Reclamation of Unconventional Oil Processed Water through the Adsorption of Naphthenic Acids by Carbon Xerogel

  • Author / Creator
    Rashed, Yara A
  • This study examines the use of carbon xerogel (CX) material for the adsorption of naphthenic acids (NAs). The adsorption of NAs is crucial for the reclamation of unconventional oil processed water, more specifically Alberta’s oil sands process-affected water (OSPW). CX material is synthesized at specific operating pH conditions to result in a material that exhibits an extensive mesoporous character. Therefore, the employment of CX as an adsorbent can not only promote the adsorption of a wider range of complex NAs present in OSPW, but can also be synthesized to provide textural characteristics that adhere to contaminants present in all forms of unconventional oil processed water. This thesis begins with a review of the fundamentals of the adsorption phenomena, then provides a comprehensive analysis of Alberta’s OSPW with an elaborate description of the characteristics of NAs present in OSPW. Furthermore, the various treatment technologies that have been studied to treat OSPW from NAs is discussed with special focus on adsorption processes. The evaluation of the adsorbents discussed in this section reveals that their performance is restricted given that they are derived from raw materials, which accordingly limits their textural properties. As a result, the utilization of synthesized CX is necessary to enhance the removal of NAs form OSPW through adsorption. As a preliminary investigation of CX to treat OSPW, identifying the adsorption mechanisms responsible for the removal of NAs is initially required to further enhance the performance of CX in actual OSPW. Therefore, this study focusses on examining the efficacy of CX in terms of adsorbing model NA compounds; more specifically, heptanoic acid (HPA), 5-cyclohexanepentanoic acid (CHPA), and 5-Phenylvaleric acid (PVA). All three model NAs contain a carboxylic acid and long chain structure, with exception to CHPA which contains an additional cyclic ring, and PVA contains an aromatic ring. Therefore, by exploring the adsorption of these three model compounds, at pH 8, onto CX, the structure-activity relations responsible for adsorption are deduced. Furthermore, HPA, the simplest compound among the three, is examined in focus at three pH conditions, pH 8, 6.5, and 5, which are above, near, and below the pH of point zero charge for CX, 6.8. Therefore, the electrostatic interactions responsible for the adsorption of NAs onto CX can be identified. Note that at all conditions, similar investigations were conducted with granular activated carbon (GAC) to evaluate the effectiveness of CX relative to the conventional adsorbent used for the removal of NAs form OSPW. Moreover, the results were analyzed per adsorbent capacity, the internal diffusion model, and adsorption rate models; pseudo-first order and pseudo-second order, to demonstrate that CX performs exceptionally well relative to GAC due to its mesoporous structure. More specifically, the results have revealed that PVA, the more complex NA is adsorbed more easily by CX due to π-π interactions, followed by HPA due to its surfactant-like structure, and finally CHPA is adsorbed least due to its high molecular weight which delays its kinetics. The role of hydrophobic-hydrophobic forces has been noted during the diffusion of the three model NAs into the stagnant film surrounding the CX surface, and the hydrophobic bonding may be recognized as negatively charged assisted hydrogen bonding (-CAHB). In terms of HPA, van der Waals attractive forces, in the form of dipole-dipole attractions, have been recognized as the probable electrostatic mechanism responsible for the stronger attraction of HPA onto CX.

  • Subjects / Keywords
  • Graduation date
    Fall 2017
  • 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.