Copper(ii) biosorption characteristics of lyophilized and thermally treated pseudomonas cells

Biosorption of copper(II) by lyophilized and thermally treated bacterial biomass of Pseudomonas aeruginosa PAO1 and Pseudomonas fluorescens BME in aqueous suspension was studied. The cell surface properties were characterized and the experimental conditions, e.g., pH, adsorption time, and initial metal concentration were optimized for efficient biosorption. The surface charge was negative at pH above 2.5 for P. aeruginosa, and above pH 4 for P. fluorescens. The highest copper(II) uptake was observed at pHs 5 to 6 for both bacteria with a maximum uptake capacity of 60.3 and 56.5 mg copper(II)/g biomass for P. aeruginosa and 56 and 29 mg/g for P. fluorescens by the lyophilized and thermally treated cells, respectively. Both, the Freundlich and the Langmuir model, using non-linear least-squares estimation, gave a good prediction to the experimental data of copper(II) biosorption equilibrium. For the biosorption kinetic study only the pseudo second-order kinetic model could be applied at various temperatures. Temperature has only a minor effect on the adsorbed amounts in the experimental conditions studied. The laboratory bacterial strain P. aeruginosa PAO1 is more efficient adsorbent for copper(II) than P. fluorescens BME in lyophilized and even in thermally inactivated form.