1726 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
influence the precipitation of Co-Mn, the saturation indi-
ces were calculated using Visual MINTEQ, based on the
concentration of these elements in AMD (Figure 2). The
results showed SI values for Co and Mn oxide formation
are positive at pH around 2 when ozone is available in the
system. The results also showed that the precipitation of
these elements using ligands required elevated pH values
(i.e., higher than 9). Moreover, in all corresponding pH,
the values of SI for Co(OH)2 and Mn(OH)2 are lower
than Co2O3 and Mn2O3 due to the higher solubility of
Mn-Co (II)-hydroxide in aqueous solution. The saturation
index data agrees with our previous experimental results as
more than 95% of Co and Mn were recovered from AMD
using ozone as an oxidizing agent at acidic or neutral pH
(Shekarian et al., 2022).
Figures 3 a&b present Eh-pH diagrams illustrating the
conditions for Co-Mn elements that undergo the formation
of insoluble compounds when subjected to ozone oxidative
precipitation. The results of Pourbaix diagrams showed that
ozone could be potentially used for the recovery of Co and
Mn at pH range from very acidic solution (i.e., MnO2 for-
mation through arrow A3 path in Figure 3a) to around 7
(following arrow A2 in Figure 3a, and arrow A1 in Figure 3b
to form Mn2O3 and Co(OH)3, correspondingly, or arrow
A1 in Figure 3a for Mn3O4 formation). These pH-Eh dia-
grams provide baselines to determine the solution param-
eters (such as potential, pH, and temperature) for the
precipitation of specific elements of interest. In this study,
we followed the path shown by arrow A2 in Figure 3a and
arrow A1 in Figure 3b to produce higher grade precipitates
Figure 2. Saturation indexes of Co and Mn as a function of solution pH
Figure 3. Eh-pH diagrams for Co (0.1 mM) and Mn (1 mM) (a&b) showing the predominant species in H2O system at 25 °C
influence the precipitation of Co-Mn, the saturation indi-
ces were calculated using Visual MINTEQ, based on the
concentration of these elements in AMD (Figure 2). The
results showed SI values for Co and Mn oxide formation
are positive at pH around 2 when ozone is available in the
system. The results also showed that the precipitation of
these elements using ligands required elevated pH values
(i.e., higher than 9). Moreover, in all corresponding pH,
the values of SI for Co(OH)2 and Mn(OH)2 are lower
than Co2O3 and Mn2O3 due to the higher solubility of
Mn-Co (II)-hydroxide in aqueous solution. The saturation
index data agrees with our previous experimental results as
more than 95% of Co and Mn were recovered from AMD
using ozone as an oxidizing agent at acidic or neutral pH
(Shekarian et al., 2022).
Figures 3 a&b present Eh-pH diagrams illustrating the
conditions for Co-Mn elements that undergo the formation
of insoluble compounds when subjected to ozone oxidative
precipitation. The results of Pourbaix diagrams showed that
ozone could be potentially used for the recovery of Co and
Mn at pH range from very acidic solution (i.e., MnO2 for-
mation through arrow A3 path in Figure 3a) to around 7
(following arrow A2 in Figure 3a, and arrow A1 in Figure 3b
to form Mn2O3 and Co(OH)3, correspondingly, or arrow
A1 in Figure 3a for Mn3O4 formation). These pH-Eh dia-
grams provide baselines to determine the solution param-
eters (such as potential, pH, and temperature) for the
precipitation of specific elements of interest. In this study,
we followed the path shown by arrow A2 in Figure 3a and
arrow A1 in Figure 3b to produce higher grade precipitates
Figure 2. Saturation indexes of Co and Mn as a function of solution pH
Figure 3. Eh-pH diagrams for Co (0.1 mM) and Mn (1 mM) (a&b) showing the predominant species in H2O system at 25 °C