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.