Uranium and Thorium Retention onto Sorbents from Raw and Modified Pomegranate Peel

Pomegranate peel was investigated as biosorbent to remove uranium as well as thorium from aqueous solutions under different experimental conditions (concentration, counter ions, temperature). The material was used in raw and modified form after treatment with acidic and alkaline solutions to increase its sorption capacity. Isotherms were obtained at pH 4 and Cinitial: 5–300 mg L−1 for uranium and at pH 3 and Cinitial: 5–100 mg L−1 for thorium, respectively. The equilibrium data of the sorption study, which were adapted to the Langmuir and Freundlich models, indicated enhanced sorption efficiency (115 and 80 mg g−1 for uranium and thorium). Furthermore, kinetic and thermodynamic data as well as investigation by FTIR, XRD, and SEM revealed the complex sorption mechanism that can be explained by a combination of physical sorption accompanied by surface precipitation.