A cost estimate for uranium recovery from seawater using a chitin nanomat adsorbent
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Even at 3.3 ppb, seawater contains a uranium supply large enough to power the world’s nuclear fleet for 13,000 years. This large supply has prompted interest in technologies for recovering uranium from seawater. Since the 1960’s, economic models of such technologies have failed to produce an economically competitive strategy when compared to conventional uranium recovery from terrestrial mining. Thus, uranium from seawater is researched as a potential price ceiling because of the large supply but high recovery cost. Such an upper bound is still valuable research because it allows for more certainty in uranium prices for planning, research, development and deployment of nuclear power systems. This thesis explores past cost estimates for uranium recovery from seawater and adds a new cost estimate to the pool of literature. The past estimates showed a development from systems that actively moved seawater to systems that allowed adsorbent to sit passively in seawater. The adsorbent material changed from hydrous titanium oxide to the higher-capacity amidoxime ligand. Capacity was the strongest driver of cost. Early models with the amidoxime ligand used an acrylic substrate or backbone. This substrate was later replaced by polyethylene because of its increased durability and lower cost. However, each of those materials could contribute to the problem of plastics in the ocean. The new technology assessed for cost in this paper attempts to address the plastics concern by replacing the plastic with a high molecular weight chitin nanomat as the substrate for the amidoxime ligand. The cost assessment showed the technology is presently cost prohibitive largely due to the adsorption capacity and chitin nanomat production costs. To increase capacity, the grafting efficiency onto the chitin substrate must be improved in order to achieve capacities comparable to those observed for the amidoxime-polyethylene adsorbent. To reduce chitin nanomat production costs, the ionic liquid (IL) consumption must be reduced and the recyclability of IL must be achieved.