Bicarbonate Elution of Uranium from Amidoxime‐Based Polymer Adsorbents for Sequestering Uranium from Seawater

Abstract

Uranium adsorbed on amidoxime‐based polyethylene fibers in simulated seawater can be quantitatively eluted using 3 M KHCO3 at 40 °C. Thermodynamic calculations are in agreement with the experimental observation that at high bicarbonate concentrations (3 M) uranyl ions bound to amidoxime molecules are converted to uranyl tris‐carbonato complex in the aqueous solution. The elution process is basically the reverse reaction of the uranium adsorption process which occurs at a very low bicarbonate concentration (∼10−3 M) in seawater. In real seawater experiments, the bicarbonate elution is followed by a NaOH treatment to remove natural organic matter adsorbed on the polymer adsorbent. Using the sequential bicarbonate and NaOH elution, the adsorbent is reusable after rinsing with deionized water and the recycled adsorbent shows no loss of uranium loading capacity based on real seawater experiments.

Extraction of uranium from seawater : design and testing of a symbiotic system

“…It has been found to result in up to 20% loss of initial capacity in a lab setting (Pan et al, 2014), though in the ocean could be considerably greater. Recent research by Pan et al (2017) has indicated that this degradation may be mitigated or removed altogether by the replacement of the acidic elution bath with a bicarbonate solution. In this process, a mixture of sodium carbonate and hydrogen peroxide is used to elute uranium from an amidoxime-based polymer adsorbent.…”

“…Unlike previous designs developed by Picard et al (2014) and , which utilize on-site continuous acidic elution and bicarbonate regeneration processes, this design employs a single, 24-hour bicarbonate elution as described by Pan et al (2017). Recent work has shown that the acidic elution process leads to degradation of the adsorbent with subsequent reuse, which may be mitigated or removed altogether by the replacement of acid by a potassium bicarbonate solution (Pan et al, 2017).…”

“…Recent work has shown that the acidic elution process leads to degradation of the adsorbent with subsequent reuse, which may be mitigated or removed altogether by the replacement of acid by a potassium bicarbonate solution (Pan et al, 2017). Additionally, the adsorbent no longer needs to be regenerated with alkaline solution since a basic solution has replaced the previously used acids.…”

“…However, more recent experimental data suggests that the adsorbent degradation rate is a function of campaign length and number of reuses, with the first reuse suffering the greatest loss in uptake , as shown in figure 8-2 (Byers and Schneider, 2016b). Work by Pan et al (2017) suggests that a bicarbonate elution process may remove uranium from the adsorbent with observed degradation rates of below 1% per reuse. Thus, the time dependent model for degradation will serves as an upper bound on the adsorbent degradation while the constant 5% loss in uptake provides the lower bound.…”

A Relativistic DFT Probe of Thorium and Protactinium Complexes Supported by Heterocalix[4]arene and Redox Properties of Early‐Middle Actinides

“…Early to middle actinides have been prevalent in the research of actinides for many years . Uranium and plutonium, for instance, are commonly used in nuclear energy production and manufacturing nuclear weapon . Due to its high abundance in the Earth's crust and high natural isotopic 232 Th abundance, thorium has been investigated as a potential nuclear fuel, which would complement uranium‐fueled reactors in the near future .…”