The role of nanoscale zero-valent iron (nZVI) in remediation of heavy metal contamination in groundwater overexploitation areas

Abstract

This study investigates the remediation of groundwater contaminated with heavy metals in overexploited areas using a modified approach involving the use of corn plant parts to produce biochar. The biochar was modified using a hydrothermal method, employing nanoscale zero-valent iron (nZVI) material to create a composite material for adsorbing heavy metals from water bodies. Adsorption experiments were conducted on the presence of Cr, Cu, and Zn ions in the water. The experimental investigations focused on the dosage of adsorption materials, solution pH, and stability of the adsorption material to validate the enhanced capability of the nanoscale zero-valent iron modified biochar composite (Fe-CBC-MO) for removing and adsorbing heavy metal ions (Cu, Cr, and Zn) from water. The results indicate that the adsorption capacity follows the sequence: Cr > Zn > Cu. Increasing the adsorbent dosage provides more adsorption sites, thereby improving the removal efficiency of heavy metals from water bodies. Considering cost-effectiveness, an optimal dosage of 0.15 g was selected. Under alkaline conditions, Cu and Zn ions precipitated significantly, leading to sustained high removal rates of heavy metals. Correspondingly, the rate constants were also relatively high. In acidic environments, the rate constant for Cr decreased significantly due to corrosion passivation. The composite material Fe-CBC-MO exhibited remarkable removal efficiency for all three heavy metals (Cr, Cu, Zn), demonstrating a strong capability for remediating heavy metal pollution.