Biosorptive capacity of Cd(II) and Cu(II) by lyophilized cells of Pseudomonas stutzeri.

The biosorptive capacity of Cd(II) and Cu(II) by lyophilized cells of Pseudomonas stutzeri was investigated based on Langmuir and Freundlich isotherms and biosorption kinetics were analyzed using first order kinetic with different initial metal concentrations. Biosorptive capacity for Cd(II) and Cu(II) decreased with an increment of metal concentration, reaching 43.5 and 36.2 mg/g at the initial concentration of 300 mg/L. Biosorption capacity for both metal ions was increased with increasing pH. The optimum pH for biosorption rate of Cu(II) and Cd(II) was pH 5; above pH 5.0 the metal cations came to be precipitated. The experimental data showed a better fit with the Langmuir model over the Freundlich model for both metal ions throughout the range of initial concentrations. The maximum sorptive capacity (q max) obtained from the Langmuir equation for Cd(II) and Cu(II) were 47.86 (r(2)=0.99) and 33.16 (r(2)=0.99), respectively. The bacterial cells have more affinity to adsorb cadmium than copper. The first order kinetic was well fitted to the experimental data for initial concentrations from 30 to 100 mg/L during reaction times of 250 min. These results suggest that biosorption of Cu(II) and Cd(II) by lyophilized cells of P. stutzeri is a potential metal removal strategy.