This study shows the effect of pH. air velocity (Jg) and frother concentration (FC) on combustible recovery, ash and sulphur rejection for four Colombian bituminous coals: Cerrejon (Guajira), Nechi (Antioquia), Jagua (Cesar) and Guachinte (Valle del Cauca) using column flotation. For the experimental development a 2(3) factorial central composite experimental design was used. The coal samples were processed in a pH range of 4 to 10, Jg in the range of 0.7 to 2.1 cm/s and FC in the range 2.1 to 6.3 kg/t. Results showed that Cerrejon and Jagua coal presented combustible recovery higher than 50%, (57.6% and 54.7% respectively), at acidic pH (pH 5), with Jg of 1 cm/s and 32 to 4.2 kg/t of FC, respectively, while Guachinte coal presented a maximum combustible recovery of 56.4% at alkali pH (pH 9), Jg of 1 cm/s and 3.2 kg/t of FC and Nechi coal obtained the highest combustible recovery (46.8%) at pH 7 with 2.1 kg/t of FC and Jg of 1.4 cm/s. For Guachinte and Nechi coal ash and sulphur rejection were high (90.3% and 88.5%) and (71.3% and 73.8%) respectively at acidic conditions (pH 4 and 5) with Jg in the range of 1.4 to 1.8 cm/s, whereas Cerrejon and Jagua coals exhibited high values of ash (85.4% and 94.7%) and sulphur rejection (81.1% and 85.1%) at alkali conditions (pH 9 and 10) with Jg in the range of 1.0 to 1.4 cm/s. In general, it was observed that Cerrejon and Jagua coals presented higher values of combustible recovery under acidic conditions than Nechi coal and Guachinte coal. (C) 2012 Elsevier B.V. All rights reserved.