Zero-valent iron (ZVI) is simply elemental iron that has an excess of electrons, giving it
an overall charge of zero. Naturally occurring iron will seek stability at the valence of 2+ or 3+
and so by forcing it to a zero valence the iron becomes an electron donor and very much reactive.
This reactivity initially led to the study of zero-valent iron for the remediation of pesticides and
herbicides and has since shown promising results towards remediating organic contaminants,
radionuclides, and even metals. More promising still have been studies with nano-scale zerovalent
iron (nZVI) that have indicated a greatly increased reaction rate and capacity associated
with the increased surface area that accompanies the decreased particle diameter of zero-valent
iron particles. One of the results of many studies on the remediation of metal contaminants by
nano-scale zero-valent iron is that a characteristic and marked increase in pH occurs as a
consequence of the reduction reaction. This effect may naturally lend itself to tailings
remediation as a consequence of stabilizing effluent pH (through neutralization) and preventing
acid mine drainage. Furthermore, reports indicate that lower initial pH increases the reaction rate
and efficiency of the metal removal process (Chen et al, 2008).