Kinetics and Rietveld XRD structural study of Cs⁺ sorption on natural and synthetic mordenites in the first 12 h

Kinetics of Cs⁺ uptake by natural and synthetic mordenites was studied. The experimental data is best fitted to the pseudo-second-order rate model and the parameters k₂ and q_e are calculated. The application of intra-particle diffusion and liquid film diffusion models show multilinear graphical dependence, indicating that both mechanisms influence the run of uptake. Rietveld XRD structural analyses were used for identification of the positions preferably occupied by Cs⁺ cations during the ion-exchange as a function of contact time. The obtained results show that the predominance of Na⁺ ions in the initial samples makes the exchanged sites more accessible by Cs⁺ ions. (author)