, Volume 283, Issue 8, pp 862-871
Date: 01 Dec 2004

The aggregation of sodium perfluorooctanoate in water

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Abstract

The self-aggregation of sodium perfluorooctanoate (SPFO) has been studied by pH, ion-selective electrodes, changes in Rhodamine 6G colour and fluorescence, conductivity, surface tension and viscosity measurements. It has been determined that the aggregation of SPFO is gradual. It starts to aggregate at 0.01 mol dm−3 with the formation of pre-micelles of perfluorooctanoate ions, which capture counterions at C=0.02 mol dm−3 and form micelles at a critical micelle concentration (CMC) of 0.03 mol dm−3. Micelles at the CMC are highly ionised and strongly hydrated. At C*=0.06 mol dm−3, a low ionisation degree was found, indicating the formation of a more compact micellar structure. Micelles at the CMC show energetic advantage in comparison with the adsorbed state at the air/solution interface, and this advantage increases at C* originating desorption.