XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3309
produced from coconut shells are characterized by its supe-
rior level of hardness (Kove, Buah, and Dankwa 2021).
Leaching Kinetics of the Ni Recovery
To determine the kinetic model of the dissolution reaction
or solid-liquid reaction system, the standard shrinking-core
model was applied by analyzing the experimental leaching
recoveries verses time at different temperatures within the
range of study. In the shrinking-core model (Levenspiel
1998), the dissolution kinetics are associated to three equa-
tions denoting interface reaction, internal diffusion, and
external diffusion as indicated in Eqs. (7), (8), and (9), cor-
respondingly (Veglio, Trifoni, Pagnanelli, and Toro 2001
Rao, Singh, Morrison, and Love 2021 Ajiboye et al. 2019
Ju et al. 2024).
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 in the FeCl3 and
AC medium
t =The leaching time (h)
k1 =The apparent rate constants for interface reaction
control model
Process Optimization and Model Validation
The optimization software in the Minitab RSM tool was
employed with the goal of obtaining the maximum leach-
ing recoveries for the valuable metals. The results of the sur-
face response model showed that the optimal leaching of
Ni using FeCl3 were as follows: FeCl3 addition of 30 g/L,
leaching temperature of 80 °C for 24 h, whereas that of
AC were: H2SO4 concentration of 1 M, AC addition of
30 g/L, and leaching temperature of 80 °C for 24 h. Under
these optimal conditions, the predicted and experimental
leaching recoveries were correspondingly 99.63% and avg.
98.02% for ferric chloride, and 98.94% and avg. 97.95%
for activated carbon. In accordance, the constructed qua-
dratic regression model was reasonable, and the fitting effect
was ideal, which can be applied to predict the recovery of
valuable metals from sulfidic rougher flotation tailings.
Considering the high Ni recovery, environmental
friendliness of activated carbon and feasibility of practical
operation, the reuse of the AC was appropriately tested.
Herein, using the optimal conditions, the activated carbon
was evaluated for regeneration and reuse. The results, as
presented in Figure 8, demonstrates that the AC performed
effectively for five consecutive cycles. This could be due to
its granular nature and the type of biomass used (Owusu,
Mends, and Acquah 2022). Typically, activated carbon
0
20
40
60
80
100
1st Cycle 2nd Cycle 3rd Cycle 4th Cycle 5th Cycle
Figure 8. The leaching recovery of Ni using AC in acidic medium and cyclic efficiency of
the residual AC
Ni
recovery
(%)
produced from coconut shells are characterized by its supe-
rior level of hardness (Kove, Buah, and Dankwa 2021).
Leaching Kinetics of the Ni Recovery
To determine the kinetic model of the dissolution reaction
or solid-liquid reaction system, the standard shrinking-core
model was applied by analyzing the experimental leaching
recoveries verses time at different temperatures within the
range of study. In the shrinking-core model (Levenspiel
1998), the dissolution kinetics are associated to three equa-
tions denoting interface reaction, internal diffusion, and
external diffusion as indicated in Eqs. (7), (8), and (9), cor-
respondingly (Veglio, Trifoni, Pagnanelli, and Toro 2001
Rao, Singh, Morrison, and Love 2021 Ajiboye et al. 2019
Ju et al. 2024).
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 in the FeCl3 and
AC medium
t =The leaching time (h)
k1 =The apparent rate constants for interface reaction
control model
Process Optimization and Model Validation
The optimization software in the Minitab RSM tool was
employed with the goal of obtaining the maximum leach-
ing recoveries for the valuable metals. The results of the sur-
face response model showed that the optimal leaching of
Ni using FeCl3 were as follows: FeCl3 addition of 30 g/L,
leaching temperature of 80 °C for 24 h, whereas that of
AC were: H2SO4 concentration of 1 M, AC addition of
30 g/L, and leaching temperature of 80 °C for 24 h. Under
these optimal conditions, the predicted and experimental
leaching recoveries were correspondingly 99.63% and avg.
98.02% for ferric chloride, and 98.94% and avg. 97.95%
for activated carbon. In accordance, the constructed qua-
dratic regression model was reasonable, and the fitting effect
was ideal, which can be applied to predict the recovery of
valuable metals from sulfidic rougher flotation tailings.
Considering the high Ni recovery, environmental
friendliness of activated carbon and feasibility of practical
operation, the reuse of the AC was appropriately tested.
Herein, using the optimal conditions, the activated carbon
was evaluated for regeneration and reuse. The results, as
presented in Figure 8, demonstrates that the AC performed
effectively for five consecutive cycles. This could be due to
its granular nature and the type of biomass used (Owusu,
Mends, and Acquah 2022). Typically, activated carbon
0
20
40
60
80
100
1st Cycle 2nd Cycle 3rd Cycle 4th Cycle 5th Cycle
Figure 8. The leaching recovery of Ni using AC in acidic medium and cyclic efficiency of
the residual AC
Ni
recovery
(%)