Synthesis and characterisation of an eco-friendly magnetic nanopowder from steel industry waste for latent fingerprint detection

The steel industry produces large volumes of waste rich in iron oxides, creating environmental and economic challenges. In this study, we report the synthesis of an eco-friendly magnetic nanopowder derived from steel industry residue for latent fingerprint detection. The powder was prepared through a simple precipitation method and characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and vibrating sample magnetometry (VSM). The synthesised powder exhibited smaller particle aggregates (~3 µm) compared to a commercial magnetic powder (~30 µm), with Fe and O as major components and minor amounts of Mn, Mg, Zn and K inherited from the residue. VSM analysis demonstrated a strong magnetic response, supporting efficient manipulation with a magnetic brush. When applied to non-porous surfaces, the waste-derived powder provided fingerprint ridge details with quality and minutiae counts statistically equivalent to those obtained using the commercial powder. These findings demonstrate that the developed material is a cost effective and environmentally sustainable alternative to commercial magnetic powders, offering reliable performance in forensic fingerprint visualisation while promoting the valorisation of industrial waste.