Adsorption of n-octanohydroxamate collector on iron oxides
The adsorption of n-octanohydroxamate on hematite and magnetite, as well as air-exposed Fe metal, pyrrhotite and pyrite, conditioned in nominally saturated aqueous solutions of potassium hydrogen n-octanohydroxamate at its unadjusted pH (~ 9.5) has been investigated by means of X-ray photoelectron spectroscopy. The adsorption of the collector on Fe oxides was found to be quite different from that on Cu oxides, in that only hydroxamate chemisorbed to Fe atoms and some co-adsorbed hydroxamic acid were detected at conditioned Fe oxide surfaces whereas multilayer Cu hydroximate is adsorbed on conditioned Cu oxides. The absence of multilayer Fe hydroxamate on the Fe oxides was corroborated by means of Raman spectroscopy. Notwithstanding relatively low collector coverage after the minerals were conditioned for periods of relevance to flotation, and the absence of multilayer Fe hydroxamate, abraded surfaces of hematite, magnetite and pyrrhotite appeared, by visual inspection, to be clearly hydrophobic. For fracture and abraded surfaces of the relatively pure pyrite investigated, only after extended air exposure prior to conditioning in collector solution was there evidence for the formation of minor multilayer Fe hydroxamate from interaction of hydroxamate with Fe sulfate. It was concluded that the principal species chemisorbed on the Fe oxides was bidentate hydroxamate, but that at higher coverage, monodentate hydroxamate was also chemisorbed. It is postulated that the monodentate species was also formed in vacuo as an alteration product by the secondary electrons inherent in the photoemission process and by the low energy electrons from a flood-gun when it was used.
International Journal of Mineral Processing
Colloid and Surface Chemistry