XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3307
concentration had no positive effect on leaching recoveries
within the range studied. Typically, increasing the lixiviant
concentration enhances recovery by increasing the avail-
able reactive species for dissolution (Kumari et al. 2024).
However, in sulfidic minerals, these species are locked and
require an oxidizing environment. Conversely, the leach-
ing recoveries increased with increasing temperature and
time (Figure 7 (c) and (d)). The mass transfer of the metal
species between the liquid and solid phases increased with
increasing temperature, which leads to enhanced recoveries
(Kumari et al. 2024 Park, Mohapatra, and Reddy 2006
McDonald and Muir 2007 Reddy et al. 2023 Crundwell,
Moats, and Ramachandran 2011). Similarly, the mass
transfer and solute diffusion rates of reaction through solids
into the liquid are influenced by time and thus, increasing
time enhances recoveries (Kumari et al. 2024).
The addition of a catalyst positively increased the
recovery as expected (Meshram and Pandey 2018 Park,
Mohapatra, and Reddy 2006 Harris, White, Demopoulos,
and Ballantyne 2008 McDonald and Muir 2007 Bhatti
et al. 2018 Mu et al. 2020). It can be observed that fer-
ric chloride performed slightly better than activated carbon
(Figure 7 (e)). However, the difference was less than 1%,
hinting that activated carbon had a similar catalyst effect
as ferric chloride. Typically, the addition of ferric chloride
leads to the increased oxidation of ferrous ions while reduc-
ing the Eh values of the leaching solution (Xu et al. 2022
Winand 1991 Watling 2013). This leads to the increase in
leaching recoveries of metal ions hosted in sulfidic minerals.
Ferric chloride is likewise a complexation agent as the
Cl– ions have the potential to form metal complexes with
nickel and copper ions (Bhatti et al. 2018). The increase
in leaching recoveries in the case of activated carbon is
thought to be as a result of the possible oxidation of ferrous
ions into ferric, as shown in Eq. 8 (Karppinen, Seisko, and
Lundström 2024). It has been reported that, in acidic solu-
tions, the dissolved ferrous ions can be oxidized by available
oxygen to ferric ions (as shown in Eq. 4) and can further
catalyze the leaching reactions (Watling 2013 Mbaya,
Ramakokovhu, and Thubakgale 2013 Karppinen, Seisko,
and Lundström 2024). Herein, sulfiwe sulfur is converted
into the elemental form, hydrogen sulfide gas, and/or dis-
solved sulfate (Eqs. 5 and 6).
4Fe2+ +4H+ +O2 → 4Fe3+ +2H2O (4)
2Fe4.5Ni4.5S8 +9O2 +36H+ →
18H2O +9Ni2+ +9Fe2+ +16S (5)
2Fe4.5Ni4.5S8 +36Fe3+ → 45Fe2+ +9Ni2+ +16S (6)
Same phenomenon has been suggested by other studies,
in that the galvanic interaction between chalcopyrite and
carbon, as well as the dissolution reactions at relatively
low redox potentials, may be responsible for the increased
20
30
40
50
60
70
80
20 30 40 50 60 70 80
Actual Ni recovery (%)
Figure 6. The correlation plot of actual and predicted leaching recoveries (%)for Ni
Predicted
Ni
recovery
(%)
concentration had no positive effect on leaching recoveries
within the range studied. Typically, increasing the lixiviant
concentration enhances recovery by increasing the avail-
able reactive species for dissolution (Kumari et al. 2024).
However, in sulfidic minerals, these species are locked and
require an oxidizing environment. Conversely, the leach-
ing recoveries increased with increasing temperature and
time (Figure 7 (c) and (d)). The mass transfer of the metal
species between the liquid and solid phases increased with
increasing temperature, which leads to enhanced recoveries
(Kumari et al. 2024 Park, Mohapatra, and Reddy 2006
McDonald and Muir 2007 Reddy et al. 2023 Crundwell,
Moats, and Ramachandran 2011). Similarly, the mass
transfer and solute diffusion rates of reaction through solids
into the liquid are influenced by time and thus, increasing
time enhances recoveries (Kumari et al. 2024).
The addition of a catalyst positively increased the
recovery as expected (Meshram and Pandey 2018 Park,
Mohapatra, and Reddy 2006 Harris, White, Demopoulos,
and Ballantyne 2008 McDonald and Muir 2007 Bhatti
et al. 2018 Mu et al. 2020). It can be observed that fer-
ric chloride performed slightly better than activated carbon
(Figure 7 (e)). However, the difference was less than 1%,
hinting that activated carbon had a similar catalyst effect
as ferric chloride. Typically, the addition of ferric chloride
leads to the increased oxidation of ferrous ions while reduc-
ing the Eh values of the leaching solution (Xu et al. 2022
Winand 1991 Watling 2013). This leads to the increase in
leaching recoveries of metal ions hosted in sulfidic minerals.
Ferric chloride is likewise a complexation agent as the
Cl– ions have the potential to form metal complexes with
nickel and copper ions (Bhatti et al. 2018). The increase
in leaching recoveries in the case of activated carbon is
thought to be as a result of the possible oxidation of ferrous
ions into ferric, as shown in Eq. 8 (Karppinen, Seisko, and
Lundström 2024). It has been reported that, in acidic solu-
tions, the dissolved ferrous ions can be oxidized by available
oxygen to ferric ions (as shown in Eq. 4) and can further
catalyze the leaching reactions (Watling 2013 Mbaya,
Ramakokovhu, and Thubakgale 2013 Karppinen, Seisko,
and Lundström 2024). Herein, sulfiwe sulfur is converted
into the elemental form, hydrogen sulfide gas, and/or dis-
solved sulfate (Eqs. 5 and 6).
4Fe2+ +4H+ +O2 → 4Fe3+ +2H2O (4)
2Fe4.5Ni4.5S8 +9O2 +36H+ →
18H2O +9Ni2+ +9Fe2+ +16S (5)
2Fe4.5Ni4.5S8 +36Fe3+ → 45Fe2+ +9Ni2+ +16S (6)
Same phenomenon has been suggested by other studies,
in that the galvanic interaction between chalcopyrite and
carbon, as well as the dissolution reactions at relatively
low redox potentials, may be responsible for the increased
20
30
40
50
60
70
80
20 30 40 50 60 70 80
Actual Ni recovery (%)
Figure 6. The correlation plot of actual and predicted leaching recoveries (%)for Ni
Predicted
Ni
recovery
(%)