Bitumen-in-water emulsion

Phase inversion may be used to emulsify highly viscous substances such as bitumen (the viscosity of which can be as high as 10 Pa-s at room temperature) [134]. The most frequent industrial technique used to prepare bitumen-in-water emulsions consists of mixing hot bitumen (130°C) with an aqueous phase ( 60°C at... 

Figure 1.9. Comparison between two bitumen-in-water emulsions prepared following (a) the classical protocol, (b) the protocol described in [134]. (Adapted from [134].)...

Figure 5.16. Sequence showing the homothetic contraction of a bitumen-in-water emulsion. (Reproduced from [49], with permission.)...

Acevedo S, Gutierrez X, Rivas H (2001) Bitumen-in-water emulsion stabilized with natural surfactants. J Colloid Interface Sci 242 230-238... 

The exact mechanism of inversion remains unclear, although obviously some processes of coalescence and dispersion are involved. In the region of the inversion point multiple emulsions may be encountered. The process is also not always exactly reversible. That is, hysteresis may occur if the inversion point is approached from different sides of the composition scale. Figure 18 shows the irreversible inversion of a diluted bitumen-in-water emulsion brought about by the application of shear (60). 

Application of DLVO Theory. Some of the concepts and expressions of Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory of colloid stabihty have been described in Chapter 1, or can be found in many different textbooks 4, 5). The application of DLVO theory to oil-in-water colloids with special reference to the stability of bitumen-in-water emulsions will be discussed here. 

In reference to the example of the stability of bitumen-in-water emulsions, production samples were obtained from the Alberta Research Coun-... 

Figure 7. The zeta potentials for bitumen-in-water emulsions as a function of electrolyte concentration. (Reproduced with permission from reference 6.

Figure 8. The energy diagram for bitumen-in-water emulsions in the presence of NaCl and CaCh. In the presence of 300 mM NaCl the emulsion should flocculate, and in the presence of the 20 mM CaCh the emulsion will coagulate. (Reproduced with permission from reference 6. Copyright 1982.)...

Non-DLVO Forces. Although DLVO theory worked very well for the electrolyte-induced coagulation of bitumen-in-water emulsions, it cannot be applied in some cases. 

Although the predicted bitumen-in-water emulsion stability can be accomplished without invoking this force, recent research has shown (23) that this force exists between liquid bilayers immersed in aqueous and nonaque-ous liquids. With some types of oils, it may be important to consider this force. 

In this section, we discuss the effects of solids addition on the rheology of oil-in-water emulsions, in particular, the effects of solids size (size distribution) and shape (spherical versus irregular). Because the type of the oil used to form an emulsion is important in determining the viscosity of the oil-in-water emulsion, the rheology of the emulsion-solids mixtures is also influenced by the type of oil. Thus, two distinct emulsion systems with added solids will be discussed (1) synthetic (Bayol-35) oil-in-water emulsions 21, 57) and (2) bitumen-in-water emulsions (58). The synthetic oil has a viscosity of 2.4 mPa s, whereas the bitumen has a viscosity of 306,000 mPa s at 25 C. The Sauter mean diameter of the oil droplets is 10 xm for synthetic oil, and 6 xm for bitumen-in-water emulsions. The synthetic OAV emulsions are fairly shear-thinning, whereas the bitumen OAV emulsions are fairly Newtonian. 

The effect of solids size on the viscosity of bitumen-in-water emulsions containing solids is shown in Figure 20. The shear stresses at which the comparison is made are 1, 14, and 50 Pa. At a very low shear stress (Figure... 

Figure 33 shows the apparent viscosity variation with shear rate for 44 fim glass beads suspended in a 50% bitumen-in-water emulsion at 25 °C. The viscosity ratio of the dispersed liquid phase (bitumen) to the... 

Briceno, M. Study of the main variables that infiuence the rheology of bitumen-in-water emulsions (Spanish), MSc thesis. University Simon Bolivar, Caracas, IS194. Polinski, A. Ryan, M. Gupta, R. Seshadi. S. Frechette. F. J, Rheol,. 32(7) 703-735. 1988. 

ML Chirinos, J Colmenares, MI Briceno, G Nunez. Slip flow in bitumen-in-water emulsions. Fifth European Congress of Rheology, SevUla, Spain, 1994. Proceedings, Darmstadt Editorial Steinkopfl pp. 182. 

Acevedo, S., Gutierrez, X., and Rivas, H., Bitumen-in-water emulsions stabilized with natural surfactants, J. Coll. Interf. Sci., 242, 230-238, 2001. 

Gutierrez X., Silva F., Chirinos M., Leiva J., Rivas H., Bitumen-in-water emulsions An overview on formation, stability and rheological properties, J. Dispersion Sci. TechnoL, 23(1-3), 2002, 405 18. 

Bricefio, M. Study of the main variables that inlluence the rheology of bitumen-in-water emulsions (Spanish), MSc thesis. University Simon Bolivar, Caracas, 1994. 

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