XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3255
respectively. Comparing the results obtained from the
pure sample and the sample without ionomer, the curves
are very nearly identical to each other. This result stands
for that there is no isopropanol left in the sample, which
was added during the sample preparation. The sample with
20 %(w/w) of Nafion is confirmed by TGA measurement
that decomposition of 19 %of the corresponding particle.
However, 40 %(w/w) of Nafion containing sample shows
only 29 %of mass loss after the complete decomposition.
The first possible explanation for this unmatched result
could be a systematic error during the sample preparation
and TGA measurement. Furthermore, the result does not
represent the entire sample because of the application of
trace amount of sample. Another feasible explanation is
that the carbon black is entrapping the decomposition
products of the Nafion in its matrix which leads to the
lower mass drop.
As shown in the Figure 2, the residual TiO2 samples of
pure, 0 %,20 %and 40 %of Nafion are 97, 97, 77 and
56 of wt. %respectively. Like the sample of carbon black,
negligible difference between the pure and no ionomer
containing samples can be found. The result of Nafion con-
taining particles also confirm that the sample contained the
expected amount of ionomers but the decomposition tem-
perature of the polymer chain has shifted to higher temper-
ature with high Nafion content. Strong interaction between
TiO2 and Nafion backbone could attribute this phenom-
ena (Devrim, 2014). Through TGA measurements, it can
be confirmed that both carbon black and TiO2 samples are
free of isopropanol residues and that the ionomer as calcu-
lated is contained in the prepared samples.
Impact of Ionomer
Zeta Potential
In our previous study, the zeta potential of commercial
carbon black, XC 72 from Cabot remained between 0 mV
and 10 mV along with increasing pH and showed no iso-
electric point (IEP) (Ahn &Rudolph, 2024). The result
of carbon black with no ionomer confirmed this finding.
The zeta potential maintains constant at 4 mV until pH 8
and marginally changes in basic solutions. The presence of
ionomer leads to the decline of the zeta potential to nearly
0 mV or even to the negative range. The amphiphilic mole-
cule, ionomer interacts with the hydrophobic carbon black
surface by van der Waals force, while the hydrophilic head
points towards, and its charge determines the overall sur-
face charge of the carbon black complex. Since Nafion is
an anionic polyelectrolyte, it was assumed that the com-
plex would have a negatively charged surface. However, as
with carbon black without the ionomer, the sample does
not show a distinguishable change in zeta potential with
pH change. Additionally, the presence of ionomer does not
significantly affect the surface charge of the particles.
The result of TiO2 is summarized at the bottom of
Figure 3. The IEP of pure rutile TiO2 particle was pH 5.5
and the zeta potential ranged between +20 mV and
–70 mV (Ahn &Rudolph, 2024). The sample with no
ionomer shows an IEP between pH 5.6 – 5.8, which cor-
responds to the formal study. However, the maximum and
minimum zeta potential values of the current sample are
between 10 mV and –15 mV, which have a high potential
to be agglomerated each other. With increasing ionomer
content, the interaction between the sulfonic acid group
and the particle affects to its zeta potential. The particles
are negatively charged with 20 %of Nafion. This kind of
phenomenon can be explained by the pristine wettability
of the particle. The carbon ionomer sidechain is oriented
towards the hydrophilic particle, while the hydrophobic
back bone heads to the surface (Olbrich, Kadyk, Sauter, &
Eikerling, 2022). The surface charge of PTFE is recognized
negative from pH 3 by many literatures (GÜLGÖNÜL,
2019 Schuetzner &Kenndler, 1992). With higher Nafion
content, zeta potential of particles increases. A possible
hypothesis could be the change of ionomer’s molecular
alignment and the degree of covering fraction of the iono-
mer on the particle surface has changed compared to 20 %
of Nafion. Both sulfonic groups and PTFE are negatively
charged along with all pH range, it is challenging to specify
a concrete explanation for the positive zeta potentials.
Single Bubble Attachment
Since aforementioned IEP of TiO2 was 5.5, the experiments
are conducted with different pH of the background solu-
tions, which are adjusted to 4 and 10 for this experiment.
The attachment probability of a particle is dependent on
the chemistry and physics of the solid particle and the bub-
ble surface. Air bubbles in the aqueous media are assumed
negatively charged and positively charged particles will be
attracted on its surface. The surface charge of each particle
will influence the interaction between air bubble and the
particles. Furthermore, the wettability of the particle also
heavily influences the coverage angle on the air bubble. Air
bubbles are seen to have a hydrophobic surface, so parti-
cles with lower wettability will be attracted to the surface
more strongly. Carbon black particles without Nafion have
hydrophobic surface showing a large bubble coverage angle
in range between 210° and 240° as shown in Figure 4. Since
the surface charge of carbon black remained positive at pH 4
and 10 regardless Nafion content, the difference derives not
from zeta potential but wettability. With increasing Nafion
respectively. Comparing the results obtained from the
pure sample and the sample without ionomer, the curves
are very nearly identical to each other. This result stands
for that there is no isopropanol left in the sample, which
was added during the sample preparation. The sample with
20 %(w/w) of Nafion is confirmed by TGA measurement
that decomposition of 19 %of the corresponding particle.
