Figure 2 - Elemental chemical composition of the feed and concentrate for the flotation tests of the first and second stages in the presence of different depressants (a) phytic acid, (b) quinic acid, (c) sodium alginate and (d) citric acid. 3.2 Rare Earth Elements (REEs) With respect to rare earth elements (REEs), cerium was identified as the most abundant element in the investigated ore, followed by lanthanum, praseodymium, and neodymium. Among the depressants evaluated, quinic acid exhibited the most promising performance in concentrating these elements in the overflow products, as shown in Figure 3, in both the first and second flotation stages. In terms of effectiveness, quinic acid was followed by phytic acid and sodium alginate, which also promoted enrichment of REEs in the concentrate, albeit to a lesser extent. In contrast, citric acid proved to be particularly effective during the second flotation stage, in which REEs were predominantly concentrated in the overflow product. A similar stagedependent enrichment of REEs has been reported for carbonatite-hosted ores from the Fen deposit, where higher TREO grades were achieved after the initial flotation products when using citric acid in combination with sodium silicate (Silva et al., 2023). Although a different reagent regime was applied in the present study, this behavior suggests that citric acid may act more effectively after partial depletion of readily floatable gangue minerals. Therefore, increasing the dosage of citric acid in the first stage could potentially enhance overall process efficiency by improving selectivity at the initial flotation step.
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