Removal of Inorganic Contaminants from Aqueous Solutions: Evaluation of the Remediation Efficiency and of the Environmental Impact of a Zero-Valent Iron Substrate

This work presents an evaluation of the remediation efficiency and of the environmental impact of a zero-valent iron commercial substrate used for the removal of heavy metals from groundwater in different conditions. A specific feature of the substrate is the presence of zero-valent iron (ZVI), organic carbon, and sulfate. The authors analyzed its composition and performances by means of batch tests in different boundary conditions. In detail, the efficacy was evaluated for metals (Cu, Cr, Pb, and Zn) and for nitrates and sulfates. Neutral and acidic pH values, imputable to dangerous waste landfill leachate or to acid mine drainage, were considered. The environmental impact of the substrate was also assessed for the investigated pHs. The product showed a high efficiency in the removal of metals (mainly described by a pseudo-second-order kinetic model), with a noticeable variability according to the pH of the polluted phase. Nitrate ion removal was inhibited by sulfates at all the considered pH values. Characterization and batch studies revealed that the substrate was a source of Mn, Cr, Pb, Cu, and sulfate ions, besides Fe. This study shows that the employment of an optimized amount of reagent, while achieving good performances, is essential to contain the leaching of undesirable substances into aqueous environment.