However, 40 %(w/w) of Nafion containing sample shows
only 29 %of mass loss after the complete decomposition.
The first possible explanation for this unmatched result
could be a systematic error during the sample preparation
and TGA measurement. Furthermore, the result does not
represent the entire sample because of the application of
trace amount of sample. Another feasible explanation is
that the carbon black is entrapping the decomposition
products of the Nafion in its matrix which leads to the
lower mass drop.
As shown in the Figure 2, the residual TiO2 samples of
pure, 0 %,20 %and 40 %of Nafion are 97, 97, 77 and
56 of wt. %respectively. Like the sample of carbon black,
negligible difference between the pure and no ionomer
containing samples can be found. The result of Nafion con-
taining particles also confirm that the sample contained the
expected amount of ionomers but the decomposition tem-
perature of the polymer chain has shifted to higher temper-
ature with high Nafion content. Strong interaction between
TiO2 and Nafion backbone could attribute this phenom-
ena (Devrim, 2014). Through TGA measurements, it can
be confirmed that both carbon black and TiO2 samples are
free of isopropanol residues and that the ionomer as calcu-
lated is contained in the prepared samples.
Impact of Ionomer
Zeta Potential
In our previous study, the zeta potential of commercial
carbon black, XC 72 from Cabot remained between 0 mV
and 10 mV along with increasing pH and showed no iso-
electric point (IEP) (Ahn &Rudolph, 2024). The result
of carbon black with no ionomer confirmed this finding.
The zeta potential maintains constant at 4 mV until pH 8
and marginally changes in basic solutions. The presence of
ionomer leads to the decline of the zeta potential to nearly
0 mV or even to the negative range. The amphiphilic mole-
cule, ionomer interacts with the hydrophobic carbon black
surface by van der Waals force, while the hydrophilic head
points towards, and its charge determines the overall sur-
face charge of the carbon black complex. Since Nafion is
an anionic polyelectrolyte, it was assumed that the com-
plex would have a negatively charged surface. However, as
with carbon black without the ionomer, the sample does
not show a distinguishable change in zeta potential with
pH change. Additionally, the presence of ionomer does not
significantly affect the surface charge of the particles.
The result of TiO2 is summarized at the bottom of
Figure 3. The IEP of pure rutile TiO2 particle was pH 5.5
and the zeta potential ranged between +20 mV and
–70 mV (Ahn &Rudolph, 2024). The sample with no
ionomer shows an IEP between pH 5.6 – 5.8, which cor-
responds to the formal study. However, the maximum and
minimum zeta potential values of the current sample are
between 10 mV and –15 mV, which have a high potential
to be agglomerated each other. With increasing ionomer
content, the interaction between the sulfonic acid group
and the particle affects to its zeta potential. The particles
are negatively charged with 20 %of Nafion. This kind of
phenomenon can be explained by the pristine wettability
of the particle. The carbon ionomer sidechain is oriented
towards the hydrophilic particle, while the hydrophobic
back bone heads to the surface (Olbrich, Kadyk, Sauter, &
Eikerling, 2022). The surface charge of PTFE is recognized
negative from pH 3 by many literatures (GÜLGÖNÜL,
2019 Schuetzner &Kenndler, 1992). With higher Nafion
content, zeta potential of particles increases. A possible
hypothesis could be the change of ionomer’s molecular
alignment and the degree of covering fraction of the iono-
mer on the particle surface has changed compared to 20 %
of Nafion. Both sulfonic groups and PTFE are negatively
charged along with all pH range, it is challenging to specify
a concrete explanation for the positive zeta potentials.
Single Bubble Attachment
Since aforementioned IEP of TiO2 was 5.5, the experiments
are conducted with different pH of the background solu-
tions, which are adjusted to 4 and 10 for this experiment.
The attachment probability of a particle is dependent on
the chemistry and physics of the solid particle and the bub-
ble surface. Air bubbles in the aqueous media are assumed
negatively charged and positively charged particles will be
attracted on its surface. The surface charge of each particle
will influence the interaction between air bubble and the
particles. Furthermore, the wettability of the particle also
heavily influences the coverage angle on the air bubble. Air
bubbles are seen to have a hydrophobic surface, so parti-
cles with lower wettability will be attracted to the surface
more strongly. Carbon black particles without Nafion have
hydrophobic surface showing a large bubble coverage angle
in range between 210° and 240° as shown in Figure 4. Since
the surface charge of carbon black remained positive at pH 4
and 10 regardless Nafion content, the difference derives not
from zeta potential but wettability. With increasing Nafion