A method for the preparation of stable dispersion of zero-valent iron nanoparticles

Reported herein is a method for the synthesis of fully dispersed and reactive nanoscale particles of zero-valent iron. Polyvinyl alcohol-co-vinyl acetate-co-itaconic acid (PV3A), a nontoxic and biodegradable surfactant, is used in the synthesis of the nanoscale zero-valent iron (nZVI). The addition of PV3A effects three key surface-related changes, which lead to significant enhancements in surface chemistry, particle stability and subsurface mobility potential. These include (1) a reduction of the mean nZVI particle size from 105 nm to 15 nm, (2) a reduction of the zeta (ζ)-potential from +20 mV to −80 mV at neutral pH, and (3) a shift of the isoelectric point (IEP) from pH ≅ 8.1 to 4.5. X-ray photoelectron spectroscopy (XPS) indicates the sorption of PV3A on the nanoparticle surface and also the existence of zero-valent iron (Fe0) in the nZVI mass. Batch experiments further confirm that the PV3A-stabilized iron nanoparticles are capable of effectively reducing trichloroethene (TCE), as has been observed with previous nZVI materials. No sedimentation of the PV3A stabilized nZVI has been observed for over 6 months, suggesting the formation of stable nZVI dispersion. The appreciably smaller mean particle sizes and ability to remain in suspension should translate into improved subsurface mobility potential.