Kinetic, Equilibrium and Thermodynamic Studies of Cerium and Lanthanum Adsorption from Aqueous Solutions by Amberlit XAD-7 ion exchange resin impregnated with bis (2,4,4–trimethylpentyl) phosphinic acid extractant

Abstract

In this study, the adsorption of cerium and lanthanum ions from aqueous solutions was investigated using Amberlite XAD-7 resin impregnated with bis (2,4,4–trimethylpentyl) phosphinic acid (Cyanex-272) in the batch system. The characterization of provided resin was performed by SEM and FTIR analysis. The effect of important parameters such as pH, contact time, temperature and initial concentration of metal ions in the solution on the adsorption process of cerium and lanthanum from aqueous solution were investigated. The results showed that with increasing the pH of solution, the adsorption of cerium and lanthanum increased and the maximum adsorption occurred at pH=6. Langmuir, Freundlich and Temkin isotherm models were applied to describe the equilibrium data. The results showed the agreement of the experimental data for Ce and La elements with Langmuir isotherm (R2 (Ce) =0.999, R2 (La) =0.998). The maximum adsorption capacity of resin for cerium and lanthanum was 11.17 and 6.48 mg.g-1, respectively. The kinetic study was performed using pseudo-first order, the pseudo-second order and intraparticle diffusion models. According to the results, kinetic data for Ce and La adsorption were fitted well to a pseudo-second-order rate equation (R2 (Ce) =0.966, R2 (La) =0.985). The thermodynamic parameters of the adsorption process such as standard enthalpy (ΔH°), Gibbs free energy (ΔG°) and entropy (ΔS°) were studied at different temperatures. The positive value of enthalpy and negative value of Gibbs free energy indicates that the cerium and lanthanum adsorption reaction is spontaneous and endothermic.