Uranium adsorption studies on aminopropyl modified mesoporous sorbent (NH 2 –MCM-41) using statistical design method S ßenol Sert ⇑ , Meral Eral Ege University, Institute of Nuclear Sciences, 35100 Bornova-Izmir, Turkey article info Article history: Received 19 March 2010 Accepted 23 August 2010 Available online xxxx abstract MCM-41 has been synthesized and modified in order to graft amine groups on its surface. The modified NH 2 –MCM-41 adsorbent was characterized by using XRD, SEM, surface area and porosity analyzer, and FT-IR. This characterized adsorbent was investigated for uranium adsorption using the batch method. The central composite design (CCD) combined with the response surface methodology (RSM) was selected to determine the effects of parameters and their interactions for the removal of UO 2þ 2 ions. The optimum values of the parameters determined were 4.2 for the initial pH, 60 °C for the temperature, 90 mg L 1 for the initial concentration and 173 min for the shaking time using the response surface meth- odology. DH° and DS° were calculated from the slope and the intercept of plots of ln K d versus 1/T. The isotherm models, Langmuir, Freundlich, Dubinin–Radushkevich (D–R) have been studied to explain the adsorption characteristics. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Uranium is likely to occur as a contaminant in the environment as a result of emissions from the nuclear industry, releases in mill tailings, the combustion of coal and other fuels, the use of phos- phate fertilizers that contain uranium, machining of depleted-U munitions and natural weathering of igneous rocks and ore bodies which can produce groundwater seeps in the hundreds to thou- sands of l lgL 1 (ppb) range of dissolved uranium [1]. The permis- sible discharge level of uranium for nuclear industries ranges from 0.1 to 0.5 mg L 1 . As per the standards of World Health Organiza- tion, the U(VI) concentration in water should not exceed 0.05 mg L 1 [2]. The use of conventional treatment methods such as chemical precipitation, reverse osmosis, ion-exchange, filtration, and evapo- rative recovery are most effective for the treatment of liquid efflu- ents containing high concentration of metal ions. However these technologies become expensive or inefficient for the treatment of effluents containing metal ions in the range of 100 mg L 1 [3]. Adsorption is one of the important techniques in separation and purification processes. Adsorption of uranium onto various solids is important from the purification, environmental and radioactive waste disposal points of view [4]. The adsorption of uranium has been the subject of several investigations; activated carbon [5], natural zeolite [6], kaolinite [7], bentonite [8] and montmorillonite [9], alginate [10], iron oxides species; goethite [11] and akaganeite [12] were used as adsorbents for uranium. Mesoporous molecular sieve materials, known as M41S, were discovered by Kresge et al. and Beck et al. in 1992 [13,14]. In the M41S family, the main structures are hexagonal phase MCM-41; cubic phase MCM-48; and MCM-50, a non stable lamellar phase [15]. MCM-41, which stands for Mobil Composition of Matter No. 41, shows a highly ordered hexagonal array of uni-dimensional pores with a very narrow pore size distribution [16]. The striking features of MCM-41 such as having a very large BET surface area, large pore volume and fast kinetics of sorption attracted many researchers to utilize it as a sorbent and study its sorption behavior towards chemical and radio-toxic metal ions from various waste streams. Stamberg et al. investigated sorption of uranium on MCM-41 as a function of pH, time, U(VI) and CO 2 3 concentrations [17]. Salicylaldehyde functionalized mesoporous silica (MCM-41) was utilized for the separation, pre-concentration and determina- tion of uranium in natural waters [18]. The spherical mesoporous silica (MCM-41) is investigated for the recovery of uranium ions from sea water by Lee et al. [19]. Carbamoylphosphonate silane was used for the modification of MCM-41 for sequestration of actinides [20,21]. Lanthanide separations were studied by Gly-UR., Ac-Phos., and Prop-Phos. silane modified MCM-41 [22]. The adsorption of pollutant metal ions by functionalized mesoporous silicas containing amino or thiol groups has been previously investigated. MCM-41 grafted with aminopropyl (NH 2 –MCM-41), functionalized with tris-(methoxy) mercapto- propylsilane, amino-functionalized with Fe 3+ coordination, and modified with thiol were used for Cr 2 O 2 7 [23], mercury [24], oxya- nions [25], and Hg +2 [26], respectively. In this work, aminopropyl modified MCM-41 (NH 2 –MCM-41) is prepared for the adsorptions of UO 2þ 2 from aqueous solutions. The 0022-3115/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2010.08.024 ⇑ Corresponding author. E-mail address: senol.sert@ege.edu.tr (S ß. Sert). Journal of Nuclear Materials xxx (2010) xxx–xxx Contents lists available at ScienceDirect Journal of Nuclear Materials journal homepage: www.elsevier.com/locate/jnucmat Please cite this article in press as: S ß. Sert, M. Eral, J. Nucl. Mater. (2010), doi:10.1016/j.jnucmat.2010.08.024