Biosorption of Remazol Black B a vinyl sulfone type reactive dye from aqueous solution was investigated to compare the binding capacities of untreated (live) and treated (dried autoclaved acid (H2SO4)-treated base (NaOH)-treated) activated sludge in this study Remazol Black B uptake was strongly affected by the solution pH and optimum adsorption pH value was determined as 2 for all the live and treated activated sludge biosorbents It was seen that the sorption capacity of each biosorbent enhanced with decreasing temperature Dye uptake also increased with increasing initial dye concentration up to 500 mgl(-1) for each biomass type Contrary to assumption it is found that all the treatment methods diminished the dye biosorption capacity of activated sludge Among the five biosorbents live activated sludge had a maximum dye uptake capacity of 134 8 mg g(-1) at 25 C The Langmuir-Freundlich adsorption model described the equilibrium data of each dye-biosorbent system accurately in the concentration and temperature ranges studied The pseudo-second-order adsorption model defined the overall adsorption kinetics of each biosorption process exactly (C) 2010 Elsevier B V All rights reserved