1730 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
of the aqueous solution. In this study, kinetics rates over
shorter and longer periods (30 seconds and 30 minutes,
respectively) and activation energy for both Co and Mn
were calculated, as the early moments of the reaction follow
a very high rate for nucleation. Afterward, growth starts,
and its rate is much higher than nucleation. The effect of
process parameters and calculated activation energy values
for Co-Mn (Figure 8) collectively indicate that the process
is more likely a diffusion-controlled reaction for Co and
Mn, suggesting that the reaction rate is less sensitive to tem-
perature compared to chemical control reactions. Instead,
the diffusion coefficient, which influences how quickly
reactants can diffuse and mix, plays a significant role. This
implies that the rate at which ozone molecules diffuse to,
possibly, the surface of the Co and Mn particles, largely
determines the reaction rate. Therefore, the mass transfer
of ozone plays a crucial role in the oxidative precipitation
of Co-Mn. To further determine the formation and mor-
phology of precipitates, the products of Co-Mn precipita-
tion through ozone treatment at two extreme temperatures
(20 °C and 80 °C) were characterized using SEM-EDS, as
depicted in Figure 9. The images from SEM-EDS revealed
that the majority of the Co-Mn particles that precipitated
were in the micron to submicron range, characterized by
irregular shapes and rough morphology. The difference in
crystallization was not obvious in SEM micrographs. A
significant amount of Mn-oxygen detected in EDS can be
attributed to the formation of Mn oxide, as it was aligned
with solution chemistry and confirmed by XRD analysis in
our previous work (Shekarian et al., 2022).
Oxidative precipitation of Co and Mn using ozone
is a process influenced by considerable factors, including
solution chemistry, process parameters, and kinetic reac-
tions. For the process scale-up, various factors, including
reactor design, gas flow rate, stirring time, and other pro-
cess parameters, should be identified to enhance the mass
transfer and reaction kinetics in practical applications for
the recovery of Co-Mn. Therefore, the interactive effects
of process parameters should be further studied in future
research.
CONCLUSIONS
In this study, the effects of temperature, gas flow rate, and
stirring rate on the oxidative precipitation of Co and Mn
using ozone from aqueous solutions were investigated.
The calculated saturation indices, supported by Pourbaix
diagram analysis, clearly demonstrate the feasibility of
Co-Mn recovery using ozone under a wide range of pH
Figure 9. SEM micrographs of precipitated solids from oxidative ozone precipitation and EDS mapping of precipitates at
temperatures 20 °C (a) and 80 °C (b)
of the aqueous solution. In this study, kinetics rates over
shorter and longer periods (30 seconds and 30 minutes,
respectively) and activation energy for both Co and Mn
were calculated, as the early moments of the reaction follow
a very high rate for nucleation. Afterward, growth starts,
and its rate is much higher than nucleation. The effect of
process parameters and calculated activation energy values
for Co-Mn (Figure 8) collectively indicate that the process
is more likely a diffusion-controlled reaction for Co and
Mn, suggesting that the reaction rate is less sensitive to tem-
perature compared to chemical control reactions. Instead,
the diffusion coefficient, which influences how quickly
reactants can diffuse and mix, plays a significant role. This
implies that the rate at which ozone molecules diffuse to,
possibly, the surface of the Co and Mn particles, largely
determines the reaction rate. Therefore, the mass transfer
of ozone plays a crucial role in the oxidative precipitation
of Co-Mn. To further determine the formation and mor-
phology of precipitates, the products of Co-Mn precipita-
tion through ozone treatment at two extreme temperatures
(20 °C and 80 °C) were characterized using SEM-EDS, as
depicted in Figure 9. The images from SEM-EDS revealed
that the majority of the Co-Mn particles that precipitated
were in the micron to submicron range, characterized by
irregular shapes and rough morphology. The difference in
crystallization was not obvious in SEM micrographs. A
significant amount of Mn-oxygen detected in EDS can be
attributed to the formation of Mn oxide, as it was aligned
with solution chemistry and confirmed by XRD analysis in
our previous work (Shekarian et al., 2022).
Oxidative precipitation of Co and Mn using ozone
is a process influenced by considerable factors, including
solution chemistry, process parameters, and kinetic reac-
tions. For the process scale-up, various factors, including
reactor design, gas flow rate, stirring time, and other pro-
cess parameters, should be identified to enhance the mass
transfer and reaction kinetics in practical applications for
the recovery of Co-Mn. Therefore, the interactive effects
of process parameters should be further studied in future
research.
CONCLUSIONS
In this study, the effects of temperature, gas flow rate, and
stirring rate on the oxidative precipitation of Co and Mn
using ozone from aqueous solutions were investigated.
The calculated saturation indices, supported by Pourbaix
diagram analysis, clearly demonstrate the feasibility of
Co-Mn recovery using ozone under a wide range of pH
Figure 9. SEM micrographs of precipitated solids from oxidative ozone precipitation and EDS mapping of precipitates at
temperatures 20 °C (a) and 80 °C (b)