Rapid in situ degradation of chlorinated solvents present as nonaqueous phase liquids (NAPL) can be accomplished
using reactive zerovalent nanoiron particles. Prior studies have shown that nanoiron transport
in the subsurface is limited, and successful delivery of the nanoiron is essential for effective remediation.
Here, the physical properties of bare and modified nanoiron are measured, and laboratory column reactors
are used to compare the transport of three types of surface-modified nanoiron; triblock polymer-modified,
surfactant-modified, and a commercially available polymer-modified nanoiron. The effect of particle
concentration and solution ionic strength on the transport of each modified nanoiron is evaluated, and
the filtration mechanisms for bare and modified particles are determined in microfluidic flow cells and
quartz crystal microbalance (QCM) experiments that probe the particle–collector grain interaction. The
effect of surface modification on nanoiron reactivity is evaluated in batch experiments. Transport of modified
nanoiron does not directly correlate with ζ-potential or colloidal stability, but rather correlates to particle–
grain interactions. Filtration of bare nanoiron is caused by straining and subsequent clogging rather
than by deposition to clean sand grains, suggesting that filter ripening models rather than clean bed filtration
models should be used to describe nanoiron transport at high particle concentrations. Surface modification
decreased nanoiron reactivity by two to four times, but as high as a factor of nine depending on
the modifier used. Amphiphilic triblock copolymer modified nanoiron with a high hydrophobe/hydrophile
ratio shows promise for in situ targeting of NAPL, but requires further optimization.
