Adsorption behavior of sodium oleate on iron minerals and its effect on flotation kinetics

Abstract

This work systematically studied the adsorption behavior of sodium oleate (NaOL) on hematite, limonite, and siderite and their corresponding flotation performance at alkaline pH. The adsorption behavior and conformation of NaOL on mineral surfaces were investigated using zeta potential analysis, Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy spectra (XPS), and atomic force microscopy (AFM) imaging characterization. The effect of NaOL adsorption on the surface wettability and bubble-particle attachment was further analyzed by contact angle measurement, attachment time tests, and wrap angle tests. Finally, batch flotation tests and kinetic analysis were carried out to evaluate three mineral flotation behaviors. The results revealed that NaOL could chemically adsorb on hematite, limonite, and siderite and caused the significant negative mobility in their zeta potentials. It was found that Fe atoms exposed on their surface were the main active centers for the chemisorption of NaOL. Hematite and limonite had more active sites for NaOL adsorption than siderite, and Fe(III) on hematite and limonite surface could interact more strongly with NaOL than Fe(II) on siderite, which resulted in the higher adsorption density and intensity of NaOL on hematite and limonite than that on siderite. This further contributed to the stronger hydrophobicity on their surface than that on siderite surface. The enhancement of hydrophobicity could increase the attachment efficiency of bubble-particle (Ea). Therefore, hematite and limonite particles had more and faster attachment with bubbles than siderite particles. As such, much higher cumulative ultimate recoveries (R∞) and flotation rate constants (k) of hematite and limonite than those of siderite were obtained.