posted on 2015-11-30, 00:00authored byHorng-Bin Pan, Li-Jung Kuo, Chien M. Wai, Naomi Miyamoto, Ruma Joshi, Jordana
R. Wood, Jonathan E. Strivens, Christopher J. Janke, Yatsandra Oyola, Sadananda Das, Richard T. Mayes, Gary A. Gill
High-surface-area amidoxime and carboxylic
acid grafted polymer
adsorbents developed at Oak Ridge National Laboratory were tested
for sequestering uranium in a flowing seawater flume system at the
PNNL-Marine Sciences Laboratory. FTIR spectra indicate that a KOH
conditioning process is necessary to remove the proton from the carboxylic
acid and make the sorbent effective for sequestering uranium from
seawater. The alkaline conditioning process also converts the amidoxime
groups to carboxylate groups in the adsorbent. Both Na2CO3–H2O2 and hydrochloric
acid elution methods can remove ∼95% of the uranium sequestered
by the adsorbent after 42 days of exposure in real seawater. The Na2CO3–H2O2 elution method
is more selective for uranium than conventional acid elution. Iron
and vanadium are the two major transition metals competing with uranium
for adsorption to the amidoxime-based adsorbents in real seawater.
Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt, 1 M)
can remove iron from the adsorbent very effectively at pH around 7.
The coordination between vanadium(V) and amidoxime is also discussed
based on our 51V NMR data.