Removal of cobalt-60 and caesium-134 ions from contaminated solutions by sorption using activated carbon

Abstract

Date pits (DP) and sawdust (SD) were used as precursors for activated carbons which were prepared by steam pyrolysis of DP and chemical activation of SD, respectively. Surface characterization of both activated carbons was undertaken using the BET method. Adsorption of the radionuclides onto the activated carbon was studied as a function of shaking time, adsorbent mass and pH employing the batch technique. Such adsorption was strongly dependent on the pH of the aqueous medium in contact with the adsorbent, with the removal efficiency attaining a maximum at pH 6. The process was very fast initially, with maximum adsorption being attained within 180 min of initial contact. The adsorption rate could be best fitted by the pseudo-second-order kinetic model. The equilibrium data were analyzed using the Freundlich, Langmuir, Langmuir-Freundlich, Dubinin-Radushkevich, Temkin and Frumkin isotherms. The Langmuir-Freundlich and Frumkin equations were found to best represent the equilibrium data for both radionuclides. The isotherm model constants were determined and used to characterize the distribution of 60Co and 34Cs ions onto the adsorbent surfaces and to provide an insight into the affinity of the adsorbents towards these ions.