The influence of synthesized ionic liquid 1-hexyl-3-methylimidazolium chloride adsorption on equilibrium interfacial tension of toluene-water was studied within concentration range of (1.00×10-4 - 6.00×10-1) mol•dm-3 and temperature range of (293.2 - 313.2) K. Very similar to conventional surfactants, interfacial tension was decreased with both of these parameters. Meanwhile, the appeared CMC values showed a minimum value within the studied temperature range. The Frumkin adsorption isotherm that accounts the nonideality of adsorption at interface, showed adequately well for modeling the experimental data. Accordingly, quantities like interface excess concentration, adsorption tendency and interaction parameter between adsorbed molecules were obtained at different temperatures. Entropy and energy changes associated with adsorption were also obtained from temperature dependency of interfacial tension. The adsorption tendency and efficiency were revealed increasing with temperature, and the maximum interface excess concentration and electrostatic repulsion were achieved at about 303.2 K.
