Iron coral: Novel fungal biomineralization of nanoscale zerovalent iron composites for treatment of chlorinated pollutants

In this research, a facile fungal biomineralization method was developed for the synthesis of nanoscale zerovalent iron (nZVI) with a unique N-doped branching structure, which showed excellent stability and mediated high degradation of carbon tetrachloride (CCl4) in aqueous solution. The ureolytic fungus Neurospora crassa was cultured in medium containing Fe2+ and urea which resulted in iron carbonate biomineral precipitation. Following carbonization at 900 degrees C, the fungal-carbonate composite became highly porous and granular nanoparticles (similar to 50 nm diameter) were distributed evenly around the carbonized hyphae in a coralline manner. This 'iron coral' composite was identified as a mixture of zerovalent iron (Fe-0), carbon iron (Fe1.91C0.09) and iron oxide (Fe3O4). The porous branching hyphal framework improved the capture efficiency of CCl4, and the N-doped sites may accelerate the electron transfer between CCl4 and nZVI. Geochemical simulation was applied to verify the formation of the biominerals, and chemical analyses confirmed its significant degradation ability for CCl4. These findings have therefore demonstrated that ureolytic fungi can provide a promising environmental friendly system for the novel preparation of nZVI through biomineralization with the resulting 'iron coral' capable of significant removal of a chlorinated compound and therefore indicating new bioremediation applications.