Flotation kinetics is an excellent tool used to evaluate flotation performance, which is controlled by several factors, such as the particle size, bubble size, and surface property. In this study, we investigated the effects of particle size and ferric hydroxo complex produced by grinding with CB and CIB media on the flotation kinetics of pyrite using Python statistical analysis software and Origin software based on five flotation kinetic models. The results showed that the pyrite particles produced when CB was used as the grinding medium exhibited better cumulative experimental recovery owing to a lower formation of ferric hydroxo complexes. In the case of grinding with CB medium, the first-order flotation kinetic model (epsilon = epsilon(infinity)(1 - e(-kt)) provided the best fit for the experimental data, whereas the first-order and second-order flotation kinetic model are considered the best in the case of grinding with the CIB medium depending on the experimental conditions. In addition, the particle size and the ferric hydroxo complex were found to be the determining factors of the flotation rate constant (k) and cumulative ultimate recovery (epsilon(infinity)), respectively, in both cases. The intermediate sizes of 10 to 120 mu m were found to be the optimal particle sizes for achieving a higher pyrite flotation rate. Less quantity of ferric hydroxo complexes formed on the surface of the pyrite particles, resulting in a higher epsilon(infinity). The presence of ferric ions inhibited the pyrite flotation recovery and its flotation rate once the pulp pH was sufficient to cause complete precipitation of the ferric hydroxo complex. (C) 2019 Elsevier B.V. All rights reserved.