Abstract
Kinetic and equilibrium models were navigated for sorption of Cs+, Co2+, and Eu3+ ions from their aqueous solutions by poly-acrylonitrile-based Ce(IV) phosphate. Pseudo-first order, pseudo-second order, intra-particle diffusion, and Boyed rate expressions were used to determine the suitable sorption pathway, in addition to their verification using the double-shell theory. Such expressions initially revealed that the sorption process is governed by the pseudo-second-order and particle diffusion protocols; DSM finally confirmed that chemical reaction and/or film diffusion control could be discarded as controlling steps. Langmuir and Freundlich isotherm models were applied and separately compared. Thermodynamic parameters were determined. Positive values of enthalpy change, Delta H (27.5, 28.2, and 29.1 kJ/mol), for Cs+, Co2+, and Eu3+ ions confirmed the endothermic nature of the sorption process and suggested that chemisorption was the predominant mechanism. The high positive values of the entropy change, Delta S (142.77, 123.10, and 118.19 J/mol/K) for the mentioned cations, showed an increased randomness at the solid/solution interface. The obtained negative values of free energy change, Delta G (-8.4 to -12.28, -4.88 to -7.951, and -3.743 to -6.757 kJ/mol), for the aforementioned species indicated the feasibility and the spontaneous nature of the sorption at different reaction temperatures.