Encapsulating magnetite nanopowder with fungal biomass: Investigating effects on chemical and mineralogical stability

Abstract

Fungal biomasses have emerged as cost-effective biosorbents. To augment their sorptive capabilities, in this study, a novel approach was explored - culturing Aspergillus fungi with magnetite nanopowder, yielding pellet-like biomass structures enclosing the nanoparticles. However, this interaction might induce undesired structural and mineralogical changes in the magnetite nanopowder. Therefore, we investigated the fungal impact on magnetite's structural and chemical stability using powder XRD and Mössbauer spectroscopy. Our findings revealed that the mineralogical alterations induced by A. niger in magnetite nanopowder remained subtle. Intriguingly, despite minimal structural changes in both magnetite (90%) and maghemite (9%), major components revealed by Mössbauer spectroscopy in commercially available magnetite nanopowder, A. niger exhibited remarkable iron extraction (approximately 40%). This highlights its capacity to dissolve magnetite nanopowder while preserving its mineralogical integrity. Conversely, A. clavatus, despite insignificant iron extraction, induced notable crystal lattice distortions in both magnetite and maghemite. This suggests its capacity to trigger structural changes even with limited bioleaching activity. Moreover, we assessed the sorptive performance of the biomass-based composite for arsenic and antimony removal, contributing to a comprehensive understanding of the intricate interaction between fungal biomass and magnetite nanopowder. These findings offer valuable insights into the mineralogical and structural modifications of magnetite induced by fungi and lay the groundwork for designing effective biomass-based sorbents for environmental applications.