Enhancing separation of oil-in-water slop oil via chemical-assisted centrifugation: Toward scalable and energy-efficient treatment of oil sands waste

Slop oil from oil sands operations presents significant environmental and operational challenges due to its complex composition and stability. This study investigates the separation performance of a field-derived oil-in-water (O/W) slop oil sample from northern Alberta, focusing on centrifugal separation, chemical demulsification, and their integration under the effects of reverse emulsion breaker (REB, branched polyethylenimine), temperature, and dilution. Centrifugal separation was significantly improved by REB addition (optimal dosage: 900 ppm), elevated temperature (70 °C), and organic solvent dilution (e.g., naphtha), enhancing water recovery, reducing turbidity and total organic carbon (TOC) content, and lowering water content in the oil phase. REB exhibited the strongest effect, followed by solvent and thermal treatment, while water dilution hindered separation unless mitigated by REB. Chemical demulsification alone was ineffective. However, when combined with mild centrifugation (5000 rpm, 10 min), REB-assisted treatment achieved results comparable to conventional high-speed centrifugation (7000 rpm, 30 min), while reducing energy input by ∼49 % and cutting process time. Two practical strategies are therefore proposed: (1) solvent dilution followed by high-speed centrifugation for fast bitumen recovery, and (2) REB-assisted mild centrifugation for energy-efficient treatment. This work provides mechanistic insights and practical guidance for the sustainable treatment of oily waste streams in oil sands operations.