2998 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Forson et al. (2022)12, who reported increased Py recov-
ery compared to Asp under lower pH conditions (6.5–8.5)
where IPETC predominantly remains neutral.
IPETC molecule has a pKa ≈11 and is known to be
predominantly in its deprotonted form at strongly alkaline
conditions.12 In light of this, an in-depth exploration of the
binding mechanism of deprotonated IPETC (IPETCdp)
was pursued through DFT calculations, focusing on dif-
ferent conformations of IPETCdp adsorbed onto Py and
Asp surfaces. The initial and optimized adsorption geom-
etries of IPETCdp on Py and Asp are displayed in Figure 4.
Specifically, IPETCdp exhibits robust adsorption on FeAsS,
establishing a potent N—As bond in addition to the Fe—S
bond. This contrasts starkly with its interaction with Py,
where only Fe—S bonding is observed. The Fe—S bond
formed between Py and IPETCdp and Fe—S/As—N
bonds formed between Asp and IPETCdp are of covalent
type as the bond distances are close to the sum of covalent
radii of individual atoms. Furthermore, the formation of a
5-membered ring by IPETCdp upon interaction with Asp
could substantially augment the interaction strength, lead-
ing to higher adsorption energy values.
Interaction of IPETC and IPETCdp with Pyrite and
Arsenopyrite in Presence of Cu1+, OH– Ions
At higher pH both Py and Asp undergo oxidataion/hydrox-
ylation, resulting in the top surfaces resembling goethite
(FeO(OH)) that is hydrophilic in nature. This causes very
little to no flotation of the minerals. Our calculations
showed that the adsorption of IPETC on goethite was
weak, with an interaction energy of –7.9 kcal/mol only.
However, addition of CuSO4 seems to significantly change
the collector adsoprtion dynamics (and flotation efficiency).
In accordance with Weisener and Gerson’s (2000)23 find-
ings, elevated solution pH levels prompt the adsorption
of Cu(II) onto sulfur sites, concurrent with a reduction to
Cu(I) facilitated by the oxidation of sulfur. This was futher
confirmed in the XPS study of Forson et al. (2022)12 which
showed that the Cu ions adsorbed on both Py and Asp sur-
faces were of Cu(I) oxidataion state. Presumably then, at
higher pH (11), the surfaces are predominantly oxidized,
with Cu(I) ions bound to exposed sulfur sites at the surface.
These Cu(I) ions promote bonding with the collector mol-
ecule by acting as a bridge between the mineral surface and
the IPETC molecule. To explore these dynamics, we carried
out DFT calculations to study the adsorption of deprot-
onated Isopropyl Ethylthiocarbamate (IPETCdp) in the
presence of Cu+ ions, with the inclusion of OH– ions on
the surface to compensate for charges. This approach not
only masks the Fe atoms (a simple surrogate to oxidized/
hydroxylated surface) but also ensures a charge-neutral sys-
tem. Two different stable optimized geometries for Py and
Asp (Figure 5) and corresponding adsorption energies are
Figure 4. Adsorption of IPETCdp on pristine FeS
2 and FeAsS
Forson et al. (2022)12, who reported increased Py recov-
ery compared to Asp under lower pH conditions (6.5–8.5)
where IPETC predominantly remains neutral.
IPETC molecule has a pKa ≈11 and is known to be
predominantly in its deprotonted form at strongly alkaline
conditions.12 In light of this, an in-depth exploration of the
binding mechanism of deprotonated IPETC (IPETCdp)
was pursued through DFT calculations, focusing on dif-
ferent conformations of IPETCdp adsorbed onto Py and
Asp surfaces. The initial and optimized adsorption geom-
etries of IPETCdp on Py and Asp are displayed in Figure 4.
Specifically, IPETCdp exhibits robust adsorption on FeAsS,
establishing a potent N—As bond in addition to the Fe—S
bond. This contrasts starkly with its interaction with Py,
where only Fe—S bonding is observed. The Fe—S bond
formed between Py and IPETCdp and Fe—S/As—N
bonds formed between Asp and IPETCdp are of covalent
type as the bond distances are close to the sum of covalent
radii of individual atoms. Furthermore, the formation of a
5-membered ring by IPETCdp upon interaction with Asp
could substantially augment the interaction strength, lead-
ing to higher adsorption energy values.
Interaction of IPETC and IPETCdp with Pyrite and
Arsenopyrite in Presence of Cu1+, OH– Ions
At higher pH both Py and Asp undergo oxidataion/hydrox-
ylation, resulting in the top surfaces resembling goethite
(FeO(OH)) that is hydrophilic in nature. This causes very
little to no flotation of the minerals. Our calculations
showed that the adsorption of IPETC on goethite was
weak, with an interaction energy of –7.9 kcal/mol only.
However, addition of CuSO4 seems to significantly change
the collector adsoprtion dynamics (and flotation efficiency).
In accordance with Weisener and Gerson’s (2000)23 find-
ings, elevated solution pH levels prompt the adsorption
of Cu(II) onto sulfur sites, concurrent with a reduction to
Cu(I) facilitated by the oxidation of sulfur. This was futher
confirmed in the XPS study of Forson et al. (2022)12 which
showed that the Cu ions adsorbed on both Py and Asp sur-
faces were of Cu(I) oxidataion state. Presumably then, at
higher pH (11), the surfaces are predominantly oxidized,
with Cu(I) ions bound to exposed sulfur sites at the surface.
These Cu(I) ions promote bonding with the collector mol-
ecule by acting as a bridge between the mineral surface and
the IPETC molecule. To explore these dynamics, we carried
out DFT calculations to study the adsorption of deprot-
onated Isopropyl Ethylthiocarbamate (IPETCdp) in the
presence of Cu+ ions, with the inclusion of OH– ions on
the surface to compensate for charges. This approach not
only masks the Fe atoms (a simple surrogate to oxidized/
hydroxylated surface) but also ensures a charge-neutral sys-
tem. Two different stable optimized geometries for Py and
Asp (Figure 5) and corresponding adsorption energies are
Figure 4. Adsorption of IPETCdp on pristine FeS
2 and FeAsS