Biosorption of heavy metals from aqueous solutions by Saccharomyces Cerevisiae

The present work evaluates the performance of the yeast Saccharomyces Cerevisiae to remove heavy metals from aqueous solutions. The effect of pH, temperature, initial concentration, contact time, and biosorbent dosage on biosorption capacity is studied. Experiment results show that metal uptake is a rapid process at pH values (5.0-6.0), and the order of accumulated metal ions is Pb > Zn > Cr > Co > Cd > Cu. The biosorption process obeys Freundlich and the Langmuir adsorption isotherms. The kinetics of metal ions biosorption could be described by Lagergren and Ho models. Nitric acid with low concentration of 0.05 N is effective in desorbing the biosorbed metal ions. Sodium hydroxide solution of 0.2 M is effective in regenerating the yeast; the regenerated yeast could be used for at least six cycles of biosorption, without losing its metal removal capacity. Carboxyl, amine, and phosphate groups present in the yeast were found to be the main biosorption sites for metal ions.