Characterization of nanoscale iron for groundwater remediation

The aim of this study is the characterization of nanoscale zero-valent iron (NZVI), used for the remediation of contaminated groundwater. This is one of the most prominent applications of nanotechnology in environmental field. Compared to the commonly used granular zero-valent iron, nanoscale zerovalent iron (NZVI) particles show a larger surface areas that leads to higher reactivity towards a wider variety of environmental contaminants. Moreover, due to the small diameters of the particles (1-100 nm) they can be injected in the subsurface as a colloidal suspension, thus providing great flexibility for in situ applications. We performed laboratory analysis on RNIP-10AP-SDS, a nanoscale iron slurry produced by Toda Kogyo Corp. We investigated chemical and physical properties either on dispersion or on its single phases (dispersed phase constituted by nanoscale iron particles and dispersing medium constituted by water solution with a biodegradable polymer). The dispersion was analyzed to determine the composition by I.C.P.-M.S. and the morphology by optical microscope and E.S.E.M. In order to investigate the surface, the morphology and the crystallography of nanoscale particles, we performed studies by X-ray diffractometry (X.R.D.), IR spectroscopy, scanning and transmission electron microscopy (SEM, TEM), BET measurements. All these analysis were performed on dried iron nanoparticles. The characterization on dispersed phase showed that particles of NZVI tend to aggregate, producing clusters that may approach microns in size. Characterization analysis were performed also on polymer by IR.-A.T.R. spectroscopy. These results suggest that the RNIP dispersion is unstable. Consequently, some uncertainties still limit the application of NZVI: (1) the reactivity and longevity over extended period of time; (2) the aggregation potential and transportability in saturated porous media; (3) potential release of pollutants (e.g. heavy metals).