Kinetic studies on the adsorption of uranium on a mesoporous impregnated activated carbon

A highly porous phosphorous-containing activated carbon derived from pistachio nutshells (PNS) was synthesis as a potential sorbent for uranium (VI) from sulfate media. The prepared phosphate activated carbon (PAC) was visualized under SEM and TEM which revealed highly porous structure. The extraction of U(VI) from acidic media using PAC has been investigated by a batch method and various parameters such as pH, equilibrium contact time, liquid to solid ratio, and initial U(VI) concentration were examined. Under the stated conditions, the optimum pH for U(VI) adsorption was found to be 3.5. The adsorption capacity of uranium upon PAC under the optimum conditions was found to be 335 mg/g. The experimental results were applied for Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) isotherm models. The thermodynamic equilibrium constant and the Gibbs free energy were determined (ΔG° from -4.72 to -7.65 kJ/mol) and results indicated the spontaneous nature of the adsorption process. Kinetics data were best described by pseudo second-order model.