Adsorption behavior of samarium(III) from aqueous solutions onto PAN@SDS core-shell polymeric adsorbent

Abstract

Adsorption behavior of samarium(III) radionuclides from aqueous solutions onto a novel polyacrylonitrile coated with sodium dodecyl sulfate (PAN@SDS), prepared by gamma radiation-induced polymerization, was studied in this work. The developed polymeric adsorbent was characterized by FT-IR, X-ray diffraction and N₂ adsorption-desorption. The influence of some experimental parameters such as pH, initial samarium(III) concentration, SDS concentration, temperature, ionic strength and contact time on the adsorption efficiency of samarium(III) was evaluated. Results showed that adsorption efficiency of about 97% was attained for samarium(III) in the pH range 3.8–7.5. The kinetic study showed that samarium(III) was efficiently removed within 10 min and equilibrium was attained at around 30 min. Six isotherm models; Freundlich, Langmuir, Generalized, Redlich–Peterson, Toth and Sips, were used to fit the adsorption equilibrium data, and the best-fit three-parameter isotherms suggest that adsorption capacity of PAN@SDS for samarium(III) to be 97.73 mg g^–1, which is a markedly high value compared to most of the other adsorbents reported for other metal ions. Using the Dubinin–Kaganer–Radushkevich (DKR) model, the mean free energy E was calculated as 1.569 kJ mol-1, which suggested that adsorption of samarium(III) was dominated by physisorption. Results of the thermodynamic parameters, ΔG^o, ΔS^o and ΔH^o, showed that adsorption of samarium(III) onto PAN@SDS was feasible, spontaneous and exothermic in nature. Of the various studied kinetic models, the experimental kinetic data were best fitted to the modified multiplex model, and the adsorption process was mainly controlled by particle diffusion. Desorption studies showed that 95% of samarium(III) loaded on PAN@SDS were recovered using 2 mol L^–1 HCl.