XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2631
150 µm and the non-passing fraction was grinded in a labo-
ratory ball mill, during 6 min. For each stage, 1 kg of +150
µm size fraction at 66% of solids in pulp was used with
10 kg of steel ball. The milled ore was wet sieved at 150 µm.
The passing fractions were all mixed and the non-passing
fraction was milled again until all the sample was milled.
After the milling stage, the sample was deslimed at 7 µm
using a two inches hydrocyclone that was operated at a pulp
flowrate of 2 m3·h–1, an inlet pressure of 2 bars, and a solids
percentage in pulp of around 5%. The underflow spigot
and vortex finder were respectively 3 mm and 11 mm. The
150+7 µm product constituted the flotation feed.
Chemical Analysis
After each flotation test, the floated and the non-floated
products were milled in a laboratory ring mill to obtain a
–10 µm powder. This powder was then analyzed by Energy
Dispersive X-Ray Fluorescence (ED-XRF) spectroscopy,
using a Thermo Scientific Niton ™ Xl3t portable XRF ana-
lyzer. The WO3 recovery values and grades given in this
study were determined by this method. The results were
corrected using a calibration curve obtained using stan-
dards previously analyzed by ICP-AES/ICP-MS at the
Service d’Analyses des Roches et des Minéraux (SARM-
CNRS, Nancy, France).
Flotation
Reagents
All reagents used were prepared using milli-Q water
(Veolia, France). Collectors used were dodecylamine and
oleate, provided by Fisher Scientific and Sigma Aldrich,
respectively. The amine was solubilized using HCl with a
1:1 molar ratio and the oleate with NaOH. Sodium silicate
(Na2SiO3) was used as depressant. It was supplied by Sigma
Aldrich and is of technical grade. pH modifiers used were
NaOH and H2SO4 and were of technical grade, provided
by Sigma Aldrich.
Tests
All tests were performed in an Agitair LA-500 apparatus
equipped with a 1.5 L cell. The cell was fed with 500 g of
ore, with a rotation speed of about 900 rpm. Both condi-
tioning and flotation were carried out at room tempera-
ture in the cell with solid ratios of 66 wt.% and 33 wt.%,
respectively. During conditioning, the pH was adjusted to
the desired value using pH modifiers. The pulp was equili-
brated at this pH value for 1 min. Then, the pulp was con-
ditioned with the depressant for 5 min and the collector
for 3 min. Flotation test started when the pulp was aer-
ated. The air flow rate was set at 0.27 m3·h–1 and the froth
was hand-scraped during 3 min. After the test, both floated
and non-floated products were recovered and dried at 80°C
overnight.
Pure Minerals
Pure crystals of scheelite and fluorite were acquired from
China and Mexico, respectively. They were hammered and
ground in an agate mortar, alternating with dry sieving to
prevent from over-grinding. Chemical analyses were carried
out by ICP-OES for major elements and ICP-MS for the
trace elements as well as by ISE for fluorine, at the Service
d’Analyses des Roches et des Minéraux (SARM-CNRS,
Nancy, France). After the grinding stage, the pure minerals
were dry sieved to produce a –20 µm size fraction that was
further ground in the agate mortar to obtain a –10 µm size
fraction for the electrophoretic measurements.
Electrophoretic Mobility Measurements
The electrophoretic mobility measurements were per-
formed on the pure above-described fluorite and scheelite
minerals, using a Zetameter V from CAD instruments.
From preliminary studies, it was determined that the min-
eral was equilibrated with the water phase in 15 min in
terms of electrophoretic mobility measurements. Hence,
all the experiments were conducted with a contact time of
15 min between the mineral and the solution before mea-
suring the electrophoretic mobility. For each experiment,
5 mg of pure mineral (10 µm size fraction) was conditioned
in 50 mL of a solution of KCl at a given concentration. The
pH value was set at the beginning of the conditioning and
maintained constant during all this phase by using HCl and
KOH. Deionized water was used (18 MΩ·cm–1) for all the
electrophoretic mobility measurements. The Smoluchowski
equation was used to calculate the zeta potential as a func-
tion of the electrophoretic mobility. For each experiment,
the value of zeta potential given is an average on 300 par-
ticles tracked by the apparatus.
RESULTS AND DISCUSSIONS
Mineralogical Characterization
The Tabuaço deposit features distinct ore types character-
ized by notable variations in geochemistry, mineralogical
composition, and average tungsten grade. The Tabuaço
skarn predominantly consisted of silicates (85 wt.%), pri-
marily calcium-bearing silicates such as vesuvianite, zois-
ite, and grossular, along with lesser amounts of feldspars
and quartz (see Figure 1b, c, d). The remaining portion
included fluorite, apatite, and scheelite. The texture was
characterized by massive coarse-grained structures, with
grain sizes ranging from a few micrometers to over 1 cm.
