Effect of Nanoscale Zero-Valent Iron (nZVI) on Heavy Metals Availability in a Calcareous Soil

Iron (in zero-valent and oxide forms) is used to remove numerous organic and inorganic contaminants in environment. However، there are few reports، especially in nano scale، on the remediation of heavy metals contaminated soils using zero-valent iron in the literature. In this study، the effect of iron on the availability of heavy metals was evaluated in a calcareous soil spiked with cadmium، zinc، lead and nickel. The soil samples، in a randomized complete design with two replications، were amended with four iron materials including micrometric zero-valent iron (ZVI)، nanoscale zero-valent iron (nZVI) and nano and micro scales iron oxides. Then، after 1، 2 and 4 weeks of the experiment، DTPA-extractable heavy metals in soil were determined. Results showed that DTPA extractable heavy metals significantly decreased in soil treated with zero-valent iron، compared to untreated soil The stabilization efficiency of Ni، Cd، Zn and Pb was 28%، 32%، 37% and 28% for ZVI and 12%، 0%، 25% and 21% for nZVI، respectively. In contrast، presence of iron oxides caused significant increase of DTPA extractable heavy metals in soil except for Ni. Moreover، Ni-DTPA decreased significantly with time whereas it was constant for the other elements examined. In this study، the observed capacity for heavy metals removal by ZVI was higher than other treatments whereas the stabilization efficiency of nZVI was not significant in the soil.