Investigation of sorption of Tb(III) by 2-thenoyltrifluoroacetone supported onto polyurethane foam

Abstract

Summary The sorption studies Tb(III) was investigated on 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 0.47 ± 0.01, reflects a surface heterogeneity of the PUR foam. Langmuir isotherm gives a saturated capacity of 0.042 ± 0.001 mmole g−1 which 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 11.32 ± 0.14 kJ mol−1 suggesting that chemisorption involving chemical bonding is responsible for the adsorption process. The isosteric heat of adsorption of Tb(III) is high which decipher the surface heterogeneity, new bond formation and endothermic type chemisorption. The thermodynamics parameters such as enthalpy (Δ H), entropy (Δ S) and Gibbs free energy (Δ G) were calculated and interpreted. The positive values of Δ H indicate that the adsorption of metal ions on HTTA-loaded PUR foam is an endothermic process. A possible explanation of this endothermicity and sorption mechanism have been discussed. The selectivity and sensitivity of the adsorbent was also studied. The sorption of Tb(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.