Nanoengineered Electrochemical Sensors for Mixed Wastes (PNNL SCOPE # 45409)
EMSL Project ID
6899
Abstract
The required characterization of the DOE?s transuranic (TRU) and mixed wastes (MW) before disposing and treatment of the wastes is currently costly and has lengthy turnaround. Research toward developing faster and more sensitive characterization and analysis tools to reduce costs and accelerate throughputs is therefore desirable. Portable microfluidics/electrochemical sensor systems have been developed at PNNL and shown very promising future for on-site waste characterization. This proposed work aims (1) to develop the electrochemical sensors that can be integrated into the portable sensor systems and (2) to investigate all related fundamental issues necessary for the successful use of the systems for MW and TRU analyses. The electrochemical sensors being investigated are based on a new class of nanoengineered sorbents, the self-assembled monolayer on mesoporous supports (SAMMS), which are highly efficient sorbents whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species. Supported by our preliminary data, immobilizing different classes of SAMMS as sensing components on the electrode surfaces allows fast and reliable detection of Pb, Hg, Cd, Cu (thiol-SAMMS), and U (AcPhos-SAMMS) in ppb level. Another class of SAMMS synthesized by installation of copper(II) ethylenediamine (Cu-EDA) complexes on the silica pore walls has shown to be highly selective for chromate and will be used as the electrode modifier for chromium detection.
Adsorptive stripping voltammetry (AdSV) will be performed on two classes of electrodes: the SAMMS modified carbon paste electrodes, and the SAMMS thin film immobilized on microelectrode arrays. Factors affecting the electrode performances (i.e., functional loading capacity, pore diameter, wall thickness, and thin-film thickness for the SAMMS thin-film electrode) and factor affecting the voltammetric detection process (i.e., preconcentration time, electrolysis time, stripping medium, pH, etc.) will be investigated in details and the optimal operating parameters will be resulted. Interfacial chemistry and electrochemistry of metal species on surfaces of SAMMS-based electrodes will also be studied: this fundamental knowledge is required for predicting how the sensors will perform in the real wastes which consist of many interferences/ligands and are varied in pH. The best electrodes for each specific waste constituent will be integrated onto the portable microfluidic platform. Finally, efforts will be focused on testing the portable microfluidics/electrochemical sensor systems with the MW and TRU waste samples at the Hanford site.
We propose to use laser spectroscopy for studying U speciation on electrode surface.
Project Details
Project type
Exploratory Research
Start Date
2004-01-20
End Date
2007-06-03
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
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