Nano-bioremediation of metal-polluted industrial wastewater using myco-synthesized iron oxide nanoparticles derived from Aspergillus niger AUMC 16028.

The presence of heavy metals in wastewater poses serious ecological and environmental issues. Using biogenic nano adsorbents to remove heavy metals from industrial wastewater could be beneficial and serve as an alternative to traditional chemical and physical methods in real-world applications. The aim of this study is to biosynthesize green iron oxide nanoparticles (IONPs) for the removal of heavy metals from industrial wastewater. This process utilizes a cell-free extract derived from heavy metal-resistant fungi that were isolated from various industrial wastewater effluents in Egypt. Several fungal strains were examined for their ability to produce IONPs. A molecular identification of the most powerful fungus was made. The color change, as observed using UV-Vis spectroscopy, indicated that IONPs were being produced. Box-Behnken design (BBD) and Plackett-Burman design (PBD) were used to optimize the mycosynthesis of IONPs. The iron oxide nanoparticles (IONPs) produced through mycosynthesis were characterized using several techniques, including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDAX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). After characterization, we evaluated their ability to extract heavy metal nanoparticles from both industrial and synthetic wastewater effluents. The results showed that different levels of IONPs were formed by various fungal strains: Aspergillus niger strain F1, A. flavus strain F2, Mucor sp. strain F3, and Alternaria sp. strain F4. Molecular analysis identified the most effective fungus for IONP production as A. niger AUMC 16028. The myco-synthesized IONPs were validated through the analyses conducted. Optimal conditions for IONP myco-synthesis included 8 g/L of yeast extract, a reaction temperature of 40 °C, and a culture period of 6 days. The myco-synthesized IONPs achieved heavy metal removal efficiencies of 92.47% for copper (Cu²⁺), 72.77% for iron (Fe³⁺), 84.76% for manganese (Mn²⁺), 70.28% for zinc (Zn²⁺), and 80.79% for chromium (Cr³⁺) in synthetic wastewater. Furthermore, the removal efficiencies of Zn²⁺ and Fe³⁺ in industrial effluent were 78.75% and 90.74%, respectively. These findings demonstrate that the heavy metals copper, iron, manganese, zinc, and chromium were effectively removed from synthetic wastewater, as well as iron and zinc from industrial wastewater, through the myco-synthesis and optimization of IONPs derived from A. niger AUMC 16028. This research offers a promising, green environmentally friendly, and efficient method for long-term industrial wastewater bioremediation and contributing to additional clean water resources.