Interfacial activity of bis(2-ethylhexyl) phosphoric acid in model liquid-liquid extraction systems

Abstract The interfacial activity of bis(2-ethylhexyl)phosphoric acid (HDEHP) has been studied at different alkane/0.1 M HCl interfaces. The experimental parameters investigated include the molecular weight of the alkane used as a diluent, temperature, and the nature and content of long chain alcohols often used as modifiers for third-phase elimination. The molecular weight of the alkanes was found to have a significant effect upon the surface excess ( Λ max HDEHP ) of HDEHP at the saturated interface: Λ max HDEHP increases as molecular weight is increased. However, the effect of temperature is very weak. Finally, it is shown that there is strong competition between HDEHP and long chain alcohols such as isodecanol and 1-octanol for adsorption at the interface. The modelling of the interfacial tension isotherms is discussed.