MECHANISM OF METAL-ION BIOSORPTION BY FUNGAL BIOMASS

Alkali extracted mycelial biomass from Aspergillus niger, referred to as Biosorb, was found to sequester metal ions (Cd2+, Cu2+, Zn2+, Ni2and Co2+) efficiently both from dilute and concentrated solutions upto 10% of its weight (w/w). Sequestration of metal ions from a mixture w as also efficient but with attendant antagonisms. The kinetics of meta l binding by Biosorb indicated that it is a rapid process and about 70 -80% of the metal is removed from solution in 5 min followed by a slow er rate, The mechanism of metal binding is shown to be due to exchange of calcium and magnesium ions of the Biosorb during which equimolar c oncentrations of both the ions were released into the medium, followin g this an efficient procedure for the regeneration and reuse of Biosor b was standardized by washing the biosorbent with calcium and magnesiu m solution (0.1 M). Biosorbents prepared from Neurospora, Fusarium and Penicillium also exhibited similar mechanisms for metal ion binding, though they had a lower metal binding capacity when compared with Bios orb, Chemical modification of carboxylic acid functional groups of the Biosorb resulted in loss of 90% of metal binding capacity which could not be restored even on regeneration, The significance of this findin g on the metal sequestration mechanisms of microbial biosorbents is di scussed.