Interaction between polyoxyethylene nonyl phenyl ether (n=9) and gold (III) ion in the adsorbed film and micelle

A thermodynamic method was employed to analyze the surface tension data for studying the adsorption at the interface and micelle formation of an aqueous solution of polyoxyethylene nonyl phenyl ether having an average of nine oxyethylene units (PONPE-9) and that of PONPE-9 and gold (III) ion mixtures at pH 3, 7, and 10. The results suggested the existence of attractive interaction between PONPE-9 and gold in the adsorbed film and micelle and that the interaction strength decreases in the order pH 3, pH 10, and pH 7. This result was in accord with the percent extraction of gold obtained from the cloud point extraction method where the efficiency relies on the strength of the interaction between analytes and the surfactant. Thus, this study confirmed the usefulness of the thermodynamic equations developed.