An attempt has been made in this paper to examine the effect of particle size on flotation parameters in the separation of diaspore and kaolinite. First of all, the basic properties such as zeta potential and contact angle and flotation behaviors of diaspore and kaolinite in sodium oleate (NaOL) and dodecylamine (DDA) solution were investigated. And then direct and reverse flotation experiments of mixed binary minerals at different size fractions were carried out. The classical first order flotation kinetics were used to fit the flotation data and first-order rate constant (k), ultimate recovery (R-infinity), modified rate constant (K-m), selectivity index (SI) and separation efficiency (SE) were calculated and used as the flotation parameters to evaluate the separation effect of the two minerals. The results show that in the separation of diaspore and kaolinite, the particle size has a significant influence on the flotation parameters. The favorable particle size fractions for direct flotation were -38 + 20 mu m and -54 + 38 mu m and the adverse particle size fractions were -10 mu m and -20 + 10 mu m. While for reverse flotation, the favorable particle size fractions were -74 + 54 mu m and -10 mu m and the adverse particle size fractions were -38 + 20 mu m and -54 + 38 mu m. The optimal flotation times for the favorable size fractions were shorter than that for unfavorable size fractions. For the same size fractions, longer flotation times were required to reach the maximum separation efficiency in reverse flotation than those in direct flotation. Under the optimized condition (direct flotation, pH = 10, NaOL dosage was 2 x 10(-4) mol/L, ore particle size was -38 + 20 mu m), concentrate products with diaspore recovery of 83.79% and A/S value of 7.96 can be obtained. (C) 2017 Elsevier B.V. All rights reserved.