Successful Coupling of a Bis-Amidoxime Uranophile with a Hydrophilic Backbone for Selective Uranium Sequestration

The amidoxime group
(−RNH2NOH) has long been used to extract uranium
from seawater on account of its high affinity toward uranium. The
development of tunable sorbent materials for uranium sequestration
remains a research priority as well as a significant challenge. Herein,
we report the design, synthesis, and uranium sorption properties of
bis-amidoxime-functionalized polymeric materials (BAP 1–3). Bifunctional amidoxime monomers were copolymerized
with an acrylamide cross-linker to obtain bis-amidoxime incorporation
as high as 2 mmol g–1 after five synthetic steps.
The resulting sorbents were able to uptake nearly 600 mg of uranium
per gram of polymer after 37 days of contact with a seawater simulant
containing 8 ppm uranium. Moreover, the polymeric materials exhibited
low vanadium uptake with a maximum capacity of 128 mg of vanadium
per gram of polymer. This computationally predicted and experimentally
realized selectivity of uranium over vanadium, nearly 5 to 1 w/w,
is one of the highest reported to date and represents an advancement
in the rational design of sorbent materials with high uptake capacity
and selectivity.