Biosorption of Hg and Ni ions on Bakers Yeast

Abstract

The present study evaluates the potential of the yeast Saccharomyces Cerevisiae to remove mercury and nickel from aqueous solutions. The effect of pH, initial concentration, contact time, and biosorbent dosage on biosorption capacity is studied in batch experiments. Experiment results show that metal uptake is a rapid process at pH values (5.0-6.0). Sorption isotherms are studied to explain the removal mechanisms of metal ions by fitting isotherm data into Langmuir and Freundlich equations, the biosorption of mercury and nickel from aqueous solutions on live yeast at an initial pH of (5.0-6.0) could be described by both the Freundlich and the Langmuir adsorption isotherms. Pretreatment using NaOH, HCL, and ethanol enhance biosorption capacity of the yeast. It was concluded that nitric acid with low concentration of 0.05 N is effective in desorbing the biosorbed metal ions. On the other hand, 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.