SURFACE CHARACTERIZATION AND THERMODYNAMICS OF ADSORPTION OF SR-2+, CE-3+, SM-3+, GD-3+, TH-4+, UO22+ ON ACTIVATED-CHARCOAL FROM AQUEOUS-SOLUTION

Surface parameters of the activated charcoal were measured using precise instrumental techniques for dehydration, carbon content, trace metals impurities, anions, bulk, tap and true densities, surface area, pore volume, porosity and average particle diameter. The adsorption of Sr2+, Ce3+, Sm3+, Gd3+, Th4+ and UO22+ ions on activated charcoal from aqueous solution was studied as a function of temperature. Thermodynamic parameters such as DELTAH-0 and DELTAS0 were calculated from the slopes and intercepts of the linear variation of In K1 vs. 1/T, where K1 is obtained from Langmuir equation. The results show endothermic heats of adsorption, but negative free energy values indicate that the adsorption process of metal ions on activated charcoal is favored at high temperature. The value of isosteric heat of adsorption, calculated from the Clausius-Clapeyron equation, shows that the surface of the activated charcoal is heterogeneous with respect to activity. A wavelength dispersive x-ray fluorescence spectrometer was used for measuring the concentration of metal ions.