XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2127
After each treatment, the treated slurry was subsequently
filtered and dried at 40° C in an oven for 24 h. Then, the
powders obtained was analyzed by FT-IR.
Regrinding Treatment
Regrinding treatment was used to study the effect of
regrinding on the collector’s removal from pyrite surface.
Pyrite was first grinded using an Agate mortar (RETSCH-
StaLab RM 200) to obtain 1 g of pyrite (P80= 80 um).
Then, it was mixed with a solution of each collector (PAX
or DTP), prepared at a concentration of 1 × 10–3 mol/L,
at natural pH. After 15 minutes of stirring, the slurry was
washed once with deionized water, and filtered. Then, the
solid residue obtained in the previously step was mixed
with water followed by the regrinding to get P80=30 μm.
After each treatment, the treated slurry was subsequently
filtered and dried at 40° C in an oven for 24 h. Then, the
powders obtained was analyzed by FT-IR.
Microflotation Test
The Microflotation tests were carried out using a modi-
fied Hallimond type flotation cell. The procedure was con-
ducted as follows: first it was conducted the flotation of
pyrite, the objective was to get high recoveries of pyrite.
Then, this activated pyrite was pre-treated using ultrasonic/
H2O2/regrinding, followed by the depression of this pre-
treated pyrite using NaOH. Finally, the recoveries were
calculated to evaluate the performance of each methodol-
ogy conducted. The operational parameters for pyrite flota-
tion were as follows: 1 g of fresh pyrite with a size fraction
of –75+150 µm was used per test, 150 mL cell volume,
nitrogen flow rate (N2= 33 mL/min), and magnetic stir-
ring between 1000 and 1200 rpm. The conditioning time
was 15 min per collector, performed into a 200 mL beaker.
Subsequently, the slurry was transferred to the Hallimond
tube for flotation. The flotation time was 3 min at natural
pH. A high collector concentration (1×10–3 mol/L) was
used. The tests were performed in duplicate. Then, the con-
centrate obtained was used to conduct the pre-treatment
with ultrasonic/H2O2/regrinding (same procedures used
for adsorption test), but using the best conditions identity
from these pre-treatments. The optimal parameters were:
for ultrasonic 20 min, for H2O2 concentration 0.1 M and
the regrinding was conducted using the same parameters
as mentioned before. Finally, this pre-treated pyrite con-
centrated was depressed. The operational parameters for
depression were as follows: 1 g, size fraction of –75+150 µm
was used per test, 150 mL cell volume, air flow rate (80 mL/
min), and magnetic stirring between 1000 and 1200 rpm.
Then, the pH was added, the conditioning time was 3 min
to get a pH=11.5 with NaOH (0.1M). Finally, the collec-
tor (2×10–5 mol/L) was added, the conditioning time was 3
min. This procedure was performed into a 200 mL beaker.
Subsequently, the slurry was transferred to the Hallimond
tube for flotation. The flotation time was 3 min. The tests
were performed in duplicate. Figure 1 shows the flowsheet
of the microflotation tests.
RESULTS
Ultrasonic Treatment
The effect of ultrasonic conditioning on pyrite and
pyrite treated with PAX and DTP collectors was assessed
through the analysis of oxygen content. Figure 2 shows
changes in the oxygen content when pyrite interacts with
ultrasonic (pyrite+ultrasonic), and when pyrite inter-
acts with collector, and is further treated with ultrasonic
(pyrite+PAX+ultrasonic and pyrite+DTP+ultrasonic).
Water+ultrasonic was used as a reference. According to
the ultrasonic phenomena there are gases and water vapor
inside the sonic cavitation bubble. Therefore, after short
period of ultrasonic these bubbles break up generating
•OH and •H free radicals. These radicals are responsible for
the generation of secondary reactions such as H2O2, this
peroxide is unstable and generates nascent oxygen, this is
highly reactive and react easily with the minerals present in
the pulp reducing the oxygen content of the pulp.
In the Figure 2a, in the sample water+ultrasonic (black
line) it can be seen that over the time the oxygen content
increases due the nascent oxygen available in the solution.
Nevertheless, once the pyrite in water interacts with the
ultrasonic (red line), there is a decreasing trend in the oxy-
gen content, this demonstrated that the oxygen available
in the solution is reacting with pyrite surface through oxi-
dation reactions (see equations 1, 2 and 3 in introduction
section). Therefore, these reactions produce hydrophilic
species such as SO42– and ferric hydroxide, which can pre-
cipitate, and it is responsible for pyrite depression due to
the formation of a passivation layer on the pyrite surface.
According to this, long periods of ultrasonic are feasible to
oxidize and depress pyrite. Then, when PAX +ultrasonic
(blue line) interacts, there is a decrease in oxygen content
but not as high as the pyrite+ultrasonic. This could be
due to the decomposition of xanthate due to the oxida-
tion with H2O2 generated during the ultrasonic treatment.
This H2O2 enables the conversion of xanthate into carbon-
ate and sulfate species. Therefore, the oxygen available is
used for the formation of these species reducing the oxygen
content. Then, in the system pyrite+PAX+ultrasonic (green
line) there is a marked decreasing trend of oxygen con-
tent. Here another type of interaction could be happening
After each treatment, the treated slurry was subsequently
filtered and dried at 40° C in an oven for 24 h. Then, the
powders obtained was analyzed by FT-IR.
