Sedimentation of fine particles of kaolinite and polymer-coated kaolinite in cyclohexane: Implications for fines removal from extracted bitumen in non-aqueous processes

Sedimentation of kaolinite microparticles (< 1 mu m) in cyclohexane was investigated in order to design efficient methods for fine particles removal in bitumen froth from oil sands processing. Kaolinite coated by copolymers (Polyethylene-block-poly(ethylene glycol) (P/P), and poly(4vinylpyridine co-styrene) (V/S)) were used as model particles to mimic the behaviour of fines present in bitumen. The model compounds were prepared by adsorption of the copolymers onto kaolinite. Characterization results (FTIR, TGA, C-13 NMR and XRD) confirmed the presence of the organic matter (2.0% for V/S and 3.4% for P/P) exclusively on the external surface of clay platelets. The presence of these copolymers reduced strongly the sedimentation rate of kaolinite in cyclohexane, as a result of the organophilic interactions between modified clay and cyclohexane. Addition of polyethylene glycol (PEG(1000) ) in the clay suspension increased the sedimentation rate. A model suggesting the adsorption of this polymer at the surface of modified clay particles with subsequent improvement of the aggregation of particles was proposed to interpret the phenomenon. When dry mature fine tailings (D-MFT) were used for sedimentation experiments, the presence of 0.0125% of PEG(1)(000) (w/w) improved the sedimentation rate by a factor of 20. The results obtained in this work are promising for the design of simple and efficient methods for fines removal in the context of non-aqueous bitumen extractions.