Biomass fly ash was treated with alkaline solution to enhance its adsorption capacity of Reactive Black 5 dye. The results revealed that the alkaline concentration, solution to fly ash ratio, treatment temperature and treatment time had a positive effect on the dye adsorption capacity of the treated fly ash (TFA), due to dissolving SiO2 and increasing the proportion of unburned carbon. In addition, the dye adsorption behavior of the TEA in aqueous solution was investigated. The effects of various experimental parameters (initial pH, initial dye concentration and contact time) were determined spectrophotometrically. The dye adsorption capacity of the TFA was maximized at an alkaline pH (8.2-10.4). The adsorption capacity of dye by the TFA increased with increasing initial dye concentration. Equilibrium data fitted well with the Langmuir model in the range of 50-700 mg L-1 and the maximum dye adsorption capacity was 107.53 mg g(-1). The sorption data provided a good fit with a pseudo-second order kinetic model. These results suggested that treating biomass fly ash with alkaline solution is an effective method for enhancing dye removal efficiency. The TFA obtained can be used as an alternative to commercial activated carbon for treating dye wastewater. (C) 2010 Elsevier B.V. All rights reserved.