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Development of awaruite flotation conditions on serpentinite ores Seiler, Santiago


Nickel is a key component of stainless steel and a wide range of applications which are critical for the transition to clean energies including electric vehicle batteries. Awaruite is a native nickel-iron alloy, found in serpentinized ultramafic rocks, which has gained interest as a possible new economic source of nickel. The objective of this study is to contribute to the development of future nickel mines based on awaruite mineralizations. The contribution is based on providing awaruite physicochemical properties that were not available in literature and proposing novel conditions for the selective awaruite flotation from the gangue minerals present in serpentinite ores. This research is focused on the large Baptiste deposit in central British Columbia, Canada where awaruite is the primary nickel mineral. The awaruite composition from the Baptiste deposit averaged 77.3% nickel, 21.0% iron, 1.1% cobalt and 0.6% copper. The measured initial volumetric magnetic susceptibility for native awaruite was 14.4 and the saturation magnetization was 750 kA/m. Awaruite readily floated in weakly acidic solution with a xanthate collector but not in neutral and alkaline solutions. The passivation layer formed in neutral and alkaline solutions showed to inhibit the interaction between xanthate and awaruite surface. Nickel recoveries of up to 65% at the rougher stage were obtained with xanthate as collector at a pH level of 4.5 in bench scale flotation tests. Rougher followed by cleaner stages of flotation showed that a high-grade concentrate can be produced with up to 45% nickel, 1.3% cobalt, 0.7% copper and negligible concentrations of penalty elements, such as arsenic, lead, selenium among others. However, high reagent dosages are required in weakly acidic conditions since xanthate decomposes at low pH and ultramafic rocks are acid consumers. To overcome the drawbacks of awaruite flotation in weakly acidic conditions, selective activation reagents were evaluated. The awaruite passivation layer formed in neutral and alkaline conditions can, at least, be partially dissolved in the presence of low concentrations of ammonium sulfate and thiosulfate in neutral conditions. This reagent scheme allows the flotation of awaruite in conditions where xanthate is stable and reduces the acid addition required to adjust the pH.

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