XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1877
indicates that Ni recovery is not significantly impacted by
increasing the molar concentration of H2SO4. The addition
of 20 g/L of FeCl3, on the other hand, boosted Ni recovery,
whilst the addition of NaCl and MgCl2 had no beneficial
effects. The influence of FeCl3 could be associated with its
oxidizing and complexing potential (Xu et al., 2022). In
a recent study, it was discovered that when solid chlorides
were employed to treat sulfidic ores, the extra SO2 created
during the oxidation of metal sulfides accelerated the leach-
ing process and enhanced the metal recoveries (Park et al.,
2006). It is noteworthy that the chemicals utilized in the
initial investigations were likewise analytically pure. Thus,
for the next series of studies, FeCl3 was chosen as the chlo-
rination/oxidizing agent.
Experimental Design
Utilizing design of experiments (DOE), an efficient tech-
nique that can be used in various experimental settings,
an empirical model was developed to determine the ideal
leaching conditions (Marion et al., 2019 Owusu et al.,
2022 Rao et al., 2021). More specifically, through apply-
ing RSM to correlate the quantitative leaching experiment
data to statistical and mathematical equations. To verify
the ideal circumstances for the leaching of the polymetallic
sample, a five-factor, three-coded level (low: –1, center: 0,
and high: +1) central composite design (CCD)-based RSM
technique was applied. A total of (2k +2k +n0) runs is typi-
cally used in CCD, where n0 is the number of tests carried
out in the center, 2k and k are the factorial design points,
face-centered points, and number of components studied,
respectively (Garg &Jain, 2020). The center locations were
duplicated in order to calculate the relative experimen-
tal error. A 25-factorial design was used in this investiga-
tion, and 32 tests were conducted to match the five CCD
parameters.
Considering that the feed sample is polymetallic, the
parameter levels and values are highlighted in Table 1, with
the recoveries of Ni and Cu being regarded as response vari-
ables (Table 3). To reduce the impact of systematic errors,
the leaching experiments were carried out in a random
order in accordance with the experimental design (Table 2)
(Garg &Jain, 2020). The experiments were designed using
Minitab software (version 21.4.2), which was also utilized
for the subsequent regression and graphical analysis of the
leaching data.
Experimental Procedure
Each experiment (shown in Table 2) was carried out in a
water bath using 100 mL of the leach solution and 10 g of
the ground material. The catalyst and lixiviant concentra-
tion, duration of milling, leaching temperature, and time
were all adjusted during the experiment. The agitator was
maintained at 200 revs per minute. At predetermined inter-
vals, solution samples from the leach liquor were collected
and filtered using a centrifuge prior to ICP-OES chemical
analysis. Using the formula provided in Eq. (1), the leach-
ing recoveries of Ni and Cu were calculated.
Ff
Cc 100% R #=(1)
where
R =The leaching recovery of Ni and Cu (%).
C =The volume of leach liquor (mL).
c =The concentration of each metal in the leach
liquor (mg/L).
F =The mass of the feed sample (g).
f =The concentration of each metal in the feed
sample (mg/kg).
Characterization
Using a particle size analyzer, the ground sample’s par-
ticle size distribution was evaluated in order to verify the
cumulative percent passing. Further analysis was also done
to ascertain the size deportment of the valuable metals in
the rougher tailings. The acid digestion procedure was used
to analyze the feed sample’s elemental composition. To do
this, a homogenous amount of the produced feed sample
was vacuum filtered, diluted with distilled water, and sub-
jected to an hour of immersion in newly made aqua regia
at 250 °C. The ICP-OES was then utilized for analysis.
