Physico-Chemical Processes for Oil Sands Process-Affected Water Treatment

• Author / Creator

  Pourrezaei,Parastoo

• Coagulation/Flocculation/Sedimentation (CFS), petroleum coke (PC) adsorption, and zero valent iron (ZVI) oxidation-enhanced by PC were applied for the remediation of oil sands process-affected water (OPSW), generated from oil sands operations in northern Alberta, Canada. OSPW is a complex mixture of various organic compounds [e.g., naphthenic acids (NAs)], dissolved and suspended solids, and a stable suspension of fine particles. Alum and cationic polymer, polydiallyldimethylammonium chloride (polyDADMAC), were used as the coagulant and coagulant aid, and the process was optimized to improve the efficiency of NAs and turbidity removals. Alum at 250 mg/L resulted in 96%, 10-37%, and 64-86% removal of turbidity, NAs and oxidized NAs, respectively. Destabilization of the particles occurred through charge neutralization by adsorption of the hydroxides on the surface of the particles. Analysis of the surface functional groups on flocs confirmed the removal of the NAs. Addition of polyDADMAC caused toxicity towards the benthic invertebrate, Chironoums dilutus, thus application of this polymer should be limited.
  
  PC, as a waste by-product generated during the oil upgrading processes, was used for the removal of NAs and extractable organic fraction (EOF). EOF and NAs removals of 60% and 75%, respectively, were achieved at a PC dose of 200 g/L after 16 h of contact. Fourier transform infrared (FT-IR) spectra of PC suggested the physisorption of organic compounds onto the PC surface. The calculated mean free energy of adsorption (E < 8 kJ/mol) also indicated the physisorption of organics. The hydrophobic interactions between the NAs and PC¬ were suggested as the dominant adsorption mechanism. Speciation analysis of the leached vanadium from PC into OSPW indicated that vanadium (V) was the predominant specie.
  
  In the presence of oxygen, ZVI at 25 g/L, added to PC, enhanced the NAs removal to 90%. PC, as an electron conductor, accelerated the electron transfer to oxygen resulting in the production of hydroxyl radicals. The hydroxyl radicals were responsible for the oxidation of NAs. Oxidized NAs concentration increased by 34% after the treatment. Toxicity of the treated OSPW to Vibrio fischeri bacteria, tested using Microtox® bioassay, showed a decrease in the toxic effects of the ZVI/PC treated samples.

• Subjects / Keywords

  • Petroleum Coke
  • Zero Valent Iron
  • Coagulation/Flocculation
  • Oil sands process-affected water

• Graduation date

  Spring 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R34H6J

• 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.