| From tensiometric measurements, critical micelle concentration (CMC), maximum surface excess concentration (max) and minimum area per molecule (Amin) of Sodium bis (2-ethyl hexyl) sulphosuccinate (AOT) at air-liquid interface in aqueous solutions with or without an added electrolyte of varying cation valence have been determined, at 288.15, 293.15 and 298.15 K. Whereas, the CMC of AOT+H2O solution invariably decreases on adding an electrolyte and is further lowered when an electrolyte of higher cation valence is mixed, on the contrary, it is raised upon increasing the solution temperature. The process of micellization in the bulk solution and adsorption at air-liquid interface are both favored by exothermic enthalpy as well as entropy gain. The CMC lowering effect upon mixing an electrolyte was found in the order: (AlCl3)>(CaCl2)>(NaCl). Thus, mixing of electrolyte with higher cation valence would be of more advantage in lowering the CMC of the surfactant. This can be exploited for improving the efficiency of the surfactant as a detergent, for managing the problem of oil spill and for more efficient extraction of petroleum oil in the tertiary process. |