Sm. Ponder et al., Surface chemistry and electrochemistry of supported zerovalent iron nanoparticles in the remediation of aqueous metal contaminants, CHEM MATER, 13(2), 2001, pp. 479-486
The microstructure, physical characteristics, corrosion behavior, and react
ivity of zerovalent iron nanoparticles synthesized on a support (primarily
a nonporous, hydrophobic polymer resin) were studied. The remediation of gr
oundwater by zerovalent iron in in situ permeable reactive barriers relies
on the redox reaction between metallic iron and a reducible contaminant. De
creasing the size of the iron particles and dispersing them on a support in
creases the specific surface area of the iron, as well as the ratio of surf
ace to bulk iron atoms, and should thereby increase both the reaction rate
and the fraction of iron atoms available for the reaction. Borohydride redu
ction of aqueous ferrous sulfate gives supported iron nanoparticles, 10-30
nm in diameter, which consist of 85% zerovalent iron by weight. These mater
ials ("ferragels") are stable in air and have corrosion behavior comparable
to iron filings. Interestingly, the presence or absence of a support, as w
ell as the boron remaining from the borohydride reduction process, influenc
es the electrochemical corrosion rate of the composite materials. Supported
and unsupported zerovalent iron nanoparticles are superior to iron filings
in both terms of initial rates of reduction and total moles of contaminant
s (Cr(VI), Pb(II), TcO4-) reduced per mole of iron. The enhanced reactivity
and passive corrosion behavior of these materials should make them good ca
ndidates for use in permeable reactive barriers.