Uranium Sorption by Poly(hexamethylenesuccinamide) (PA46) as Cation-Exchange Resin from Wet-Process Egyptian Phosphoric Acid

The study deals with U(VI) sorption from phosphoric acid media onto poly(hexamethylenesuccinamide) (PA46) (-CO(CH2)2)CO-NH(CH2)6NH-)n as a cation-exchange resin. The process was studied using SEM, FT-IR, and surface area determination. The effect exerted on the process by the contact time, liquid to solid ratio, temperature, stirring rate, and initial U(VI) concentration was examined. The adsorption capacity for uranium under the optimum conditions was found to be 25 mg/g. The sorption data were described using Langmuir, Freundlich, and Temkin isotherm models. The thermodynamic equilibrium constant and the Gibbs free energy were determined: Delta G degrees from -19.08 to -22.49 kJ/mol, Delta H -78.63 kJ/mol, and Delta S -199.83 J/(mol K). These data show that the adsorption is spontaneous. The kinetic data are best described by the pseudo-second-order model.