Adsorption syntax of Au(III) on unloaded polyurethane foam

The nature of adsorption behavior of Au(III) on polyurethane (PUR) foam was studied in 0.2M HCl aqueous solution. The effect of shaking time and amount of adsorbent were optimized for 3.16·10^-5 M solution of Au(III) in 0.2M HCl. The classical Freundlich and Langmuir adsorption isotherms have been employed successfully. The Freundlich parameters 1/n and adsorption capacity K are 0.488 ± 0.016 and (1.40 ± 0.22)·10^-2 mol·g^-1, respectively. The Langmuir constants of saturation capacity M and binding energy b are (1.66 ± 0.08)·10^-4 mol·g^-1 and 40294 ± 2947 l·g^-1, respectively, indicating the monolayer chemical sorption. The mean free energy (E) of adsorption of Au(III) on PUR foam has been evaluated using D-R isotherm and found to be 11.5 ± 0.16 KJ·mol^-1 reflecting the ion exchange type of chemical adsorption. The effect of temperature on the adsorption has also been studied. The isosteric heat of adsorption was found to be 44.03 ± 1.66 kJ·mol^-1. The thermodynamic parameters of ΔG, ΔH, ΔS and equilibrium constant K(c) have been calculated. The negative values of ΔG, ΔH and ΔS support that the adsorption of Au(III) on PUR roam is spontaneous, exothermic and of ion exchange chemisorption. The nature of the Au(III) species sorbed on PUR foam have been discussed.