Uranium collection from seawater with adsorbent prepared by radiation-induced graft-polymerization

Tamada, Masao; Kasai, Noboru; Seko, Noriaki; Shimizu, Takao*

The uranium dissolved in seawater is extremely low concentration of 3.3 ppb. However, the total amount of uranium resource in seawater is 4.5 billons tons which is one thousand times of that in terrestrial ores. For uranium collection from seawater, amidoxime group was selected as a high affinity group in adsorbent. This adsorbent was synthesized by grafting of acrylonitrile and subsequent chemical treatment with hydroxylamine. The collection of uranium from seawater was performed in marine experiments at Aomori and Okinawa, Japan. In Aomori, 350 kg of the fibrous adsorbent stacks were dipped at 7 km offing of Aomori seashore. In total 9 tests over three years, 1 kg of uranium could be collected successfully as a yellow cake. A new braid type adsorbent has been developed to achieve the practical cost of uranium collection. The adsorption performance in Okinawa marine experiment indicated 1.5 g-U/kg-ad for 30 day soaking. The promising collection cost reached 25 thousand yen/kg-U which is equivalent to 96/lb-UO.