Chelant screening and refinement tests - Phase I, Task 2. Topical progress report, December 1993--June 1994 Page: 28 of 236
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
Test 27 was considered to represent a total success. Test 28 was performed to verify that
the results could be duplicated. Test 28 again used DTPA at about 100 g/L. To save on
chemical usage, a decision was made to add only 15 g/L (NH4)2CO3. Hydrogen peroxide (H202)
was also reduced to a concentration of about 1.5%. As with Test 27, the H202 was added just
prior to introduction of solvent into the reaction flask. No corrosion coupons were used in this
Table 2 summarizes the analytical results from Test 28. The results were essentially
identical to Test 27. Uranium dissolution was rapid and essentially complete within the first
hour of exposure. Weight loss at the end of testing again indicated greater than 99% uranium
dissolution.. The lower concentration of H202 added resulted in less of a temperature rise
(29.9*C maximum temperature) and also less destruction of the free chelate (DTPA in this case).
Analytical Data From Test 28
Low Temperature/Oxidizing Test Sequence
Time [DTPA] [Uranium] Temperature
(Hours) pH (g/L) (ppm) (*C)
0* 8.99 103.8 - 23.9
1 8.56 81.3 3612 29.0
2 8.52 68.7 3682 29.9
4 8.53 50.0 3819 27.9
* - Hour analysis just prior to addition of concentrated H202 solution - [DTPA]
after addition = 98.6 g/L
The results of Test 28 essentially duplicated the results of Test 27, even with the lower
carbonate and peroxide concentration. The next step was to determine the effect of carbonate
on the dissolution process. Test 28 was repeated with a solvent containing just chelant (DTPA)
and H202. All other parameters were identical. This test was designated Test 29. Table 3
summarizes the analytical results from Test 29. Figure 3 graphically shows a comparison
between Tests 28 and 29 for uranium dissolution effectiveness.
From Table 3 and Figure 3 it is apparent that a solvent containing just chelant and
peroxide was not as effective as the carbonate/chelant solvent. The solvent containing only
chelant and -peroxide dissolved only 16% of the uranium dioxide placed in the test flask versus
essentially 100% for the carbonate/chelant solvent. These results indicated that complexation
of the uranium by carbonate was essential to the dissolution process. It is likely that a mixed
chelate complex was formed in the presence of carbonate and chelant (Reference 25); this
assumption was supported by color differences observed between solutions containing uranium
dissolved by carbonate alone, and by mixed carbonate/chelant solvents.
Here’s what’s next.
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Chelant screening and refinement tests - Phase I, Task 2. Topical progress report, December 1993--June 1994, report, July 1, 1995; United States. (https://digital.library.unt.edu/ark:/67531/metadc680875/m1/28/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.