The interfacial properties of HDEHP in different diluent -0.05mol/L(H2, Na2)SO4(pH=2.40) systems have been studied with the drop method. The interfacial parameters, Cmin, Tmax, Ai and △Gad, of HDEHP have been obtained. It was suggested that the monomeric HDEHP molecule was the species absorbed on the interface. The interfacial activity of HDEHP in different system decreased as follows: aliphatic hydrocarbon, aromatic hydrocarbon, carbon tetrachloride, chloroform, MIBK. This might be attributed to the molecular interaction between diluent and extractant or (and) diluent and water immediately adjacent to the interface. The extraction kinetics with HDEHP in different diluents has also been discussed.

Key words: SULFURIC ACID, EXTRACTIVE AGENT, SODIUM SULFATE, DILUENTS, EXTRACTION KINETICS