It is well known than the energy barrier defines the particle-bubble attachment in a flotation process. In this study, the energy barrier of aggregates coal particle-bubble was determined using the extended DLVO theory. The effect of pH and frother concentration (FC) about energy barrier using four Colombian coals was evaluated. Experiments were carried out using a column flotation of 5 m of height at pH range of 4 to 10, FC in the range of 2 to 6 ml of frother/kg of coal. In order to evaluate the bubble diameter were used air velocities (Jg) in the range of 0.7 to 2.1 cm/s. Results showed that using acid condition (pH 4 and 5), all coals did not exhibit energy barrier. It was determined that, in general, the energy barrier of Cerrejon and Guachinte coals was higher than those of the Nechi and Jagua coals. (C) 2011 Elsevier B.V. All rights reserved.