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The batch extraction of Co(I1) from aqueous solutions with open cell polyethertype HTTA-loaded polyurethane (PU) foam has been studied using a radiotracer technique. The effect of pH, shaking time, and loading capacity has been investigated. The membrane properties of loaded PU foam sorbent offer unique advantage of adsorption. The fundamental studies of adsorption show that the classical Freundlich and Langmuir isotherms are followed in the entire concentration range of a to lo-* M solution of cobalt. The sorption mean free energy from the Dubinin-Radushkevich isotherm is found to be 13.8 kJ.mo1-I and the loading capacity 4.44 mg.g-I , suggesting that the ion-exchange or chemisorption mechanism operates. The kinetic parameters of adsorption also support a chemisorption mechanism and the first-order rate law. The rate constants and activation energies of sorption and desorption have been evaluated. The thermodynamic function of adsorption of A H , AS, AG, and equilibrium constant KC have been calculated.The process of adsorption is established to be endothermic and chemisorption, stabilized through thermodynamic functions. 43

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 (∆H), entropy (∆S) and Gibbs free energy (∆G) were calculated and interpreted. The positive values of ∆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.

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