Contaminant Organic Complexes: Their Structure and Energetics in Surface Decontamination Page: 4 of 5
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Dissolution studies were conducted by equilibrating the U solids with DFB as a function
of pH, molality and temperature (Table 2). The differential concentration-time gradient
(6c/6t) increased up to nearly 2 fold with the rise in temperature. This was evidently due
to escalation in the U dissolution rate at the higher temperature. Solution U at 25 0C
reached steady state after 24 hr and remained unchanged even after 72 hr of
dissolution. At 10-3 M of DFB, a maximum value of 5 was reached for U dissolution
gradient (6U/6DFB) per unit DFB molality rise. At STP (25 0C and 1 atmosphere), the
U:DFB molal dissolution ratio was about 11 with a half-life (t ) close to 100 hr. The t%
increased by 2.5 fold with a 200C rise in temperature. The activation energy for U
dissolution by DFB was 36 kJM-1, and the amount dissolved was 6 to 40 times higher
than that by water.
Table 2. U Dissolution by DFB under variable reaction conditions.
T (OK) k (h-) t0.5 (h) M DFB % Usoin
298.15 0.007 103 0 0.7
318.15 0.017 41 10-5 1.7
----------------------------------------------- 10-4 9.3
Eactivation = 36.3 kJM-1 10-3 42
10-2 81
Max 6U/6DFB (-5) at 10-3 M of DFB
U dissolution % U:DFB
ID pHf pHe H20 DFB (mole)
S#L2 1 5.7 4 25 13
S#2 3 6.2 2 32 9
S#6 5 6.9 0.5 21 11
Structural mapping and identification of solid phase species of uranium associated with
iron are critical in understanding the remediation chemistry of the passivity layers. The
data indicated that DFB effectively dissolved U formed under diverse chemical
conditions. Results of this study, in combination with other work, will be useful for
optimizing efficient U clean up strategies at iron and steel surplus facilities, and provide
further insight for future work involving actinides and lanthanides. We would like to
thank Drs. David Shuh and Tolek Tyliszczak of LBNL for helping with the STXM.Traina and Sharma (2005 report)
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Traina, Samuel & Sharma, Shankar. Contaminant Organic Complexes: Their Structure and Energetics in Surface Decontamination, report, July 12, 2005; United States. (https://digital.library.unt.edu/ark:/67531/metadc783206/m1/4/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.