Uranium in Seawater

Overview of Research

This project active from 2014 to 2018 built upon the efforts within the DOE's Fuel Cycle Research and Development program by offering infrastructure and expertise for marine testing of an adsorbent fiber designed specifically to extract uranium from seawater. We are testing the fibers in the lab and ocean to quantify sorptive properties and uranium uptake in real ocean conditions. There is currently a gap between detailed lab studies and potential large-scale applications of these technologies. To fill this gap our group has tested fibers under varying flow conditions using filtered seawater as well as dock testing in a coastal ocean environment. We tested biofouling mitigation techniques by using copper, steel or nylon enclosures on the dock in fall 2015. In fall 2016 we tested the reuse of the fibers after deployment in the ocean. Lastly as a collaboration with A. Slocum at MIT and PhD student Maha Haji we examined the effect of enclosures on the fiber adsorption as well as explored deploying the fibers on a engineered system that would couple with a wind turbine platform.

Our objectives were as follows:

1. To test the extraction efficiency of the uranium adsorbents under changing environmental conditions (temperature, flow rate, salinity, particulate matter) in a controlled laboratory setting and in the ocean
2. To determine, by field tests, the most efficient methods for collecting (pumping versus passive) and the best platform (mooring type, sorbent material) to expose the fibers in high current regimes.
3. To design a mooring contingent on the findings in objective 2 that will be amenable to scaling up small batch extraction of uranium from seawater using these new large volume in-situ methods.

Results of Ocean Testing

Details regarding methods used for this project can be found in both the forthcoming paper Drysdale et al. (2019) or in the project reports linked below. Overall we tested the amidoxime-based polymer type AI8 developed at Oak Ridge National Laboratory (DOE). Fibers were deployed in a variety of experiments to test the effects of biofouling or reusing the fibers.

Overall fibers were negatively affected by biofouling, where uranium adsorption was reduced by up to 70% on fouled fibers. Increased temperatures allowed for increased uranium adsorption, but also increased the amount of creatures that grew on the fibers. There is a delicate balance to be found between optimal temperature and one at which the biofouling does not interfere substantially on uranium uptake. Reusing the fibers was not found to be particularly effective as the total harvestable uranium after a single 56 day deployment was comparable to that of fibers deployed 2 or 3 times over 84 days.