Remediation of Hexavalent Chromium Contaminated Clay Soil by Injection of Nanoscale Zero Valent Iron (nZVI)

Abstract

Toxic metal contamination in soils is a major problem that poses risk to public health and the environment. Among the metal contaminants, hexavalent chromium (Cr(VI)) is known to be highly toxic and mobile in the soils, creating major environmental liabilities around the world. This study evaluates the efficiency of applying the pressure injected nanoscale zero-valent iron (nZVI) suspension to remediate Cr(VI)-contaminated clay soil. After nZVI injection, soil samples were collected in different depths, radial distances, and time intervals. The nZVI dosage used was 12.5 g/kg. The effect of nZVI on Cr(VI) reduction was observed at all radial and depth locations analyzed, with an initial reduction of up to 51.08% for the deepest layer. nZVI dispersivity was found to be homogeneous in the analyzed sample, with an average Cr(VI) reduction of 76.52% in 15 days. The nZVI migration patterns had an influence on the experimental results, with Cr(VI) reduction up to 56.92% higher at deeper points of the experiment. Moisture content was a key parameter for the effectiveness of the remediation and its control was necessary. Overall, the application of nZVI by the pressure injection technique was found to be an effective alternative for the remediation of Cr(VI)-contaminated clay soil.