Solid colloidal particles inducing coalescence in bitumen-in-water emulsions

Area of Science:

• Colloid and Surface Science
• Materials Science
• Rheology

Background:

• Bitumen-in-water emulsions are utilized in various industrial applications.
• Understanding emulsion stability under dynamic conditions is crucial for process design.
• The role of nanoparticles in emulsion rheology requires further investigation.

Purpose of the Study:

• To investigate the destabilization mechanism of silica-stabilized bitumen-in-water emulsions under shear.
• To analyze the influence of various parameters on emulsion rheological behavior and stability.
• To determine the kinetic evolution of viscosity and the characteristic time of destabilization.

Main Methods:

• Microscopic observation of emulsion structure under shear.
• Rheological measurements to track viscosity changes over time at constant shear rate.
• Systematic variation of parameters including silica concentration, bitumen droplet size, and shear rate.

Main Results:

• Emulsions remain stable at rest but rapidly destabilize upon application of shear.
• Microscopy reveals bitumen droplet gelation and coalescence under shear.
• Viscosity remains constant initially, followed by a dramatic increase after a characteristic time (tau).
• The characteristic time (tau) is influenced by silica particle size and concentration, bitumen droplet characteristics, and shear rate.

Conclusions:

• Silica particles induce shear-induced destabilization in bitumen-in-water emulsions through colloidal gel formation.
• The observed viscosity increase is linked to droplet coalescence and network formation.
• The study provides insights into controlling emulsion stability by tuning particle and droplet characteristics.