3382 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Based on these findings, a mechanism was proposed
where xanthate chemisorbs onto awaruite through a redox
reaction (Seiler, et al., 2022). This chemisorbed xanthate
then oxidizes to dixanthogen, promoting hydrophobicity
and enabling flotation. Open circuit potential and micro-
flotation experiments revealed a remarkably rapid activa-
tion process, with awaruite regaining its floatable state
within approximately 10 minutes. This rapid activation
suggested that the passivation layer formed during grind-
ing under natural alkaline conditions can be effectively
removed within a short conditioning stage prior to flota-
tion, simplifying the overall process (Seiler, et al., 2022).
Bench-Scale Flotation of Ground Ore Sample
The next stage of the project involved the validation of flo-
tation behavior at bench scale with an actual rock sample,
that allowed for an evaluation of the possible interaction
effects of other minerals present in the sample. There was
no prior detailed study of the effect of pH conditioning on
the flotation of awaruite in fresh rock samples containing
serpentine. The understanding of the effect of pH on the
flotation of awaruite in the presence of serpentine minerals
is fundamentally important to the development of a reliable
mineral processing flowsheet to recover awaruite.
In this second experimental stage, microflotation
experiments were confirmed. Awaruite was selectively
floated using xanthate collector under weakly acidic condi-
tions (pH 4.5), achieving nickel recoveries of up to 65%
in rougher stages from samples containing 0.22% nickel
(Seiler, Sánchez and Pawlik, et al. 2023). This selectivity in
weakly acidic pH aligns with the proposed xanthate inter-
action mechanism, suggesting the potential for efficient
separation from gangue minerals and other nickel-bearing
phases. Nickel sulfides, that are present in the sample in
minor quantities, were also recovered to the flotation con-
centrate, representing 10% of the nickel reported to the
concentrate.
Employing weakly acidic conditions for awaruite flota-
tion presents two major drawbacks: high acid consumption
and rapid degradation of the xanthate collector (Iwasaki
and Cooke 1958). To address this challenge, alternative
strategies were evaluated and are presented below. Magnetic
separation has shown to effectively concentrate awaruite,
but assessing the flotation performance in different mag-
netic products is important to evaluate the feasibility of
magnetic separation as preconcentration method (Seiler,
Sánchez and Bradshaw, et al. 2023). Additionally, activa-
tors to enable the interaction of awaruite and xanthate in
neutral or alkaline pH are presented.
Flotation of awaruite – Magnetic separation as
preconcentration
Figure 2 shows the nickel grade and recovery for sample A
for different grind sizes (P80). Interestingly, recovery shows
minimal variation, maintaining around 60% throughout the
tested P80 range of 60 to 150 mm. Even with progressively
Figure 2. Nickel recovery and grade distributions for Sample A at different grind sizes
Based on these findings, a mechanism was proposed
where xanthate chemisorbs onto awaruite through a redox
reaction (Seiler, et al., 2022). This chemisorbed xanthate
then oxidizes to dixanthogen, promoting hydrophobicity
and enabling flotation. Open circuit potential and micro-
flotation experiments revealed a remarkably rapid activa-
tion process, with awaruite regaining its floatable state
within approximately 10 minutes. This rapid activation
suggested that the passivation layer formed during grind-
ing under natural alkaline conditions can be effectively
removed within a short conditioning stage prior to flota-
tion, simplifying the overall process (Seiler, et al., 2022).
Bench-Scale Flotation of Ground Ore Sample
The next stage of the project involved the validation of flo-
tation behavior at bench scale with an actual rock sample,
that allowed for an evaluation of the possible interaction
effects of other minerals present in the sample. There was
no prior detailed study of the effect of pH conditioning on
the flotation of awaruite in fresh rock samples containing
serpentine. The understanding of the effect of pH on the
flotation of awaruite in the presence of serpentine minerals
is fundamentally important to the development of a reliable
mineral processing flowsheet to recover awaruite.
In this second experimental stage, microflotation
experiments were confirmed. Awaruite was selectively
floated using xanthate collector under weakly acidic condi-
tions (pH 4.5), achieving nickel recoveries of up to 65%
in rougher stages from samples containing 0.22% nickel
(Seiler, Sánchez and Pawlik, et al. 2023). This selectivity in
weakly acidic pH aligns with the proposed xanthate inter-
action mechanism, suggesting the potential for efficient
separation from gangue minerals and other nickel-bearing
phases. Nickel sulfides, that are present in the sample in
minor quantities, were also recovered to the flotation con-
centrate, representing 10% of the nickel reported to the
concentrate.
Employing weakly acidic conditions for awaruite flota-
tion presents two major drawbacks: high acid consumption
and rapid degradation of the xanthate collector (Iwasaki
and Cooke 1958). To address this challenge, alternative
strategies were evaluated and are presented below. Magnetic
separation has shown to effectively concentrate awaruite,
but assessing the flotation performance in different mag-
netic products is important to evaluate the feasibility of
magnetic separation as preconcentration method (Seiler,
Sánchez and Bradshaw, et al. 2023). Additionally, activa-
tors to enable the interaction of awaruite and xanthate in
neutral or alkaline pH are presented.
Flotation of awaruite – Magnetic separation as
preconcentration
Figure 2 shows the nickel grade and recovery for sample A
for different grind sizes (P80). Interestingly, recovery shows
minimal variation, maintaining around 60% throughout the
tested P80 range of 60 to 150 mm. Even with progressively
Figure 2. Nickel recovery and grade distributions for Sample A at different grind sizes