Synergistic Effect of Mixed Biosurfactant System on Emulsification of Heavy Crude Oil

In this study, the synergistic impact of rhamnolipid and saponin emulsifiers on the emulsion processing of heavy oil was studied. Emulsions were formulated by ۱۰, ۲۰, and ۳۰% water content using mixed biosurfactants at various HLB values (۹.۶–۱۰.۸) to determine the optimum HLB. The total biosurfactant concentration was adjusted to ۱.۲ g/L, with the rhamnolipid to saponin ratios adjusted according to HLB calculations. Emulsion droplet sizes were measured microscopically, and stability was assessed using the emulsification index (E۲۴) over a temperature range of ۴۵–۱۲۰°C. Results showed that the optimum HLB for stable W/O emulsions was ۱۰.۴, corresponding to an ۸۲% rhamnolipid and ۱۸% saponin composition. At this HLB, when the water content increased from ۱۰% to ۳۰%, the droplet size ranged between ۱۶ and ۷۰ µm, and emulsions remained stable at temperatures up to ۹۰°C. The combination of rhamnolipid and saponin exhibited a clear synergistic effect, forming a compact interfacial film and enhancing emulsion stability compared with individual biosurfactants. These findings suggest that mixed biosurfactants represent promising and sustainable substitutes to synthetic emulsifiers in heavy oil upgrading and other industrial applications.

کلیدواژه ها:

Heavy crude oil ، Water-in-oil (W/O) emulsions ، Mixed biosurfactants ، Rhamnolipid ، Saponin ، HLB optimization ، Synergistic effect ، Emulsion stability