Osmotic dewatering of diluted bitumen using draw solutions

Efficient dehydration and desalination of diluted bitumen are essential for reducing corrosion and fouling in downstream refining, yet conventional separation technologies remain energy intensive. This study investigates a water–water osmotic drawing strategy as a lower‑energy alternative for removing emulsified water and dissolved salts during bitumen froth treatment. The approach applies small quantities of highly concentrated aqueous draw solutions containing osmotically active substances (OAS) to generate chemical‑potential gradients between water droplets. Systematic experiments were performed on aged synthetic diluted bitumen and fresh industrial dilbit using ionic and non‑ionic OAS to assess the effects of dosage, interfacial activity, and sample history on dewatering performance. Osmotic drawing consistently reduced water content in centrifuged products, with a sucrose + 8% PS80 formulation achieving the strongest response in fresh dilbit, yielding a final water content of 452 ppm (98.4% removal) and a 91.1% reduction in chlorides. The results indicate that diluted bitumen and asphaltene‑stabilized films can behave as semipermeable barriers, where the transition from selective solvent migration to bulk coalescence depends on both interfacial chemistry and prior sample aging. Complementary gravity‑settling tests showed that mechanical agitation increased transport rates by more than two orders of magnitude, suggesting a pathway to meet refinery specifications while reducing reliance on secondary centrifugation. Overall, this work establishes osmotic drawing as a novel dewatering mechanism for diluted bitumen and provides new insight into the non‑equilibrium transport processes governing solvent and ion redistribution during froth treatment.