New insight into surface adsorption thermodynamic, kinetic properties and adsorption mechanisms of sodium oleate on ilmenite and titanaugite

Titanaugite particles are detrimental to the flotation of fine ilmenite. In this work, the surface adsorption thermodynamic, kinetic properties and the adsorption mechanism of sodium oleate on ilmenite and titanaugite surfaces were investigated by measuring surface wettability, lipophilic hydrophilic ratio, surface free energy, adsorption rate, adsorption density and adsorption thickness. The hydrophilicity of the minerals were determined by the contact angle, lipophilic hydrophilic ratio, gamma(LW)(s) value, and gamma(AB)(s)/gamma(s) value. The surface wettability results showed that the hydrophilicity of the minerals decreased following: -20 mu m titanaugite >-20 mu m ilmenite >-38 + 20 mu m ilmenite >- 74 + 38 mu m ilmenite. The adsorption process can be represented with Langmuir isotherm and a pseudo second-order kinetic model. Calculation of the adsorption thermodynamic parameters confirmed that the adsorption of sodium oleate on ilmenite surfaces is spontaneous, feasible, and endothermic. And it was also confirmed that sodium oleate was adsorbed onto ilmenite due to both physical and chemical adsorption. In situ AFM imaging visually demonstrated that the adsorption density and thickness of the sodium oleate adsorbed onto titanaugite were lower than those of sodium oleate on ilmenite, which was consistent with the adsorption thermodynamic parameters. It was further confirmed that the electrostatic interaction, chemisorption, hydrogen-bonding adsorption and specific hydrogen-bonding adsorption were the main mechanisms for the sodium oleate adsorbed onto ilmenite, as the zeta potential and XPS spectra analyses. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.