Adsorption of Thorium from Aqueous Solution using Nanoporous Adsorbents: Effect of Contact Time, pH, Initial Concentration, and Temperature

Nanoporous silicates MCM-41 have been prepared using different surfactants such as cetyltrimethylammonium bromide (C(16)TAB) and dodecyltrimethylammonium bromide (C(12)TAB) as template. The adsorbents are characterized using powder x-ray diffraction, nitrogen adsorption-desorption isotherm data, scanning electron microscopy, and transmission electron microscopy. The thorium sorption was studied as a function of shaking time, pH, initial concentration, and temperature. The sorption of thorium at the determined optimum conditions follows Langmuir and Freundlich isotherms. The results show that the nanoporous MCM-41 synthesized by C(12)TAB has more adsorption capacity than the MCM-41 synthesized by C(16)TAB (77.6 mu molg(-1) vs. 52.1 mu molg(-1)) at 25 degrees C. Th(IV) adsorption onto nanoporous adsorbents was very fast process and therefore, this adsorbent is suitable for column separation. Thermodynamic parameters such as H degrees, S degrees and G degrees were found to be 47.76KJmol(-1), 196.21Jmol(-1)K(-1), and 19.00KJmol(-1), respectively (at 298K). The positive value H degrees suggested the endothermic nature of adsorption and negative G degrees indicates the feasibility and spontaneity of the adsorption process.