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THE ROLE OF COLLOIDAL FORCES IN BITUMEN EXTRACTION
Juan Ma and Roe-Hoan Yoon
Center for Advanced Separation Technologies
Virginia Tech, Blacksburg, VA 24061, United States
ABSTRACT
A bubble-against-plate apparatus equipped with a high-speed camera has been used to record the optical
interference patterns of the wetting films on bitumen, asphaltene and maltene. The recorded interference
patterns are then analyzed offline to construct the temporal and spatial profiles of the wetting films that are
useful to study the kinetics of film thinning and determine the colloidal forces affecting bitumen extraction.
The results show that the kinetics of film thinning increases with temperature.
150
80 °C
35
 ( °)
120
22
90
60
0
10
20
30
Time (s)
o
35 C
0
55
-500
80
-1000
-1500
Bitumen
Natual pH
0
100
200
300
h (nm)
KEYWORDS
Bitumen, asphaltene, maltene, contact angle,
disjoining pressure, hydrophobic force, aeration,
liberation.
40
Figure 1 - Dynamic contact angles for bitumen at
different temperatures.
h (Pa)
In addition to obtaining the kinetic information, the
film profiles have been used to determine the
disjoining pressures () in the wetting films using the
methods described previously (Pan, et al., 2011). The
results show that  < 0 for maltene and bitumen, while
 > 0 for asphaltene. The disjoining pressure data have
been analyzed to determine the contributions from the
different colloidal forces in bitumen extraction from
oil sands. The results show that the hydrophobic force
increases with temperature, which corroborates well
with the finding that contact angles () also increase
sharply with temperature. Thus, the primary role of
temperature in bitumen extraction may be to increase
hydrophobicity and hence the hydrophobic force of the
bitumen droplets to be aerated. A thermodynamic
analysis based on the Frumkin-Derjaguin isotherm
suggests that disjoining pressure remains positive until
the hydrophobic force becomes strong enough (due to
temperature increase) to overcome the repulsive
colloidal forces created during the course of bitumen
liberation.
Figure 2- Effect of temperature on the
hydrophobic disjoining pressure in the wetting
films of water on bitumen.
References:
Pan, L., Jung, S. and Yoon, R.-H., 2011, J Colloid Interface. Sci., 261, 321-330.
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