XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3381
conditioned for another minute. Air was then turned on,
and four concentrates were collected sequentially, each with
a 2-min collection time. Between collection of each con-
centrate, the pulp level was re-adjusted, and fresh collector
and frother were added using the same regime. Cleaner flo-
tation, test conditions were selected based on the results of
the rougher flotation stage the objective was to obtain the
highest possible Ni recovery at the lowest acid consump-
tion. In the cleaner circuit, three stages of flotation were
applied to increase the final product grade (1st, 2nd, and
3rd cleaner).
The collected products were filtered, dried, and analyzed
for Ni, Fe, and S content. In all flotation tests, the collector
reagent used was industrial grade potassium amyl xanthate
(KC6H11OS2). The collector was kept in petroleum ether
in the fridge, and fresh solutions were prepared daily.
RESULTS AND DISCUSION
Flotation of Awaruite—Weakly Acidic Condition
While xanthate interactions with nickel sulfide minerals
such as pentlandite are well-established, prior to the research
carried out by the authors, the specific case of awaruite flo-
tation was not investigated. This lack of knowledge posed a
significant challenge for the selective separation of awaruite
from magnetite, which presents different properties and
challenges compared to pentlandite. The first stage of the
research aimed to bridge this gap by investigating the inter-
action of xanthate with awaruite under various conditions.
Based on existing knowledge about its behavior with other
nickel-bearing minerals, it was hypothesized that acidic
conditions might be needed for achieving awaruite flota-
tion due to similarities of the surface chemistry of awaruite
to other-nickel bearing minerals.
Microflotation with Pure Awaruite Sample
Microflotation experiments revealed that native awaruite
only floats with potassium amyl xanthate in acidic solutions,
with negligible recovery observed in neutral and alkaline
solutions (Seiler, et al., 2022). Voltammetry data suggested
an active-passive transition of awaruite in acidic solutions,
indicating surface oxidation in neutral and alkaline envi-
ronments. This passivation layer, evidenced by the absence
of xanthate-related peaks in infrared spectra at lower poten-
tials, likely hinders the interaction between xanthate and
the awaruite surface, explaining the poor recovery at these
conditions (Seiler, et al., 2022). These findings highlighted
the important role of surface chemistry and solution pH
in awaruite flotation, providing valuable insights for opti-
mizing selective separation from magnetite in industrial
settings.
Figure 1. Magnetic separation flowsheet indicating the sample streams used in this research
Table 1. List of samples used in this research and their corresponding nickel grades
Sample ID Sample Description Nickel grade [%]
A Fresh feed – direct flotation 0.22
B Rougher concentrate from LIMS – 1100 G 0.98
C Scavenger concentrate from MIMS – 3500 G 0.20
D Cleaner magnetic concentrate after 2 stages of cleaning and regrinding 2.10
conditioned for another minute. Air was then turned on,
and four concentrates were collected sequentially, each with
a 2-min collection time. Between collection of each con-
centrate, the pulp level was re-adjusted, and fresh collector
and frother were added using the same regime. Cleaner flo-
tation, test conditions were selected based on the results of
the rougher flotation stage the objective was to obtain the
highest possible Ni recovery at the lowest acid consump-
tion. In the cleaner circuit, three stages of flotation were
applied to increase the final product grade (1st, 2nd, and
3rd cleaner).
The collected products were filtered, dried, and analyzed
for Ni, Fe, and S content. In all flotation tests, the collector
reagent used was industrial grade potassium amyl xanthate
(KC6H11OS2). The collector was kept in petroleum ether
in the fridge, and fresh solutions were prepared daily.
RESULTS AND DISCUSION
Flotation of Awaruite—Weakly Acidic Condition
While xanthate interactions with nickel sulfide minerals
such as pentlandite are well-established, prior to the research
carried out by the authors, the specific case of awaruite flo-
tation was not investigated. This lack of knowledge posed a
significant challenge for the selective separation of awaruite
from magnetite, which presents different properties and
challenges compared to pentlandite. The first stage of the
research aimed to bridge this gap by investigating the inter-
action of xanthate with awaruite under various conditions.
Based on existing knowledge about its behavior with other
nickel-bearing minerals, it was hypothesized that acidic
conditions might be needed for achieving awaruite flota-
tion due to similarities of the surface chemistry of awaruite
to other-nickel bearing minerals.
Microflotation with Pure Awaruite Sample
Microflotation experiments revealed that native awaruite
only floats with potassium amyl xanthate in acidic solutions,
with negligible recovery observed in neutral and alkaline
solutions (Seiler, et al., 2022). Voltammetry data suggested
an active-passive transition of awaruite in acidic solutions,
indicating surface oxidation in neutral and alkaline envi-
ronments. This passivation layer, evidenced by the absence
of xanthate-related peaks in infrared spectra at lower poten-
tials, likely hinders the interaction between xanthate and
the awaruite surface, explaining the poor recovery at these
conditions (Seiler, et al., 2022). These findings highlighted
the important role of surface chemistry and solution pH
in awaruite flotation, providing valuable insights for opti-
mizing selective separation from magnetite in industrial
settings.
Figure 1. Magnetic separation flowsheet indicating the sample streams used in this research
Table 1. List of samples used in this research and their corresponding nickel grades
Sample ID Sample Description Nickel grade [%]
A Fresh feed – direct flotation 0.22
B Rougher concentrate from LIMS – 1100 G 0.98
C Scavenger concentrate from MIMS – 3500 G 0.20
D Cleaner magnetic concentrate after 2 stages of cleaning and regrinding 2.10