Comparative Structure and Arsenate Removal Performance of Chemically Synthesized and Eucalyptus globulus-Mediated Sulfurised Zero-Valent Iron Nanoparticles.

Sulfurised zerovalent iron nanoparticles (S-nZVI) are highly reactive materials for arsenic removal; however, the influence of green synthesis routes on their surface chemistry and adsorption behavior remains insufficiently understood. In this study, sulfurized iron nanoparticles were synthesized through two distinct pathways: conventional chemical reduction (S-nZVI) and a plant-mediated route using Eucalyptus globulus leaf extracts (GS-nZVI), enabling a direct comparison of their structural properties and arsenate removal performance. Structural characterization revealed that chemically synthesized S-nZVI exhibit more compact aggregates and relatively homogeneous surfaces, whereas GS-nZVI display smaller particle sizes, reduced aggregation, and broader diffraction features associated with organic capping derived from plant metabolites. Adsorption experiments showed that S-nZVI present faster initial kinetics and higher maximum adsorption capacity, consistent with greater availability of reactive surface sites. In contrast, GS-nZVI exhibit more heterogeneous adsorption behavior, better described by the Freundlich model, reflecting the influence of phenolic compounds and organic functional groups on the nanoparticle surface. These results demonstrate that plant-mediated synthesis not only provides an environmentally benign route for nanoparticle production but also modifies the physicochemical properties of sulfurized iron nanoparticles, resulting in distinct arsenate removal pathways.