1888 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
effectively used to the leaching process of nickel sulfide tail-
ings to recover valuable constituents.
Leaching Kinetics
Studying the mechanism of Ni and Cu leaching from the
rougher tailings requires an understanding of the kinetics of
dissolution. To provide theoretical guidance for industrial
applications, it is also critical to create a kinetic model (Mu
et al., 2020 Nazemi et al., 2011). By examining the experi-
mental leaching recoveries as a function of time at various
temperatures within the scope of the study, the standard
shrinking-core model was employed to ascertain the kinetic
model of the dissolving reaction or solid-liquid reaction
system.
The dissolution kinetics in the shrinking-core model
(Levenspiel, 1998) are linked to three equations that rep-
resent the interface reaction, internal diffusion, and exter-
nal diffusion, respectively, as shown in Eqs. (7), (8), and
(9), (Ajiboye et al., 2019 Ju et al., 2024 Rao et al., 2021
Veglio et al., 2001).
1 − (1 − X)1/3 =k1t (7)
1 +2(1 − X) − 3(1 − X)2/3 =k2t (8)
1 − (1 − X)2/3 =k3t (9)
where
X =The leaching recoveries of Ni and Cu.
t =The leaching time (h).
k1 =The apparent rate constants for interface reac-
tion control model.
k2 =The apparent rate constants for internal diffu-
sion control model.
k3 =The apparent rate constants for external diffu-
sion control model.
The analysis of the experimental recoveries using the
above kinetic equations displayed significant and almost
linear fitting for Ni and Cu (as presented in Figure. 9).
Based on the R2 values, the internal diffusion control
model fitted well for the leaching of Ni and Cu (Figure. 9)
from the rougher tailings. Comparable observations were
made recently by researchers studying the extraction of Mn,
Fe, Co, Ni, and Cu from oceanic cobalt-rich crust (Ju et
al., 2024). They observed that reaction of Ni, Cu, Co, and
Cr were predominantly internal and thus chemically con-
trolled. In that, these elements were locked in the Fe-Mg
silicate matrix, and the lixiviants could only diffuse into the
interior of the particles and encounter them for the sulfa-
tion process after the pentlandite grains were oxidized.
Consequently, the models of good fit were used to cal-
culate a range of experimental activation energies to validate
the kinetic models, based on the Arrhenius plots presented
in Figure. 10. The analysis of the data revealed apparent
activation energies 19.17 kJ/mol and 15.54 kJ/mol for Ni
and Cu, respectively. Typically, higher apparent activation
energies are observed for internal diffusion control models,
since the activation energy required to catalyze the chemical
reaction occurring at the surface of the particles is higher
compared to the activation energy needed for the diffusion
of the reactant at the interface of the particles (Ajiboye et
al., 2019).
k =Aexp(− Ea/RT) (10)
where
k =The apparent rate constant (h−1).
A =The pre-exponential factor (h−1).
Ea =The activation energy (J/mol).
R =The molar gas constant (8.314 J/(mol⋅k)).
T =The thermodynamic temperature (K).
CONCLUSIONS
Rougher flotation tailings were successfully leached under
atmospheric circumstances in a lab-scale water bath, with
ferric chloride at different milling times, leaching tempera-
tures, leaching times, and concentrations of sulfuric acid,
as operational parameters. The recovery of the valuable
contents (98.92% and 93.68% Ni 99.14% and 98.27%
Cu) was achieved using the optimal conditions from CCD-
based RSM studies. Among the parameters studied, the
most effect parameter was the catalyst dosage, grind time
and leaching temperature in the case of Ni, and leaching
temperature and catalyst addition greatly affected the recov-
ery of Cu. The kinetic studies have shown that during the
leaching of the rougher tailings, the dissolution rates of Ni
and Cu were controlled by internal diffusion, and respec-
tively the apparent activation energies are 19.17 kJ/mol and
15.54 kJ/mol. This study indicates that ferric chloride addi-
tion tends to facilitate sulfidic component oxidation, which
accelerates leaching kinetics and facilitates effective recov-
ery of important elements hosted in the sulfide matrix.
Considering the green energy transition, the findings from
this current investigation offer significant new insights into
the sustainable processing of nickel sulfide flotation tailings.
effectively used to the leaching process of nickel sulfide tail-
ings to recover valuable constituents.