150 µm and the non-passing fraction was grinded in a labo-
ratory ball mill, during 6 min. For each stage, 1 kg of +150
µm size fraction at 66% of solids in pulp was used with
10 kg of steel ball. The milled ore was wet sieved at 150 µm.
The passing fractions were all mixed and the non-passing
fraction was milled again until all the sample was milled.
After the milling stage, the sample was deslimed at 7 µm
using a two inches hydrocyclone that was operated at a pulp
flowrate of 2 m3·h–1, an inlet pressure of 2 bars, and a solids
percentage in pulp of around 5%. The underflow spigot
and vortex finder were respectively 3 mm and 11 mm. The
150+7 µm product constituted the flotation feed.
Chemical Analysis
After each flotation test, the floated and the non-floated
products were milled in a laboratory ring mill to obtain a
–10 µm powder. This powder was then analyzed by Energy
Dispersive X-Ray Fluorescence (ED-XRF) spectroscopy,
using a Thermo Scientific Niton ™ Xl3t portable XRF ana-
lyzer. The WO3 recovery values and grades given in this
study were determined by this method. The results were
corrected using a calibration curve obtained using stan-
dards previously analyzed by ICP-AES/ICP-MS at the
Service d’Analyses des Roches et des Minéraux (SARM-
CNRS, Nancy, France).
Flotation
Reagents
All reagents used were prepared using milli-Q water
(Veolia, France). Collectors used were dodecylamine and
oleate, provided by Fisher Scientific and Sigma Aldrich,
respectively. The amine was solubilized using HCl with a
1:1 molar ratio and the oleate with NaOH. Sodium silicate
(Na2SiO3) was used as depressant. It was supplied by Sigma
Aldrich and is of technical grade. pH modifiers used were
NaOH and H2SO4 and were of technical grade, provided
by Sigma Aldrich.
Tests
All tests were performed in an Agitair LA-500 apparatus
equipped with a 1.5 L cell. The cell was fed with 500 g of
ore, with a rotation speed of about 900 rpm. Both condi-
tioning and flotation were carried out at room tempera-
ture in the cell with solid ratios of 66 wt.% and 33 wt.%,
respectively. During conditioning, the pH was adjusted to
the desired value using pH modifiers. The pulp was equili-
brated at this pH value for 1 min. Then, the pulp was con-
ditioned with the depressant for 5 min and the collector
for 3 min. Flotation test started when the pulp was aer-
ated. The air flow rate was set at 0.27 m3·h–1 and the froth
was hand-scraped during 3 min. After the test, both floated
and non-floated products were recovered and dried at 80°C
overnight.
Pure Minerals
Pure crystals of scheelite and fluorite were acquired from
China and Mexico, respectively. They were hammered and
ground in an agate mortar, alternating with dry sieving to
prevent from over-grinding. Chemical analyses were carried
out by ICP-OES for major elements and ICP-MS for the
trace elements as well as by ISE for fluorine, at the Service
d’Analyses des Roches et des Minéraux (SARM-CNRS,
Nancy, France). After the grinding stage, the pure minerals
were dry sieved to produce a –20 µm size fraction that was
further ground in the agate mortar to obtain a –10 µm size
fraction for the electrophoretic measurements.
Electrophoretic Mobility Measurements
The electrophoretic mobility measurements were per-
formed on the pure above-described fluorite and scheelite
minerals, using a Zetameter V from CAD instruments.
From preliminary studies, it was determined that the min-
eral was equilibrated with the water phase in 15 min in
terms of electrophoretic mobility measurements. Hence,
all the experiments were conducted with a contact time of
15 min between the mineral and the solution before mea-
suring the electrophoretic mobility. For each experiment,
5 mg of pure mineral (10 µm size fraction) was conditioned
in 50 mL of a solution of KCl at a given concentration. The
pH value was set at the beginning of the conditioning and
maintained constant during all this phase by using HCl and
KOH. Deionized water was used (18 MΩ·cm–1) for all the
electrophoretic mobility measurements. The Smoluchowski
equation was used to calculate the zeta potential as a func-
tion of the electrophoretic mobility. For each experiment,
the value of zeta potential given is an average on 300 par-
ticles tracked by the apparatus.
RESULTS AND DISCUSSIONS
Mineralogical Characterization
The Tabuaço deposit features distinct ore types character-
ized by notable variations in geochemistry, mineralogical
composition, and average tungsten grade. The Tabuaço
skarn predominantly consisted of silicates (85 wt.%), pri-
marily calcium-bearing silicates such as vesuvianite, zois-
ite, and grossular, along with lesser amounts of feldspars
and quartz (see Figure 1b, c, d). The remaining portion
included fluorite, apatite, and scheelite. The texture was
characterized by massive coarse-grained structures, with
grain sizes ranging from a few micrometers to over 1 cm.