Comparison of copper(II) biosorptive properties of live and treated Candida sp

Biosorption of copper(II) ions from aqueous solutions was studied to compare the binding capacities of untreated (live) or treated (dried, autoclaved, perchloric acid (HClO4)-washed, ethanol-treated, formaldehyde-treated) Candida sp. Due to the ion exchange nature of metal biosorption, copper(II) uptake was strongly affected by the solution pH and optimum adsorption pH value was determined as 5.0 for all the live and treated Candida sp. At the optimal conditions, metal ion uptake increased with increasing initial copper(II) concentration up to 300 mg l-1 for all the biomass types. It is found that all the treatment methods used to kill the yeast (except for formaldehyde treatment) increased the copper(II) biosorption capacity of Candida cells. The results also indicated that copper(II) biosorption by live, autoclaved and formaldehyde-treated yeasts was consisted of an initial, rapid surface binding of copper(II) followed by a second, slower intracellular uptake of copper(II), but copper(II) uptake by the other treated yeasts took place only via surface binding. Both the Freundlich and Langmuir adsorption models were suitable for describing the short-term biosorption of copper(II) by all the untreated and treated Candida.