Abstract
Extraction of uranium (U) from seawater for use as a nuclear fuel is a significant challenge due to the low concentration of U in seawater (~3.3 ppb) and difficulties to selectively extract U from the background of major and trace elements in seawater. The Pacific Northwest National Laboratory (PNNL)¡s Marine Sciences Laboratory (MSL) has been serving as a marine test site for determining performance characteristics (adsorption capacity, adsorption kinetics, and selectivity) of novel amidoxime-based polymeric adsorbents developed at Oak Ridge National Laboratory (ORNL) under natural seawater exposure conditions. This manuscript describes the performance of three formulations (38H, AF1, AI8) of amidoxime-based polymeric adsorbents produced at ORNL in MSL¡s ambient seawater testing facility. The adsorbents were produced in two forms, fibrous material (40.100 mg samples) and braided material (5.10 g samples), and exposed to natural seawater using flow-through columns and recirculating flumes. All three formulations demonstrated high 56 day uranium adsorption capacity (>3 g U/kg adsorbent). The AF1 formulation had the best uranium adsorption performance, with a 56 day capacity of 3.9 g U/ kg adsorbent, a saturation capacity of 5.4 g U/kg adsorbent, and ¡25 days half-saturation time. The two exposure methods, flowthrough columns and flumes, were demonstrated to produce similar performance results, providing confidence that the test methods were reliable, that scaling up from 10¡s of mg quantities of exposure in flow-through columns to gram quantities in flumes produced similar results, and confirm that the manufacturing process produces a homogeneous adsorbent. Adsorption kinetics appear to be element specific, with half-saturation times ranging from minutes for the major cations in seawater, to 8.10 weeks for V and Fe. Reducing the exposure time provides a potential pathway to improve the adsorption capacity of U by reducing the V/U ratio on the adsorbent.
| Original language | English |
|---|---|
| Pages (from-to) | 4285-4293 |
| Number of pages | 9 |
| Journal | Industrial and Engineering Chemistry Research |
| Volume | 55 |
| Issue number | 15 |
| DOIs | |
| State | Published - Nov 19 2015 |
Funding
This work was funded by the U.S. Department of Energy, Office of Nuclear Energy, Fuel Cycle Research and Development Program, Fuel Resources Program (Contract No. DE-AC05-76RL01830). We thank Mr. Nicholas J. Schlafer and Mr. Brett A. Romano for their help with construction, maintenance, and operation of the marine testing facility. We also thank Ms. Carolynn R. Suslick and Ms. Julie K. Snelling for quality assurance and database management support. This work was funded by the U.S. Department of Energy, Office of Nuclear Energy, Fuel Cycle Research and Development Program, Fuel Resources Program (Contract No. DEAC05-76RL01830). We thank Mr. Nicholas J. Schlafer and Mr. Brett A. Romano for their help with construction, maintenance, and operation of the marine testing facility. We also thank Ms. Carolynn R. Suslick and Ms. Julie K. Snelling for quality assurance and database management support.