XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2397
done by Li and coworkers (Li et al. 2022). This means
that the phosphate groups in STPP effectively removed
magnesium cations on serpentine surfaces to form solu-
ble complexes. Same experiment was repeated for CO2-
conditioned serpentine suspension and the Mg 2s peak area
reads 12426.1 CPS.eV (Figure 10). Thus, magnesium ions
on serpentine surfaces are complexed by STPP and CO2,
which is in line with results obtained from ICP-OES analy-
sis for metal release. However, STPP demonstrated a much
stronger suppression ability by complexing about half of
the Mg2+. As previously mentioned, the phosphate groups
in STPP easily chelate Mg2+ present on serpentine’s surface,
facilitating its suppression in mixed mineral systems.
Infact, the composition of atomic and mass concen-
tration further demonstrated that the initial concentration
of metal ions present in the baseline case were reduced
because of the complexation reaction that took place
upon the introduction of the reagents in the treated cases
(Figure 11). Therefore, chelating of Mg2+ by phosphate
group leads to the formation of Mg-O-P chemical bonding
as demonstrated through high resolution scans performed
in a previous study (Li et al. 2022). These trends validate
the serpentine suppression observed in flotation tests and
zeta potential measurements for STPP and CO2 cases.
Further discussion
By using CO2 as either a flotation gas or as a conditioning
reagent for gangue mineral depression, improvements in
the valuable mineral recovery was achieved. However, when
CO2 was used as both a flotation gas and as a conditioning
reagent, higher pentlandite recoveries were observed. This
validates that CO2 bubbles are more effective in colliding
and attaching to pentlandite particles. Because CO2 gas
produces smaller bubbles than air, they are able to increase
their probability of collision with fine pentlandite particles
and therefore, increasing the flotation rates. As has been
demonstrated by various collision studies, the probability
of collision between air bubbles and fine particles is small,
which in turn slows the rate of flotation (Miettinen and
Fornasiero 2010 Verrelli et al. 2011).
Thus, by introducing CO2 bubbles which are generally
smaller than air bubbles, collision probability and flotation
rates were enhanced which is demonstrated by increased
pentlandite recovery. Increased flotation rates achieved
when CO2 bubbles were introduced also confirms that liq-
uid film thinning and rupture, establishment of a wetting
perimeter and a three-phase contact line were faster than
the case with air bubbles. Therefore, induction time is faster
for CO2 bubbles than other gas bubbles used in mineral
13533.15
7207.25
12426.1
Baseline case STPP case CO2 case
Experiment type
Figure 10. Peak raw area of Mg 2s of the serpentine before and after treatment with
STPP and CO2
Raw
area
(
done by Li and coworkers (Li et al. 2022). This means
that the phosphate groups in STPP effectively removed
magnesium cations on serpentine surfaces to form solu-
ble complexes. Same experiment was repeated for CO2-
conditioned serpentine suspension and the Mg 2s peak area
reads 12426.1 CPS.eV (Figure 10). Thus, magnesium ions
on serpentine surfaces are complexed by STPP and CO2,
which is in line with results obtained from ICP-OES analy-
sis for metal release. However, STPP demonstrated a much
stronger suppression ability by complexing about half of
the Mg2+. As previously mentioned, the phosphate groups
in STPP easily chelate Mg2+ present on serpentine’s surface,
facilitating its suppression in mixed mineral systems.
Infact, the composition of atomic and mass concen-
tration further demonstrated that the initial concentration
of metal ions present in the baseline case were reduced
because of the complexation reaction that took place
upon the introduction of the reagents in the treated cases
(Figure 11). Therefore, chelating of Mg2+ by phosphate
group leads to the formation of Mg-O-P chemical bonding
as demonstrated through high resolution scans performed
in a previous study (Li et al. 2022). These trends validate
the serpentine suppression observed in flotation tests and
zeta potential measurements for STPP and CO2 cases.
Further discussion
By using CO2 as either a flotation gas or as a conditioning
reagent for gangue mineral depression, improvements in
the valuable mineral recovery was achieved. However, when
CO2 was used as both a flotation gas and as a conditioning
reagent, higher pentlandite recoveries were observed. This
validates that CO2 bubbles are more effective in colliding
and attaching to pentlandite particles. Because CO2 gas
produces smaller bubbles than air, they are able to increase
their probability of collision with fine pentlandite particles
and therefore, increasing the flotation rates. As has been
demonstrated by various collision studies, the probability
of collision between air bubbles and fine particles is small,
which in turn slows the rate of flotation (Miettinen and
Fornasiero 2010 Verrelli et al. 2011).
Thus, by introducing CO2 bubbles which are generally
smaller than air bubbles, collision probability and flotation
rates were enhanced which is demonstrated by increased
pentlandite recovery. Increased flotation rates achieved
when CO2 bubbles were introduced also confirms that liq-
uid film thinning and rupture, establishment of a wetting
perimeter and a three-phase contact line were faster than
the case with air bubbles. Therefore, induction time is faster
for CO2 bubbles than other gas bubbles used in mineral
13533.15
7207.25
12426.1
Baseline case STPP case CO2 case
Experiment type
Figure 10. Peak raw area of Mg 2s of the serpentine before and after treatment with
STPP and CO2
Raw
area
(