Immobilisation of Cadmium, Copper, Lead, and Nickel in Soil Using Nano Zerovalent Iron Particles: Ageing Effect on Heavy Metal Retention

Nano zerovalent iron (nZVI) is one of the most widely used nanotechnologies in soil remediation, but its long-term performance can be limited due to its high reactivity and rapid ageing. The aim of this study was to compare the immobilisation of Cd, Cu, Ni, and Pb in artificially contaminated soil samples using nZVI and to evaluate their retention over a 1-year period. Single-metal-contaminated soil samples were amended using 0–1.05% of nZVI. Leaching, using CaCl 2 solution and a sequential extraction procedure, was performed to evaluate the immobilisation efficiency and fractionation of heavy metals before and after ageing. The results of the extractions showed that the application of nZVI initially reduced the exchangeable fraction of all heavy metals. The greatest immobilisation efficiency was achieved for Cu. The retention of heavy metals by nZVI was studied by constantly humidifying soil samples for a 12-month period. The results showed that over this period, the efficiency of nZVI treatment decreased, due to the decrease in the amount of reactive iron oxides in soil samples. Retention of immobilised heavy metals by nZVI strongly depended on their ionic radius. The highest retention results were obtained for Cu and Ni, whereas the lowest results were obtained for Cd and Pb.