3280 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
reduced in concentration prior to the ultrasound exposure,
which was already demonstrated by the analysis of compo-
sition of the size fractions after sieving.
After 30 seconds of ultrasound exposure, the particles
show significantly less perovskite material (Figure 3b). Only
a few residues are visible on the surface. The perovskites
therefore appear to have been selectively separated by the
ultrasonic stressing. To verify this, the composition of the
remaining coarse and fine particles was analyzed by ICP-
AES. It was found that the detached fine particles of the
fraction 1 mm exhibited a perovskite concentration of
approximately 42 wt.-%, whereby approximately 98 wt.-%
of the perovskites previously adhering to the particle frac-
tion could be detached. This observation corresponds to an
enrichment by weight percentage for perovskites in the fine
particles by a factor of approximately 31, indicating that
the process is highly selective for perovskites.
For the fraction 315 µm x ≤ 1 mm the detached
fine particles show a perovskite content of about 25 wt.-
%,which means a detachment of about 96% of the pre-
viously present perovskites from the particles. This means
an enrichment by weight percentage for perovskites in the
fine particles by a factor of around 27, which is slightly
lower than that observed for the coarser fraction (1 mm).
Nevertheless, this result also indicates, that the method
exhibits a high degree of selectivity for perovskites.
In order to check whether it was pure selective decoat-
ing or rather a selective comminution, the particle size dis-
tribution was measured before and after every 10 s exposure
using static image analysis. Selective decoating is expected
to produce purer products than selective comminution
because comminution can produce small particles of all
materials due to fracturing, whereas decoating focuses the
particle removal on the surfaces. The particle size distribu-
tions are shown in Figure 4. For the particle size fraction ×
1 mm (Figure 4a), the particle size distribution shifts
toward finer particles as the stress duration increases. The
particles are thus being comminuted by the stress. This is
also shown by quantiles in Table 2. While about 50 %of
the particles were still larger than 1.68 mm before stress-
ing, after 30 s 90 %were smaller than or equal to 1.5 mm.
The particles are comminuted the most within the first
ten seconds. This can be seen from the fact that the differ-
ence in the distribution function and quantiles before and
after 10 s shows the largest shift. As the stress progresses,
the shifts become smaller indicating a limit in particle size
below which comminution by fracturing no longer occurs.
Given that the cell particles 1 mm have been commi-
nuted, both the selective comminution of the cell particles
and the decoating can contribute to the accumulation of
perovskite materials in the detached particles.
The fact that there is a limit in particle size to the com-
minution by fracturing is shown by the sum distribution
0
0.5
1
1.5
2
2.5
0 10 20 30
Sonication time t /s
1 mm =51 mm, 315 μmm
b)
c)
a)
x 1 mm x 1
Figure 3. a) Cumulative sum of the mass ratio between the detached particle mass and the total mass for the particle size class
x 1 mm and 315 µm x ≤ 1 mm with corresponding images for the particle size class 315 µm x ≤ 1 mm b) before stressing
and c) after 30 s of stressing
Cumulativedetached
m
as s
r
w/
%
reduced in concentration prior to the ultrasound exposure,
which was already demonstrated by the analysis of compo-
sition of the size fractions after sieving.
After 30 seconds of ultrasound exposure, the particles
show significantly less perovskite material (Figure 3b). Only
a few residues are visible on the surface. The perovskites
therefore appear to have been selectively separated by the
ultrasonic stressing. To verify this, the composition of the
remaining coarse and fine particles was analyzed by ICP-
AES. It was found that the detached fine particles of the
fraction 1 mm exhibited a perovskite concentration of
approximately 42 wt.-%, whereby approximately 98 wt.-%
of the perovskites previously adhering to the particle frac-
tion could be detached. This observation corresponds to an
enrichment by weight percentage for perovskites in the fine
particles by a factor of approximately 31, indicating that
the process is highly selective for perovskites.
For the fraction 315 µm x ≤ 1 mm the detached
fine particles show a perovskite content of about 25 wt.-
%,which means a detachment of about 96% of the pre-
viously present perovskites from the particles. This means
an enrichment by weight percentage for perovskites in the
fine particles by a factor of around 27, which is slightly
lower than that observed for the coarser fraction (1 mm).
Nevertheless, this result also indicates, that the method
exhibits a high degree of selectivity for perovskites.
In order to check whether it was pure selective decoat-
ing or rather a selective comminution, the particle size dis-
tribution was measured before and after every 10 s exposure
using static image analysis. Selective decoating is expected
to produce purer products than selective comminution
because comminution can produce small particles of all
materials due to fracturing, whereas decoating focuses the
particle removal on the surfaces. The particle size distribu-
tions are shown in Figure 4. For the particle size fraction ×
1 mm (Figure 4a), the particle size distribution shifts
toward finer particles as the stress duration increases. The
particles are thus being comminuted by the stress. This is
also shown by quantiles in Table 2. While about 50 %of
the particles were still larger than 1.68 mm before stress-
ing, after 30 s 90 %were smaller than or equal to 1.5 mm.
The particles are comminuted the most within the first
ten seconds. This can be seen from the fact that the differ-
ence in the distribution function and quantiles before and
after 10 s shows the largest shift. As the stress progresses,
the shifts become smaller indicating a limit in particle size
below which comminution by fracturing no longer occurs.
Given that the cell particles 1 mm have been commi-
nuted, both the selective comminution of the cell particles
and the decoating can contribute to the accumulation of
perovskite materials in the detached particles.
The fact that there is a limit in particle size to the com-
minution by fracturing is shown by the sum distribution
0
0.5
1
1.5
2
2.5
0 10 20 30
Sonication time t /s
1 mm =51 mm, 315 μmm
b)
c)
a)
x 1 mm x 1
Figure 3. a) Cumulative sum of the mass ratio between the detached particle mass and the total mass for the particle size class
x 1 mm and 315 µm x ≤ 1 mm with corresponding images for the particle size class 315 µm x ≤ 1 mm b) before stressing
and c) after 30 s of stressing
Cumulativedetached
m
as s
r
w/
%