3090 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
a DX concentration of 10 mg/L, a value difficult to mea-
sure due to being a very small angle. The results confirmed
the importance of oxygen in the reaction with MBS. As
shown in Figure 4, the red circles indicate a steeper slope in
the reduction of the pyrite contact angle, using the scheme:
aeration +MBS +DX. The goal was to oxidize the surface
to increase DX adsorption.
Figure 5 shows the flotation performance of pyrite
with the addition of DX and MBS, both individually and
combined, in the presence of PAX. Pyrite showed good
floatability throughout all depressant dosages studied, as
the hydrophobicity established by PAX was not inhibited
by the individual addition of depressants (see Figure 5a).
This confirms the behavior observed in Figure 3. In con-
trast, Figure 5b shows the floatability of pyrite with the
concentration of DX and MBS (combined effect) with
pulp oxygenation. With 150 mg/L of MBS and air, a rapid
reduction in floatability is observed, reaching 45.85% with
25 mg/L of DX. On the other hand, with 1000 mg/L of
MBS and air, a significant depression of pyrite is observed
(see Figure 5b). These results indicate that the combined
effect of the depressants significantly reduces the float-
ability of pyrite, which is not achieved with the individual
addition of reactants.
Figure 6 illustrates the ORP measurement during the
conditioning time of pyrite for contact angle and microflo-
tation tests. An increase in ORP is observed upon initiating
pulp aeration, followed by an increase after adding MBS
and a subsequent decrease. Ten minutes after adding DX,
no significant change in ORP is recorded. With the addi-
tion of PAX, ORP significantly decreases to approximately
–150 mV.
The ORP behavior can be explained by oxidation phe-
nomena. It has been reported that the sulfite ion oxidizes to
sulfate (reactions 1–3), and there are intermediate propa-
gation reactions where oxidizing radicals are formed (reac-
tions 4–6), as suggested by Connick et al. (1995) and Mu
et al. (2019).
2SO 2H S O H O
2 5
2-
2 3
2- +=++(1)
2O SO SO
3
2-
2 4
2-
ach +=
^
(2)
2 S O O SO H O
2 5
2-
2 4
2-
2 ach +=+
^(3)
SO3 O SO5
2^ach "+
--(4)
SO SO SO SO
5 3
2-
5
2-
3
"++
--(5)
The increase in ORP after adding MBS could be related
to the formation of radicals in reactions 4 and 5. Brandt
and Van Eldik (1995) and Mu and Peng (2019) proposed
the formation of these oxidizing radicals (*SO5−) and dem-
onstrated the formation of oxidized species on the mineral
surface. In this study, we suggest that MBS oxidizes the
Figure 5. Microflotation with DX and MBS at pH 8 in the presence of 1×10–3 M PAX. a) Pyrite floatability with individual
concentrations of depressants, b) Pyrite floatability with concentrations of DX at 150 and 1000 mg/L of MBS with pulp
aeration (150 mL/min of air)
a DX concentration of 10 mg/L, a value difficult to mea-
sure due to being a very small angle. The results confirmed
the importance of oxygen in the reaction with MBS. As
shown in Figure 4, the red circles indicate a steeper slope in
the reduction of the pyrite contact angle, using the scheme:
aeration +MBS +DX. The goal was to oxidize the surface
to increase DX adsorption.
Figure 5 shows the flotation performance of pyrite
with the addition of DX and MBS, both individually and
combined, in the presence of PAX. Pyrite showed good
floatability throughout all depressant dosages studied, as
the hydrophobicity established by PAX was not inhibited
by the individual addition of depressants (see Figure 5a).
This confirms the behavior observed in Figure 3. In con-
trast, Figure 5b shows the floatability of pyrite with the
concentration of DX and MBS (combined effect) with
pulp oxygenation. With 150 mg/L of MBS and air, a rapid
reduction in floatability is observed, reaching 45.85% with
25 mg/L of DX. On the other hand, with 1000 mg/L of
MBS and air, a significant depression of pyrite is observed
(see Figure 5b). These results indicate that the combined
effect of the depressants significantly reduces the float-
ability of pyrite, which is not achieved with the individual
addition of reactants.
Figure 6 illustrates the ORP measurement during the
conditioning time of pyrite for contact angle and microflo-
tation tests. An increase in ORP is observed upon initiating
pulp aeration, followed by an increase after adding MBS
and a subsequent decrease. Ten minutes after adding DX,
no significant change in ORP is recorded. With the addi-
tion of PAX, ORP significantly decreases to approximately
–150 mV.
The ORP behavior can be explained by oxidation phe-
nomena. It has been reported that the sulfite ion oxidizes to
sulfate (reactions 1–3), and there are intermediate propa-
gation reactions where oxidizing radicals are formed (reac-
tions 4–6), as suggested by Connick et al. (1995) and Mu
et al. (2019).
2SO 2H S O H O
2 5
2-
2 3
2- +=++(1)
2O SO SO
3
2-
2 4
2-
ach +=
^
(2)
2 S O O SO H O
2 5
2-
2 4
2-
2 ach +=+
^(3)
SO3 O SO5
2^ach "+
--(4)
SO SO SO SO
5 3
2-
5
2-
3
"++
--(5)
The increase in ORP after adding MBS could be related
to the formation of radicals in reactions 4 and 5. Brandt
and Van Eldik (1995) and Mu and Peng (2019) proposed
the formation of these oxidizing radicals (*SO5−) and dem-
onstrated the formation of oxidized species on the mineral
surface. In this study, we suggest that MBS oxidizes the
Figure 5. Microflotation with DX and MBS at pH 8 in the presence of 1×10–3 M PAX. a) Pyrite floatability with individual
concentrations of depressants, b) Pyrite floatability with concentrations of DX at 150 and 1000 mg/L of MBS with pulp
aeration (150 mL/min of air)