1612 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
resolution of the images are spatiotemporally heteroge-
neous, as the crack network develops mostly during the
early stages of leaching, and they form selectively in certain
particles. This behaviour may be explained by early-stage
reactions in which other minerals are rapidly attacked or
dissolved by the leaching solution. This hypothesis is sup-
ported by the high acid consumption reported during the
first days of leaching (see Figure 4).
Figure 6 aims only to prove how the methodology can
provide data leading to a more thorough understanding of
the spatiotemporal heterogeneity that governs changes in
the crack network during column leaching. A more detailed
analysis can quantify the formation of cracks and assess
whether the formed cracks are increasing the accessibility
of the leaching solution to target grains. Likewise, a 3D
mineral map associated with the images could be used to
study if the cracks form preferentially over specific minerals
or not.
Surface-Level Analysis
XPS and SEM/EDX were used to study changes occur-
ring at the surface of samples. A selection of some of the
surface-level results corresponding to a particle located at
the bottom of the first column are shown in Figure 7. This
figure includes the high-resolution regions of the XPS spec-
trum corresponding to sulphur and iron, along with back-
scattered electron micrographs of the regions where the
XPS acquisition took place, which is overlayed with their
respective copper elemental maps (EDX). To track tempo-
ral changes, these results are shown for three acquisition
times: before leaching (day 0), and after 3 and 35 days of
leaching. The description presented herein does not intend
to provide specific identification of the peaks found in the
spectra, but only to discuss the main features observed in
the spectra. Likewise, other than those of copper, the ele-
mental maps that were generated through SEM/EDX are
not included here.
As shown in the first panel of the figure, XPS detected
that most of the sulphur at the surface of the sample was in
the form of sulphides, which is expected since a chalcopy-
rite grain was targeted. However, after 3 days of leaching,
while the sulphide peaks are still visible, a significant pair of
peaks formed in the region corresponding to sulphates and
other oxidised forms of sulphur, suggesting that some sul-
phates have formed or been deposited at the surface. After
35 days of leaching, the sulphide peaks are no longer vis-
ible and the sulphur content at the surface is dominated by
sulphates. Similarly, peaks corresponding to iron sulphates
formed during the leaching process, as observed in the sec-
ond panel of Figure 7.
Figure 6. Changes in the crack network for a slice
corresponding to the first column before leaching (day 0),
and after 22 days and 72 days of leaching
resolution of the images are spatiotemporally heteroge-
neous, as the crack network develops mostly during the
early stages of leaching, and they form selectively in certain
particles. This behaviour may be explained by early-stage
reactions in which other minerals are rapidly attacked or
dissolved by the leaching solution. This hypothesis is sup-
ported by the high acid consumption reported during the
first days of leaching (see Figure 4).
Figure 6 aims only to prove how the methodology can
provide data leading to a more thorough understanding of
the spatiotemporal heterogeneity that governs changes in
the crack network during column leaching. A more detailed
analysis can quantify the formation of cracks and assess
whether the formed cracks are increasing the accessibility
of the leaching solution to target grains. Likewise, a 3D
mineral map associated with the images could be used to
study if the cracks form preferentially over specific minerals
or not.
Surface-Level Analysis
XPS and SEM/EDX were used to study changes occur-
ring at the surface of samples. A selection of some of the
surface-level results corresponding to a particle located at
the bottom of the first column are shown in Figure 7. This
figure includes the high-resolution regions of the XPS spec-
trum corresponding to sulphur and iron, along with back-
scattered electron micrographs of the regions where the
XPS acquisition took place, which is overlayed with their
respective copper elemental maps (EDX). To track tempo-
ral changes, these results are shown for three acquisition
times: before leaching (day 0), and after 3 and 35 days of
leaching. The description presented herein does not intend
to provide specific identification of the peaks found in the
spectra, but only to discuss the main features observed in
the spectra. Likewise, other than those of copper, the ele-
mental maps that were generated through SEM/EDX are
not included here.
As shown in the first panel of the figure, XPS detected
that most of the sulphur at the surface of the sample was in
the form of sulphides, which is expected since a chalcopy-
rite grain was targeted. However, after 3 days of leaching,
while the sulphide peaks are still visible, a significant pair of
peaks formed in the region corresponding to sulphates and
other oxidised forms of sulphur, suggesting that some sul-
phates have formed or been deposited at the surface. After
35 days of leaching, the sulphide peaks are no longer vis-
ible and the sulphur content at the surface is dominated by
sulphates. Similarly, peaks corresponding to iron sulphates
formed during the leaching process, as observed in the sec-
ond panel of Figure 7.
Figure 6. Changes in the crack network for a slice
corresponding to the first column before leaching (day 0),
and after 22 days and 72 days of leaching
