Fundamental aspects of biosorption of lead (II) ions onto a Rhodococcus opacus strain for environmental applications

Lead is present in different types of industrial effluents, being responsible for environmental pollution. Biosorption of heavy metal ions by biological material is a promising technology with a potential for treating mineral processing wastewater. In this fundamental work, the biosorption of Pb(II) ions from aqueous solutions using the bacteria Rhodococcus opacus was investigated as a function of contact time, initial metal ion concentration and temperature. The equilibrium studies showed that the biosorption is well described through the Langmuir isotherm model in comparison to the Freundlich model in the concentration range studied (20-200 mg/L). The biosorption capacity obtained from Langmuir equation increased from 86.2 to 95.2 mg/g as the temperature was increased from 15 to 35 degrees C. Experimental data were also tested in terms of biosorption kinetics using pseudo-first order and pseudo-second-order kinetic models. The result showed that the biosorption processes of lead ions followed well pseudo-second-order kinetics and the adsorption rate constant increased with increasing temperature. The activation energy of biosorption (E-a) was determined (30.4 kilmol) using the pseudo-second-order rate constants. The positive values of both H Delta(0) and Delta S-0 obtained suggest that the biosorption of lead (II) ion on the R. opacus was spontaneous and endothermic in nature. (C) 2011 Elsevier Ltd. All rights reserved.