Biosorption of heavy metal ions on immobilized white-rot fungus Trametes versicolor.

Trametes versicolor mycelia were immobilized in carboxymethylcellulose, CMC, beads via entrapment, and the bead containing immobilized fungus spores were incubated at 30 degrees C for 3 days to attain uniform growth on the bead surface. After incubation, the live and heat inactivated immobilized fungus on the CMC beads were used for the biosorption of Cu(2+), Pb(2+) and Zn(2+) ions. Plain CMC beads were used as a control system. The biosorption of Cu(2+), Pb(2+) and Zn(2+) ions by the CMC and both live and inactivated immobilized preparations increased as the initial concentration of Cu(2+), Pb(2+) and Zn(2+) ions in the medium increased. The maximum biosorption capacities for both immobilized live and heat inactivated Trametes versicolor were 1.51 and 1.84mmol Cu(2+), 0.85 and 1.11mmol Pb(2+) and 1.33 and 1.67mmol Zn(2+) per g of dry biosorbents, respectively. Biosorption equilibrium was established in about 1.0h and the equilibrium was well described by Langmuir and Freundlich isotherms. A temperature change in the range of 15-45 degrees C did not affect the biosorption capacity. The affect of pH was also investigated and the maximum adsorption of Cu(2+), Pb(2+) and Zn(2+) ions on the CMC and both live and inactivated immobilized fungal biomass was observed between pH 4.0 and 6.0. The CMC beads with the immobilized fungus can be regenerated using 10mM HCl, with up to 97% recovery of the metal ions; the biosorbents reused up to five biosorption-desorption cycles without any major loss in the biosorption capacity.