The uranium recovery from aqueous solutions using amidoxime modified cellulose derivatives. IV. Recovery of uranium by amidoximated hydroxypropyl methylcellulose

Amidoxime modified hydroxypropyl methylcellulose (HPMC) films (HPMC-g-AO) were used for the recovery of uranium from aqueous solutions by a complexation process. The adsorption experiments were carried out by immersion of a certain amount of films in UO₂²⁺ solutions (resultant pH 4.1) ranging in concentration from 100 to 1,000 ppm. The effect of temperature (25-50 °C) on the adsorption capacity of HPMC-g-AO was investigated at the optimized time. The adsorption kinetics and the thermodynamics as well as the adsorption capacity of HPMC-g-AO films were investigated. The adsorption capacity was found as 765 mg UO₂²⁺/g dry film. The kinetic and the thermodynamic parameters (i. e. activation energy, enthalpy, entropy and Gibbs free energy) for the interaction of UO₂²⁺ with HPMC-g-AO were calculated based on known basic relations. The results showed that adsorption occurred through strong electrostatic interactions with an enthalpy of -36.5 kJ/mol. The desorption of UO₂²⁺ were investigated using different desorption agents such as EDTA, HCl, NaHCO₃, and NaOH. After the 2 weeks treatment period, the highest desorption yield were found as 23 % with NaHCO₃.