Biosorption of lead(II), chromium(III) and copper(II) by R. opacus: Equilibrium and kinetic studies

Micro-organisms and microbial products can be highly efficient to uptake soluble and particulate forms of metals, particularly from dilute solutions. The aim of this work was to evaluate the fundamental aspects of the biosorption of Pb(II), Cr(III) and Cu(II) metal species using Rhodococcus opacus strain. Zeta potential studies and adsorption experiments were carried out in order to evaluate the sorption metals uptake and the possible interaction mechanisms between the metal species and the surface cell wall. The electrophoretic studies showed that the presence of the metal species affected the zeta potential profiles. Moreover, the equilibrium biomass – metals systems followed the Langmuir isotherm model and the pseudo-second order kinetic model. The influence of Cr(III) and Cu(II) on Pb(II) biosorption capacity in binary and ternary systems was evaluated and biosorption capacity of the Pb(II) ions was found to be reduced by the presence of the other competing metal ions. The nature of possible cell–metal ions interactions was also evaluated by FT-IR and SEM/EDS analysis. These examinations indicated the involvement of –COOH, –OH and –NH groups in the biosorption process.