XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1729
addition of the ozone while maintaining pH at 7. Increasing
the level of a precipitant or an oxidizer in a supersaturated
solution can enhance the precipitation rate by altering the
equilibrium state, increasing the level of supersaturation,
and leading to a considerably high nucleation rate of the
Co-Mn. This corroborates previous research, which indi-
cated that elements precipitate more rapidly at increased
levels of supersaturation (Myerson, 2002 Vaziri Hassas et
al., 2023). In addition, following the initial minutes of reac-
tion, it was observed that the precipitation of Co and Mn
initially slightly decreased and then gradually increased over
the duration of the experiments. This pattern suggests the
occurrence of Ostwald ripening in the system, indicating
the dissolution of smaller particles. Particles smaller than a
critical nucleation size in a solution have a higher chemical
potential than larger ones, leading to their dissolution in
the aqueous solution (Myerson, 2002 Vaziri Hassas et al.,
2022). It’s important to highlight that while the precipi-
tation was noticeable for up to five minutes, it continued
until the experiment concluded in 30 minutes. The differ-
ences in precipitation rate of Mn and Co with respect to
temperature may be attributed to a combination of factors,
including differences in solubility, the significance of ozone
in promoting precipitation, the required ORP in the aque-
ous solution, the concentration of the metal ions in the
solution, and the presence of other compounds in the solu-
tion (Kim &Baird, 2005 Ichlas et al., 2020).
In this study, the activation energy values of the reac-
tion were calculated to understand the mechanism govern-
ing the ozone oxidative precipitation of Co and Mn during
the first 30 seconds and 30 minutes of precipitation using
the three models. It was found that Pseudo-homogeneous
model was the best fit with the precipitation data at the first
30 seconds and 30 minutes (Figure 8).
Providing a specific mechanism for Co-Mn precipitation
using ozone is challenging as it involves several concurrent
phenomena (i.e., mass transfer of ozone, ozone conversion
to oxygen, co-precipitation and adsorption effects on pre-
cipitates of elements, and competing reactions), making it
difficult to deconvolute the different processes. Specifically,
the interfacial mass transfer of ozone to the aqueous phase
plays a significant role as it is continuously injected into
the reaction throughout the process. Once ozone reaches
the gas-liquid interface, it should dissolve into the liquid
phase, and the rate at which it dissolves is influenced by
the system’s transport of gaseous species from the bubble
surface due to convection and diffusion, and factors such
as temperature, pressure, and the solubility of ozone in
the liquid. Once dissolved in the liquid, ozone undergoes
various chemical reactions depending on the composition
Figure 8. The activation energy for Co and Mn solution at two different times (60 seconds and 30 minutes)
addition of the ozone while maintaining pH at 7. Increasing
the level of a precipitant or an oxidizer in a supersaturated
solution can enhance the precipitation rate by altering the
equilibrium state, increasing the level of supersaturation,
and leading to a considerably high nucleation rate of the
Co-Mn. This corroborates previous research, which indi-
cated that elements precipitate more rapidly at increased
levels of supersaturation (Myerson, 2002 Vaziri Hassas et
al., 2023). In addition, following the initial minutes of reac-
tion, it was observed that the precipitation of Co and Mn
initially slightly decreased and then gradually increased over
the duration of the experiments. This pattern suggests the
occurrence of Ostwald ripening in the system, indicating
the dissolution of smaller particles. Particles smaller than a
critical nucleation size in a solution have a higher chemical
potential than larger ones, leading to their dissolution in
the aqueous solution (Myerson, 2002 Vaziri Hassas et al.,
2022). It’s important to highlight that while the precipi-
tation was noticeable for up to five minutes, it continued
until the experiment concluded in 30 minutes. The differ-
ences in precipitation rate of Mn and Co with respect to
temperature may be attributed to a combination of factors,
including differences in solubility, the significance of ozone
in promoting precipitation, the required ORP in the aque-
ous solution, the concentration of the metal ions in the
solution, and the presence of other compounds in the solu-
tion (Kim &Baird, 2005 Ichlas et al., 2020).
In this study, the activation energy values of the reac-
tion were calculated to understand the mechanism govern-
ing the ozone oxidative precipitation of Co and Mn during
the first 30 seconds and 30 minutes of precipitation using
the three models. It was found that Pseudo-homogeneous
model was the best fit with the precipitation data at the first
30 seconds and 30 minutes (Figure 8).
Providing a specific mechanism for Co-Mn precipitation
using ozone is challenging as it involves several concurrent
phenomena (i.e., mass transfer of ozone, ozone conversion
to oxygen, co-precipitation and adsorption effects on pre-
cipitates of elements, and competing reactions), making it
difficult to deconvolute the different processes. Specifically,
the interfacial mass transfer of ozone to the aqueous phase
plays a significant role as it is continuously injected into
the reaction throughout the process. Once ozone reaches
the gas-liquid interface, it should dissolve into the liquid
phase, and the rate at which it dissolves is influenced by
the system’s transport of gaseous species from the bubble
surface due to convection and diffusion, and factors such
as temperature, pressure, and the solubility of ozone in
the liquid. Once dissolved in the liquid, ozone undergoes
various chemical reactions depending on the composition
Figure 8. The activation energy for Co and Mn solution at two different times (60 seconds and 30 minutes)