Leaching Kinetics
Studying the mechanism of Ni and Cu leaching from the
rougher tailings requires an understanding of the kinetics of
dissolution. To provide theoretical guidance for industrial
applications, it is also critical to create a kinetic model (Mu
et al., 2020 Nazemi et al., 2011). By examining the experi-
mental leaching recoveries as a function of time at various
temperatures within the scope of the study, the standard
shrinking-core model was employed to ascertain the kinetic
model of the dissolving reaction or solid-liquid reaction
system.
The dissolution kinetics in the shrinking-core model
(Levenspiel, 1998) are linked to three equations that rep-
resent the interface reaction, internal diffusion, and exter-
nal diffusion, respectively, as shown in Eqs. (7), (8), and
(9), (Ajiboye et al., 2019 Ju et al., 2024 Rao et al., 2021
Veglio et al., 2001).
1 − (1 − X)1/3 =k1t (7)
1 +2(1 − X) − 3(1 − X)2/3 =k2t (8)
1 − (1 − X)2/3 =k3t (9)
where
X =The leaching recoveries of Ni and Cu.
t =The leaching time (h).
k1 =The apparent rate constants for interface reac-
tion control model.
k2 =The apparent rate constants for internal diffu-
sion control model.
k3 =The apparent rate constants for external diffu-
sion control model.
The analysis of the experimental recoveries using the
above kinetic equations displayed significant and almost
linear fitting for Ni and Cu (as presented in Figure. 9).
Based on the R2 values, the internal diffusion control
model fitted well for the leaching of Ni and Cu (Figure. 9)
from the rougher tailings. Comparable observations were
made recently by researchers studying the extraction of Mn,
Fe, Co, Ni, and Cu from oceanic cobalt-rich crust (Ju et
al., 2024). They observed that reaction of Ni, Cu, Co, and
Cr were predominantly internal and thus chemically con-
trolled. In that, these elements were locked in the Fe-Mg
silicate matrix, and the lixiviants could only diffuse into the
interior of the particles and encounter them for the sulfa-
tion process after the pentlandite grains were oxidized.
Consequently, the models of good fit were used to cal-
culate a range of experimental activation energies to validate
the kinetic models, based on the Arrhenius plots presented
in Figure. 10. The analysis of the data revealed apparent
activation energies 19.17 kJ/mol and 15.54 kJ/mol for Ni
and Cu, respectively. Typically, higher apparent activation
energies are observed for internal diffusion control models,
since the activation energy required to catalyze the chemical
reaction occurring at the surface of the particles is higher
compared to the activation energy needed for the diffusion
of the reactant at the interface of the particles (Ajiboye et
al., 2019).
k =Aexp(− Ea/RT) (10)
where
k =The apparent rate constant (h−1).
A =The pre-exponential factor (h−1).
Ea =The activation energy (J/mol).
R =The molar gas constant (8.314 J/(mol⋅k)).
T =The thermodynamic temperature (K).
CONCLUSIONS
Rougher flotation tailings were successfully leached under
atmospheric circumstances in a lab-scale water bath, with
ferric chloride at different milling times, leaching tempera-
tures, leaching times, and concentrations of sulfuric acid,
as operational parameters. The recovery of the valuable
contents (98.92% and 93.68% Ni 99.14% and 98.27%
Cu) was achieved using the optimal conditions from CCD-
based RSM studies. Among the parameters studied, the
most effect parameter was the catalyst dosage, grind time
and leaching temperature in the case of Ni, and leaching
temperature and catalyst addition greatly affected the recov-
ery of Cu. The kinetic studies have shown that during the
leaching of the rougher tailings, the dissolution rates of Ni
and Cu were controlled by internal diffusion, and respec-
tively the apparent activation energies are 19.17 kJ/mol and
15.54 kJ/mol. This study indicates that ferric chloride addi-
tion tends to facilitate sulfidic component oxidation, which
accelerates leaching kinetics and facilitates effective recov-
ery of important elements hosted in the sulfide matrix.
Considering the green energy transition, the findings from
this current investigation offer significant new insights into
the sustainable processing of nickel sulfide flotation tailings.