 hours,
samples were collected then filtered using a filter press, to
separate the residue from the solution. The residues were
washed twice using distilled water then dried for 24 hours
in an oven at a temperature of 60°C. The gold content in
the leach residues and solution was analysed by fire assay
wet chemical analysis method using atomic absorption
spectrometry (AAS).
Cyanide Leaching in an Agitated Vessel
These cyanide leaching tests were conducted in a jacketed
5L agitated reactor at 25oC. The reactor was equipped with
pH, Eh and DO meters. The slurry was preconditioned
using lime (Ca(OH)2) to raise the pH and maintain it
between 10.5–11.5. Then sodium cyanide was added as
the main lixiviant at a concentration of 5 kg/ton of ore.
These tests were conducted in a continuous process and the
mixing speed maintained at 500 rpm. Pure oxygen gas was
provided directly into the leaching reactor at a flow rate of
10 ml/min.
Ultrasound Assisted Pre-Treatment and Leaching
Ultrasound leaching experiments were conducted in a jack-
eted reactor equipped with Hielscher UP400ST Ultrasonic
Processor with 400W maximum power rating and 24 kHz
frequency. The experimental setup consisted of an agitated
leaching vessel, equipped with pH, Eh, DO meter and an
ultrasonic probe. During these experiments, pure oxygen
gas was directly fed into the leaching vessel using a small
gas pipe. The pipe was connected to the oxygen bottle via a
regulator to control the oxygen flow rate. 400 ml of slurry
sample of gold leach tailings was added to the ultrasonic
reactor.
Before pre-treatment, the slurry was preconditioned
using lime (Ca(OH)2) to raise the pH and maintained
between 10.5–11.5. After preconditioning, the ultrasonic
generator was started and the air flow rate of air was main-
tained at10 ml/min. Ultrasound pre-treatment was hold for
30 minutes, 2 h, 5 h and 8h intervals. After every pre-treat-
ment interval, samples were collected then filtered using a
filter press, to separate the residue from the solution. The
residues were washed twice using distilled water then dried
for 24 hours in an oven at a temperature of 60°C. The gold
content in the leach residues and solution were analysed
by fire assay wet chemical analysis method using atomic
absorption spectrometry (AAS).
Sono-leaching process followed after pre-treatment
where sodium cyanide was added as the main lixiviant at a
concentration of 5 kg/ton of ore to the pre-treated samples.
Pure oxygen gas was injected directly into the sono-leach-
ing reactor at a flow rate of 10 ml/min. The sono-leaching
process was carried out for 24 hours and samples collected
after every 10 minutes for 2 hours and at 4, 8, 12, 16, 20
and 24-hours intervals.
Oxidation of Pyrite and Silicate Crystals Experiments
These tests were undertaken to verify the hypothesis that
the increased leaching efficiency of gold from the tailings in
the presence of the ultrasonic power were probably due to
physical impact on the pyrite and silicate minerals as most
of the gold in the sample was found associated with these
minerals. Pure pyrite and silicate crystals were however used
in the study instead of the gold tailings.
In pyrite and silicate oxidation experiments, the ultra-
sound power was set to 250 W, the distance between crystal
surface and ultrasound probe was 3 cm and the temperature
was controlled by thermostatic water bath. After 5 hours of
oxidation, the processed crystal was collected and analysed.
The surface morphology of pyrite and silicate slice before
and after sonication was characterized by scanning electron
microscope, SEM.