Mn-SS as a Novel Depressant of the Flotation Process of Scheelite and Calcite: Role and Mechanism

In this study, the effect of a novel depressant system consisting of manganese chloride and sodium silicate (Mn-SS) on the selective flotation of scheelite from calcite was investigated. When the Mn-SS ratio and dosage were 1:3 and 100 mg/L, respectively, the scheelite recovery was 87.6% higher than that of calcite. The zeta potential and infrared spectroscopy (IR) measurements revealed that Mn-SS chemisorbed onto the calcite surface and inhibited the subsequent adsorption of sodium oleate collector. The X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the chemisorption of Mn-SS altered the chemical state of Ca on the calcite surface. The contact angle test indicated that the hydrophobicity of the calcite surface was significantly reduced by Mn-SS treatment. The scanning electron microscopy (SEM) images confirmed that Mn-SS formed a precipitate layer on the calcite surface. The density functional theory (DFT) simulation corroborated that the Mn-SS system had a stronger affinity for the calcite surface than for the scheelite surface, which agreed well with the flotation performance.