Adsorption Mechanism of Mixed Cationic/Anionic Collectors in Quartz–Hematite Flotation System

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The adsorption mechanism of mixed cationic C12 amine and anionic sulfate / oleate reagent schemes was examined through Hallimond flotation studies using pure quartz and hematite minerals. The flotation response of both quartz and hematite with cationic and anionic collectors in isolation and with mixed cationic / anionic collector systems was evaluated as well. The flotation response as a function of pH and collector concentration was analyzed, wherein quartz was not responsive to floatation in single mineral flotation tests in the presence of anionic collectors but C12 amine flotation of quartz was observed to be pH and concentration dependent. Maximum hematite floatation recovery was observed at acidic pH with sulfate, neutral pH with oleate, and at basic pH about 9.5 with C12 amine. Accelerated adsorption of cationic collector in the presence of anionic collector apart from its own co-adsorption was observed in flotation results with quartz and hematite. Assimilation of oleate in between the C12 amine molecules retards the electrostatic head–head repulsion, thereby intensifying the adsorption of C12 amine due to attractive tail–tail hydrophobic bonds, besides forming a compact adsorbed layer with elevated hydrophobicity. Incremental oleate concentration beyond C12 amine concentration leads to the formation of soluble amine–oleate complex/precipitate and the adsorption of these species decrements the flotation since the alkyl chains are in chaotical orientation with conceivable number of head groups propelling toward the solution phase.