Span8012

E ffect of Temperature on Interfacial Tension in Kerosene-Surfactant-Water Systems
Y OSHIRO KITAMURA, 1 QINGFA H U A N G , AKIYOSHI MIYACHI,
K ENJI YOSHIZAKO, AND T E R U O TAKAHASHI
Department of Applied Chemistry, Okayama University, Tsushima-Naka, Okayama 700, Japan
R eceived November 15, 1991; accepted May 13, 1992
T he temperature dependence of interracial tension in oil-surfactant-water systems was investigated t o evaluate the adsorption of surfactants under superheated conditions; the adsorption under such cond itions is necessary in order to provide fundamental information for discussing the superheat limit of
W / O emulsions. As surfactants, Span 80 and NPEx ( x = 2, 5, and 7.5 ) were used. The interfacial tension w as measured by the Wilhelmy method in the temperature range from 301 to 355 K. The saturation a dsorption obtained from the interfacial tension data for the kerosene-water system is almost independent o f temperature, while that for the n-tetradecane-water system decreases slightly with increasing temp erature. The adsorption equilibrium constant is correlated as a function of temperature which contains t he free energy of adsorption. From these constants, the adsorption of the surfactants under superheated c onditions can be predicted. © 1992AcademicPress,Inc.

INTRODUCTION

U tilization of emulsified fuels is a viable m eans for pollutant reduction and enhanced f uel economy (1, 2). Such improvement in c ombustion arises from microexplosions; the w ater droplets dispersed in the fuel phase are s uperheated to a temperature far above their b oiling point and then explode violently. This m icroexplosion is closely related to the superh eat limit of water which is determined by the r ates of bubble nucleation at the interface (3).
W e have reported the superheat limit of water i n fuel emulsions and suggested that the bubble n ucleation is accelerated by the presence of s urfactants absorbed on the interface (4). In