UBC Theses and Dissertations
Thixotropy and slip of model kaolinite hybrid and oil tailings suspensions Piette, Jourdain
In this thesis, two clay colloidal systems are studied and rheologically characterized. The first is a suspension of kaolinite particles with and without the addition of cationic and anionic surfactant, namely Cetyl Trimethyl Ammonium Bromide (CTAB), and sodium dodecyl sulfate (SDS). The second system is Mature Fine Tailings (MFT), a by-product of oil sands bitumen extraction. The former system is studied as a model system to understand the more complex behavior of oil tailings. The steady-shear behavior of the kaolinite suspensions with surfactant is explored above and below the critical micelle concentration (CMC). SDS was shown to weaken the network structure at concentrations below the CMC. At concentrations greater than the CMC, SDS causes an increase in the yield stress due to network formation of micellar structures The yield stress was found to increase monotonically with CTAB concentration, which can be explained by the improved network strength. Both kaolinite and kaolinite-CTAB systems were found to exhibit thixotropic and anti-thixotropic behavior at short and longtime scales respectively. The rheological characteristics of mature fine tailings (MFTs) were examined in steady shear flow. MFT samples exhibited thixotropic behavior as well as apparent slip, which was suppressed by using sandpaper of grit 80 (200 μm) at the wall of the parallel-plate geometry. The real yield stress of MFTs with shear-thinning behavior was retrieved after fitting to a Herschel–Bulkley equation. The presence of bitumen remaining in the MFTs (up to 2 wt. %) suppressed the apparent slip to a substantial extent due to the immobilization of the particles at the interface. Finally, the effect of temperature on the rheology of both suspension systems was studied in detail over the range of 0–50 °C, showing a minimum viscosity and yield stress at about 20 °C, demonstrating a non-monotonic increase with the increase in temperature. This was found to be due to the increase of kaolinite particle charge with increase of temperature.
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