Reagent adsorption on modified mineral surfaces: isotherm, kinetic and thermodynamic aspects

Abstract

This study has been designed to investigate the effect of surface dissolution on the isotherm, kinetics, and thermodynamics of collector adsorption on the surface of ilmenite (IL) and its accompanied gangue minerals including olivine (Ol), pyroxene (Px), tremolite (Tr), and clinochlore (Cch). For this purpose, some laboratory techniques such as flotation experiments, adsorption tests, ICP-Mass analysis, UV–Visible spectroscopy, BET analysis, and scanning electron microscopy were employed. The flotation experiments showed that after surface dissolution, the selectivity of ilmenite flotation is improved by increasing its flotation recovery and by the decrease of gangue minerals floatabilities. As revealed by adsorption tests, this can be attributed to the more adsorption density of collector on the surface of treated ilmenite and its reduction on the modified surface of olivine-pyroxene (Ol-Px) and tremolite-clinochlore (Tr-Cch) having less surface active cations (Fe2+, Ca2+, and Mg2+) after surface modification by oxalic acid. Also, the equilibrium data analysis indicated that the Langmuir model is the most appropriate model to describe the adsorption of sodium oleate as a collector on the surface of studied minerals. The kinetics studies showed that unlike the gangue minerals, the adsorption kinetics of collector on the surface of modified ilmenite is significantly enhanced. According to the thermodynamic parameters, positive Enthalpy (ΔH), negative Gibbs free energy (ΔG), and positive Entropy (ΔS) were found for the collector adsorption process before and after treatment, showing the endothermic, spontaneous and more favorable nature of adsorption reaction at high temperatures. Also, the surface dissolution changes the ΔG and ΔS of ilmenite into the more negative and positive values, respectively, while it changes these thermodynamic parameters inversely for both gangue phase samples.