XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 667
Figure 2. All experiments were performed with a solution
of 60 mg/L MIBC and 80 ml/min nitrogen gas. In all the
tests, 1.0 g of mineral was mixed and conditioned in a bea-
ker for 5 min at the required pH (adjusted using NaOH),
and MIBC concentration. Then, PAM solution at defined
concentrations was added to the beaker and conditioned for
an additional 5 minutes this mixture was transferred to the
cell. To initiate microflotation, the gas valve was opened,
and the flotation is for 2 min and the froth was removed
at 10 s intervals. The concentrates and tailings were oven
dried at 105 °C for 8 h, and the mineral recovery was cal-
culated by dividing the mass of concentrate by the total
mass of concentrate plus tailings. All tests were performed
in triplicate at the required concentrations of PAM and at
different pH and potential levels.
RESULTS AND DISCUSSIÓN
Microflotation Analysis
The recovery of molybdenite at different pH in water of
varying ionic strength is presented in Figure 3. For pH 7
the mineral recovery is higher compared to pH 9 and 11,
at this measure of acidity its lowest recovery was 33.1%
for MgSO4 with LPAM 10 mg/L concentration. CaSO4
presented the highest recovery for all acidity measurements
and MgCl2 had the lowest recovery for pH 9 and 11.
The study of the effect of Ca+ ions on molybdenite flo-
tation has led to several theories that have emerged from
different experimental conditions such as the effect of its
pH, presence of other ions, among others. Some authors
affirmed that calcium ions influence its recovery in the pH
range 9–11, the depressive effect it causes on molybdenite
in this pH range is caused by the adsorption of CaCO3 pre-
cipitates on the molybdenite surface (Álvarez et al., 2018
Lucay et al., 2015 Ramirez et al., 2020 Rebolledo et al.,
2017 Suyantara et al., 2018 Yepsen et al., 2021).
In some studies, it was shown that magnesium hydrox-
ide adsorbs polyacrylamide with high affinity but decreases
the sedimentation rate. This phenomenon is caused because
magnesium hydroxide occurs as a colloidal particle that cov-
ers its surface of hydrolyzed PAM but is not large enough
to sediment and short PAM tails prevent the formation of
polymeric bridges (Quezada et al., 2021). In the context
of molybdenite flotation, the decrease in mineral recovery
at pH 9 and 11 is attributed to the formation of magne-
sium hydroxide. This phenomenon is due to the creation
of Mg(OH) precipitates, which adsorb LPAM, thus pre-
venting the latter from causing any significant effect on the
flotation process (Hirajima et al., 2016 Suyantara et al.,
2016 Han et al., 2004 Ramos et al., 2013).
Figure 1. XRD diffractogram of the molybdenite sample. The sample was analyzed using a
Bruker D4-Endeavor operated with Ni-filtered Cu radiation
Figure 2. All experiments were performed with a solution
of 60 mg/L MIBC and 80 ml/min nitrogen gas. In all the
tests, 1.0 g of mineral was mixed and conditioned in a bea-
ker for 5 min at the required pH (adjusted using NaOH),
and MIBC concentration. Then, PAM solution at defined
concentrations was added to the beaker and conditioned for
an additional 5 minutes this mixture was transferred to the
cell. To initiate microflotation, the gas valve was opened,
and the flotation is for 2 min and the froth was removed
at 10 s intervals. The concentrates and tailings were oven
dried at 105 °C for 8 h, and the mineral recovery was cal-
culated by dividing the mass of concentrate by the total
mass of concentrate plus tailings. All tests were performed
in triplicate at the required concentrations of PAM and at
different pH and potential levels.
RESULTS AND DISCUSSIÓN
Microflotation Analysis
The recovery of molybdenite at different pH in water of
varying ionic strength is presented in Figure 3. For pH 7
the mineral recovery is higher compared to pH 9 and 11,
at this measure of acidity its lowest recovery was 33.1%
for MgSO4 with LPAM 10 mg/L concentration. CaSO4
presented the highest recovery for all acidity measurements
and MgCl2 had the lowest recovery for pH 9 and 11.
The study of the effect of Ca+ ions on molybdenite flo-
tation has led to several theories that have emerged from
different experimental conditions such as the effect of its
pH, presence of other ions, among others. Some authors
affirmed that calcium ions influence its recovery in the pH
range 9–11, the depressive effect it causes on molybdenite
in this pH range is caused by the adsorption of CaCO3 pre-
cipitates on the molybdenite surface (Álvarez et al., 2018
Lucay et al., 2015 Ramirez et al., 2020 Rebolledo et al.,
2017 Suyantara et al., 2018 Yepsen et al., 2021).
In some studies, it was shown that magnesium hydrox-
ide adsorbs polyacrylamide with high affinity but decreases
the sedimentation rate. This phenomenon is caused because
magnesium hydroxide occurs as a colloidal particle that cov-
ers its surface of hydrolyzed PAM but is not large enough
to sediment and short PAM tails prevent the formation of
polymeric bridges (Quezada et al., 2021). In the context
of molybdenite flotation, the decrease in mineral recovery
at pH 9 and 11 is attributed to the formation of magne-
sium hydroxide. This phenomenon is due to the creation
of Mg(OH) precipitates, which adsorb LPAM, thus pre-
venting the latter from causing any significant effect on the
flotation process (Hirajima et al., 2016 Suyantara et al.,
2016 Han et al., 2004 Ramos et al., 2013).
Figure 1. XRD diffractogram of the molybdenite sample. The sample was analyzed using a
Bruker D4-Endeavor operated with Ni-filtered Cu radiation