1. Modification of hectorite by organofunctionalization for use in removing U(VI) from aqueous media: thermodynamic approach.
- Author
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Guerra DL, Airoldi C, and Viana RR
- Subjects
- Adsorption, Hydrogen-Ion Concentration, Osmolar Concentration, Spectrum Analysis, Thermodynamics, Time Factors, X-Ray Diffraction, Organosilicon Compounds chemistry, Silicates chemistry, Uranium isolation & purification, Water Pollutants, Radioactive isolation & purification
- Abstract
A Hectorite sample (H) has been chemically modified with N-propyldiethylenetrimethoxysilane and bis[3-(triethoxysilyl)propyl]tetrasulfide. The resulting materials (H(3TPT) and H(NPTM)) have been characterized through elemental analysis, X-ray diffractometry, carbon nuclear magnetic resonance in the solid state, textural analysis, and thermogravimetric analysis. The adsorption experiments were performed under batch process with pH, ionic strength, contact time, and uranyl concentration as variables. The attached basic centers adsorbed uranyl cation to give maxima adsorption capacity of 5.55+/-0.21, 14.86+/-0.05, and 18.99+/-0.05 x 10(-3) mmol g(-1) for H, H(3TPT), and H(NPTM), respectively. From calorimetric determinations the quantitative thermal effects for UO(2)(2+)/center interactions gave exothermic enthalpy (Delta(int)H=-6.90 to -7.88 kJ mol(-1)), negative Gibbs free energy (Delta(int)G=-22.34 to -24.56 kJ mol(-1)), and positive entropy (Delta(int)S=51.80-56.00 JK(-1)mol(-1)). These thermodynamic data confirmed the energetically favorable condition of such interaction solid/liquid for all systems., (Copyright 2009. Published by Elsevier Ltd.)
- Published
- 2010
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