SURFACE-TENSION OF TOLUENE-EXTRACTED BITUMENS FROM UTAH OIL SANDS AS DETERMINED BY WILHELMY PLATE AND CONTACT-ANGLE TECHNIQUES

The surface tension values for toluene-extracted bitumens from Whitero cks, Sunnyside, PR Spring, Asphalt Ridge, and Circle Cliffs oil sands were measured with the Wilhelmy plate technique and found to vary from 20.6 to 31.2 mN m-1 at 333 K. A linear relationship between the bitum en surface tension and temperature was observed in the temperature ran ge 310-356 K, which allowed for the calculation of the temperature coe fficients of surface tension. The temperature coefficients were found to vary among the bitumens from -0.063 mN m-1 deg-1 to -0.097 mN m-1 d eg-1. Also, the surface tensions of these bitumens at room temperature were calculated from contact angle measurements using Neumann's equat ion-of-state. Satisfactory agreement between the results for bitumen s urface tensions as determined from contact angle data and direct surfa ce tension measurements with the Wilhelmy plate technique were obtaine d for the Whiterocks, Sunnyside, and PR Spring bitumens. However, larg e discrepancies, 6.4-9.4 mN m-1, were observed between the bitumen sur face tension data obtained from Neumann's equation-of-state and the bi tumen surface tensions determined by direct Wilhelmy plate measurement s for the Asphalt Ridge and Circle Cliffs bitumens.