XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3253
pastel. The final particles are then obtained by sieving using
a 100 μm sieve. An example of the prepared samples can be
seen in Figure 1.
Methods
Validation of Nafion Content
To validate the Nafion content in the prepared samples,
5 mg of particulate samples are analyzed with thermogravi-
metric analysis (TGA) with the following condition: (i)
heating up the samples by purging inert argon gas until
800°C with a heating rate of 20 K/min, (ii)at 800°C, hold-
ing for 30 min. The inert gas will decompose the iono-
mer but not the catalyst representing particles so that the
authentic ionomer content can be quantified. Furthermore,
pure particles that have not gone through the sample prepa-
ration process are tested under the same condition to dis-
tinguish any remnants of isopropanol from the Nafion
quantification.
Methodology for Identification of Ionomer Impact
The wettability of pure particles are characterized and
explained in detail in our previous study (Ahn &Rudolph,
2024). However, the presence of ionomer can influence
each sample hydrophobicity, so the surface properties of
the particle containing ionomer are needed to be charac-
terized in this study. First, the impact of the ionomer is
identified by measuring the zeta potential. The evalua-
tion of zeta potential is examined with an AcoustoSizer
II, Electrokinetic Sonic Amplitude (ESA), Colloidal
Dynamics, USA. The dispersions are prepared with 500 mg
of Nafion containing particles and 200 ml of 0.01 M KCl
solution as a background. During the measurement, the
solution is continuously agitated under 200 rpm and pH
is adjusted from 4 to 11 with 1 M hydrochloric acid, HCl
and 1 M sodium hydroxide, NaOH.
The wetting behavior of the particles can be described
by the degree to which particles attach to an air bubble.
The hydrophobic air interface in water attracts particles
which have a hydrophobic surface. The air bubble surface is
covered by particles and by determining the bubble cover-
age angle, the wettability of particles can be determined by
using the OCA 50 Pro optical contour analysis device from
Dataphysics, Germany. For the measurement, a silanized
needle with an inner diameter of 1.82 mm is positioned
at the end of the syringe. Particle dispersions consisting of
100 ml of DI water with a concentration of 0.01 M KCl
and 100 mg of solid particles are mechanically suspended
in a cuvette under 500 rpm with a magnetic stirrer for one
minute. The system generates 8 μl of a single air bubble
after the agitation while the particles are attached to its
surface during the settling process. A high-resolution cam-
era takes the air bubble images and ImageJ is used for the
image processing (Schneider, Rasband, &Eliceiri, 2012).
Particle mixtures with sizes below 10 μm are challeng-
ing to be separated mechanically. For that reason, one of
the well-established techniques, liquid-liquid phase trans-
fer can help to understand surface properties of micro par-
ticles. Equivalent volumes of two immiscible liquids for
instance, water and cyclohexane are prepared for the experi-
ment. A strong interfacial force between two fluid phases
disturb unconstrained movement of particles and the
hydrophobicity of each particle determines where they will
be dispersed in the two liquids. The particles could be accu-
mulated in the interface of two liquids when the interfacial
Figure 1. Back scattered electron scanning microscopy (BSE-SEM) images of the particles, carbon black (A) and TiO2(B)
containing 40% of Nafion
pastel. The final particles are then obtained by sieving using
a 100 μm sieve. An example of the prepared samples can be
seen in Figure 1.
Methods
Validation of Nafion Content
To validate the Nafion content in the prepared samples,
5 mg of particulate samples are analyzed with thermogravi-
metric analysis (TGA) with the following condition: (i)
heating up the samples by purging inert argon gas until
800°C with a heating rate of 20 K/min, (ii)at 800°C, hold-
ing for 30 min. The inert gas will decompose the iono-
mer but not the catalyst representing particles so that the
authentic ionomer content can be quantified. Furthermore,
pure particles that have not gone through the sample prepa-
ration process are tested under the same condition to dis-
tinguish any remnants of isopropanol from the Nafion
quantification.
Methodology for Identification of Ionomer Impact
The wettability of pure particles are characterized and
explained in detail in our previous study (Ahn &Rudolph,
2024). However, the presence of ionomer can influence
each sample hydrophobicity, so the surface properties of
the particle containing ionomer are needed to be charac-
terized in this study. First, the impact of the ionomer is
identified by measuring the zeta potential. The evalua-
tion of zeta potential is examined with an AcoustoSizer
II, Electrokinetic Sonic Amplitude (ESA), Colloidal
Dynamics, USA. The dispersions are prepared with 500 mg
of Nafion containing particles and 200 ml of 0.01 M KCl
solution as a background. During the measurement, the
solution is continuously agitated under 200 rpm and pH
is adjusted from 4 to 11 with 1 M hydrochloric acid, HCl
and 1 M sodium hydroxide, NaOH.
The wetting behavior of the particles can be described
by the degree to which particles attach to an air bubble.
The hydrophobic air interface in water attracts particles
which have a hydrophobic surface. The air bubble surface is
covered by particles and by determining the bubble cover-
age angle, the wettability of particles can be determined by
using the OCA 50 Pro optical contour analysis device from
Dataphysics, Germany. For the measurement, a silanized
needle with an inner diameter of 1.82 mm is positioned
at the end of the syringe. Particle dispersions consisting of
100 ml of DI water with a concentration of 0.01 M KCl
and 100 mg of solid particles are mechanically suspended
in a cuvette under 500 rpm with a magnetic stirrer for one
minute. The system generates 8 μl of a single air bubble
after the agitation while the particles are attached to its
surface during the settling process. A high-resolution cam-
era takes the air bubble images and ImageJ is used for the
image processing (Schneider, Rasband, &Eliceiri, 2012).
Particle mixtures with sizes below 10 μm are challeng-
ing to be separated mechanically. For that reason, one of
the well-established techniques, liquid-liquid phase trans-
fer can help to understand surface properties of micro par-
ticles. Equivalent volumes of two immiscible liquids for
instance, water and cyclohexane are prepared for the experi-
ment. A strong interfacial force between two fluid phases
disturb unconstrained movement of particles and the
hydrophobicity of each particle determines where they will
be dispersed in the two liquids. The particles could be accu-
mulated in the interface of two liquids when the interfacial
Figure 1. Back scattered electron scanning microscopy (BSE-SEM) images of the particles, carbon black (A) and TiO2(B)
containing 40% of Nafion