Assessment of kinetic and isotherm models for competitive sorption of Cs⁺ and Sr²⁺ from binary metal solution onto nanosized zeolite

This study examined the sorption performance of synthesized nanosized zeolite for the elimination of Cs⁺ and Sr²⁺ cations in a binary metal system. The influence of pH, sorbent amount, temperature, and contact time was studied. The relationship between each of these parameters and the removal efficiency was investigated. An analysis of the rate data was performed using both pseudo-first- and second-order reaction models. The ranking of three equilibrium sorption isotherm models used (Redlich–Peterson, Langmuir, and Freundlich) with a variety of numbers of parameters was determined using the corrected Akaike’s information criterion. The results demonstrate that a pseudo-second-order model fits the sorption kinetic data better than a pseudo-first-order model. The isotherm model rank order that best described the data statistically was Redlich–Peterson > Langmuir > Freundlich for the cesium ions and Langmuir > Redlich–Peterson > Freundlich for the strontium ions. Our results revealed that the existence of Sr²⁺ caused a significant reduction of Cs⁺ sorption in the binary metal mixture according to a lumped parameter model and vice versa. The results show that the synthesized material’s surface had a relatively stronger affinity for Cs⁺ than for Sr^2+.