The biosorption abilities of Rhodococcus opacus were studied for cadmium and zinc removal for liquid aqueous streams. The influence of pH, initial metal concentration and time removal were evaluated on the biosorption studies, in a batch scale basis. The Cd2+ and Zn2+ species uptake capacity by R. opacus has been also compared using Langmuir and Freundlich models. At pH 7.0 and 26 degrees C C, Cd2+ removal achieved a value around 60% from an initial concentration of 15 ppm. On the other hand, Zn removal achieved a value around 88% from an initial concentration of 5 ppm. Kinetics studies revealed that the biosorption process followed a pseudo-second order model for the two metal species (Cd2+ and Zn2+) and the kinetic constants were 3.90 and 3.37 g mg(-1) min(-1), for an initial concentration of 15 and 5 ppm for cadmium and zinc, respectively. The results showed that the R. opacus is a potential engineering biosorbent for environmental and extractive metallurgy sustainable applications. (c) 2007 Elsevier Ltd. All rights reserved.