3088 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
The study assessed both the individual and combined
effects of adding MBS and DX. In the mixed reagent study,
the impact of aeration (150 mL/min) in the presence of
MBS was analyzed to enhance its oxidizing effect, followed
by the addition of DX.
The pulp’s pH was adjusted to 8 using HCl and NaOH
solutions. Then, the depressants (MBS, DX) were added
and maintained in contact for 10 minutes before measur-
ing the contact angle. When both depressants were used,
conditioning was first performed with MBS and then with
DX. Finally, PAX was added at the desired concentration
and allowed to react for 5 minutes.
Throughout the conditioning process, the oxidation-
reduction potential (ORP) of the pulp was continuously
monitored using a platinum electrode and a saturated Ag/
AgCl reference. The procedure was carried out in a glass
cell, introducing a 1 mm diameter bubble using a Hamilton
0.10 mL syringe (series 700) with a hooked tip. The shadow
of the bubble in equilibrium with the crystal and solution
was photographed, then processed with ImageJ software
and the Contact-Angle plugin (Brugnara, 2006) to deter-
mine the contact angle. Three bubbles were placed per
measurement, and the average angle was reported as the
result. Figure 2 illustrates the equipment used. In addition,
all measurements were consistently conducted at a constant
temperature of 25°C to ensure environmental stability dur-
ing the experiments.
Microflotation Studies
Microflotation studies were conducted using a Hallimond
tube. One gram of pyrite with particle sizes of –100+75
micrometers was used in a 100 mL suspension of deionized
water. The mineral was conditioned following the same
reagent addition sequence as in the contact angle tests
that is, depressants were added first, followed by the col-
lector (Lopéz-Valdivieso et al., 2018). After the condition-
ing period, the dispersions were transferred to the flotation
tube and floated for 1 minute with a constant flow of 30
mL/min of high-purity nitrogen. At the end of the test,
floatability was calculated by weight difference.
RESULTS AND DISCUSSION
Figure 3 displays the contact angle of pyrite as a function
of the addition of MBS and DX depressants, applied indi-
vidually and without a collector. Without a depressant, the
natural contact angle of pyrite is higher, decreasing progres-
sively with the increase in the MBS or DX dosage. At a pH
of 8, the natural contact angle of pyrite decreases in the
presence of MBS, reducing from 54.70° to 42° at the maxi-
mum addition. Similarly, the presence of DX at 300 mg/L
results in a maximum reduction of about 29°, being slightly
more effective than MBS in decreasing the wettability of
pyrite. Dávila-Pulido et al. (2011) state that the depression
of pyrite by MBS is due to the oxidation of Fe species on
the mineral surface, increasing its hydrophilicity and reduc-
ing its floatability. However, both depressants do not com-
pletely suppress the natural hydrophobicity of pyrite at low
dosages.
The subsequent experiment sought to increase the
depression of pyrite by evaluating the combined effect of
both depressants, keeping the MBS concentration con-
stant, with and without pulp aeration. In Figure 4, it is
observed that without aeration, the combination of depres-
sants accelerates the contact angle reduction compared to
Figure 2. Contact angle measurement using the captive bubble technique
The study assessed both the individual and combined
effects of adding MBS and DX. In the mixed reagent study,
the impact of aeration (150 mL/min) in the presence of
MBS was analyzed to enhance its oxidizing effect, followed
by the addition of DX.
The pulp’s pH was adjusted to 8 using HCl and NaOH
solutions. Then, the depressants (MBS, DX) were added
and maintained in contact for 10 minutes before measur-
ing the contact angle. When both depressants were used,
conditioning was first performed with MBS and then with
DX. Finally, PAX was added at the desired concentration
and allowed to react for 5 minutes.
Throughout the conditioning process, the oxidation-
reduction potential (ORP) of the pulp was continuously
monitored using a platinum electrode and a saturated Ag/
AgCl reference. The procedure was carried out in a glass
cell, introducing a 1 mm diameter bubble using a Hamilton
0.10 mL syringe (series 700) with a hooked tip. The shadow
of the bubble in equilibrium with the crystal and solution
was photographed, then processed with ImageJ software
and the Contact-Angle plugin (Brugnara, 2006) to deter-
mine the contact angle. Three bubbles were placed per
measurement, and the average angle was reported as the
result. Figure 2 illustrates the equipment used. In addition,
all measurements were consistently conducted at a constant
temperature of 25°C to ensure environmental stability dur-
ing the experiments.
Microflotation Studies
Microflotation studies were conducted using a Hallimond
tube. One gram of pyrite with particle sizes of –100+75
micrometers was used in a 100 mL suspension of deionized
water. The mineral was conditioned following the same
reagent addition sequence as in the contact angle tests
that is, depressants were added first, followed by the col-
lector (Lopéz-Valdivieso et al., 2018). After the condition-
ing period, the dispersions were transferred to the flotation
tube and floated for 1 minute with a constant flow of 30
mL/min of high-purity nitrogen. At the end of the test,
floatability was calculated by weight difference.
RESULTS AND DISCUSSION
Figure 3 displays the contact angle of pyrite as a function
of the addition of MBS and DX depressants, applied indi-
vidually and without a collector. Without a depressant, the
natural contact angle of pyrite is higher, decreasing progres-
sively with the increase in the MBS or DX dosage. At a pH
of 8, the natural contact angle of pyrite decreases in the
presence of MBS, reducing from 54.70° to 42° at the maxi-
mum addition. Similarly, the presence of DX at 300 mg/L
results in a maximum reduction of about 29°, being slightly
more effective than MBS in decreasing the wettability of
pyrite. Dávila-Pulido et al. (2011) state that the depression
of pyrite by MBS is due to the oxidation of Fe species on
the mineral surface, increasing its hydrophilicity and reduc-
ing its floatability. However, both depressants do not com-
pletely suppress the natural hydrophobicity of pyrite at low
dosages.
The subsequent experiment sought to increase the
depression of pyrite by evaluating the combined effect of
both depressants, keeping the MBS concentration con-
stant, with and without pulp aeration. In Figure 4, it is
observed that without aeration, the combination of depres-
sants accelerates the contact angle reduction compared to
Figure 2. Contact angle measurement using the captive bubble technique