(532d) Evaluating the Dynamics of An Integrated Electrokinetic and Zero-Valent Iron Nanoparticle System for Treatment of Hexavalent Chromium In Groundwater

Electrokinetic
technology is a promising groundwater treatment strategy capable of transporting
ionic contaminants through groundwater by application of an electric potential
across a contaminated area. While this is effective in the transport and
concentration of contaminants at an electrode, complimentary remedial action
may still be required to enhance treatment of the contaminants. Zero-valent
iron nanoparticles (nZVI) may potentially offer an ideal solution for this
genre of in-situ environmental
remediation. Their small size coupled with their high surface area to volume
ratio as well as reductive capacity, make nZVI a seemingly ideal medium for
subsurface remediation where other classical remediation strategies such as
excavation are not possible. This may be in deep aquifers, urban areas, or
under existing infrastructure.

A
comprehensive understanding of the fate and transport of nZVI in the subsurface
is just as critical to in-situ
remediation as the high reactivity. Upon introduction to an aquifer
environment, nZVI must be readily dispersible and remain stable so that they
reach the targeted contamination zone. Several researchers have investigated
transport of nZVI through porous media, however most of the published work is
conducted in idealized batch studies. These investigations have indeed provided
a good knowledge base, but limited information exists concerning the fate,
transport, and toxicity of nZVI in the natural environment. The challenging
issues at hand include: nanoparticle agglomeration, nZVI storage and age,
components of soil matrices, aquifer hydraulic properties, presence of natural
organic matter, pH, and redox potential, among others.

This
study investigates the treatment of simulated groundwater containing hexavalent
chromium (Cr^VI), a known carcinogen, in a dynamic system using
combined electrokinetic and zero-valent iron nanoparticle technology.
Continuous flow columns are charged with simulated natural soils, followed by
saturation with solutions containing Cr^VI, variable humic acid
concentration, and at multiple pH values. Upon saturation, electric potential
is applied, and dilute solutions of nZVI are added at regular intervals for the
entirety of the experiment.

This
presentation will discuss the influence of natural aquifer characteristics such
as pH, natural buffer, and natural organic matter content on the transport of
nZVI through subsurface environments, and how this impacts treatment of
contaminants. Furthermore, this research will evaluate the dynamics of coupling
electrokinetic and nZVI technologies in decontamination of the subsurface
environment.