XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2633
K. I. Marinakis and Kelsall, 1987). Scheelite and fluorite
display different surface charges for pH values ranging from
2 to 5. This suggests that these minerals might have differ-
ent floatability behavior between pH 2 and 5. Furthermore,
scheelite exhibits a negative zeta potential, which indicates
that a cationic collector such as dodecylamine could be used
to achieve the floatability behavior of both scheelite and
fluorite for pH values between 2 and 5. From zeta potential
measurements, it is therefore suggested that scheelite could
be recovered using this flotation route, without promot-
ing fluorite flotation. Given the consistently high negative
zeta potential of scheelite across the entire pH spectrum,
cationic collectors hold substantial promise for scheelite
collection due to their known ability to adsorb through
electrostatic interactions. Among these cationic collectors,
amines are widely employed for the collection of silicates,
oxides, and various minerals, including scheelite. Some
studies in the literature have explored the use of amines
in scheelite flotation. Arnold and co-workers, for instance,
investigated the floatabilities of scheelite and calcite using
amines through microflotation and performed separation
tests on mixtures (Arnold et al., 1978). Despite the favorable
floatabilities of each mineral, they found that the flotation
separation of scheelite from calcite remained challenging
when employing amines. Additionally, Atademir and co-
workers achieved impressive scheelite recovery using dodec-
ylamine hydrochloride (Atademir et al., 1981). However,
this approach proved unsuitable for industrial applica-
tion due to the high silicate contents in conventional ores.
Subsequently, Hiçyìlmaz and co-workers explored various
amines and determined that amine D acetate, a dodecyl-
amine neutralized with acetate radicals, yielded acceptable
scheelite recoveries (91%) but demonstrated poor selectiv-
ity between scheelite and calcite (Hiçyìlmaz et al., 1993).
More recently, Gao and co-workers investigated the use of
dodecylamine (DDA) for the flotation separation of schee-
lite from calcite, focusing on adsorption mechanisms (Gao
et al., 2015). Notably, they revealed that, at low pH, elec-
trostatic bonds form between the positively charged amine
(NH3+ head group) and WO42– surface sites. Furthermore,
DDA exhibited superior adsorption on scheelite compared
to calcite, forming a more compact monolayer, and conse-
quently enhancing the contact angle of scheelite.
Flotation Tests
Flotation tests were carried out on 3 different dosages of
collector (121 g·t–1, 243 g·t–1, 487 g·t–1) at 3 different pH
values, namely 2, 3, and 4, for a fixed dosage in depressant
(4268 g·t–1). The WO3 recovery for all the above-mentioned
tests are displayed in Figure 3. From this figure, it can be seen
that the higher the collector dosage, the higher the recovery
is achieved. For a concentration in DDA of about 250 g·t–
1, the WO3 recovery decreases by about 40% compared to a
dosage of 500 g·t–1, considering a pH value of 4 (Figure 3).
Figure 2. Evolution of the zeta potential of fluorite (blue dots) and scheelite (red dots) as a function of
the pH in solution, after 15 min of equilibration, using KCl 0.1 mol·L–1 as background electrolyte. The
values are averaged on at least 300 tracked particles.
K. I. Marinakis and Kelsall, 1987). Scheelite and fluorite
display different surface charges for pH values ranging from
2 to 5. This suggests that these minerals might have differ-
ent floatability behavior between pH 2 and 5. Furthermore,
scheelite exhibits a negative zeta potential, which indicates
that a cationic collector such as dodecylamine could be used
to achieve the floatability behavior of both scheelite and
fluorite for pH values between 2 and 5. From zeta potential
measurements, it is therefore suggested that scheelite could
be recovered using this flotation route, without promot-
ing fluorite flotation. Given the consistently high negative
zeta potential of scheelite across the entire pH spectrum,
cationic collectors hold substantial promise for scheelite
collection due to their known ability to adsorb through
electrostatic interactions. Among these cationic collectors,
amines are widely employed for the collection of silicates,
oxides, and various minerals, including scheelite. Some
studies in the literature have explored the use of amines
in scheelite flotation. Arnold and co-workers, for instance,
investigated the floatabilities of scheelite and calcite using
amines through microflotation and performed separation
tests on mixtures (Arnold et al., 1978). Despite the favorable
floatabilities of each mineral, they found that the flotation
separation of scheelite from calcite remained challenging
when employing amines. Additionally, Atademir and co-
workers achieved impressive scheelite recovery using dodec-
ylamine hydrochloride (Atademir et al., 1981). However,
this approach proved unsuitable for industrial applica-
tion due to the high silicate contents in conventional ores.
Subsequently, Hiçyìlmaz and co-workers explored various
amines and determined that amine D acetate, a dodecyl-
amine neutralized with acetate radicals, yielded acceptable
scheelite recoveries (91%) but demonstrated poor selectiv-
ity between scheelite and calcite (Hiçyìlmaz et al., 1993).
More recently, Gao and co-workers investigated the use of
dodecylamine (DDA) for the flotation separation of schee-
lite from calcite, focusing on adsorption mechanisms (Gao
et al., 2015). Notably, they revealed that, at low pH, elec-
trostatic bonds form between the positively charged amine
(NH3+ head group) and WO42– surface sites. Furthermore,
DDA exhibited superior adsorption on scheelite compared
to calcite, forming a more compact monolayer, and conse-
quently enhancing the contact angle of scheelite.
Flotation Tests
Flotation tests were carried out on 3 different dosages of
collector (121 g·t–1, 243 g·t–1, 487 g·t–1) at 3 different pH
values, namely 2, 3, and 4, for a fixed dosage in depressant
(4268 g·t–1). The WO3 recovery for all the above-mentioned
tests are displayed in Figure 3. From this figure, it can be seen
that the higher the collector dosage, the higher the recovery
is achieved. For a concentration in DDA of about 250 g·t–
1, the WO3 recovery decreases by about 40% compared to a
dosage of 500 g·t–1, considering a pH value of 4 (Figure 3).
Figure 2. Evolution of the zeta potential of fluorite (blue dots) and scheelite (red dots) as a function of
the pH in solution, after 15 min of equilibration, using KCl 0.1 mol·L–1 as background electrolyte. The
values are averaged on at least 300 tracked particles.