Biosorption of Ternary Cadmium, Nickel and Cobalt Ions from Aqueous Solution onto Saccharomyces cerevisiae Cells: Batch and Column Studies

The aim of this study was to remove cadmium, nickel and cobalt ions from aqueous solutions using yeast, Saccharomyces cerevisiae, pre-treated with ethanol. The cells are immobilized using polysulfone in both batch and continuous systems. To optimize the adsorption capacity of the yeast biomass, a batch system was used to investigate the effects of initial pH, initial biomass dose and initial metal ion concentration. Optimum conditions were obtained at pH 8 with a biomass of and ion concentrations of 8 and 100 mg L^-1, respectively. Under these conditions, the maximum uptake capacity was 3.1 mg g^-1 for cadmium, 1.2 mg g^-1 for nickel and 0.68 mg g^-1 for cobalt. To estimate the biomass uptake capacity of the ethanol pretreated S. cerevisiae, the isothermal Langmuir model was found to be a better fit with a correlation coefficient of R² <0.964. Factors observed affecting biomass ion adsorption in the continuous system are initial concentration of single or multi-metallic ions, the column height of bead system and the input flow rate. The optimum conditions for the continuous system were determined at pH 8, initial metal ion concentration of 100 mg L^-1, bead column height of 25 cm and the input flow rate of 1 mL min^-1. The calculated uptake capacity of the metal ions was 3.74 mg g^-1 for cadmium, 1.57 mg g^-1 for nickel and 1.56 mg g^-1 for cobalt. The Thomas model (0.9524<R²<0.9957) was shown to be more consistent compared with the test results. Polysulfone immobilization of yeast was found to increase removal by 48% compared to non-immobilized ethanol pr-treated yeast.