Novel insights into the surface microstructures of lead(II) benzohydroxamic on oxide mineral.

Lead(II)-benzohydroxamic acid (lead-BHA) is a metal-organic complex system used as a highly selective collector in the flotation separation of oxide minerals. In the current study, the surface microstructures and adsorption mechanism of lead-BHA on mineral surfaces were comprehensively investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Raman spectroscopy, atomic force microscopy (AFM) and first-principles calculations. The characteristic Raman peak indicated that lead-BHA adsorbs on mica surfaces. The AFM topography of a mica surface (0 0 1) treated with lead-BHA at a ratio of 1:1 showed many local adsorption layers, but no obvious adsorption layer was observed for the same surface treated with lead-BHA at a ratio of 1:2, which suggests that Pb(BHA) + might be the effective species for mineral flotation. First-principles density functional theory (DFT) calculations indicated that the lowest unoccupied molecular orbital (LUMO) of Pb(BHA) + was mainly localized on the lead atom, while the LUMO of Pb(BHA) 2 was distributed over the whole molecule, implying that Pb(BHA) + exhibits better affinity to the mica surface than Pb(BHA) 2 , and further suggesting that Pb(BHA) + might be an effective specie. The further first-principle calculation, from the molecular level on mica surface, showed that the Pb(BHA) + could produce a higher adsorption energy than Pb(BHA) 2 , revealing that the Pb(BHA) + should be an effective specie that can efficiently adsorb onto the mica surface. This work may shed new light on the effective species of metal-organic complex collectors on oxide mineral surfaces in flotation separation. [ABSTRACT FROM AUTHOR]