Characterization of fresh and corroded nano zero-valent iron (nZVI) to remove Cr (VI) in soil environment

Abstract

To understand the transformation of nano zero-valent iron (nZVI) in soil environments, a magnetic adsorption method was employed to recover nZVI from remediated soil, and the properties of the recovered (corroded) nZVI were characterized. Scanning Electron Microscope (SEM) analysis showed that the remediated soil consisted of stacked sheet-like layers, still rich in intergranular micropores. A significant portion of nZVI remained as spherical particles, with their average particle size increasing by 22.97% compared with fresh nZVI. X-Ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) analyses indicated that the nZVI in the soil mainly comprised magnetite (Fe₃O₄), magnet hematite (γ-Fe₂O₃) and a small amount of lepidocrocite (γ-FeOOH). Although nZVI underwent oxidation and corrosion during the soil remediation process, it remained in nanoparticle form. Increasing the amount of nZVI and lowering the initial pH of the soil could improve the removal efficiency of soil Cr (VI). However, the removal efficiency of fresh nZVI was higher than that of the corroded nZVI, with adsorption capacities of 6.18 mg/g for fresh nZVI and 1.85 mg/g for the corroded nZVI. Despite the reduced efficiency, the corroded nZVI retained its nanoparticle characteristics. This study provides important insights into the environmental behavior of nZVI in soil remediation.