Biosorption of Hg 2+, Cd 2+, and Zn 2+ by Ca-alginate and immobilized wood-rotting fungus Funalia trogii

Abstract

Funalia trogii biomass was immobilized in Ca-alginate gel beads. The live and heat inactivated immobilized forms were used for the biosorption of Hg 2+, Cd 2+ and Zn 2+ ions by using plain Ca-alginate gel beads as a control system. The effect of pH was investigated and the maximum adsorption of metal ions on the Ca-alginate and both live and inactivated immobilized fungal preparations were observed at pH 6.0. The temperature change between 15 and 45 °C did not affect the biosorption capacity. The biosorption of Hg 2+, Cd 2+ and Zn 2+ ions on the Ca-alginate beads and on both immobilized forms was studied in aqueous solutions in the concentration range of 30–600 mg/L. The metal biosorption capacities of the heat inactivated immobilized F. trogii for Hg 2+, Cd 2+ and Zn 2+ were 403.2, 191.6, and 54.0 mg/g, respectively, while Hg 2+, Cd 2+ and Zn 2+ biosorption capacities of the immobilized live form were 333.0, 164.8 and 42.1 mg/g, respectively. The same affinity order on a molar basis was observed for single or multi-metal ions (Hg 2+>Cd 2+>Zn 2+). The Langmuir and the Freundlich type models were found to exhibit good fit to the experimental data. The experimental data were analyzed using the first-order (Langergren equations) and the second order (Ritchie equations). The experimental biosorption capacity with time is found to be best fit the second-order equations. The alginate-fungus system could be regenerated by washing with a solution of hydrochloride acid (10 mM). The percent desorption achieved was as high as 97. The biosorbents were reused in five biosorption–desorption cycles without significant loss of their initial biosorption capacity.