Review of the flotation of molybdenite. Part I: Surface properties and floatability

• This paper reviews the surface chemistry and floatability of molybdenite, usually by-product in Cu/Mo sulfide ores.
• Oil collectors are used to improve molybdenite flotation and the comparison with thiol collectors is discussed.
• Some inorganic ions are strong molybdenite depressants, such as, calcium ions and lime.
• Magnesium ions are also strong depressants for molybdenite flotation when saline, hypersaline or seawater are employed at pH > 10.0.
• The depressant effect of polymers on molybdenite flotation is discussed, and particularly the effect of flocculants.

Molybdenite (MoS2) is a naturally hydrophobic mineral with anisotropic surface properties. Its floatability is influenced by a number of factors such as, particle size and shape, face/edge ratio, degree of crystallization, face heterogeneity, pH, etc. Molybdenite is floated by using oily collectors, and its recovery is strongly affected by slime coating phenomena. A number of hydrolyzable cations, such as Ca2 + and Mg2 +, depress molybdenite in alkaline solutions. Depression of molybdenite in seawater and saline waters is mainly induced by the precipitation of colloidal magnesium hydroxide when pH is raised to depress pyrite. Other metal cations present in recycled process water can also reduce the flotation recovery of molybdenite (e.g., Al3 +, Fe2 +, Cu2 + ions). The native floatability of molybdenite is highly depressed by natural polymers (starch, dextrin, guar gum, humic acids, etc.) and synthetic polymers (e.g., flocculants of the polyacrylamide type). The advances in understanding the surface chemistry of these systems are reviewed and discussed in this paper.

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