The Influence of a Flotation Solution’s Surface Tension on Pyrochlore Flotation

The low recovery (∼50%) in industrial pyrochlore flotation highlights the need for optimization. This study evaluates the influence of surface tension (γ) of flotation solutions on pyrochlore/gangue separation of samples from Boa Vista mine (Brazil) using gamma flotation. Surface tension was adjusted using ethanol–water mixtures of reagent-conditioned samples in gamma flotation tests at pH 5.5, with recoveries measured via XRF analysis and separation efficiency calculated using Schulz’s criterion. After reagent conditioning at pH 5.5, the critical surface tension needed for flotability (γc) was determined to be 27 mN/m for pyrochlore and gangue minerals. Recoveries increased steeply from 0% at γ=27 mN/m to plateaus at γ>39 mN/m. The maximum Nb2O5 recovered (99%) occurred at γ=48.9 mN/m. Schulz’s separation efficiency peaked at γ = 48.9 mN/m for pyrochlore/carbonates (68%) and at γ = 39 mN/m for pyrochlore/silicates+oxides. Results suggest operating industrial direct flotation at lower γ values (39 mN/m) than the current method (61 mN/m) for improved selectivity, bridging theory and practice in niobium processing.