A Model Study on Water Soluble Polymeric Nanofibers for Rapid Flocculation and Enhanced Dewatering of Fine Oil Sands Tailings Simulated Through Kaolin

  • Author / Creator
    Afacan, Christopher
  • Nanofibers are fibers with diameters lower than 100 nm, traditionally made from natural or synthetic polymers. Properties of nanofibers, such as low density, controllable surface functionality, and high surface area to volume ratio, allowed researchers to use them in a multitude of applications such as filtration, cosmetics, and drug delivery. The most common method to produce nanofibers is electrospinning because it is robust and straightforward to setup. However, the relatively low yield and high cost of producing nanofibers by this method has been a major hurdle in its industrial exploitation. In this study, this method was improved upon to increase the output of nanofibers generated by bubble spinning. Instead of a needle producing a single thread of fiber, a continuous process of forming bubbles in a polymer solution was used which created hundreds of threads when the bubbles broke. Hot water is used to remove bitumen from oil sands ores. The tailings produced from this process contain a mixture of clays, sands, salts, and residual bitumen. These tailings are disposed into open pits called tailing ponds to allow further settlement of solids. However, these tailings ponds are toxic to the environment and require large amounts of land that is difficult to reclaim. The mature fine tailings (MFT) layer in tailings ponds, produced by the bitumen extraction processes, consists of fine particle and water suspensions that take several years to settle. This poses a major environmental problem. Recently, rapid flocculation and dewatering of oil sands tailings using polymeric nanofibers has been considered. Water-soluble polymers, combined with flocculation techniques, have been used in the industry to efficiently release entrapped water by bridging small particles to create large, heavier flocs, which can then settle. Currently, there is no technology that can effectively dewater MFT to desired levels of solids content because of the high water retention resulting from the use of polymeric flocculants. Due to their immediate initial interaction with fine particles and the nanofiber length, polymer nanofibers have the potential to perform better than their parent polymers. To further understand the mechanism and the effect of these nanofibers on mature fine tailings compared to their original polymer counterparts, a model study was conducted in a less complicated environment. Kaolin was used throughout this analysis since it is one of the major clay minerals in MFT. Poly(acrylamide-co-diallyldimethylammonium chloride) was chosen as it is commercially available and currently being used in industry. The original polymer was also fabricated as a powder to further reduce variability during flocculation tests. The initial settling rate, turbidity of supernatant, water recovery, capillary suction time, and solid content were measured to determine the effect of nanofibers on the solid-liquid separation. In addition to the kaolin flocculation tests, MFT trials were conducted to further investigate nanofiber performance compared to the equivalent polymer solution and polymer powder. It was shown that the solid forms of the polymer (either as nanofiber or powder) perform better than the polymer solution throughout each test, with optimum dosages of 5 wt. % MFT loading. Nanofibers were able to achieve settling rates of 60 m/h while the other forms were only able to achieve 42 m/h. Additionally, the turbidity of the supernatant obtained after flocculation with nanofibers was 15 NTU, while the polymer solution and powder produced turbidites of 162 and 70 NTU, respectively. Polymer nanofibers and powder generated larger flocs compared to the polymer solution, which produced small, homogenized flocs. The kaolin studies showed that polymer nanofibers could absorb onto clay particles faster and produce flocs more rapidly due to their high surface area to volume ratio. Our results indicate that polymer nanofibers, as well as polymer powders, may be successfully used to treat the MFT produced from oil sands.

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  • Degree
    Master of Science
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