Gangue Entrainment in Olivine Flotation: Effect of MIBC Dosage on the Mitigation of Lizardite Recovery

Abstract

Background: Olivine is an important industrial raw material especially for metallurgical applications like foundry sand, refractory, slag conditioning, etc. Loss On Ignition (LOI) value (>1%) is the main specification of olivine ore/concentrate for those areas together with the chemical specifications. Objective: This flotation study was conducted in natural pH condition with Na-oleate as collector to clarify the effect of frother (MIBC) dosage on the LOI value of olivine concentrate. Methods: Characterization of ore sample for this study was made by XRD, XRF and petrographic analyses. Lizardite, a serpentine group mineral, was found to be a hydrated soft fraction of ore sample in addition to hard olivine and pyroxene minerals constituting ore. Results: Finely ground soft lizardite adversely affected the olivine flotation in a way of entraining mechanically into concentrate. LOI value of concentrate was observed mainly to be froth volume depended issue, and therefore, mainly water recovery dependent. LOI value increased proportionally with water recovery at longer flotation time and MIBC dosages indicating the entrainment of lizardite as the suspending hydrophilic component of water phase. Certain rate of the hydrated lizardite mineral was thought to be recovered via hydrophobization, which was clearly seen especially at the initial stages of flotation period in the presence of excess frother. This experimental finding was attributed to similar chemical composition of minerals constituting ore, and accidental activation of lizardite. Conclusions: Lizardite recovery in froth was explained with accidental activation and/or weak attachment of locked particles onto froth bubble although main recovery mechanism was determined to be mechanical entrainment. Olivine concentrate obeying the specifications of metallurgical applications could be obtained at suitable MIBC dosage and flotation time.