Regrinding Treatment
Regrinding treatment was used to study the effect of
regrinding on the collector’s removal from pyrite surface.
Pyrite was first grinded using an Agate mortar (RETSCH-
StaLab RM 200) to obtain 1 g of pyrite (P80= 80 um).
Then, it was mixed with a solution of each collector (PAX
or DTP), prepared at a concentration of 1 × 10–3 mol/L,
at natural pH. After 15 minutes of stirring, the slurry was
washed once with deionized water, and filtered. Then, the
solid residue obtained in the previously step was mixed
with water followed by the regrinding to get P80=30 μm.
After each treatment, the treated slurry was subsequently
filtered and dried at 40° C in an oven for 24 h. Then, the
powders obtained was analyzed by FT-IR.
Microflotation Test
The Microflotation tests were carried out using a modi-
fied Hallimond type flotation cell. The procedure was con-
ducted as follows: first it was conducted the flotation of
pyrite, the objective was to get high recoveries of pyrite.
Then, this activated pyrite was pre-treated using ultrasonic/
H2O2/regrinding, followed by the depression of this pre-
treated pyrite using NaOH. Finally, the recoveries were
calculated to evaluate the performance of each methodol-
ogy conducted. The operational parameters for pyrite flota-
tion were as follows: 1 g of fresh pyrite with a size fraction
of –75+150 µm was used per test, 150 mL cell volume,
nitrogen flow rate (N2= 33 mL/min), and magnetic stir-
ring between 1000 and 1200 rpm. The conditioning time
was 15 min per collector, performed into a 200 mL beaker.
Subsequently, the slurry was transferred to the Hallimond
tube for flotation. The flotation time was 3 min at natural
pH. A high collector concentration (1×10–3 mol/L) was
used. The tests were performed in duplicate. Then, the con-
centrate obtained was used to conduct the pre-treatment
with ultrasonic/H2O2/regrinding (same procedures used
for adsorption test), but using the best conditions identity
from these pre-treatments. The optimal parameters were:
for ultrasonic 20 min, for H2O2 concentration 0.1 M and
the regrinding was conducted using the same parameters
as mentioned before. Finally, this pre-treated pyrite con-
centrated was depressed. The operational parameters for
depression were as follows: 1 g, size fraction of –75+150 µm
was used per test, 150 mL cell volume, air flow rate (80 mL/
min), and magnetic stirring between 1000 and 1200 rpm.
Then, the pH was added, the conditioning time was 3 min
to get a pH=11.5 with NaOH (0.1M). Finally, the collec-
tor (2×10–5 mol/L) was added, the conditioning time was 3
min. This procedure was performed into a 200 mL beaker.
Subsequently, the slurry was transferred to the Hallimond
tube for flotation. The flotation time was 3 min. The tests
were performed in duplicate. Figure 1 shows the flowsheet
of the microflotation tests.
RESULTS
Ultrasonic Treatment
The effect of ultrasonic conditioning on pyrite and
pyrite treated with PAX and DTP collectors was assessed
through the analysis of oxygen content. Figure 2 shows
changes in the oxygen content when pyrite interacts with
ultrasonic (pyrite+ultrasonic), and when pyrite inter-
acts with collector, and is further treated with ultrasonic
(pyrite+PAX+ultrasonic and pyrite+DTP+ultrasonic).
Water+ultrasonic was used as a reference. According to
the ultrasonic phenomena there are gases and water vapor
inside the sonic cavitation bubble. Therefore, after short
period of ultrasonic these bubbles break up generating
•OH and •H free radicals. These radicals are responsible for
the generation of secondary reactions such as H2O2, this
peroxide is unstable and generates nascent oxygen, this is
highly reactive and react easily with the minerals present in
the pulp reducing the oxygen content of the pulp.
In the Figure 2a, in the sample water+ultrasonic (black
line) it can be seen that over the time the oxygen content
increases due the nascent oxygen available in the solution.
Nevertheless, once the pyrite in water interacts with the
ultrasonic (red line), there is a decreasing trend in the oxy-
gen content, this demonstrated that the oxygen available
in the solution is reacting with pyrite surface through oxi-
dation reactions (see equations 1, 2 and 3 in introduction
section). Therefore, these reactions produce hydrophilic
species such as SO42– and ferric hydroxide, which can pre-
cipitate, and it is responsible for pyrite depression due to
the formation of a passivation layer on the pyrite surface.
According to this, long periods of ultrasonic are feasible to
oxidize and depress pyrite. Then, when PAX +ultrasonic
(blue line) interacts, there is a decrease in oxygen content
but not as high as the pyrite+ultrasonic. This could be
due to the decomposition of xanthate due to the oxida-
tion with H2O2 generated during the ultrasonic treatment.
This H2O2 enables the conversion of xanthate into carbon-
ate and sulfate species. Therefore, the oxygen available is
used for the formation of these species reducing the oxygen
content. Then, in the system pyrite+PAX+ultrasonic (green
line) there is a marked decreasing trend of oxygen con-
tent. Here another type of interaction could be happening