This work reports the batch and dynamic flow biosorption conditions for Orange G dye using Pyracantha coccinea which was modified by a hegzadecylethyldimethylammonium bromide. Experiments were performed to determine optimum pH, biosorbent dose, contact time, temperature, dye concentration, flow rate and column internal diameter. The optimum conditions were pH 4.0 for Orange G at initial dye concentration of 100 mg L-1 with equilibrium time of 30 min. Under the optimized batch conditions, 95.96% dye could be removed from the solution. Kinetic data followed the pseudo-second-order model while the equilibrium data were well predicted by the Langmuir isotherm model. The maximum monolayer biosorption capacity for modified biomass was determined as 1.28 x 10(-4) mol g(-1) at pH 4.0. The biosorbent was investigated using energy-dispersive X-ray spectroscopy and Fourier transform infra-red spectroscopy techniques. This study suggested that the modified P. coccinea could effectively be used to remove azo dyes from wastewater. (C) 2013 Elsevier B.V. All rights reserved.