Cationic and Anionic Dual Polymer Pairs for Mature Fine Tailings Flocculation and Dewatering

  • Author / Creator
  • The accumulation of oil sands tailings poses serious environmental issues in Alberta, Canada. In the tailings ponds, the fine clays and residual bitumen form the so-called mature fine tailings (MFT) which contain 30~40 wt% fine solid particles primarily below 44 µm in size, 1~3 wt% residual bitumen with the balance water. Without any physical or chemical treatment, the MFT remains as a stable suspension in tailings ponds indefinitely. Adding a polymer as a process aid to treat the oil sands tailings has been investigated for many years to cause fine solids to flocculate and thus accelerate dewatering. However, the performance of single polymer treatment is generally unsatisfactory. Recent studies in sewage treatment suggest that a dual polymer method, in which two different polymers are added in sequence, has a better flocculation performance. In this study, the use of dual polymer pairs in the flocculation and dewatering of MFT was investigated. A cationic polydiallyldimethylammonium chloride (polyDADMAC) polymer (Alcomer 7115, from BASF) and an anionic linear polyacrylamide polymer (A3335, from SNF) were found to be an effective combination in MFT dewatering treatment by filtration. The effects of polymer dosage, filtration pressure and the sequence of polymer addition were studied. Capillary suction time (CST) and specific resistance to filtration (SRF) were measured to evaluate the dewaterability of treated MFT. From the experimental data, MFT treated with the polymer combination of Alcomer 7115 and A3335 can give low CST results around 50 s, compared with around 3000 s of untreated MFT. Also the SRF was decreased from a magnitude of 1014 m/kg to 1012 ~ 1013 m/kg, indicating treated MFT being relatively much easier to dewater. Cryogenic scanning electron microscopic (Cryo-SEM) images of the treated MFT were taken to show the morphology of the MFT with or without treatment with either a single polymer or dual polymer pairs. The results demonstrated that the pore sizes are larger when the dual polymer pairs were used, implying higher dewaterability of MFT in this case.

  • Subjects / Keywords
  • Graduation date
    Spring 2016
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
  • Specialization
    • Materials Engineering
  • Supervisor / co-supervisor and their department(s)
  • Examining committee members and their departments
    • Phillip Choi (Chemical and Materials Engineering)
    • Qi Liu (Chemical and Materials Engineering)
    • Rajender Gupta (Chemical and Materials Engineering)
    • Dongyang Li (Chemical and Materials Engineering)