Direct uranium recovery from brine concentrate using amidoxime adsorbents for possible future energy source

Recovery of uranium from concentrated brine rejection from a small seawater reverse osmosis plant in Thailand using four types of the amidoxime adsorbents was experimentally performed. Adsorbents were directly submerged in continuously flowing discharged brine concentrate. Studied adsorbents were amidoximated polymer gel prepared from gamma irradiation, amidoximated polymer gel prepared from UV radiation curing, amidoximated polyacrylonitrile fibers, and chromic-acid-treated low-density polyethylene fibers grafted with amidoxime functional group using gamma radiation. Uranium concentration in brine concentrate and input seawater was analyzed to be 4.8 and 3.1 ppb, respectively. Gel adsorbent synthesized by gamma irradiation exhibited the highest uranium loading capacity of 1.39 mg/g-ad with 20 000 L/h rejected brine flow-rate after 6 weeks of soaking. The estimated uranium recovery cost is 406.81 USD/kg uranium. If the adsorption capacity was increased to 2 mg/g-ad, the projected cost was reduced to 338.95 USD/kg. Under this land-based recovery scheme, no work is performed in an open ocean environment, thus, ensuring safety and reducing cost and time, especially the costs associated with ships, personnel, and diesel fuel to bring the materials to the ocean and back to the shore. The present study demonstrates that direct uranium recovery from discharged brine concentrate is possible using amidoxime-based adsorbents developed to study uranium extraction from natural seawater. This should pave the way for further experimental studies in larger seawater reverse osmosis (SWRO) plants for the possible future energy source. A proposed large-scale, yet very simple, deployment strategy at a hypothetical SWRO plant is also presented. Novelty statement Successful uranium adsorption by directly submerging adsorbents in continuously flowing discharged brine concentrate from seawater reverse osmosis plant Mooring and recovery costs largely eliminated because of land-based deployment Highest uranium uptake capacity of 1.39 mg/g adsorbent after 6 weeks of soaking