Study of Thermoresponsive Hybrid Polymer for Oil Sands Applications

  • Author / Creator
    Ng, Jason K.H.
  • Many tailings treatment technologies rely on the use of water-soluble polyacrylamides (PAM) to flocculate fine solids. However, PAM-induced flocs are often loosely-structured and retain significant volume of water due to the hydrophilicity of PAM and fine clays in oil sands fine tailings. Thermoresponsive polymers and inorganic-organic hybrid polymers are both promising alternative flocculants to accelerate solids settling and improve sediment consolidation. As such, a multifunctional hybrid polymer (Al-NIPAM) was synthesized in this study by integrating inorganic Al(OH)3 colloidal particle into the organic molecular structure of poly(N-isopropylacrylamide) (poly(NIPAM)) for the flocculation of mature fine tailings (MFT) suspension. The hybrid polymer responded to temperature changes, with a lower critical solution temperature (LCST) transition from hydrophilic coils to hydrophobic globules close to poly(NIPAM). Zeta potential measurements showed that Al-NIPAM reduced the surface charges of fine solids in MFT, indicating polymer-particle adsorption interactions. The hybrid polymer exhibited charge selective adsorption in QCM-D with strong electrostatic attraction between the cationic Al(OH)3-core in hybrid polymer and the negatively-charged surface. Furthermore, the adsorbed Al-NIPAM polymer layer became dehydrated and collapsed upon heating. Results from the adsorption and conformation experiments provided a basis for the use of Al-NIPAM as a flocculant in oil sands tailings treatment, where the cationic Al(OH)3-cores in the hybrid molecules attract and bind negatively-charged fine clays while the poly(NIPAM) chains provide the thermal response for enhanced floc densification. Laboratory settling tests and FBRM experiments showed that Al-NIPAM outperformed poly(NIPAM) and its respective mixture blend of Al(OH)3 and poly(NIPAM) in flocculation of MFT suspension, producing larger and more shear-resistant flocs that lead to higher settling rate, clearer supernatant and better sediment consolidation due to synergism of the hybrid polymer structure. Furthermore, two settling temperatures were investigated: 21°C (below LCST) and 40°C (above LCST). At elevated temperature, the coil-globule transition of thermoresponsive polymers resulted in accelerated settling and improved consolidation due to floc densification and hydrophobic interaction. The potential effects of the hybrid Al-NIPAM on bitumen extraction were also studied. The hybrid polymer was interfacially-active at the model toluene-water interface due to the amphiphilic nature of poly(NIPAM). Preliminary results showed that Al-NIPAM increased the degree of bitumen liberation and reduced the induction time for bitumen-bubble attachment in the presence of fines. This study presented some insights on the potential benefits of thermoresponsive hybrid polymer for oil sands mining applications.

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  • Degree
    Master of Science
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