The Feasibility of Activation of Manganese Minerals Flotation

Abstract

The feasibility and the mechanism of activation of pyrolusite, manganite, and rhodochrosite with Fe (III), Cu (II) and Mn (II) in an anionic collector system using oleic acid as the collector have been investigated. The results obtained showed a certain regularity as basically determined by the acidity of the heavy metal cation and the pH of its precipitation, the pK_a of the oleic acid, the chemical composition of the manganese mineral tested, and the pH of its isoelectric point. Thus, Cu (II) and Mn (II) which are basic and hydrolyze at pHs above those of the isoelectric points of the manganese minerals investigated could, within certain specific limits of medium pH, act as activators for pyrolusite and manganite. On the other hand, Fe (H₂O)₆⁺⁺⁺ which is acidic, ionizes at pH 2.2 and is precipitated at pH 3.7, which is below than both the isoelectric point of the manganese minerals studied and the pK_a of oleic acid, is of no particular advantage in the activation and flotation. The response of rhodochrosite, without pre-activation, to soap flotation seems to be due to the basic property of the bivalent manganese sites in its crystalline lattice, which produces a tendency for the attachment of oleic acid. Owing to the negative surface charge of the manganese minerals at pH above 5 and the positive surface charge of the gangue minerals (barite, gypsum, calcite), the anion, Al₂SiO₃(OH)₆⁻⁻, resulting from the conjunction of Na₂SiO₃ with Al₂(SO₄)₃ is adsorbed preferentially to the surface of the latter leading to a successful differential flotation.