Biosorption equilibria of binary Cd(II) and Ni(II) systems onto Saccharomyces cerevisiae and Ralstonia eutropha cells: application of response surface methodology.

Present study investigated the biosorption of Cd(II) and Ni(II) from aqueous solution onto Saccharomyces cerevisiae and Ralstonia eutropha non-living biomass. Biomass inactivated by heat and pretreated by ethanol was used in determination of optimum conditions. The important process parameters, such as initial solution pH (2-8), initial Ni(II) concentration (11-42 mg/l), initial Cd(II) concentration (11-42 mg/l), and biomass dosage (0.2-4.7 g/l) were optimized using design of experiments (DOE). A central composite design (CCD) under response surface methodology (RSM) was applied to evaluate and optimize the efficiency of removing each adsorbent. Moreover, the two responses were simultaneously studied by using a numerical optimization methodology. The optimum removal efficiency of Cd(II) and Ni(II) onto S. cerevisiae was determined as 43.4 and 65.5% at 7.1 initial solution pH, 4.07 g/l biomass dosage, 16 mg/l initial Ni(II) concentration and 37 mg/l initial Cd(II) concentration. The optimum removal efficiency of Cd(II) and Ni(II) onto R. eutropha was ascertained as 52.7 and 50.1% at 5.0 initial solution pH, 2.32 g/l biomass dosage, 28 mg/l initial Ni(II) concentration and 37 mg/l initial Cd(II) concentration. The present analysis suggests that the predicted values are in good agreement with experimental data. The characteristics of the possible interactions between biosorbents and metal ions were also evaluated by scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy analysis.