Optimization the removal of lead ions by fungi: Explanation of the mycosorption mechanism

The potential utilization of fungal biomass (Rhizopus arrhizus) as a biosorbent for the efficient removal of lead (Pb2+) ions from aqueous solutions was optimized in the current work. The maximum Pb2+ biosorption capacity of fungal biosorbent was 0.501 mol kg−1 at pH 4.0 and 25 ◦C. The biosorption process follows the intra-particle diffusion and pseudo-second-order rate kinetics. Thermodynamic studies showed that Pb2+ biosorption by this fungal biosorbent is spontaneous and endothermic. The fungus has good biosorption/desorption performance for Pb2+ ions according to desorption studies. The biosorption free energy calculated from the Dubinin-Radushkevich isotherm showed that the biosorption process was accomplished chemically. Moreover, the mechanism of the Pb2+ biosorption on to the fungal biosorbent was evaluated by infrared spectral analysis coupled with pattern recognition techniques using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). The ATR-FTIR spectral analysis of the fungal biosorbent revealed changes in particular spectral bands emerging from functional groups of biomolecules. Possibly, these functional groups of biomolecules are active fungal biosorbent sites involved in the interaction with Pb2+ ions. Thus, the surface of the fungal biosorbent is attractive for the sorption of metal ions making the fungal biomass as an effective and efficient biosorbent for the removal of Pb2+ ions.