Synergistic effects of plasma electrolysis and ultrasound on the viscosity and density reduction of bitumen

Bitumen is difficult to extract, pump, and transport because of its high viscosity and density. Here, a coupled plasma electrolysis-ultrasound (PE-US) process was used to improve the flowability of a concentrated bitumen slurry in an ethylene glycol/tetralin medium under near-atmospheric reflux. A small amount of aqueous NaOH adjusted the liquid conductivity to 14.5 mS cm −1 , enabling reproducible microdischarges under 800 V and 100 Hz square-wave excitation. Ultrasound-generated cavitation bubbles provided transient gas-rich sites for electrical breakdown and promoted stronger spark-like discharge events. Under optimized laboratory conditions, 180 s of PE-US treatment reduced the apparent slurry viscosity at 90 °C to 56.12 mPa s and decreased the bulk density from 1.057 to 0.924 g cm −3 . This short treatment window does not indicate low energy consumption. The discharge-specific and combined discharge-plus-acoustic energy inputs were 4.1 and 5.7 MJ kg −1 -bitumen, respectively, indicating that further energy optimization is needed. Rheological, gas/ion, GC–MS, SARA, simulated distillation, GPC, and TEM analyses showed weakened viscoelasticity, H 2 -dominated gas formation, redistribution toward more mobile/distillable fractions, modest molecular-weight reduction, and disrupted asphaltene-rich aggregation. The improved flowability mainly arose from cavitation-assisted discharge intensification, accelerated dissolution, and aggregate disruption rather than extensive deep cracking.