Mixtures of Sodium Iso-Butyl Xanthate and Sodium Di-Ethyl Dithiophosphate on the Flotation of a Cu-Ni-PGM Ore in Ca(NO₃)₂ and NaNO₃  ^†

Abstract

The use of mixtures of thiol collectors has been reported to benefit the flotation of Cu-Ni-PGM ores. However, the increasing reliance on recycled water in mineral processing may alter the performance of flotation reagents. This necessitates a deeper understanding of flotation reagents into their behaviour in different components or constituents of process water. This is crucial for better decision-making when determining the quality of process water that optimises reagent performance for specific ores. Ca²⁺ and Na⁺ are common cations in process water and are known to exert various effects in both the pulp and froth phases, making them frequent subjects of recent investigations into water quality. In contrast, NO₃⁻ anions have received less research attention compared to other common ions in process water, such as Cl⁻, SO₄²⁻, and S₂O₃²⁻, despite being present in significant concentrations. NO₃⁻ ions are understood to originate from blasting chemicals used during mining, leaching into solution during milling, and thus can be considered key players in the interactions occurring in the pulp phase. Their interactions in the pulp phase and their role in flotation are therefore important to consider. This work presents results from bench-scale batch flotation tests conducted on a Cu-Ni-PGM ore from the Merensky Reef, using mixtures of thiol collectors, namely sodium isobutyl xanthate and sodium diethyl dithiophosphate, in solutions containing Ca(NO₃)₂ and NaNO₃. NaNO₃ solutions showed higher solids recoveries for all thiol collector mixtures compared to Ca(NO₃)₂ solutions, this was attributed to increased gangue entrainment in Na⁺ compared to Ca²⁺. Higher Cu and Ni recoveries were observed in NaNO₃ solutions across all thiol collector mixtures; however, higher Cu and Ni grades were achieved in Ca(NO₃)₂ solutions compared to NaNO₃.