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-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.

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Cyclic voltammetric and chronoamperometric methods were used to study the initial stage of Au electrodeposition on an indium tin oxide (ITO) surface. The nucleation process was controlled by the diffusion of [AuCl4] -. The cyclic voltammetry curves showed that the electrochemical reduction included two steps which were [AuCl4] -→ [AuCl2] -, and [AuCl2] -→ Au. Only one reduction peak was observed when the scan rate was comparatively slow and this peak separated into two peaks when the scan rate was increased. This phenomenon resulted from the disproportionation of [AuCl2] -during the electrodeposition process. Chronoamperometry also proved the two step reaction mechanism and the diffusion coefficient of [AuCl4] -was calculated to be 1.3 × 10 -5 cm 2 •s -1 . From the theoretical nucleation curves, an instantaneous three-dimensional nucleation mechanism was proposed for the nucleation of gold on ITO. Au electrodeposits were observed by field emission scanning electron microscopy (FE-SEM). SEM images of the electrodeposits showed that the morphology of the gold deposits was affected by the electrochemical deposition potential and time.