Abstract: The thermodynamics of micella formation,interfacial characteristics,synergistic effects and interfacial kinetics for synergistic extraction system D_2 EHPA-MPA-Fe~(3+) have been studied.It was found that D_2EHPA in the mixed system strongly exhibits the effect on the micella formation thermodynamics and interracial characteristics of MPA.Some ther- modynamic parameters for constants of micelles formation(K_m).free energies of micelles formation(ΔG_m)and critical micella concentrations(CMC)were obtained.The inter- facial adsorption behaviour of D_2EHPA is opposite to that of MPA.The emulsification for single MPA and the mixed system was discussed.The synergistic effects were found in this mixed extraction system.It is proved that the process of the Fe~(3+) extraction for non-mixed extraction system is controlled by chemical reaction and the controlling reaction occurs at the interface.

Key words: interfacial chemistry, synergistic effect, Fe~(3+), extraction kinetics