Removal of heavy mercury(II), cadmium(II) and zinc(II) metal ions by live and heat inactivated Lentinus edodes pellets

The live and heat inactivated forms of Lentinus edodes pellets were used for the biosorption of Hg2+, Cd2+ and Zn2+ ions. The maximum adsorption of metal ions on the live and heat inactivated pellets of fungus was observed at pH 6.0 for all the used metal ions. The effect of temperature on the biosorption capacity was negligible in the range of 15-45 degrees C. The biosorption of Hg2+, Cd2+ and Zn2+ ions on the live and heat inactivated pellets of fungus was studied in aqueous solutions in the concentration range of 25-600 mg/L. The metal biosorption capacities of the live fungal pellets Hg2+, Cd2+ and Zn2+ were 336.3 +/- 3.7, 78.6 +/- 2.6 and 33.7 +/- 1.6 mg/g, respectively, while Hg2+, Cd2+ and Zn2+ the biosorption capacities of the heat inactivated pellets were 403.0 +/- 2.9, 274.3 +/- 3.6 and 57.7 +/- 1.1 mg/g, respectively. The adsorption capacities of the heat inactivated fungus for metals were markedly increased compared to native form. For both forms the same affinity order on a molar basis were observed for single or multi-metal ions (Hg2+ > Cd2+ > Zn2+). The Langmuir and Freundlich equilibrium models represent well the experimental data. The experimental kinetic data were analyzed using the first- and second-order kinetic models and the second-order kinetic model described the biosorption kinetics accurately for each metal ions. (C) 2008 Elsevier B.V. All rights reserved.