Summary
Theoretical calculation of both the kinetics and thermodynamic parameters for the adsorption of ultrace amount of uranium ion in uranyl nitrate salt (UO22+) on activated carbon showed the applicability of Langmuir isothermal model. Equilibrium isotherm studies gave the maximum calculated sorption capacity as 30.95 μg/g for 100 μg/L at 0.8 g activated carbon (AC), compared to the experimental result 24.9 μg/g, with correlation coefficient of 0.999 compared to 0.985 and 0.901 for Freundlich and/or D–R Dubinin–Raduschkevich, respectively. It was found that the adsorption process is mainly exothermic, where the thermodynamic parameters are as follows: ΔHads −90.5 (kJ/mol), ΔS°ads 0.224 (kJ/mol/K) and ΔGads −23.75 (kJ/mol) (T=298 K). Kinetically the process was assured the first order rate of reaction with the rate constant equal to 0.304 min−1 (100 μg/L) and 0.387 min−1 (50 μg/L) respectively, compared to 3.3×10−4 and 4.4×10−4 min−1 for the second order kinetics mechanism.
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