Microbubble-enhanced cold plasma activation (MB-CPA) for effective treatment of oil-laden slurries

Air cold plasma is considered a sustainable approach for generating reactive species that drive chemical conversion processes. However, the application of plasma treatment to oil-laden slurries with complex chemical compositions remains largely unexplored. In this work, the effects of microbubble-enhanced dielectric barrier discharge (DBD) plasma activation on slurry-phase treatment were investigated. Using oil sands tailings as a model system, MB-CPA was shown to simultaneously enhance water remediation and modify the quality of residual oil. Tailings solvent recovery unit (TSRU) tailings and fluid fine tailings (FFTs) were treated using an air-fed plasma discharge system. Plasma activation notably enhanced solids sedimentation, nearly doubling the settling rate in TSRU tailings within 60 min and tripling the 7-day settling performance for FFTs. This enhancement was attributed to zeta potential neutralization and a shift in particle size distribution toward large aggregates. Dean-Stark separation and total organic carbon (TOC) analysis indicated reductions in dissolved and suspended organic species. DBD treatment also altered the chemical composition of the recovered heavy hydrocarbon fraction, reducing sulfur content from approximately 7 wt.% (untreated) to 2 wt.% after 60 min treatment at 20 SLM, along with an increase in the H/C ratio, as supported by Fourier-transform infrared (FTIR) spectroscopy. These findings suggest that MB-CPA integrated with DBD is a promising approach for the sustainable treatment of residual oil sand waste streams, enabling simultaneous environmental remediation together with partial oxidative transformation and compositional modification of sulfur-containing hydrocarbon fractions.