Adsorption profile and thermodynamic parameters of the preconcentration of Eu(III) on 2-thenoyltrifluoroacetone loaded polyurethane (PUR) foam

Abstract

The adsorption studies of Eu(III) was investigated on 2-thenoyltrifluoroacetone (HTTA) loaded PUR foam. The adsorption conditions were optimized with respect to pH, shaking time, loading capacity and adsorbent weight. The adsorption data followed the classical Freundlich and Langmuir type isotherms successfully. The Freundlich constant (1/n) is estimated to be 0.35±0.02, reflects a surface heterogeneity of the PUR foam. Langmuir isotherm gives a saturated capacity of 0.082±0.002 mmol^.g^-1 suggests a monolayer coverage of the surface. The Dubinin-Radushkevich (D-R) isotherm is applied and the sorption mean free energy (E) is calculated and found to be 13.36±0.12 kJ^.mol^-1 suggesting that chemisorption involving chemical bonding is responsible for the adsorption process. The thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) were calculated and interpreted. The positive value of ΔH indicates that the adsorption of metal ions on HTTA-loaded PUR foam is an endothermic process. A possible explanation of this endothermicity has been given. The selectivity and sensitivity of the adsorbent was also studied. The sorption of Eu(III) is greatly affected in the presence of oxalate and fluoride. The sorptive affinity of different cations towards HTTA loaded PUR foam was also discussed.