Uranium Recovery from Seawater Using Amidoxime-Based Braided Polymers Synthesized from Acrylic Fibers

Global demand for nuclear energy is expected to rise in the coming decades. To meet these growing needs, new uranium resources must be explored. One of the potential alternatives to traditional uranium mining is oceanic uranium. The capture and recovery of uranium from the ocean have been under investigation for some time, with many recent studies focused on amidoxime-based adsorbents. These adsorbents, while able to achieve high uranium recovery capacities, are, nevertheless, expensive to produce and adsorb a significant amount of hard-to-remove vanadium. The purpose of this study is to evaluate the adsorption performance of amidoxime-based polymer braids synthesized from acrylic fibers that are designed to significantly cut polymer synthesis and conditioning costs. Adsorption experiments were performed in a mesoscale recirculating raceway flume system at environmental conditions, approximately 10.8 degrees C, with 40-mu m prefiltered seawater over 28 days for small- and large-sized polymer braids. For both braid sizes, the adsorption of vanadium was far lower on the acrylic adsorbent considered in the present study than on previously tested adsorbents developed at Oak Ridge National Laboratory (ORNL AF1 and AI8). The small acrylic braids also outperformed both ORNL materials with respect to uranium adsorption under similar conditions. Adsorption modeling was used to simulate the performance at higher temperatures based on 20 degrees C experiments previously performed with these materials. Simulation results indicated that the small acrylic braids would have a somewhat less significant advantage with respect to uranium adsorption over both ORNL AF1 and AI8 at 20 degrees C and will continue to outperform both ORNL adsorbents at 31 degrees C. Vanadium adsorption on the small acrylic braids was less than one-third of the vanadium adsorption on either AF1 or AI8 for all temperatures. This behavior indicates that the newly developed acrylic adsorbents are able to achieve superior uranium adsorption compared to other amidoxime adsorbents previously developed while being cheaper to produce and adsorbing significantly less vanadium.