Adsorption modeling of antimony(V) on diphenylthiocarbazone loaded polyurethane foam

Abstract

The uptake behavior of Sb(V) onto diphenylthiocarbazone (H2DZ) loaded polyurethane foam (PUF) from aqueous solutions of different acids in the presence of KI have been studied. The maximum adsorption was found from 0.5N HNO₃ containing 0.2M KI. The maximum equilibrium was achieved within twenty minutes shaking time. The sorption behavior followed the Freundlich and Langmuir adsorption isotherms. The Freundlich constants 1/n and K_f are 0.57 and 3.26^.10^-2 mol^.g^-1, respectively. The Langmuir constants M and b are 2.18^.10^-4 mol^.g^-1 and 2.4^.10⁴ l^.g^-1, respectively. The value of sorption free energy (E) evaluated from D-R isotherm is 10.8 kJ^.mol^-1 indicating the ion exchange type chemisorption of Sb(V) on H2DZ loaded PUF. The thermodynamic parameters of enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) have also been investigated and found to be -51.8 kJ^.mol^-1, -127.3 J^.mol^-1.deg^-1 and -13.8 kJ^.mol^-1, respectively. The negative values of (ΔH) and (ΔG) indicate that the sorption is exothermic and spontaneous in nature. The effect of anions and cations and sorption mechanism are discussed.