Thermodynamic and Kinetics for Synergistic Aeration Adsorption Uranium(Ⅵ) on Banyan Leaves-Activated Sludge

Synergistic aeration adsorption of uranium from aqueous solution using banyan leaves(BL) and activated sludge(AS) was investigated by thermodynamic and kinetics batch experiments in the temperature range of 20-50 ℃. The results show that the adsorption ratio of U(Ⅵ) with the initial concentration of 100 mg/L on BL-AS is more than 99%, and the maximal adsorption capacity is 13.055 mg/g for 60 min, at pH=3.0 and 20 ℃. Pseudo 2nd-order model best describes the reaction kinetics； the adsorption capacity calculated by the model is consistent with that actual measured (r²>0.99). The experimental data better follow Freundlich isotherm model and Langmuir isotherm model at 20 ℃（r²＞0.98）. For the whole adsorption process, the enthalpy change is -45.2 kJ/mol, the entropy change is -46.2 J/(mol·K), and the Gibbs free energy chang is -31.7 (20 ℃), -31.2 (30 ℃), -30.7 (40 ℃), -30.3 (50 ℃)kJ/mol respectively, which indicates that the process is spontaneous, radiative, irreversible and physical adsorption process.