XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2791
the interface from liquid-like to solid-like. This limits the
attachment of the GBs to the bubble surface, resulting in
a gap or void between the GBs on the bubble surface. It
should be noted that the formation of such a gap is rather
random and does not occur in all cases. It appears that in
some cases the GBs push the adsorbed NPs to a specific
location where they form a connected network of NPs, i.e.,
the gap in Figure 6 d-f, while in other cases, NPs remain
only between the GBs, reducing their packing density, as
shown in Figure 6 b and c.
Next, the packing density of GBs on the surface of a
pre-compressed NP-laden bubble is investigated. This is
done to increase the surface concentration of NPs. For these
experiments, first, a bubble with a diameter of 2.5 mm is
created in NP solution (2.0 wt.% NP9 +0.3 CMC CTAB)
and aged for about 1000 s. Then it is reduced to 1.5 mm and
the surface coverage experiments are performed. To provide
a reference and ensure that what is observed is caused by
the compression of the interface and not affected by the
bubble size, similar surface coverage experiments are per-
formed with uncompressed 1.5 mm bubbles. Furthermore,
to achieve a significant compression effect, the bubble size
had to be significantly reduced. This explains why the bub-
ble size had to be reduced from 2.5 mm to 1.5 mm instead
of from 2.5 mm to 2 mm. Nevertheless, no significant dif-
ference in the packing density of GBs is observed between
uncompressed bubbles of 1.5 mm and 2 mm. Therefore,
the following results can only be attributed to the structural
change of the NPs upon compression.
As can be seen from Figure 7, reducing the surface area
by compressing the bubble significantly changes the distri-
bution of the GBs at the interface, and one can assume that
the adsorbed NPs create a barrier for GBs attachment. As
already mentioned and shown in Figure 6 b-f, adsorbed NPs
without any compression reduce the number of attached
GBs. However, the effect is much more pronounced with
compressed interfaces, where NPs can almost prevent the
attachment of GBs.
Figure 6. Qualitative representation of the packing density of GBs (3gr of 66 µm GBs, conditioned with 0.006 CMC CTAB,
and stirred at 400 rpm) on bubble surface for a) water, and b-f) NPSCs (2.0 wt.% NP9 +0.3 CMC CTAB), following a 1000
s waiting time. Fig. b and c are different images of one experimental run and Fig. d, e and f are different images of another
experimental run, all under the same conditions (i.e., same composition, stirring and waiting time)
the interface from liquid-like to solid-like. This limits the
attachment of the GBs to the bubble surface, resulting in
a gap or void between the GBs on the bubble surface. It
should be noted that the formation of such a gap is rather
random and does not occur in all cases. It appears that in
some cases the GBs push the adsorbed NPs to a specific
location where they form a connected network of NPs, i.e.,
the gap in Figure 6 d-f, while in other cases, NPs remain
only between the GBs, reducing their packing density, as
shown in Figure 6 b and c.
Next, the packing density of GBs on the surface of a
pre-compressed NP-laden bubble is investigated. This is
done to increase the surface concentration of NPs. For these
experiments, first, a bubble with a diameter of 2.5 mm is
created in NP solution (2.0 wt.% NP9 +0.3 CMC CTAB)
and aged for about 1000 s. Then it is reduced to 1.5 mm and
the surface coverage experiments are performed. To provide
a reference and ensure that what is observed is caused by
the compression of the interface and not affected by the
bubble size, similar surface coverage experiments are per-
formed with uncompressed 1.5 mm bubbles. Furthermore,
to achieve a significant compression effect, the bubble size
had to be significantly reduced. This explains why the bub-
ble size had to be reduced from 2.5 mm to 1.5 mm instead
of from 2.5 mm to 2 mm. Nevertheless, no significant dif-
ference in the packing density of GBs is observed between
uncompressed bubbles of 1.5 mm and 2 mm. Therefore,
the following results can only be attributed to the structural
change of the NPs upon compression.
As can be seen from Figure 7, reducing the surface area
by compressing the bubble significantly changes the distri-
bution of the GBs at the interface, and one can assume that
the adsorbed NPs create a barrier for GBs attachment. As
already mentioned and shown in Figure 6 b-f, adsorbed NPs
without any compression reduce the number of attached
GBs. However, the effect is much more pronounced with
compressed interfaces, where NPs can almost prevent the
attachment of GBs.
Figure 6. Qualitative representation of the packing density of GBs (3gr of 66 µm GBs, conditioned with 0.006 CMC CTAB,
and stirred at 400 rpm) on bubble surface for a) water, and b-f) NPSCs (2.0 wt.% NP9 +0.3 CMC CTAB), following a 1000
s waiting time. Fig. b and c are different images of one experimental run and Fig. d, e and f are different images of another
experimental run, all under the same conditions (i.e., same composition, stirring and waiting time)