Zerovalent iron (ZVI) is jargon that describes forms of iron metal that are proposed for used in Groundwater remediation.
ZVI operates by electron transfer from Fe toward some organochlorine compounds, a common class of pollutants.  The remediation process is proposed to generate Fe and Cl and halide-free organic products, all of which are relatively innocuous.  The technology is not however been implemented, despite many proofs of principle.