Iron and Iron Oxide Nanoparticles for Environmental Remediation: Fenton-like Dye Degradation and Arsenic/Heavy-Metal Removal

Abstract

Iron and iron oxide nanoparticles (Fe NPs, nanoscale zero-valent iron/NZVI, magnetite Fe3O4, maghemite/hematite Fe2O3) play a key role in water and soil remediation made possible by nanotechnology because iron is abundant, affordable, non-toxic at environmentally relevant doses, redox-active across multiple oxidation states, and, in its zero-valent form, both a strong reductant and an efficient adsorbent once partially oxidised. The use of these nanomaterials as heterogeneous Fenton-like catalysts for the oxidative degradation of synthetic dyes and as adsorbents and reductants for arsenic and other heavy metals (cadmium, lead, chromium, nickel, copper, zinc, and selenium) in contaminated water and soil are two of the most well-documented environmental applications of these materials. Green, plant-extract-mediated synthesis methods, which substitute plant polyphenols for dangerous reducing agents like sodium borohydride and have been demonstrated time and time again to produce catalytically superior, better-dispersed, and more environmentally friendly nanoparticles than their chemically synthesised counterparts, are given special attention. Evidence gathered from plant-derived systems such as green tea, olive leaf, jackfruit peel, clove, coffee, Duranta erecta, Eucalyptus globulus, and others shows that heavymetal and arsenic removal efficiencies in several nanoscale zero-valent iron systems exceed 99 percent under optimal pH and dosage conditions, and dye removal efficiencies frequently exceed 80–95 percent within tens of minutes. The underlying Fenton and adsorption mechanisms, the effects of pH, dose, temperature, and competing ions on performance, the unresolved issues of nanoparticle aggregation, reusability, and the necessity of validation at the pilot and field scales outside of laboratory batch studies are all covered in the review.