ISSN 1066-3622, Radiochemistry, 2016, Vol. 59, No. 2, pp. 152–159. © Pleiades Publishing, Inc., 2017. Published in Russian in Radiokhimiya, 2017, Vol. 59, No. 2, pp. 135–141. 152 Sorption of Uranium from Waste Effluent Solutions by Mesoporous Carbon Impregnated with Trioctylamine 1 A. M. A. Morsy and A. H. Ali* Nuclear Materials Authority, P.O. Box 530, Maadi, Cairo, Egypt *e-mail: amr_nma@yahoo.com Received March 17, 2016; in final form, October 14, 2016 Abstract—A new mesoporous adsorbent for uranium removal from waste effluents was prepared, character- ized, and impregnated with trioctylamine. The adsorption efficiency was investigated as a function of pH, con- tact time, initial uranium concentration, competing ions, solid/liquid ratio, and temperature using batch sorption techniques. The maximum adsorption capacity was 21.9 mg g –1 at pH 5. The equilibrium data fit well with the Langmuir adsorption isotherm. Kinetic study showed that the process was fast and reached equilibrium within 60 min. The kinetic data fit well with the pseudo-second-order law. Thermodynamic data show that the process is spontaneous and exothermic. Key words: adsorption, uranium, mesoporous carbon, elution Over the past few decades, different technologies were developed for the removal and recovery of ura- nium from nuclear fuel effluents, mine tailings, sea- water, and other waste sources [1]. However, because of its superior binding affinity for biomolecules [2], ingestion and inhalation of uranium could cause cer- tain acute and/or chronic harmful effects, especially the kidney damage [3]. Uranium is a highly biotoxic radionuclide. It can be introduced into the fragile eco- system through a combination of natural processes as well as anthropogenic activities [4]. On the other hand, the global demand for uranium as an energy source tends to increase, whereas the available natural ura- nium resources are limited. Therefore, separation and recovery of uranium are of great practical significance [5]. The importance of uranium separation extends to the protection of both human health and environment. Being an effective separation technique, the solid– liquid extraction technique offers wide opportunities for removing from water hazardous species [6], cad- mium [7], lead [8], chromium [9], platinum [10], and uranium [11, 12]. As compared to liquid–liquid extrac- tion, it has such advantages as minimal solvent con- sumption, flexibility, and no emulsion formation [13], especially in strongly acidic media. Such carbonaceous materials as activated carbon [14], carbon nanotubes [15, 16], and carbon fiber [17] have been used recently for solid-phase extraction. The advantages of these materials are their higher resistance to heat and radia- tion, compared to organic ion-exchange resins, and higher resistance to acids and bases, compared to com- mon inorganic sorbents [14]. Moreover, ordered meso- porous carbon attracted considerable attention because of its unique features, such as high surface area, regu- lar pore structure, narrow pore size distribution, large pore volume, as well as excellent chemical and physi- cal stability [18]. These features make mesoporous carbon more attractive as catalyst support, electrode material, and energy storage medium [19, 20]. On the other hand, the hydrophobic surface of mesoporous carbon is unfavorable for sorbing heavy metal ions from the aqueous solution. Therefore, the surface should be functionalized or modified. Chemi- cal modification is a useful method in this regard. High-molecular-mass tertiary amines [(C n H 2n+1 ) 3 N] are selective to uranium and readily available and have been used in the solvent extraction of uranium [21]. The stripping of uranium from amines involves no problems. In this study work, trioctylamine was immobilized onto mesoporous carbon through impregnation. The DOI: 10.1134/S1066362217020072 1 The text was submitted by the authors in English.