Flotation characteristics of spodumene using oleic acid as collector have been investigated through micro-flotation tests, adsorption measurement, surface tension measurement and solution chemistry calculation. It is concluded that the pH values at which the maximum flotation recovery, maximum adsorption amount and minimum surface tension achieved, correspond to the formation of oleic acid ionic-molecular complexes. By the means of Hydrophile-Lipophile Balance (HLB), Critical Micelle Concentration (CMC) and density functional theory (DFT) calculation, it is determined that the hydrophobicity of ionic oleic acid is strengthened by associating with molecular oleic acid, and the bonding ability of COO- on minerals surface is intensified as well. FTIR measurement revealed that the carboxyl groups of the ionic-molecular complexes react with Al sites on the surface of spodumene by chemical adsorption. A concrete modality of ionic-molecular complexes was ascertained and a molecular model of ionic-molecular complexes of oleic acid adsorbing on spodumene surface was established. (C) 2014 Elsevier Ltd. All rights reserved.