ADSORPTION-KINETICS OF ALKYLPHOSPHINE OXIDES AT WATER HEXANE INTERFACE .1. PENDANT DROP EXPERIMENTS/

A pendant drop technique has been used to study the adsorption of a no nionic surfactant, an alkyldimethylphosphine oxide (C(13)DMPO), at the water/hexane interface. The measured interfacial tensions exhibit a s teep initial decrease, pass through a minimum, and then level off at a value which depends on the initial surfactant concentration in the dr op. This time dependence of the interfacial tension can be interpreted by an adsorption with a subsequent transfer of the surfactant into th e second bulk phase, hexane. Measurements of the distribution coeffici ent show that the solubility of C(13)DMPO is much higher in hexane tha n in water. A qualitative model is proposed which describes the observ ed dynamic interfacial tensions. (C) 1997 Academic Press