Selective flotation of galena from pyrite utilizing 5-heptyl-1,3,4-oxadiazole-2-thione under medium alkaline conditions

The flotation separation of galena from its ores with traditional xanthate collectors needs the high alkaline media maintained by lime which production releases CO_2. In this study, a novel collector, 5-heptyl-1,3,4-oxadiazole-2-thione (HPODT), was investigated in flotation separation of galena from pyrite under a moderate alkaline pulp without addition of lime. The micro-flotation results demonstrated that at pH ∼10.0, 6 × 10⁻⁶ mol·L⁻¹ HPODT and octyl xanthate sodium (OXS) floated out 99.3 % and 83.8 % galena, as well as 5.3 % and 75.6 % pyrite from their mixture, respectively, deducing the much better selectivity of HPODT for flotation separation of galena against pyrite than OXS. UV spectra exhibited that under pH ∼10.0, the adsorption amount of HPODT on galena was much bigger than that on pyrite, which supported their flotation and contact angle results. In situ AFM gave out clear evidences that HPODT formed self-assembled aggregates on galena surface. XPS confirmed that the exo-S and endo-N atoms of HPODT’s oxadiazole-thione group bonded with the Pb atom(s) on galena to deliver the Pb(II)-HPODT complexes. As a big conjugated configuration, the oxadiazole-thione group possessed the weak electron-donating and strong electron-accepting ability through electron delocalization effect, which improved the selective affinity of HPODT towards Pb(II) on galena against Fe(III)/Fe(II) on pyrite.