Surfactant-impregnated activated carbon for enhanced adsorptive removal of Ce(IV) radionuclides from aqueous solutions

Abstract

The surfactants cetyltrimethylammonium bromide (CTAB) and sodium lauryl sulfate (NaLS) were utilized for modifying the activated carbon’s surface. The materials were characterized using BET–N2, scanning electron microscope, and Fourier transform infrared (FT-IR) spectroscopy. Adsorption of Ce(IV) radionuclides from aqueous solutions by activated carbon (AC) and surfactant-impregnated AC was studied. The obtained data showed that adsorption of Ce(IV) is strongly dependent on the solution pH and AC–NaLS exhibits the widest pH-range of maximum removal. The experimental adsorption capacity of AC–NaLS (0.069mmol/g) for Ce(IV) is found to be nearly twice greater than that of AC (0.036mmol/g). The adsorption kinetics of Ce(IV) onto AC and AC–NaLS were analyzed by linear and non-linear fittings to the pseudo-first-order, pseudo-second-order and Elovich kinetic models. Of these models, the pseudo-second-order is the best kinetic expression for describing the experimental data. The diffusion studies indicated that adsorption of Ce(IV) radionuclides on AC and AC–NaLS is controlled by film diffusion. Linear and non-linear fittings of the adsorption equilibrium data for Ce(IV) onto AC and AC–NaLS revealed that the Dubinin–Radushkevich (D–R) isotherm model fits the experimental data better than Freundlich and Langmuir models. The values of adsorption free energy, E, calculated from both linear and non-linear methods suggested that Ce(IV) radionuclides are physically adsorbed onto AC and AC–NaLS.