Neutron activation analysis method for the quantification of biofouling mitigation for the recovery of uranium from seawater
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The ocean naturally contains uranium at a concentration of 3.3ng/g, thus offering thousands of years’ worth of nuclear fuel. Although ample uranium currently exists from terrestrial sources, the ability to recover seawater uranium would provide supply security for nuclear power generation, putting it on equal footing with renewable energy technologies. Furthermore, this acts as a hedge against the possibility that conventionally sourced uranium experiences a cost increase. Lastly, extracting uranium from seawater circumvents the environmental impact associated with the retrieval of any land-based resource. This work supports research being conducted by a consortium of national laboratory and university partners focused on the development of advanced materials with the ability to passively adsorb uranium out of seawater. In experiments by PNNL, the adsorption capacity of these fibers decreased by 30% due to accumulation of marine microorganism. Since the uranium capacity of adsorbents has been identified as a major cost driver of final uranium production cost there is significant impetus to mitigate the effects of biofouling to maximize uranium uptake. Therefore the aims of this research are to develop and demonstrate a method for mitigating marine biofouling in adsorbents similar to those synthesized by ORNL and to quantify the efficacy and uncertainty of the mitigation technique using neutron activation analysis. Existing marine antifouling strategies were considered for coupling with the recovery of uranium from seawater via the passive scheme but none of these strategies could be directly applied due to their prevention mechanisms or implementation cost. Growing research in the field of silver nanoparticles however offered a possible adsorbent modification. This research aims to take advantage of the proven antibacterial capabilities of silver nanoparticles and extend them to a novel application, the recovery of uranium from seawater. The doping of surrogate adsorbents with silver nanoparticles was successful in observing a decrease in bioaccumulation and subsequent partial restoration of capacity. The degree to which the capacity was restored was not sufficient however to outweigh the implementation cost of this adsorbent modification. Therefore a break-even analysis was conducted to determine the combinations of adsorbent formulation and resulting performance that would result in a cost savings.