Comparison of gravity separation and flotation for pyrite recovery from tailings

Tailings generated during the production of lead, zinc, and copper concentrates contain significant amounts of sulfide minerals, particularly pyrite. Pyrite, which remains in tailings after the recovery of other metals, is one of the main contributors to acid mine drainage (AMD). Therefore, recovering pyrite from tailings is environmentally and economically an important issue. In this study, pyrite recovery from tailings was investigated using flotation and gravity separation methods. Mineralogical characterization and liberation analyses were conducted by Mineral Liberation Analysis (MLA), indicating that pyrite is the major sulfide mineral with over 76% liberation degree even in the coarsest fractions. Flotation tests were performed using two collectors – potassium amyl xanthate (KAX) and Tomamine M73 – on both as-received and ground samples.  Grinding improved the performance of Tomamine M73 but reduced that of KAX, reflecting KAX’s greater sensitivity to surface oxidation. Pyrite recovery was higher in the case of gravity separation (94%) compared to flotation (84%). Overall, gravity separation appears to be a simpler, more sustainable, and more cost-effective method for processing tailings containing mostly liberated pyrite.