The effect of temperature on the interfacial tension between crude oil and ethoxylated nonylphenols

ABSTRACTIn this study, the effect of temperature on interfacial tension between crude oil and ethoxylated nonylphenols, with ethoxy group numbers of 4 and 9, was investigated. The interfacial tension was measured using the rising drop technique. Above the critical micelle concentration, the interfacial tension passed through a minimum when the temperature increased. Below the critical micelle concentration, the interfacial tension and time needed to reach equilibrium interfacial tension was reduced when the temperature increased. For a mixture of a two-surfactant system, interfacial tension was not sensitive to the temperature because of formation of mixed micellar aggregates.