Nanoscale Zerovalent Iron Particles for Treatment of Metalloids

In the past few decades, the remediation ability of nanoscale zerovalent iron (NZVI) particles has been exploited in both lab-scale and real-world scenarios. These studies and application examples brought about numerous breakthrough results. Therefore, NZVI has proved to be an excellent candidate for the efficient remediation of even challenging and complicated polluted aqueous systems. Herein, we emphasize the treatment of heavy metals (e.g., copper, cobalt, nickel, zinc, uranium, mercury, cadmium, lead, etc., and also hexavalent chromium) and metalloids (e.g., arsenic) as pollutants in water by NZVI. The mechanisms involved in the metal removal by NZVI are described and explained in terms of selectivity and reaction pathways. Analytical aspects, mainly represented by X-ray photoelectron spectroscopy as tool for deep understanding of the mechanism of metal removal, are mentioned, while an extensive report of examples of metal cations that can be removed by NZVI is overviewed. Specifically, the cases of chromium and arsenic removal are analyzed thoroughly, explaining the efficiency of various NZVI-based systems for immobilization and/or reduction of such toxic species. Finally, success stories of pilot and full-scale tests where NZVI was employed for metal removal are presented, describing the conditions, the effects, and the advantages of NZVI in large-scale applications.