1724 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
AMD sample at pH 7, obtained from the carbonate pre-
cipitation process (Shekarian et al., 2022).
Ozone Oxidative Precipitation
This study evaluated the effect of process parameters such
as stirring rate, gas flow rate, and temperature on oxidative
precipitation of Co-Mn using ozone from AMD, aiming
to treat AMD effectively while addressing associated envi-
ronmental concerns. The AMD was first subjected to our
patented carbonate stage precipitation process for the selec-
tive recovery of Fe, Al, and REE at pH values of 4, 5, and
7 (Rezaee et al., 2021&2022 Shekarian et al., 2022). The
neutralized AMD (pH 7) was then subjected to the ozone
oxidative precipitation to recover Co and Mn. ACS grade
NaOH was used to adjust the solutions’ pH during oxida-
tive precipitation. For the oxidative ozone precipitation, two
1000 mg/h ozone generators (T-king Enaly Model), with
99% purity oxygen as the input gas, were utilized to sparge
ozone using a porous bubble diffuser into the solution. The
volumetric flow rate of ozone injected into the system was
controlled by a flowmeter, and the setup was equipped with
a potential control as shown in Figure 1. The flow rate of
the oxygen was manually regulated via a flow meter feeding
to the generator. A diffuser introduced the resulting O2/
O3 mix into a 500 ml reactor. During the experiment, pH
and redox potential were consistently monitored within the
reactor. Samples collection was performed at different time
increments (0sec, 5sec, 15sec, 30sec, 45sec, 60sec, 90sec,
120sec, 5 min, 10 min, 15 min, 20 min, and 30 min). A 5
ml sample was collected at each time interval and promptly
filtered using EZFlow ® syringe filters with a 0.22 µm pore
size to monitor the concentration of elements. Following
filtration, the filtrates were quickly acidified with 70%
HNO3, ensuring a 5% HNO3 concentration in the solu-
tion to inhibit additional precipitation. Triplicate experi-
ments were performed to report data in a 95% confidence
interval (CI). The choice of process parameters and reagents
for each stage was informed by earlier research studies
(Shekarian et al., 2022 Vaziri Hassas et al., 2023) and a
patented procedure (Rezaee et al., 2022). The experimen-
tal setup used in this study is schematically illustrated in
Figure 1.
Kinetic of Precipitation
Experiments were conducted by changing one parameter at
a time to obtain the required kinetic data while keeping the
other parameters constant. A total of 13 experiments were
conducted for AMD samples to study the effect of individ-
ual parameters. Various parameters studied in these experi-
ments are flow rate (@200, 800, 1400, and 2000 cc/min),
stirring rate (@0, 400, 800, 1200, and 1500 rpm), and
temperatures (20 °C, 40 °C, 60 °C, and 80 °C). All flow
and stirring rate variation tests were performed in 500 ml
solutions at room temperature (20±2.5°C). Experiments to
measure the kinetics rate and activation energy were carried
out at four distinct temperatures to assess the influence of
temperature on the precipitation rate of Co and Mn.
Figure 1. Experimental setup for parametric study
AMD sample at pH 7, obtained from the carbonate pre-
cipitation process (Shekarian et al., 2022).
Ozone Oxidative Precipitation
This study evaluated the effect of process parameters such
as stirring rate, gas flow rate, and temperature on oxidative
precipitation of Co-Mn using ozone from AMD, aiming
to treat AMD effectively while addressing associated envi-
ronmental concerns. The AMD was first subjected to our
patented carbonate stage precipitation process for the selec-
tive recovery of Fe, Al, and REE at pH values of 4, 5, and
7 (Rezaee et al., 2021&2022 Shekarian et al., 2022). The
neutralized AMD (pH 7) was then subjected to the ozone
oxidative precipitation to recover Co and Mn. ACS grade
NaOH was used to adjust the solutions’ pH during oxida-
tive precipitation. For the oxidative ozone precipitation, two
1000 mg/h ozone generators (T-king Enaly Model), with
99% purity oxygen as the input gas, were utilized to sparge
ozone using a porous bubble diffuser into the solution. The
volumetric flow rate of ozone injected into the system was
controlled by a flowmeter, and the setup was equipped with
a potential control as shown in Figure 1. The flow rate of
the oxygen was manually regulated via a flow meter feeding
to the generator. A diffuser introduced the resulting O2/
O3 mix into a 500 ml reactor. During the experiment, pH
and redox potential were consistently monitored within the
reactor. Samples collection was performed at different time
increments (0sec, 5sec, 15sec, 30sec, 45sec, 60sec, 90sec,
120sec, 5 min, 10 min, 15 min, 20 min, and 30 min). A 5
ml sample was collected at each time interval and promptly
filtered using EZFlow ® syringe filters with a 0.22 µm pore
size to monitor the concentration of elements. Following
filtration, the filtrates were quickly acidified with 70%
HNO3, ensuring a 5% HNO3 concentration in the solu-
tion to inhibit additional precipitation. Triplicate experi-
ments were performed to report data in a 95% confidence
interval (CI). The choice of process parameters and reagents
for each stage was informed by earlier research studies
(Shekarian et al., 2022 Vaziri Hassas et al., 2023) and a
patented procedure (Rezaee et al., 2022). The experimen-
tal setup used in this study is schematically illustrated in
Figure 1.
Kinetic of Precipitation
Experiments were conducted by changing one parameter at
a time to obtain the required kinetic data while keeping the
other parameters constant. A total of 13 experiments were
conducted for AMD samples to study the effect of individ-
ual parameters. Various parameters studied in these experi-
ments are flow rate (@200, 800, 1400, and 2000 cc/min),
stirring rate (@0, 400, 800, 1200, and 1500 rpm), and
temperatures (20 °C, 40 °C, 60 °C, and 80 °C). All flow
and stirring rate variation tests were performed in 500 ml
solutions at room temperature (20±2.5°C). Experiments to
measure the kinetics rate and activation energy were carried
out at four distinct temperatures to assess the influence of
temperature on the precipitation rate of Co and Mn.
Figure 1. Experimental setup for parametric study