| Summary: | Awaruite is a native nickel-iron alloy with high nickel content and mainly present in serpentinized ultramafic rocks. Recent discoveries have demonstrated the potential for awaruite to contribute to the economics of a nickel deposit. Awaruite selectively floats in weakly acidic conditions with xanthate as collector. However high reagent dosages are required in such conditions since xanthate decomposes and ultramafic rocks are acid consumers. In this work, a novel reagent scheme including ammonium sulfate and sodium thiosulfate is proposed to float awaruite in neutral conditions from ultramafic rocks. Electrochemical studies were carried out on awaruite samples to demonstrate the effect of low concentrations of these reagents on the awaruite surface. The awaruite passivation layer formed in alkaline conditions (natural slurry pH) can, at least, be partially dissolved in the presence of low concentrations of ammonium sulfate and thiosulfate in neutral conditions. After the passivation layer is partially removed, the xanthate collector reacts with the awaruite surface and induces hydrophobicity, thus enabling the awaruite flotation. Microflotation and bench scale flotation tests demonstrate the applicability of the reagent scheme herein proposed. 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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