Sorption of reactive dye from aqueous solution on biomass fly ash

This study investigates the adsorption behavior of Reactive Black 5 (RB) and Reactive Yellow 176 (RY) from aqueous solution on coal fly ash (FA-CO), HCl-treated coal fly ash (TFA-HCl), and biomass fly ash (FA-BM). In preliminary study, the FA-BM showed the greatest dye adsorption capacity of both dyes, compared to FA-CO and TFA-HCl. Hence only for the FA-BM, the effects of various experiment parameters (e.g. solution pH, ionic strength, initial dye concentration, contact time) were spectrophotometrically determined. At the final pH of 8.1-8.5, the adsorption capacity of both dyes on the FA-BM was maximum and decreased above or below this pH. A positive effect of salt addition on the dye adsorption capacity was observed. The adsorption capacity of dye on the FA-BM increased with increasing C-0. The equilibrium data of both dyes on the FA-BM were fitted to both Langmuir and Freundlich isotherms, but the experimental data of the RB was found to be little better fitted by the Langmuir model. The sorption data was good fit with the pseudo second-order kinetic model. These results indicate that biomass fly ash is an interesting alternative for dye removal from the wastewater. (C) 2007 Elsevier B.V. All rights reserved.