Influence of Solution Chemistry on the Selective Adsorption of Uranium and Thorium Onto Activated Carbon

Radioactive element separation is of particular interest in nuclear technology. For this purpose, batch experiments were carried out in order to find the best separation conditions of uranium [U(VI)] and thorium [Th(IV)] from aqueous solution using rice straw activated carbon. The influence of pH and contact time on selective adsorption of U(VI) and Th(IV) was investigated. The results indicate that the velocity of these species from liquid phase to the surface of carbon is rapid enough. The reaction rate was fast, requiring only a short contact time of 40 min for U(VI) and 100 min for Th(IV). Sorption reaches maximum at pH 4 for Th(IV) and at pH 5.5 for U(VI). U(VI) and Th(IV) can be separated by the judicious controlling of pH and contact time. They can be separated from each other at pH 4 with different contact time [Th(IV) at lower time and U(VI) at 200 min]. Studies were conducted to examine the change in the adsorption behavior of U(VI) and Th(IV) on adsorbent as a function of employing different complexing agents of mineral and organic acids that are important in industrial and environmental processes, including hydrochloric, nitric, acetic, sulfuric, and phosphoric acids at 0.1M concentration. Acetic acid enhances U(VI) and Th(IV) uptake compared to mineral acids. These procedures may be useful in the separation of U(VI) and Th(IV) from natural or industrial samples containing these elements.