Adsorption of sodium oleate at the microfine hematite/aqueous solution interface and its consequences for flotation

Abstract

The adsorption of sodium oleate (NaOL) at the microfine hematite/aqueous solution interface was investigated in this paper. Experimental research indicated that negative effects stemmed from the dissolution of the microfine hematite (D50=19.21 μm) could be effectively eliminated via the appropriate dosage of NaOL at alkali pH conditions. Solution chemistry calculation and adsorption test results indicated that RCOO− and (RCOO)22− ions were responsible for microfine hematite flotation at pH 8.2. Zeta potential and FTIR measurements confirmed the co-adsorption of molecular and ionic oleate species occurred at pH 8.2. X-ray photoelectron spectroscopy (XPS) results further indicated that oleate species interacted with hematite surfaces mainly through chemisorption, giving rise to molecule/colloid formation of oleate and Fe―OL complex compound. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) results demonstrated that oleate species adsorbed onto the hematite surfaces with a thickness of a few nanometers. Furthermore, the normalized peak intensity of C4H7+ ions on the hematite sample at pH 8.2 increased remarkably comparing with corresponding result of hematite sample at pH 6.8. The new findings of the present study well revealed the dissolution of microfine hematite and the pH effects on the hematite flotation, as well as the adsorption characteristics of oleate species.

Keywords

• Microfine hematite
• Oleate species
• Chemisorptions
• Dissolution
• ToF-SIMS