The pollution caused by heavy metals is one of the major environmental problems that is imperative to be solved. New technologies, easy to implement and to adapt to any system, deserve special attention and are a focus of this work. The ability of a biofilm of Escherichia coli supported on kaolin to remove Cr(VI), Cd(II), Fe(III) and Ni(II) from aqueous solutions was investigated in batch assays for the treatment of diluted aqueous solutions. The biosorption performance, in terms of uptake, followed the sequence: Fe(III) > Cd(II) > Ni(II) > Cr(VI). The equilibrium data in batch systems were described by Langmuir, Sips and Redlich-Peterson model isotherms. The best fit for chromium and nickel was obtained with the Redlich-Peterson model and for cadmium the best fit was obtained with the Sips model. The presence of functional groups on the cell wall surface of the biomass that may interact with the metal ion was confirmed by FTIR. Kaolin samples have been fully characterized by chemical analyses. The results obtained are very promising for the removal of metal ions from effluents. (C) 2008 Elsevier B.V. All rights reserved.