Adsorption of uranium on natural and thermally activated zeolitic tuff: Kinetic, thermodynamic and isotherm studies

The adsorption capacity of natural and thermally activated ZT for uranium was investigated under different conditions. The obtained results indicated that the Jordanian ZT has obtained high removal efficiency up to 99% at low U concentration (10 mg/L) and a maximum uptake capacity of 14.22 mg/g at an optimum pH of 5. About 78% removal can be achieved within the first 10 min of contact time. Thermal activation of ZT at temperatures of 100-250°C decreased the removal efficiency and then increased at a temperature of 300°C. Kinetic study indicated high impact of temperature on the adsorption rate with best fitting with the pseudo second order model. Langmuir isotherm model provided better simulation of the experimental data than Freundlich and R-P models, indicating monolayer, homogenous and spontaneous process. Positive ΔHo (56-87 kJ/mole), positive S* (0.25 to 0.36 kJ/mole.K), and negative ΔG° (-18.85 to -27.77 kJ/mole) indicated endothermic, high adsorption affinity and physiochemical process. © 2019 Inderscience Enterprises Ltd.