Nitrate Removal and Nitrogen Sequestration from Polluted Waters Using Zero‐Valent Iron Nanoparticles Synthesized under Ultrasonic Irradiation


The main purpose of this chapter is to address the conditions in which improvements on the surface area and surface reactivity of zero-valent iron nanosized particles (ZVI NPs) can be achieved. A synthesis method based on liquid-phase reduction (LPR) under selected conditions was adopted. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and gas adsorption (using BET isotherm) confirmed the changes on the size of the ZVI NPs, when ultrasonic irradiation (UI) was used. The NPs prepared with and without UI were tested in a removal procedure of nitrate from contaminated waters. A L-8 Taguchi experimental design was utilized to investigate the efficiency of the synthesized NPs. Nitrate concentrations were determined by ion chromatography and considered as response data. The results indicated that the reactivity of the NPs was significantly higher for NPS prepared under UI. The investigation of the mechanisms involved in nitrate reduction demonstrated that ammonium ions were the dominant end-product. Furthermore ammonium ions could be precipitated as struvite (NH4 MgPO46H2O), a valuable fertilizer, and also a good candidate for the removal of environmental contaminants such as heavy metals.


Mohammadreza Kamali, Maria Elisabete Costa, Isabel Capela

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