Kinetics and thermodynamics of adsorption of trace amount of uranium on activated carbon

摘要

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 mu g/g for 100 mu g/L at 0.8 g activated carbon (AC), compared to the experimental result 24.9 mu g/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: Delta H-ads -90.5 (kJ/mol), Delta S-ads(o) 0.224 (kJ/mol/K) and Delta G(ads) -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 mu g/L) and 0.387 min(-1) (50 mu g/L) respectively, compared to 3.3 x 10(-4) and 4.4 x 10(-4) min(-1) for the second order kinetics mechanism.