C OF ULTRALOW INTERFACIAL TENSION SYSTEMS FORMULATED WITH CARBOXYMETHYL ETHOXYLATES UNDER EXTREMELY HIGH CALCIUM ION CONCENTRATION

ABSTRACT

Physicochemical measurements have been applied to study the micellar properties of some commercial surfactant systems exhibiting ultralow interfacial tension under extremely high calcium ion concentration (0.5-1.5 M). These surfactant systems were prepared from Hills B433 surfactant sample containing carboxy-methyl ethoxylated anionic and ethoxylated nonionic surfactant with an average ethylene oxide number of 4.5. Micellar dissociation concentration (mdc) values were determined by turbidity and surface tension methods at different CaCl₂- concentrations. The mdc value decreases with the increase of Cacl₂- concentration. UV absorption measurements were also performed in these surfactant systems by varying the surfactant and CaCl₂- concentrations. The absorption peak around 277 nm has an absorbance proportional to the surfactant concentration. This peak may be useful for quantitative determination of the surfactant. Other peaks in the spectrum seem to be related with surfactant association and could be useful for such studies. It appears that around surfactant concentration of 0.02%, the association is much strengthened, especially at high CaCl₂- concentrations. Micellar size was measured with laser light scattering. The effect of CaCl₂ on the surfactant association of this type of surfactant will be discussed. Data obtained in these studies will be correlated with surfactant performance on other papers of this series.