Microbial Transformation of TRU and Mixed Wastes: Actinide Speciation and Waste Volume Reduction Page: 2 of 3
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ligands, hydroxyl groups, and some features normally associated with alkali-treated paper. These features
were identified during preliminary analysis of the data. The samples have degraded heterogeneously as
observed by the slight differences in spectra obtained from various spots on the same sample. Optical and
infrared images of the samples do show more extrememphysical degradation of the samples, including
some separation of individual fibers. While some chemical differences have been noted between samples,
these are only on the order of differences found within a single sample. For statistical purposes, we have
averaged a series of spectra obtained from the same sample. This averaging has undermined the intensity of
degradation. Currently, the spectra are being analyzed individually to determine the heterogeneity in
degradation. Identifying particular ligands will also assist in understanding spectra to be gathered from
TRU-cellulosic material interactions.
Future work on Objective I:
One of the main problems in characterizing cellulosic samples is that the absorption features for carboxylic
and aromatic groups fall in the region where the H-O-H angle vibration group absorption from water is
intense (-1650 cm-1). The presence of moisture in the samples gives rise to broad unresolved bands
compromising the amount of information that can be derived from these spectra. One of the methods to
overcome this problem is to expose the samples to a controlled D20 atmosphere to replace the adsorbed
water molecules with deuterated water. D20 absorb at lower frequencies and hence will not compromise
the effect of aliphatic and aromatic absorption features. We plan to build a system to expose cellulosic
materials in controlled D20 atmosphere. The results from such experiments will be included in future
reports.
Results for Objective II:
Establishment of electrochemical equipment and protocol for study of electron transfer kinetics associated
with TRU/bacterial interactions in aqueous media.
Progress has been made in the preliminary stages of this objective, including: (a) a Gamry Femtostat
(capable of accurately detecting currents in the femtoampere range) has been set up on site at BNL to
perform analysis of TRU and related materials in solution; (b) a preliminary testing protocol has been
established by which bacteria are to be immobilized on glassy carbon electrodes to monitor electrochemical
activity in solution containing low concentrations of TRU. Glassy carbon has been shown to be an ideal
surface for immobilization of bacterial material. This immobilization may be assisted using medical
dialysis membrane material or other chemically inert membrane material with appropriate hole size. Open
circuit potential monitoring will be conducted in specially designed cells inoculated with bacteria to
analyze kinetics during metabolic processes, with and without the presence of TRU. In addition, analogs
for TRU will be analyzed in equivalent electrochemical conditions at Stony Brook using in situ Raman
spectroscopy to monitor transformation.
Recently, we have completed a series of experiments using in situ X-ray absorption analysis at the National
Synchrotron Light Source during electrochemical polarization of solutions containing very low
concentrations (< 5 mM) of uranium-organic ligands. The success of these experiments has been the result
of optimization of a custom-designed sealed cell using polished glassy carbon electrodes with data
collection greatly enhanced by using a thirty element Si detector. This has made possible identification of
outer sphere adsorption and inner sphere transformations of organically liganded uranium as a result of
electron transfer kinetics. As far as we can tell, this is the first time such experiments have been used or
have yielded useful data, and we expect this to become a model for our future work with actinides.
Results for Objective III:Molecular modeling of inorganic complexes and organically-liganded TRU
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Halada, Gary P. Microbial Transformation of TRU and Mixed Wastes: Actinide Speciation and Waste Volume Reduction, report, December 1, 2004; United States. (https://digital.library.unt.edu/ark:/67531/metadc780111/m1/2/: accessed May 7, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.