(396f) Testing of Amidoxime-Based Adsorbent for the Recovery of Uranium From Seawater

A polymeric adsorbent with amidoxime functional groups, synthesized at Oak Ridge National Laboratory (ORNL), has been employed in batch 5-gallon seawater experiments; flow-through 110-gallon seawater experiments; and field experiments at two marine sites. The effect of temperature on uranium adsorption kinetics and equilibrium in the range of 10 to 35°C has been investigated in batch experiments. From the experimental data, the adsorption kinetics and isotherm parameters will be determined. Kinetic models, coupled with mass transfer and equilibrium models, are employed to analyze the experimental data. A thermodynamic analysis will be also performed to provide changes in enthalpy, entropy, and free energy through the van’t Hoff equation. Flow-through experiments with continuous recycle through 110-gallon seawater tanks have been conducted to test the effect of adsorbent packing in columns. Based on the results of laboratory experiments, marine testing has been conducted at two sites: (1) the Marine Sciences Laboratory of the Pacific Northwest National Laboratory at Sequim, WA, and (2) the Rosenstiel School of Marine & Atmospheric Science of the University of Miami, FL. Several weeks have been allowed for equilibrium to be reached in all types of the experiments. The parameters investigated in marine tests are temperature and flow-rate. Results are compared with experimental data obtained in parallel with Japanese adsorbents. The ORNL adsorbent has shown a capacity of 4 mg U per g of adsorbent, which is five times the capacity of the Japanese adsorbent. This study is expected to improve our current understanding of the influence of temperature on uranium adsorption by polymeric amidoxime-based adsorbents form seawater and provide guidelines for ocean deployment.