Simultaneous biosorption of phenol and chromium(VI) ions to Mowital((R))B30H resin immobilized activated sludge from binary mixture was studied and compared with single phenol or chromium(VI) biosorption in a continuous packed bed column. The phenol and chromium(VI) binding capacity of biosorbent was shown as a function of single and dual pollutant concentrations at a flow rate of 0.8 ml min(-1) and at a pH value of 1.0. The equilibrium uptake (or column biosorption capacity) of each pollutant was determined by evaluating the breakthrough curves obtained at different inlet concentrations changing 50-500 mg l(-1) in single and binary systems. The maximum column biosorption capacity of dried activated sludge was 9.0 mg g(-1) for phenol and 18.5 mg g(-1) for chromium(VI) at single ion situation. The column sorption capacity of immobilized dried activated sludge for phenol (or for chromium(Vi)) decreased notably due to the presence of other component. The mono- and multi-component sorptions in packed bed were expressed by the Yoon and Nelson model to determine the kinetic constants and to predict the breakthrough curves of each component. The functional relationship between Yoon and Nelson kinetic constant of each component and concentrations of phenol and chromium(VI) in binary mixture was determined by using Response Surface Methodology. (c) 2005 Elsevier B.V. All rights reserved.