Filamentous fungal-mediated melanin nanoparticles for heavy metal detoxification via bioadsorption: a sustainable approach

Abstract

The eradication of heavy metal contamination has emerged as a paramount objective in preserving and conserving global water resources. The present study highlights the potential of halophilic fungal melanin derived from Curvularia lunata as an eco-friendly, cost-effective, highly stable, and efficient biosorbent for removing toxic heavy metals. UV and FTIR spectroscopy characterization confirmed the presence of functional groups typical of eumelanin. Particle size analysis revealed a notable reduction in size from unmodified melanin (54.22–87.94 nm) to melanin nanoparticles (MNPs) (22.74–26.41 nm), indicating improved surface area for adsorption. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) data further validated the superior adsorption capabilities of MNPs compared to unmodified melanin. Specifically, the MNPs exhibited a 100% removal efficiency of over 18 metals out of 24 at a concentration of 0.15 mg/L and at pH 7, surpassing the performance of native melanin. X-ray photoelectron spectroscopy (XPS) was applied to specify the elemental composition of the solid surfaces and the chemical forms of adsorbed metals. Ultrasound-assisted extraction (UAE) significantly enhances adsorption efficacy by facilitating better dispersion and generating a higher surface area, thereby increasing the Number of active binding sites available on MNPs for heavy metal chelation. This mycoremediation-based approach presents a scalable and industrially adaptable solution for water detoxification, offering an advantageous alternative to conventional high-performance membrane technologies with minimal process modifications.