Using Cu Kα radiation, X-ray diffraction (XRD) was used
to determine the mineral components. Using an Energy
Table 1. The coded parameter levels and values used in the experimental design
Parameter Units Symbols
Coded variables and levels
–1 0 +1
Grind time mins n
1 0 5 10
Catalyst dosage wt.% n
2 0 15 30
H2SO4 concentration M n3 0 0.5 1
Leaching time h n4 4 8 12
Leaching temp. °C n
5 20 50 80
indicates that Ni recovery is not significantly impacted by
increasing the molar concentration of H2SO4. The addition
of 20 g/L of FeCl3, on the other hand, boosted Ni recovery,
whilst the addition of NaCl and MgCl2 had no beneficial
effects. The influence of FeCl3 could be associated with its
oxidizing and complexing potential (Xu et al., 2022). In
a recent study, it was discovered that when solid chlorides
were employed to treat sulfidic ores, the extra SO2 created
during the oxidation of metal sulfides accelerated the leach-
ing process and enhanced the metal recoveries (Park et al.,
2006). It is noteworthy that the chemicals utilized in the
initial investigations were likewise analytically pure. Thus,
for the next series of studies, FeCl3 was chosen as the chlo-
rination/oxidizing agent.
Experimental Design
Utilizing design of experiments (DOE), an efficient tech-
nique that can be used in various experimental settings,
an empirical model was developed to determine the ideal
leaching conditions (Marion et al., 2019 Owusu et al.,
2022 Rao et al., 2021). More specifically, through apply-
ing RSM to correlate the quantitative leaching experiment
data to statistical and mathematical equations. To verify
the ideal circumstances for the leaching of the polymetallic
sample, a five-factor, three-coded level (low: –1, center: 0,
and high: +1) central composite design (CCD)-based RSM
technique was applied. A total of (2k +2k +n0) runs is typi-
cally used in CCD, where n0 is the number of tests carried
out in the center, 2k and k are the factorial design points,
face-centered points, and number of components studied,
respectively (Garg &Jain, 2020). The center locations were
duplicated in order to calculate the relative experimen-
tal error. A 25-factorial design was used in this investiga-
tion, and 32 tests were conducted to match the five CCD
parameters.
Considering that the feed sample is polymetallic, the
parameter levels and values are highlighted in Table 1, with
the recoveries of Ni and Cu being regarded as response vari-
ables (Table 3). To reduce the impact of systematic errors,
the leaching experiments were carried out in a random
order in accordance with the experimental design (Table 2)
(Garg &Jain, 2020). The experiments were designed using
Minitab software (version 21.4.2), which was also utilized
for the subsequent regression and graphical analysis of the
leaching data.
Experimental Procedure
Each experiment (shown in Table 2) was carried out in a
water bath using 100 mL of the leach solution and 10 g of
the ground material. The catalyst and lixiviant concentra-
tion, duration of milling, leaching temperature, and time
were all adjusted during the experiment. The agitator was
maintained at 200 revs per minute. At predetermined inter-
vals, solution samples from the leach liquor were collected
and filtered using a centrifuge prior to ICP-OES chemical
analysis. Using the formula provided in Eq. (1), the leach-
ing recoveries of Ni and Cu were calculated.
Ff
Cc 100% R #=(1)
where
R =The leaching recovery of Ni and Cu (%).
C =The volume of leach liquor (mL).
c =The concentration of each metal in the leach
liquor (mg/L).
F =The mass of the feed sample (g).
f =The concentration of each metal in the feed
sample (mg/kg).
Characterization
Using a particle size analyzer, the ground sample’s par-
ticle size distribution was evaluated in order to verify the
cumulative percent passing. Further analysis was also done
to ascertain the size deportment of the valuable metals in
the rougher tailings. The acid digestion procedure was used
to analyze the feed sample’s elemental composition. To do
this, a homogenous amount of the produced feed sample
was vacuum filtered, diluted with distilled water, and sub-
jected to an hour of immersion in newly made aqua regia
at 250 °C. The ICP-OES was then utilized for analysis.
Using Cu Kα radiation, X-ray diffraction (XRD) was used
to determine the mineral components. Using an Energy
Table 1. The coded parameter levels and values used in the experimental design
Parameter Units Symbols
Coded variables and levels
–1 0 +1
Grind time mins n
1 0 5 10
Catalyst dosage wt.% n
2 0 15 30
H2SO4 concentration M n3 0 0.5 1
Leaching time h n4 4 8 12
Leaching temp. °C n
5 20 50 80