Chemical pathways of Nanoscale Zero-Valent Iron (NZVI) during its transformation in aqueous solutions

The current application of Nanoscale Zero-Valent Iron (NZVI) is subject to the countermeasure of water contamination that escalates with increasing population. Some of the NZVI advantages include; environmental friendliness, high reactivity and cost-effectiveness. NZVI was synthesized through the reduction of a ferric ion by sodium borohydride in anoxic medium and the resulting particles were characterized by the Transmission Electron Microscope with Energy-dispersive X-ray (TEM-EDX). The NZVI evolution and dissolution in water were examined through a series of batch experiments conducted in varying experimental conditions which include; pH, temperature, dosage, oxygen and interferences. The dissolution of iron was enhanced in the acidic pH due to the presence of H⁺ ions thus favoring release of hydrogen gas. More iron ions were present in the lowest temperature (5 °C) due to decreased crystallization and proton assisted dissolution. Furthermore, highest NZVI dosage (3 g/L) resulted in the highest iron ions concentrations in solution due to the increased number of nanoparticles hence providing surface-active sites. Ultimately, more iron ions were present in limited oxygen supply condition involving initial air saturation showed due to decreased crystallization and precipitation which were favored in continuous supply. These results are a useful guidance during real-life application of NZVI.