Grantee Research Project Results
Surface Specific Studies of Physical and Chemical Processes Involving Metal Contaminants in Soils Using Nonlinear Laser Spectroscopy Techniques
EPA Grant Number: F5B20242Title: Surface Specific Studies of Physical and Chemical Processes Involving Metal Contaminants in Soils Using Nonlinear Laser Spectroscopy Techniques
Investigators: Mifflin, Amanda L.
Institution: Northwestern University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2005 through August 1, 2006
Project Amount: $103,572
RFA: STAR Graduate Fellowships (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
Objective:
This project investigates the physical and chemical processes that control hexavalent chromium interactions with mineral/water interfaces using nonlinear optical laser spectroscopy.
To gain a detailed kinetic and thermodynamic understanding of pollutant binding to geosorbent surfaces for developing improved models that predict the fate and transport of heavy metal ions and toxic chemicals released into the environment, leading to more cost-effective remediation strategies.
Approach:
The sorption behavior of Cr(VI) is tracked in situ and in real time using the surface-specific spectroscopy technique second harmonic generation (SHG). The ligand-to-metal charge transfer bands of the chromate ions allow us to track Cr(VI) binding to various aqueous/solid interfaces, chosen as a simple heterogeneous mineral oxide/water system for these laboratory studies. Thermodynamic, kinetic and spectroscopic data are obtained in real time at environmentally relevant chromate concentrations and pH ranges.
Expected Results:
Experiments will examine Cr(VI) binding to various organic functional groups found in soils that have been chemically tethered to the silica surface. Binding parameters for each surface will be determined quantitatively and with surface-specificity. Kinetic parameters, such as adsorption and desorption rate constants, will be obtained through adsorption-desorption studies in the submonolayer regime. We have determined that these parameters are able to differentiate between the chemistries of the different surfaces, and are investigating how they can be best incorporated into transport models.